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  • 101.
    Johansson, Arvid
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Johansson, David
    Inledande studie inför utveckling av ett virtuellt mikroskop för utbildning inom livsvetenskaperna2010Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Forskning med hjälp av mikroskopi har med tiden ställt mer

    specialicerade krav på utrustning som används. Utrustningen

    har blivit mer bättre men samtidigt också dyrare. En

    hög kostnad innebär att avancerad mikroskopi inte kan användas

    som ett utbildningsverktyg inom grundutbildning.

    Dagens studenter tvingas på så sätt förberedas för framtidens

    forskning genom att använda gårdagens utrustning.

    I detta arbete visar vi hur virtuell mikroskopi kan användas

    för utbildning och forskning. Virtuell mikroskopi kan

    användas som komplement, eller möjligtvis ersättning, för

    befintlig undervisning. Vi har demonstrerat detta genom

    att utveckla en pilotapplikation som simulerar de två metoderna

    FLIP och FRAP. Applikationen har utvärderats

    med hjälp av erfarna mikroskopianvändare på

     

    som har kommit med åsikter och förslag. Det har

    visat sig att virtuell mikroskopi kan användas i flera olika

    syften. Som ett pedagogiskt verktyg kan det användas som

    ett träningsredskap både för mikroskophandhavande och

    för att lära sig plattformen Endrov. För att utveckla en

    tillfredsställande simulation av ett prov, så väl som abberationer

    i det optiska systemet, är det viktigt att skapa en

    god balans mellan ett trovärdigt visuellt uppträdande och

    en hög nivå av interaktion med systemet. Därav nödvändigheten

    att implementera optimerade algoritmer. Särskilt

    diffusionen av proteiner i en cell kräver beräkningskraft.

    ”Ni har övertygat mig om användbarheten med

    detta virtuella mikroskop. Jag hoppas att det

    kommer att användas i utbildningssyfte.”

    Kommentar från deltagare

    i mikroskopienkät

     

    Karolinska

     

     

    institutet

  • 102. Johansson, Arvid
    et al.
    Johansson, David
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Inledande studie inför utveckling av ett virtuelltmikroskop för utbildning inom livsvetenskaperna2010Independent thesis Advanced level (professional degree), 30 poäng / 45 hpOppgave
    Abstract [sv]

    Forskning med hjälp av mikroskopi har med tiden ställt mer

    specialicerade krav på utrustning som används. Utrustningen

    har blivit mer bättre men samtidigt också dyrare. En

    hög kostnad innebär att avancerad mikroskopi inte kan användas

    som ett utbildningsverktyg inom grundutbildning.

    Dagens studenter tvingas på så sätt förberedas för framtidens

    forskning genom att använda gårdagens utrustning.

    I detta arbete visar vi hur virtuell mikroskopi kan användas

    för utbildning och forskning. Virtuell mikroskopi kan

    användas som komplement, eller möjligtvis ersättning, för

    befintlig undervisning. Vi har demonstrerat detta genom

    att utveckla en pilotapplikation som simulerar de två metoderna

    FLIP och FRAP. Applikationen har utvärderats

    med hjälp av erfarna mikroskopianvändare på

     

    som har kommit med åsikter och förslag. Det har

    visat sig att virtuell mikroskopi kan användas i flera olika

    syften. Som ett pedagogiskt verktyg kan det användas som

    ett träningsredskap både för mikroskophandhavande och

    för att lära sig plattformen Endrov. För att utveckla en

    tillfredsställande simulation av ett prov, så väl som abberationer

    i det optiska systemet, är det viktigt att skapa en

    god balans mellan ett trovärdigt visuellt uppträdande och

    en hög nivå av interaktion med systemet. Därav nödvändigheten

    att implementera optimerade algoritmer. Särskilt

    diffusionen av proteiner i en cell kräver beräkningskraft.

    ”Ni har övertygat mig om användbarheten med

    detta virtuella mikroskop. Jag hoppas att det

    kommer att användas i utbildningssyfte.”

    Kommentar från deltagare

    i mikroskopienkät

     

    Karolinska

     

     

    institutet

  • 103. Johansson, Bjoern
    et al.
    Sundelin, Staffan
    Wikberg-Matsson, Anna
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Behndig, Anders
    Visual and optical performance of the akreos adapt advanced optics and tecnis Z9000 intraocular lenses - Swedish multicenter study2007Inngår i: Journal of cataract and refractive surgery, ISSN 0886-3350, E-ISSN 1873-4502, Vol. 33, nr 9, s. 1565-1572Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    PURPOSE: To compare the subjective visual and objective optical performance of 2 aspherical intraocular lenses (IOLs), the Akreos Adapt Advanced Optics (AO) (Bausch & Lomb, Inc.) and the Tecnis Z9000 (Advanced Medical Optics, Inc.). SETTING: Four university hospitals in Sweden. METHODS: This study comprised 80 patients, 20 each from 4 university hospital centers in Sweden. All patients had bilateral clear corneal phacoemulsification with implantation of an Akreos Adapt AO IOL in 1 eye and Tecnis Z9000 IOL in the other eye according to a randomization protocol. Preoperatively, 90% contrast Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity was measured and the mesopic pupil sizes were determined. Ten to 12 weeks postoperatively, 12.5% and 90% contrast ETDRS visual acuities and photopic and mesopic Functional Acuity Contrast Test chart contrast sensitivities were determined. Wavefront analysis was performed with the Zywave 11 aberrometer (Bausch & Lomb, Inc.), and a questionnaire on the subjective quality of vision was completed by each patient. RESULTS: The Akreos AD IOL and Tecnis Z9000 IOL produced similar high- and low-contrast visual acuities as well as photopic and mesopic contrast sensitivities. The Tecnis Z9000 IOL resulted in lower spherical aberrations of the eye (mean 0.05 +/- 0.13 pm versus 0.35 +/- 0.13 mu m root mean square, 6.0 mm pupil) (P<.001); however, the Akreos AO IOL provided a larger depth of field (mean 1.22 diopter [D] +/- 0.48 [SD] versus 0.86 +/- 0.50 D, 6.0 mm pupil) (P<.001). Patient satisfaction was generally high, although 68.8% of the patients reported some type of visual disturbance postoperatively. Twenty-eight percent of patients reported better subjective visual quality in the Akreos AD eye and 14%, in the Tecnis Z9000 eye (P<.0001). Accordingly, 33% perceived more visual disturbances in the Tecnis Z9000 eye and 11%, in the Akreos AID eye (P<.0001). CONCLUSIONS: Maximum reduction of spherical aberration did not maximize subjective visual quality. The higher perceived quality of vision with the Akreos AD IOL could be because of differences in depth of field, IOL material, or IOL design.

  • 104.
    Johansson, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Enlund, J.
    Johansson, S.
    Katardjiev, I.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Yantchev, V.
    Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel2012Inngår i: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 22, nr 2, s. 025018-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surface acoustic wave (SAW) excitation of an acoustic field in a trapezoidal glass microfluidic channel for particle manipulation in continuous flow has been demonstrated. A unidirectional interdigital transducer (IDT) on a Y-cut Z-propagation lithium niobate (LiNbO3) substrate was used to excite a surface acoustic wave at approximately 35 MHz. An SU8 layer was used for adhesive bonding of the superstrate glass layer and the substrate piezoelectric layer. This work extends the use of SAWs for acoustic manipulation to also include glass channels in addition to prior work with mainly poly-di-methyl-siloxane channels. Efficient alignment of 1.9 mu m polystyrene particles to narrow nodal regions was successfully demonstrated. In addition, particle alignment with only one IDT active was realized. A finite element method simulation was used to visualize the acoustic field generated in the channel and the possibility of 2D alignment into small nodal regions was demonstrated.

  • 105. Johansson, Ulf
    et al.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Mikkelsen, Anders
    NanoMAX: a hard x-ray nanoprobe beamline at MAX IV2013Inngår i: SPIE Optical Engineering+ Applications, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We describe the design of the NanoMAX beamline to be built among the first phase beamlines of the MAX IV facility inLund, Sweden. NanoMAX will be a hard X-ray imaging beamline providing down to 10 nm in direct spatial resolution,enabling investigations of very small heterogeneous samples exploring methods of diffraction, scattering, absorption,phase contrast and fluorescence. The beamline will have two experimental stations using Fresnel zone plates andKirkpatrick-Baez mirror optics for beam focusing, respectively. This paper focuses on the optical design of the beamlineexcluding the experimental stations but also describes general ideas about the endstations and the nano-focusing optics tobe used. The NanoMAX beamline is planned to be operational late 2016.

  • 106. Kang, G.
    et al.
    Rahomäki, Jussi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Dong, J.
    Honkanen, S.
    Turunen, J.
    Enhanced deep ultraviolet inverse polarization transmission through hybrid Al-SiO2 gratings2013Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, nr 13, s. 131110-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the enhancement of inverse polarization transmission of deep ultraviolet light, with the TE transmittance ηTE largely exceeding the TM transmittance ηTM, through a hybrid Al-SiO 2 grating: The grating slits are conformally filled with SiO 2. Strong coupling of the incident wave to surface plasmon polaritons greatly reduces the TM transmittance, whereas the coupling to the low-loss TE mode, with its effective refractive index approaching that of the substrate, leads to the enhanced TE transmittance. At resonance, a pronounced inverse polarization extinction ratio of 35 dB was obtained in our experiment, much higher than any previously reported values.

  • 107. Kertmen, Ahmet
    et al.
    Torruella, Pau
    Coy, Emerson
    Yate, Luis
    Nowaczyk, Grzegorz
    Gapinski, Jacek
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Toprak, Muhammet
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Estrade, Sonia
    Peiro, Francesca
    Milewski, Slawomir
    Jurga, Stefan
    Andruszkiewicz, Ryszard
    Acetate-Induced Disassembly of Spherical Iron Oxide Nanoparticle Clusters into Monodispersed Core-Shell Structures upon Nanoemulsion Fusion2017Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 39, s. 10351-10365Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has been long known that the physical encapsulation of oleic acid-capped iron oxide nanoparticles (OA-IONPs) with the cetyltrimethylammonium (CTA(+)) surfactant induces the formation of spherical iron oxide nanoparticle clusters (IONPCs). However, the behavior and functional properties of IONPCs in chemical reactions have been largely neglected and are still not well-understood. Herein, we report an unconventional ligand-exchange function of IONPCs activated when dispersed in an ethyl acetate/acetate buffer system. The ligand exchange can successfully transform hydrophobic OA-IONP building blocks of IONPCs into highly hydrophilic, acetate-capped iron oxide nanoparticles (Ac-IONPs). More importantly, we demonstrate that the addition of silica precursors (tetraethyl orthosilicate and 3-aminopropyltriethoxysilane) to the acetate/oleate ligand-exchange reaction of the IONPs induces the disassembly of the IONPCs into monodispersed iron oxide-acetate-silica core-shell-shell (IONPs@acetate@SiO2) nanoparticles. Our observations evidence that the formation of IONPs@acetate@SiO2 nanoparticles is initiated by a unique micellar fusion mechanism between the Pickering-type emulsions of IONPCs and nanoemulsions of silica precursors formed under ethyl acetate buffered conditions. A dynamic rearrangement of the CTA(+)-oleate bilayer on the IONPC surfaces is proposed to be responsible for the templating process of the silica shells around the individual IONPs. In comparison to previously reported methods in the literature, our work provides a much more detailed experimental evidence of the silica-coating mechanism in a nanoemulsion system. Overall, ethyl acetate is proven to be a very efficient agent for an effortless preparation of monodispersed IONPs@acetate@SiO2 and hydrophilic Ac-IONPs from IONPCs.

  • 108.
    Khachatourian, Malek Adrine
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik. Iran University of Science and Technology, Iran.
    Golestani-Fard, F.
    Sarpoolaky, H.
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vasileva, Elena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Mensi, Mounir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Microwave synthesis of Y2O3:Eu3+ nanophosphors: A study on the influence of dopant concentration and calcination temperature on structural and photoluminescence properties2016Inngår i: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 169, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Red fluorescent emitting monodispersed spherical Y<inf>2</inf>O<inf>3</inf> nanophosphors with different Eu3+ doping concentrations (0-13 mol%) are synthesized by a novel microwave assisted urea precipitation, which is recognized as a green, fast and reproducible synthesis method. The effect of Eu3+ doping and calcination temperature on the structural characteristics and luminescence properties of particles is investigated in detail. The as prepared powders have (Y,Eu)(OH)(CO<inf>3</inf>) structure which converts to Y<inf>2</inf>O<inf>3</inf>:Eu3+ from 500 °C and become crystalline at higher temperatures. The crystallite size of nanophosphors increased from 15 nm to 25 nm as the calcination temperature increased from 700 °C to 1050 °C. The efficient incorporation of Eu3+ ions in cubic Y<inf>2</inf>O<inf>3</inf> host matrix is confirmed by the calculated X-ray Powder diffraction (XRPD) structural parameters. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs show that the as obtained and calcined particles are spherical, monodispersed and non-agglomerated. The overall size of particles increases from 61±8 nm to 86±9 nm by increasing Eu3+ concentration from 0 mol% to 13 mol%. High resolution TEM revealed polycrystalline nature of calcined particles. The particles exhibit a strong red emission under ultraviolet (UV) excitation. The photoluminescence (PL) intensity of the peaks increases proportionally with Eu3+ concentration and the calcination temperature with no luminescence quenching phenomenon observed even for Y<inf>2</inf>O<inf>3</inf>:13%Eu3+. The fluorescent emission properties combined with the monodispersity and narrow size distribution characteristics make the Y<inf>2</inf>O<inf>3</inf>:Eu3+ heavy metal free nanophosphors applicable in fluorescence cell imaging and as fluorescence biolabels.

  • 109.
    Khachatourian, Malek Adrine
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik. IUST-Iran University of Science and Technology, Iran.
    Golestani-Fard, F.
    Sarpoolaky, H.
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Zhao, Yichen
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Green synthesis of Y2O3:Eu3+ nanocrystals for bioimaging2015Inngår i: Materials Research Society Symposium Proceedings, Materials Research Society, 2015, Vol. 1720, s. 59-64Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Rare earth (e.g., Eu, Er, Yb, Tm) doped Y<inf>2</inf>O<inf>3</inf> nanocrystals are promising fluorescent bioimaging agents which can overcome well known problems of currently used organic dyes like photobleaching, phototoxicity, and light scattering. Furthermore, the alternative quantum dots (QDs) composed of heavy metals (e.g., CdSe) possess inherently low biocompatibility due to the heavy metal content. In the present work, monodisperse spherical Y<inf>2</inf>O<inf>3</inf>:Eu3+ nanocrystals were successfully synthesized by microwave assisted urea precipitation method followed by thermochemical treatment. This is a green, fast and reproducible synthesis method, which is surfactant and hazardous precursors free. The as prepared particles were non-aggregated, spherical particles with a narrow size distribution. The calcined particles have a polycrystalline structure preserving the monodispersity and the spherical morphology of the as prepared particles. After calcination of Y(OH)CO<inf>3</inf>:Eu3+ precursors at 900°C for 2 hours, a highly crystalline cubic Y<inf>2</inf>O<inf>3</inf> structure was obtained. The Y<inf>2</inf>O<inf>3</inf>:Eu3+ spherical particles showed a strong red emission peak at 613nm due to the 5D<inf>0</inf>-7F<inf>2</inf> forced electric dipole transition of Eu3+ ions under UV excitation (235 nm) as revealed by the photoluminescence analysis (PL). The effect of reaction time on size and photoluminescence properties of calcined particles and also the effect of reaction temperature and pressure on the size and the yield of the precipitation process have been studied. The intense red fluorescent emission, excellent stability and potential low toxicity make these QDs promising for applications in bio-related areas such as fluorescence cell imaging or fluorescence bio labels.

  • 110. Kim, Kyung Hwan
    et al.
    Pathak, Harshad
    Spah, Alexander
    Perakis, Fivos
    Mariedahl, Daniel
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Katayama, Tetsuo
    Harada, Yoshihisa
    Ogasawara, Hirohito
    Pettersson, Lars G. M.
    Nilsson, Anders
    Temperature-Independent Nuclear Quantum Effects on the Structure of Water2017Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, nr 7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nuclear quantum effects (NQEs) have a significant influence on the hydrogen bonds in water and aqueous solutions and have thus been the topic of extensive studies. However, the microscopic origin and the corresponding temperature dependence of NQEs have been elusive and still remain the subject of ongoing discussion. Previous x-ray scattering investigations indicate that NQEs on the structure of water exhibit significant temperature dependence [Phys. Rev. Lett. 94, 047801 (2005)]. Here, by performing wide-angle x-ray scattering of H2O and D2O droplets at temperatures from 275 K down to 240 K, we determine the temperature dependence of NQEs on the structure of water down to the deeply supercooled regime. The data reveal that the magnitude of NQEs on the structure of water is temperature independent, as the structure factor of D2O is similar to H2O if the temperature is shifted by a constant 5 K, valid from ambient conditions to the deeply supercooled regime. Analysis of the accelerated growth of tetrahedral structures in supercooled H2O and D2O also shows similar behavior with a clear 5 K shift. The results indicate a constant compensation between NQEs delocalizing the proton in the librational motion away from the bond and in the OH stretch vibrational modes along the bond. This is consistent with the fact that only the vibrational ground state is populated at ambient and supercooled conditions.

  • 111. Kim, Kyung Hwan
    et al.
    Spah, Alexander
    Pathak, Harshad
    Perakis, Fivos
    Mariedahl, Daniel
    Amann-Winkel, Katrin
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lee, Jae Hyuk
    Kim, Sangsoo
    Park, Jaehyun
    Nam, Ki Hyun
    Katayama, Tetsuo
    Nilsson, Anders
    Maxima in the thermodynamic response and correlation functions of deeply supercooled water2017Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, nr 6370Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Femtosecond x-ray laser pulses were used to probe micrometer-sized water droplets that were cooled down to 227 kelvin in vacuum. Isothermal compressibility and correlation length were extracted from x-ray scattering at the low-momentum transfer region. The temperature dependence of these thermodynamic response and correlation functions shows maxima at 229 kelvin for water and 233 kelvin for heavy water. In addition, we observed that the liquids undergo the fastest growth of tetrahedral structures at similar temperatures. These observations point to the existence of a Widom line, defined as the locus of maximum correlation length emanating from a critical point at positive pressures in the deeply supercooled regime. The difference in the maximum value of the isothermal compressibility between the two isotopes shows the importance of nuclear quantum effects.

  • 112.
    Kim, Kyung Hwan
    et al.
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Spah, Alexander
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Pathak, Harshad
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Perakis, Fivos
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Mariedahl, Daniel
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Amann-Winkel, Katrin
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lee, Jae Hyuk
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Kim, Sangsoo
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Park, Jaehyun
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Nam, Ki Hyun
    Pohang Accelerator Lab, Pohang 37673, Gyeongbuk, South Korea..
    Katayama, Tetsuo
    Japan Synchrotron Radiat Res Inst, Kouto 1-1-1, Sayo, Hyogo 6795198, Japan..
    Nilsson, Anders
    Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Response to Comment on "Maxima in the thermodynamic response and correlation functions of deeply supercooled water"2018Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 360, nr 6390, artikkel-id eaat1729Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Caupin et al. have raised several issues regarding our recent paper on maxima in thermodynamic response and correlation functions in deeply supercooled water. We show that these issues can be addressed without affecting the conclusion of the paper.

  • 113.
    Kothapalli, Satya V. V. N.
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Janerot-Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik. Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Paradossi, Gaio
    Grishenkov, Dmitry
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik. Karolinska Institute, Sweden; Karolinska University Hospital, Sweden.
    Investigation of polymer-shelled microbubble motions in acoustophoresis2016Inngår i: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 70, s. 275-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this paper is to explore the trajectory motion of microsize (typically smaller than a red blood cell) encapsulated polymer-shelled gas bubbles propelled by radiation force in an acoustic standing-wave field and to compare the corresponding movements of solid polymer microbeads. The experimental setup consists of a microfluidic chip coupled to a piezoelectric crystal (PZT) with a resonance frequency of about 2.8 MHz. The microfluidic channel consists of a rectangular chamber with a width, w, corresponding to one wavelength of the ultrasound standing wave. It creates one full wave ultrasound of a standing-wave pattern with two pressure nodes at w/4 and 3w/4 and three antinodes at 0, w/2, and w. The peak-to-peak amplitude of the electrical potential over the PZT was varied between 1 and 10 V. The study is limited to no-flow condition. From Gor'kov's potential equation, the acoustic contrast factor, Phi, for the polymer-shelled microbubbles was calculated to about -60.7. Experimental results demonstrate that the polymer-shelled microbubbles are translated and accumulated at the pressure antinode planes. This trajectory motion of polymer-shelled microbubbles toward the pressure antinode plane is similar to what has been described for other acoustic contrast particles with a negative Phi. First, primary radiation forces dragged the polymer-shelled microbubbles into proximity with each other at the pressure antinode planes. Then, primary and secondary radiation forces caused them to quickly aggregate at different spots along the channel. The relocation time for polymer-shelled microbubbles was 40 times shorter than that for polymer microbeads, and in contrast to polymer microbeads, the polymer-shelled microbubbles were actuated even at driving voltages (proportional to radiation forces) as low as 1 V. In short, the polymer-shelled microbubbles demonstrate the behavior attributed to the negative acoustic contrast factor particles and thus can be trapped at the antinode plane and thereby separated from particles having a positive acoustic contrast factor, such as for example solid particles and cells. This phenomenon could be utilized in exploring future applications, such as bioassay, bioaffinity, and cell interaction studies in vitro in a well-controlled environment.

  • 114. Kurta, Ruslan P.
    et al.
    Donatelli, Jeffrey J.
    Yoon, Chun Hong
    Berntsen, Peter
    Bielecki, Johan
    Daurer, Benedikt J.
    DeMirci, Hasan
    Fromme, Petra
    Hantke, Max Felix
    Maia, Filipe R. N. C.
    Munke, Anna
    Nettelblad, Carl
    Pande, Kanupriya
    Reddy, Hemanth K. N.
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Sierra, Raymond G.
    Svenda, Martin
    van der Schot, Gijs
    Vartanyants, Ivan A.
    Williams, Garth J.
    Xavier, P. Lourdu
    Aquila, Andrew
    Zwart, Peter H.
    Mancuso, Adrian P.
    Correlations in Scattered X-Ray Laser Pulses Reveal Nanoscale Structural Features of Viruses2017Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, nr 15, artikkel-id 158102Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use extremely bright and ultrashort pulses from an x-ray free-electron laser (XFEL) to measure correlations in x rays scattered from individual bioparticles. This allows us to go beyond the traditional crystallography and single-particle imaging approaches for structure investigations. We employ angular correlations to recover the three-dimensional (3D) structure of nanoscale viruses from x-ray diffraction data measured at the Linac Coherent Light Source. Correlations provide us with a comprehensive structural fingerprint of a 3D virus, which we use both for model-based and ab initio structure recovery. The analyses reveal a clear indication that the structure of the viruses deviates from the expected perfect icosahedral symmetry. Our results anticipate exciting opportunities for XFEL studies of the structure and dynamics of nanoscale objects by means of angular correlations.

  • 115. Lakshminarayanan, Vasudevan
    et al.
    Varadharajan, L. Srinivasa
    Diaz-Santana, Luis
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vision Science and Ophthalmic Optics2011Inngår i: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, nr 19-20, s. 1679-1680Artikkel i tidsskrift (Annet vitenskapelig)
  • 116.
    Larsson, Daniel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Small-Animal Imaging with Liquid-Metal-Jet X-Ray Sources2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Small-animal x-ray imaging is an important tool for medical research. The penetration power of x-rays makes it possible to investigate the 3D structure of small animals and other thick biological samples by computed tomography (CT). However, small-animal x-ray imaging often requires high resolution due to the small structures involved, and short exposure times due to sample movement. This constitutes a challenge, since these two properties require compact x-ray sources with parameters that are not widely available.

    In this Thesis we present the first application of liquid-metal-jet sources for small-animal imaging. This source concept was invented at KTH just over ten years ago. The use of a high-speed metal jet as electron-beam target, instead of a solid anode, enables higher x-ray flux while maintaining a small x-ray spot for high-resolution imaging. In the present work, a liquid-metal jet source with a higher-energy spectrum has been developed. It has stronger 24 keV radiation compared to previous sources, which makes it more suitable for imaging of small animals and other few-cm-thick objects, which require the higher penetration of 20-35 keV x-rays.

    We have applied the liquid-metal-jet x-ray sources for whole-body imaging of sacrificed mice and zebrafish. With high-resolution absorption-contrast CT we have visualized fine bone details of mice. We have also used phase contrast, a new method that can considerably improve imaging of, e.g., soft tissue, for demarcation of mm-sized tumors inside a full mouse and for mouse cartilage imaging. In zebrafish imaging, we have exploited the greatly enhanced contrast of phase-imaging to resolve single muscle fibers (and possibly even myofibrils) in whole zebrafish in a laboratory setting for the first time. The muscle structures have diameters in the 5-7 μm range and extremely low contrast, which makes them difficult to observe.

    With phase contrast, we have demonstrated low-dose and high-resolution angiography of mouse and rat organs and tissues ex vivo. We show detection of blood vessels with diameters below 10 μm with radiation doses compatible with living small animals, which is not possible with absorption contrast and iodinated contrast agents. In addition, we have investigated the vascular network of tumors in mouse ears and visualized the chaotic arrangement of newly-formed blood vessels.

    Finally, we present the first results from a new high-power liquid-metal-jet x-ray source prototype, operating at 10× the power of our previous sources, with the same x-ray spot size. This source constitutes an important step towards future in-vivo small-animal laboratory imaging with high resolution.

  • 117.
    Larsson, Daniel H.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Westermark, U.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Arsenian Henriksson, M.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Small-animal tomography with a liquid-metal-jet x-ray source2012Inngår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE, SPIE - International Society for Optical Engineering, 2012, Vol. 8313, s. 83130N-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    X-ray tomography of small animals is an important tool for medical research. For high-resolution x-ray imaging of few-cm-thick samples such as, e.g., mice, high-brightness x-ray sources with energies in the few-10-keV range are required. In this paper we perform the first small-animal imaging and tomography experiments using liquid-metal-jet-anode x-ray sources. This type of source shows promise to increase the brightness of microfocus x-ray systems, but present sources are typically optimized for an energy of 9 keV. Here we describe the details of a high-brightness 24-keV electron-impact laboratory microfocus x-ray source based on continuous operation of a heated liquid-In/Ga-jet anode. The source normally operates with 40 W of electron-beam power focused onto the metal jet, producing a 7×7 μm 2 FWHM x-ray spot. The peak spectral brightness is 4 × 10 9 photons/( s × mm 2 × mrad 2 × 0.1%BW) at the 24.2 keV In K α line. We use the new In/Ga source and an existing Ga/In/Sn source for high-resolution imaging and tomography of mice.

  • 118.
    Larsson, Daniel H.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Westermark, Ulrica K.
    Arsenian Henriksson, Marie
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    First application of liquid-metal-jet sources for small-animal imaging: High-resolution CT and phase-contrast tumor demarcation2013Inngår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 40, nr 2, s. 021909-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: Small-animal studies require images with high spatial resolution and high contrast due to the small scale of the structures. X-ray imaging systems for small animals are often limited by the microfocus source. Here, the authors investigate the applicability of liquid-metal-jet x-ray sources for such high-resolution small-animal imaging, both in tomography based on absorption and in soft-tissue tumor imaging based on in-line phase contrast. Methods: The experimental arrangement consists of a liquid-metal-jet x-ray source, the small-animal object on a rotating stage, and an imaging detector. The source-to-object and object-to-detector distances are adjusted for the preferred contrast mechanism. Two different liquid-metal-jet sources are used, one circulating a Ga/In/Sn alloy and the other an In/Ga alloy for higher penetration through thick tissue. Both sources are operated at 40-50 W electron-beam power with similar to 7 mu m x-ray spots, providing high spatial resolution in absorption imaging and high spatial coherence for the phase-contrast imaging. Results: High-resolution absorption imaging is demonstrated on mice with CT, showing 50 mu m bone details in the reconstructed slices. High-resolution phase-contrast soft-tissue imaging shows clear demarcation of mm-sized tumors at much lower dose than is required in absorption. Conclusions: This is the first application of liquid-metal-jet x-ray sources for whole-body small-animal x-ray imaging. In absorption, the method allows high-resolution tomographic skeletal imaging with potential for significantly shorter exposure times due to the power scalability of liquid-metal-jet sources. In phase contrast, the authors use a simple in-line arrangement to show distinct tumor demarcation of few-mm-sized tumors. This is, to their knowledge, the first small-animal tumor visualization with a laboratory phase-contrast system.

  • 119.
    Larsson, Daniel H.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Takman, Per A.C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Burvall, Anna
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    A 24 keV liquid-metal-jet x-ray source for biomedical applications2011Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 82, nr 12, s. 123701-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a high-brightness 24-keV electron-impact microfocus x-ray source based on continuous operation of a heated liquid-indium/gallium-jet anode. The 30–70 W electron beam is magnetically focused onto the jet, producing a circular 7–13 μm full width half maximum x-ray spot. The measured spectral brightness at the 24.2 keV In Kα line is 3 × 109 photons/(s × mm2 × mrad2 × 0.1% BW) at 30 W electron-beam power. The high photon energy compared to existing liquid-metal-jet sources increases the penetration depth and allows imaging of thicker samples. The applicability of the source in the biomedical field is demonstrated by high-resolution imaging of a mammography phantom and a phase-contrast angiography phantom.

  • 120.
    Larsson, Daniel H.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Stanford University, United States.
    Vågberg, William
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Yaroshenko, Andre
    Yildirim, Ali Oender
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution short- exposure small-animal laboratory x-ray phase-contrast tomography2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 39074Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten mu m spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.

  • 121.
    Larsson, Jakob C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Laboratory x-ray fluorescence tomography2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    X-ray fluorescence (XRF) tomography is an emerging bio-imaging modality with potential for high-resolution molecular imaging in 3D. In this technique the fluorescence signal from targeted nanoparticles (NPs) is measured, providing information about the spatial distribution and concentration of the NPs inside the object. However, present laboratory XRF tomographysystems typically have limited spatial resolution (>1 mm) and suffer from long scan times and high radiation dose even at high NP concentrations, mainly due to low efficiency and poor signal-to-noise ratio (SNR). Other macroscopic biomedical imaging methods provide either structural information with high spatial resolution (e.g., CT) or functional/molecularinformation with lower resolution (e.g., PET).

    In this Thesis we present a laboratory XRF tomography system with high spatial resolution (sub-200 μm), low NP concentration and vastly reduced scan times and dose, opening up the possibilities for in vivo small-animal imaging research. The system consists of a high-brightness liquid-metal-jet microfocus x-ray source, x-ray focusing optics and two photon counting detectors. By using the source’s characteristic 24 keV line emission together with spectrally matched molybdenum NPs the Compton background is greatly reduced, increasing the SNR. Each measurement provides information about the spatial distribution and concentration of the NPs, as well as the absorption of the object. An iterative method is used to get aquantitative reconstruction of the XRF image. The reconstructed absorption and XRF images are finally combined into a single 3D overlay image.

    Using this system we have demonstrated high-resolution dual CT and XRF imaging of both phantoms and mice at radiation doses compatible with in vivo small-animal imaging.

  • 122.
    Larsson, Jakob C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging2016Inngår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 43, nr 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose: High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. Methods: The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency and effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. Results: There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28-38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. Conclusions: The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.

  • 123.
    Larsson, Jakob C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Shaker, Kian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Focused anti-scatter grid for background reduction in x-ray fluorescence tomography2018Inngår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 43, nr 11, s. 2591-2594Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray fluorescence (XRF) tomography is an emerging imaging technology with the potential for high spatial resolution molecular imaging. One of the key limitations is the background noise due to Compton scattering since it degrades the signal and limits the sensitivity. In this Letter, we present a linear focused anti-scatter grid that reduces the Compton scattering background. An anti-scatter grid was manufactured and evaluated both experimentally and theoretically with Monte Carlo simulations. The measurements showed a 31% increase in signal-to-background ratio, and simulations of an improved grid showed that this can easily be extended up to > 75%. Simulated tomographies using the improved grid show a large improvement in reconstruction quality. The anti-scatter grid will be important for in vivo XRF tomography since the background reduction allows for faster scan times, lower doses, and lower nanoparticle concentrations.

  • 124.
    Larsson, Jakob C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vågberg, William
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Toprak, Muhammet
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Dzieran, Johanna
    Arsenian-Henriksson, Marie
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    High-spatial-resolution x-ray fluorescence tomography with spectrally matched nanoparticles2018Inngår i: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 63, s. 164001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Present macroscopic biomedical imaging methods provide either morphology with high spatial resolution (e.g. CT) or functional/molecular information with lower resolution (e.g. PET). X-ray fluorescence (XRF) from targeted nanoparticles allows molecular or functional imaging but sensitivity has so far been insufficient resulting in low spatial resolution, despite long exposure times and high dose. In the present paper, we show that laboratory XRF tomography with metal-core nanoparticles (NPs) provides a path to functional/molecular biomedical imaging with ~100 µm resolution in living rodents. The high sensitivity and resolution rely on the combination of a high-brightness liquid-metal-jet x-ray source, pencil-beam optics, photon-counting energy-dispersive detection, and spectrally matched NPs. The method is demonstrated on mice for 3D tumor imaging via passive targeting of in-house-fabricated molybdenum NPs. Exposure times, nanoparticle dose, and radiation dose agree well with in vivo imaging.

  • 125.
    Larsson, Jakob C.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vågberg, William
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Ulf
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Larsson, Daniel H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-spatial-resolution nanoparticle X-ray fluorescence tomography2016Inngår i: MEDICAL IMAGING 2016: PHYSICS OF MEDICAL IMAGING, 2016, artikkel-id 97831VKonferansepaper (Fagfellevurdert)
    Abstract [en]

    X-ray fluorescence tomography (XFCT) has potential for high-resolution 3D molecular x-ray bio-imaging. In this technique the fluorescence signal from targeted nanoparticles (NPs) is measured, providing information about the spatial distribution and concentration of the NPs inside the object. However, present laboratory XFCT systems typically have limited spatial resolution (>1 mm) and suffer from long scan times and high radiation dose even at high NP concentrations, mainly due to low efficiency and poor signal-to-noise ratio. We have developed a laboratory XFCT system with high spatial resolution (sub-100 mu m), low NP concentration and vastly decreased scan times and dose, opening up the possibilities for in-vivo small-animal imaging research. The system consists of a high-brightness liquid-metal-jet microfocus x-ray source, x-ray focusing optics and an energy-resolving photon-counting detector. By using the source's characteristic 24 keV line-emission together with carefully matched molybdenum nanoparticles the Compton background is greatly reduced, increasing the SNR. Each measurement provides information about the spatial distribution and concentration of the Mo nanoparticles. A filtered back-projection method is used to produce the final XFCT image.

  • 126. Legall, H.
    et al.
    Blobel, G.
    Stiel, H.
    Sandner, W.
    Seim, C.
    Takman, Per
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Martz, Dale H.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Selin, Mårten
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Esser, D.
    Sipma, H.
    Luttmann, J.
    Höfffer, M.
    Hoffmann, H. D.
    Yulin, S.
    Feigl, T.
    Rehbein, S.
    Guttmann, P.
    Schneider, G.
    Wiesemann, U.
    Wirtz, M.
    Diete, W.
    Compact X-ray microscope for the water window based on a high brightness laser plasma source2012Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, nr 16, s. 18362-18369Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a laser plasma based x-ray microscope for the water window employing a high-average power laser system for plasma generation. At 90 W laser power a brightness of 7.4 x 10(11) photons/(s x sr x mu m(2)) was measured for the nitrogen Ly alpha line emission at 2.478 nm. Using a multilayer condenser mirror with 0.3 % reflectivity 10(6) photons/(mu m(2) x s) were obtained in the object plane. Microscopy performed at a laser power of 60 W resolves 40 nm lines with an exposure time of 60 s. The exposure time can be further reduced to 20 s by the use of new multilayer condenser optics and operating the laser at its full power of 130 W.

  • 127. Legall, H.
    et al.
    Stiel, H.
    Blobel, G.
    Seim, C.
    Baumann, J.
    Yulin, S.
    Esser, D.
    Hoefer, M.
    Wiesemann, U.
    Wirtz, M.
    Schneider, G.
    Rehbein, S.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    A compact laboratory transmission X-ray microscope for the water window2013Inngår i: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 463, nr 1, s. 012013-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the water window (2.2-4.4 nm) the attenuation of radiation in water is significantly smaller than in organic material. Therefore, intact biological specimen (e.g. cells) can be investigated in their natural environment. In order to make this technique accessible to users in a laboratory environment a Full-Field Laboratory Transmission X-ray Microscope (L-TXM) has been developed. The L-TXM is operated with a nitrogen laser plasma source employing an InnoSlab high power laser system for plasma generation. For microscopy the Ly α emission of highly ionized nitrogen at 2.48 nm is used. A laser plasma brightness of 5 × 1011 photons/(s × sr × μm2 in line at 2.48 nm) at a laser power of 70 W is demonstrated. In combination with a state-of-the-art Cr/V multilayer condenser mirror the sample is illuminated with 106 photons/(μm2 × s). Using objective zone plates 35-40 nm lines can be resolved with exposure times &lt; 60 s. The exposure time can be further reduced to 20 s by the use of new multilayer condenser optics and operating the laser at its full power of 130 W. These exposure times enable cryo tomography in a laboratory environment.

  • 128. Lemor, Robert
    et al.
    Günther, Christian
    Fuhr, Günther
    Wiklund, Martin
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Metod och anordning för akustisk manipulering av partiklar, celler och virus2005Patent (Annet (populærvitenskap, debatt, mm))
  • 129. Lewis, Peter
    et al.
    Baskaran, Karthikeyan
    Rosén, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Objectively Determined Refraction Improves Peripheral Vision2014Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 91, nr 7, s. 740-746Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose. The purpose of this study was twofold: to verify a fast, clinically applicable method for determining off-axis refraction and to assess the impact of objectively obtained off-axis refractive correction on peripheral low-contrast visual acuity. Methods. We measured peripheral low-contrast resolution acuity with Gabor patches both with and without off-axis correction at 20 degrees in the nasal visual field of 10 emmetropic subjects; the correction was obtained using a commercial open-field Hartmann-Shack wavefront sensor, the COAS-HD VR aberrometer. Off-axis refractive errors were calculated for a 5-mm circular pupil inscribed within the elliptical wavefront by COAS using the instruments' inbuilt "Seidel sphere" method. Results. Most of the subjects had simple myopic astigmatism, at 20 degrees in the nasal visual field ranging from -1.00 to -2.00 DC, with axis orientations generally near 90 degrees. The mean uncorrected and corrected low-contrast resolution acuities for all subjects were 0.92 and 0.86 logMAR, respectively (an improvement of 0.06 logMAR). For subjects with a scalar power refractive error of 1.00 diopters or more, the average improvement was 0.1 logMAR. The observed changes in low-contrast resolution acuity were strongly correlated with off-axis astigmatism (Pearson r = 0.95; p < 0.0001), the J(180) cross-cylinder component (Pearson r = 0.82; p = 0.0034), and power scalar (Pearson r = -0.75; p = 0.0126). Conclusions. The results suggest that there are definite benefits in correcting even moderate amounts of off-axis refractive errors; in this study, as little as -1.50 DC of off-axis astigmatism gave improvements of up to a line in visual acuity. It may be even more pertinent for people who rely on optimal peripheral visual function, specifically those with central visual field loss; the use of open-field aberrometers could be clinically useful in rapidly determining off-axis refractive errors specifically for this patient group who are generally more challenging to refract.

  • 130. Lewis, Peter
    et al.
    Rosén, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Resolution of static and dynamic stimuli in the peripheral visual field2011Inngår i: Vision Research, ISSN 0042-6989, E-ISSN 1878-5646, Vol. 51, nr 16, s. 1829-1834Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a clinical setting, emphasis is given to foveal visual function, and tests generally only utilize static stimuli. In this study, we measured static (SVA) and dynamic visual acuity (DVA) in the central and peripheral visual field on healthy, young emmetropic subjects using stationary and drifting Gabor patches. There were no differences between SVA and DVA in the peripheral visual field; however, SVA was superior to DVA in the fovea for both velocities tested. In addition, there was a clear naso-temporal asymmetry for both SVA and DVA for isoeccentric locations in the visual field beyond 10 degrees eccentricity. The lack of difference in visual acuity between static and dynamic stimuli found in this study may reflect the use of drift-motion as opposed to displacement motion used in previous studies.

  • 131. Lewis, Peter
    et al.
    Venkataraman, Abinaya Priya
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Lundström, Linda
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Optical correction and stimulus motion improve peripheral vision in eyes with central scotomaManuskript (preprint) (Annet vitenskapelig)
  • 132.
    Li, Yuyang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Shaker, Kian
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Larsson, Jakob C.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Carmen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Toprak, Muhammet S.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    A Library of Potential Nanoparticle Contrast Agents for X-Ray Fluorescence Tomography Bioimaging2018Inngår i: Contrast Media & Molecular Imaging, ISSN 1555-4309, E-ISSN 1555-4317, artikkel-id UNSP 8174820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanoparticles (NPs) have been used as contrast agents for several bioimaging modalities. X-ray fluorescence (XRF) tomography can provide sensitive and quantitative 3D detection of NPs. With spectrally matched NPs as contrast agents, we demonstrated earlier in a laboratory system that XRF tomography could achieve high-spatial-resolution tumor imaging in mice. Here, we present the synthesis, characterization, and evaluation of a library of NPs containing Y, Zr, Nb, Rh, and Ru that have spectrally matched K-shell absorption for the laboratory scale X-ray source. The K-shell emissions of these NPs are spectrally well separated from the X-ray probe and the Compton background, making them suitable for the lab-scale XRF tomography system. Their potential as XRF contrast agents is demonstrated successfully in a small-animal equivalent phantom, confirming the simulation results. The diversity in the NP composition provides a flexible platform for a better design and biological optimization of XRF tomography nanoprobes.

  • 133.
    Liljeborg, Anders V. G.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Tellefsen, G.
    Johannsen, G.
    The use of a profilometer for both quantitative and qualitative measurements of toothpaste abrasivity2010Inngår i: International Journal of Dental Hygiene, ISSN 1601-5029, E-ISSN 1601-5037, Vol. 8, nr 3, s. 237-243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aim: To evaluate the abrasivity of different toothpastes both quantitatively and qualitatively with a profilometer technique and to correlate these findings to the radioactive dentin abrasivity (RDA) value. Materials and methods: Acrylic plates were exposed to brushing in a brushing machine with 11 different toothpastes. The results were evaluated using a profilometer. A surface roughness value (Ra-value), that is, a qualitative measurement, and also a volume value, that is, a quantitative measurement, were calculated from the profilometer results. These values were then correlated to each other and to the RDA-value. A comparison between RDA, Ra and volume measurements was performed using linear fitting procedure. Results: The results showed that the correlation between RDA and Ra measurements was low (R-2 = 0.04) and also that the correlation between RDA and volume measurements was low (R-2 = 0.00002). Correlation between Ra and abraded volume was high (R-2 = 0.87). Conclusions: It is important to consider not only the RDA-value when evaluating toothpaste abrasivity. From the profilometer results both a quantitative (volume) and qualitative (roughness) measurement of the abrasivity of a toothpaste can be obtained.

  • 134.
    Lindblom, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nanofabrication of Diffractive Soft X-ray Optics2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis summarizes the present status of the nanofabrication of diffractive optics, i.e. zone plates, and test objects for soft x-ray microscopy at KTH. The emphasis is on new and improved fabrication processes for nickel and germanium zone plates. A new concept in which nickel and germanium are combined in a zone plate is also presented. The main techniques used in the fabrication are electron beam lithography for the patterning, followed by plasma etching and electroplating for the structuring of the optical materials. The process for fabricating nickel zone plates has been significantly improved. The reproducibility of the electroplating step has been increased by the implementation of an in-situ rate measurement and an end-point detection method. We have also shown that pulse plating can be used to obtain zone plates with a uniform height profile. New plating mold materials have been introduced and electron-beam curing of the molds has been investigated and implemented to increase their mechanical stability so that pattern collapse in the electroplating step can be avoided. The introduction of cold development has improved the achievable resolution of the process. This has enabled the fabrication of zone plates with outermost zone widths down to 16 nm. The nickel process has also recently been adapted to fabrication of gold structures intended for test objects and hard x-ray zone plates. For the fabrication of germanium zone plates we developed a highly anisotropic plasma-etch process using Cl2 feed and sidewall passivation. Germanium zone plates have been fabricated with zone widths down to 30 nm. The diffraction efficiency is comparable to that of nickel zone plates, but the process does not involve electroplating and thus has for potential for highyield fabrication. The combination of nickel and germanium is a new fabrication concept that provides a means to achieve high diffraction efficiency even for thin nickel. The idea is to fabricate a nickel zone plate on a germanium film. The nickel zone plate itself is then used as etch mask for a highly selective CHF3- plasma etch into the germanium layer. Proof of principle experiments showed an efficiency increase of about a factor of two for nickel zone plates with a 50- nm nickel thickness.

  • 135.
    Lindblom, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Reinspach, Julia
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Bertilson, Michael
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    von Hofsten, Olov
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Hertz, Hans
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Nickel-germanium soft x-ray zone plates2009Inngår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 27, nr 3, s. L5-L7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents a fabrication process for soft x-ray zone plates in which nickel and germanium are combined to achieve high diffraction efficiency. A nickel zone plate is first fabricated on a germanium film and then used as a hardmask for a CHF3-plasma etch into the germanium. Zone plates with 50-60 nm nickel and 110-150 nm of germanium are presented. The measured diffraction efficiencies were 10%-11% at lambda=2.88 nm, which shows that high efficiency is possible even with thin nickel. Thus, the method has a potential for improving the efficiency of high-resolution zone plates for which the high-aspect-ratio structuring of nickel is difficult.

  • 136.
    Lindblom, Magnus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Tuohimaa, Tomi
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Holmberg, Anders
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Wilhein, Thomas
    Hertz, Hans M.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vogt, Ulrich
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    High-resolution differential-interference-contrast x-ray zone plates: Design and Fabrication2007Inngår i: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 62, nr 6-7, s. 539-543Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Differential interference contrast is a potentially powerful technique for contrast enhancement in soft X-ray microscopy. We describe the design and fabrication of single-element diffractive optical elements suitable as objectives for high-resolution differential interference contrast microscopy in the water-window spectral range. A one-dimensional pattern calculation followed by an extension to two dimensions results in a pattern resolution of 1 nm, which is well below fabrication accuracy. The same fabrication process as for normal zone plates is applicable, but special care must be taken when converting the calculated pattern to a code for e-beam lithography.

  • 137. Lindskoog Pettersson, Anna
    et al.
    Jarkö, Caroline
    Alvin, Åsa
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Brautaset, Rune
    Spherical aberration in contact lens wear2008Inngår i: Contact lens & anterior eye, ISSN 1367-0484, E-ISSN 1476-5411, Vol. 31, nr 4, s. 189-193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Introduction: The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. Methods: A wavefront analyser (Zywave™, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). Results: Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (p < 0.05) with all lenses. Conclusion: Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.

  • 138.
    Lobov, G. S.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Marinins, A.
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Etcheverry, S.
    Zhao, Yichen
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Vasileva, Elena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Sugunan, A.
    Laurell, F.
    Thylén, Lars
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wosinski, L.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Toprak, M. S.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Popov, Sergei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Direct birefringence and transmission modulation via dynamic alignment of P3HT nanofibers in an advanced opto-fluidic component2017Inngår i: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 7, nr 1, s. 52-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Poly-3-hexylthiophene (P3HT) nanofibers are semiconducting high-aspect ratio nanostructures with anisotropic absorption and birefringence properties found at different regions of the optical spectrum. In addition, P3HT nanofibers possess an ability to be aligned by an external electric field, while being dispersed in a liquid. In this manuscript we show that such collective ordering of nanofibers, similar to liquid crystal material, significantly changes the properties of transmitted light. With a specially fabricated opto-fluidic component, we monitored the phase and transmission modulation of light propagating through the solution of P3HT nanofibers, being placed in the electric field with strength up to 0.1 V/μm. This report describes a technique for light modulation, which can be implemented in optical fiber-based devices or on-chip integrated components.

  • 139.
    Lundholm, Ida V.
    et al.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Sellberg, Jonas A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Ekeberg, Tomas
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Hantke, Max F.
    Univ Oxford, Oxford, England..
    Okamoto, Kenta
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    van der Schot, Gijs
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Andreasson, Jakob
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Czech Acad Sci, Inst Phys, ELI Beamlines, Slovance 2, CZ-18221 Prague, Czech Republic.;Chalmers Univ Technol, Dept Phys, Condensed Matter Phys, Gothenburg, Sweden..
    Barty, Anton
    DESY, Ctr Free Electron Laser Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Bielecki, Johan
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany..
    Bruza, Petr
    Chalmers Univ Technol, Dept Phys, Condensed Matter Phys, Gothenburg, Sweden..
    Bucher, Max
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA.;Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany.;Argonne Natl Lab, Chem Sci & Engn Div, 9700 South Cass Ave, Lemont, IL 60439 USA..
    Carron, Sebastian
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA..
    Daurer, Benedikt J.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Ferguson, Ken
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA.;PULSE Inst, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA.;SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA..
    Hasse, Dirk
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Krzywinski, Jacek
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA..
    Larsson, Daniel S. D.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Morgan, Andrew
    DESY, Ctr Free Electron Laser Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Muhlig, Kerstin
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Mueller, Maria
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany..
    Nettelblad, Carl
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Uppsala Univ, Dept Informat Technol, Sci Life Lab, Div Sci Comp, Lagerhyddsvagen 2,Box 337, SE-75105 Uppsala, Sweden..
    Pietrini, Alberto
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Reddy, Hemanth K. N.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Rupp, Daniela
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany..
    Sauppe, Mario
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany..
    Seibert, Marvin
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Svenda, Martin
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Swiggers, Michelle
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA..
    Timneanu, Nicusor
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Ulmer, Anatoli
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany..
    Westphal, Daniel
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Williams, Garth
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA.;Brookhaven Natl Lab, NSLS 2, POB 5000, Upton, NY 11973 USA..
    Zani, Alessandro
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden..
    Faigel, Gyula
    Res Inst Solid State Phys & Opt, H-1525 Budapest, Hungary..
    Chapman, Henry N.
    DESY, Ctr Free Electron Laser Sci, Notkestr 85, D-22607 Hamburg, Germany..
    Moeller, Thomas
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany..
    Bostedt, Christoph
    SLAC Natl Accelerator Lab, Linac Coherent Light Source, Stanford, CA 94309 USA.;Argonne Natl Lab, Chem Sci & Engn Div, 9700 South Cass Ave, Lemont, IL 60439 USA.;PULSE Inst, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA.;SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA.;Northwestern Univ, Dept Phys, 2145 Sheridan Rd, Evanston, IL 60208 USA..
    Hajdu, Janos
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Czech Acad Sci, Inst Phys, ELI Beamlines, Slovance 2, CZ-18221 Prague, Czech Republic..
    Gorkhover, Tais
    Tech Univ Berlin, Inst Opt & Atomare Phys, Hardenbergstr 36, D-10623 Berlin, Germany.;PULSE Inst, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA.;SLAC Natl Accelerator Lab, 2575 Sand Hill Rd, Menlo Pk, CA 94025 USA..
    Maia, Filipe R. N. C.
    Uppsala Univ, Dept Cell & Mol Biol, Lab Mol Biophys, Husargatan 3,Box 596, SE-75124 Uppsala, Sweden.;Lawrence Berkeley Natl Lab, NERSC, 1 Cyclotron Rd, Berkeley, CA 94720 USA..
    Considerations for three-dimensional image reconstruction from experimental data in coherent diffractive imaging2018Inngår i: IUCrJ, ISSN 0972-6918, E-ISSN 2052-2525, Vol. 5, s. 531-541Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffraction before destruction using X-ray free-electron lasers (XFELs) has the potential to determine radiation-damage-free structures without the need for crystallization. This article presents the three-dimensional reconstruction of the Melbournevirus from single-particle X-ray diffraction patterns collected at the LINAC Coherent Light Source (LCLS) as well as reconstructions from simulated data exploring the consequences of different kinds of experimental sources of noise. The reconstruction from experimental data suffers from a strong artifact in the center of the particle. This could be reproduced with simulated data by adding experimental background to the diffraction patterns. In those simulations, the relative density of the artifact increases linearly with background strength. This suggests that the artifact originates from the Fourier transform of the relatively flat background, concentrating all power in a central feature of limited extent. We support these findings by significantly reducing the artifact through background removal before the phase-retrieval step. Large amounts of blurring in the diffraction patterns were also found to introduce diffuse artifacts, which could easily be mistaken as biologically relevant features. Other sources of noise such as sample heterogeneity and variation of pulse energy did not significantly degrade the quality of the reconstructions. Larger data volumes, made possible by the recent inauguration of high repetition-rate XFELs, allow for increased signal-to-background ratio and provide a way to minimize these artifacts. The anticipated development of three-dimensional Fourier-volume-assembly algorithms which are background aware is an alternative and complementary solution, which maximizes the use of data.

  • 140.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Rehabilitation Engineering Research, Department of Design Science, Lund University.
    Svensson, Ingrid
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Assessment of objective and subjective eccentric refraction2005Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 82, nr 4, s. 298-306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose. When performing perimetry, refracting subjects with central visual field loss, and in emmetropization studies, it is important to accurately measure peripheral refractive errors. Traditional methods for foveal refraction often give uncertain results in eccentric angles as a result of the large aberrations and the reduced retinal function. The aim of this study is therefore to compare and evaluate four methods for eccentric refraction. Methods. Four eccentric methods were tested on 50 healthy subjects: one novel subjective procedure, optimizing the detection contrast sensitivity with different trial lenses, and three objective ones: photorefraction with a PowerRefractor, wavefront measurements with a Hartmann-Shack sensor, and retinoscopy. The peripheral refractive error in the horizontal nasal visual field of the right eye was measured in 20 degrees and 30 degrees. Results. In general, the eccentric refraction methods compared reasonably well. However, the following differences were noted. Retinoscopy showed a significant difference from the other methods in the axis of astigmatism. In 300 eccentric angle, it was not possible to measure 15 of the subjects with the PowerRefractor and the instrument also tended to underestimate high myopia (<-6 D). The Hartmann-Shack sensor showed a myopic shift of approximately 0.5 D in both eccentricities. The subjective method had a relatively larger spread. Conclusions. This study indicates that it is possible to assess the eccentric refraction with all methods. However, the Hartmann-Shack technique was found to be the most useful method. The agreement between the objective methods and the subjective eccentric refraction shows that detection contrast sensitivity in the periphery is affected by relatively small amounts of defocus.

  • 141.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Population distribution of wavefront aberrations in the peripheral human eye2009Inngår i: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 26, nr 10, s. 2192-2198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a population study of peripheral wavefront aberrations in large off-axis angles in terms of Zernike coefficients. A laboratory Hartmann-Shack sensor was used to assess the aberrations in 0 degrees, 20 degrees, and 30 degrees in the nasal visual field of 43 normal eyes. The elliptical pupil meant that the quantification could be done in different ways. The three approaches used were (1) over a circular aperture encircling the pupil, (2) over a stretched version of the elliptical pupil, and (3) over a circular aperture within the pupil (MATLAB conversion code given). Astigmatism (c(2)(2)) increased quadratically and coma (c(3)(1)) linearly with the horizontal viewing angle, whereas spherical aberration (c(4)(0)) decreased slightly toward the periphery. There was no correlation between defocus and angle, although some trends were found when the subjects were divided into groups depending on refractive error. When comparing results of different studies it has to be kept in mind that the coefficients differ depending on how the elliptical pupil is taken into consideration.

  • 142.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Vision Enabling Laboratory, School of Optometry, Kalmar University.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Vision evaluation of eccentric refractive correction2007Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 84, nr 11, s. 1046-1052Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose. This study investigates the benefits of eccentric refractive correction to resolution and detection thresholds in different contrasts for seven subjects with central visual field loss (CFL) and for four healthy control subjects with normal vision.

    Methods. Refractive correction in eccentric viewing angles, i.e., the preferred retinal location for the CFL subjects and 20 degrees off-axis for the control subjects, was assessed by photorefraction with the PowerRefractor instrument and by wavefront analysis using the Hartmann-Shack principle. The visual function with both eccentric and central corrections was evaluated using number identification and grating detection.

    Results. For the CFL subjects, the resolution and detection thresholds varied between individuals because of different preferred retinal locations and cause of visual field loss. However, all seven CFL subjects showed improved visual function for resolution and detection tasks with eccentric correction compared with central correction. No improvements in high-contrast resolution were found for the control subjects.

    Conclusions. These results imply that optical eccentric correction can improve the resolution acuity for subjects with CFL in situations where healthy eyes do not show any improvements.

  • 143.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Manzanera, Silvestre
    Laboratorio de Optica, Universidad de Murcia.
    Prieto, Pedro
    Laboratorio de Optica, Universidad de Murcia.
    Ayala, Diego
    Laboratorio de Optica, Universidad de Murcia.
    Gorceix, Nicolas
    Laboratorio de Optica, Universidad de Murcia.
    Gustafsson, Jörgen
    School of Optometry, Kalmar University.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Artal, Pablo
    Laboratorio de Optica, Universidad de Murcia.
    Effect of optical correction and remaining aberrations on peripheral resolution acuity in the human eye2007Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 15, nr 20, s. 12654-12661Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Retinal sampling poses a fundamental limit to resolution acuity in the periphery. However, reduced image quality from optical aberrations may also influence peripheral resolution. In this study, we investigate the impact of different degrees of optical correction on acuity in the periphery. We used an adaptive optics system to measure and modify the off-axis aberrations of the right eye of six normal subjects at 20 degrees eccentricity. The system consists of a Hartmann-Shack sensor, a deformable mirror, and a channel for visual testing. Four different optical corrections were tested, ranging from foveal sphero-cylindrical correction to full correction of eccentric low- and high-order monochromatic aberrations. High-contrast visual acuity was measured in green light using a forced choice procedure with Landolt C's, viewed via the deformable mirror through a 4.8-mm artificial pupil. The Zernike terms mainly induced by eccentricity were defocus and with- and against-the-rule astigmatism and each correction condition was successfully implemented. On average, resolution decimal visual acuity improved from 0.057 to 0.061 as the total root-mean-square wavefront error changed from 1.01 mu m to 0.05 mu m. However, this small tendency of improvement in visual acuity with correction was not significant. The results suggest that for our experimental conditions and subjects, the resolution acuity in the periphery cannot be improved with optical correction.

  • 144.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rosen, Robert
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Van der Mooren, Marrie
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Piers, Patricia A.
    Abbott Med Opt Groningen BV, Appl Res, Groningen, Netherlands..
    Low Amounts of Scattering Reduce Central as well as Peripheral Contrast Sensitivity2014Inngår i: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 55, nr 13Artikkel i tidsskrift (Annet vitenskapelig)
  • 145.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rosén, R.
    Peripheral aberrations2017Inngår i: Handbook of Visual Optics, Volume One: Fundamentals and Eye Optics, CRC Press , 2017, s. 313-335Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    The schematic of Figure 21.1 is highly simplified, assuming spherical and aligned surfaces. Nevertheless, it demonstrates two important facts regarding the optical errors of the human eye: that the blur increases with the off-axis angle to the object and that it depends on the size of the pupil. For instance, spherical aberration has a cubic dependence on pupil size and coma has a quadratic dependence, whereas TCA is independent. To exemplify, Figure 21.2 shows the variation in monochromatic image quality over the visual field measured for one subject. The following paragraphs will briefly explain the origin of the four largest peripheral aberrations, namely, astigmatism, field curvature, coma, and TCA. © 2017 by Taylor & Francis Group, LLC.

  • 146.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Rosén, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Baskaran, K.
    Jaeken, B.
    Gustafsson, J.
    Artal, P.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Symmetries in peripheral ocular aberrations2011Inngår i: Journal of Modern Optics, ISSN 0950-0340, E-ISSN 1362-3044, Vol. 58, nr 19-20, s. 1690-1695Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mirror symmetry in the aberrations between the left and right eyes has previously been found foveally, but while a similar symmetry for the peripheral visual field is likely, it has not been investigated. Nevertheless, the peripheral optical quality is often evaluated in only one eye, because it is more time efficient than analyzing the whole visual field of both eyes. This study investigates the correctness of such an approach by measuring the peripheral wavefront aberrations in both eyes of 22 subjects out to +/- 40 degrees horizontally. The largest aberrations (defocus, astigmatism, and coma) were found to be significantly correlated between the left and right eyes when comparing the same temporal or nasal angle. The slope of the regression line was close to +/- 1 (within 0.05) for these aberrations, with a negative slope for the horizontally odd aberrations, i.e. the left and right eyes are mirror symmetric. These findings justify that the average result, sampled in one of the two eyes of many subjects, can be generalized to the other eye as well.

  • 147.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Transformation of Zernike coefficients: scaled, translated, and rotated wavefronts with circular and elliptical pupils2007Inngår i: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, nr 3, s. 569-577Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zernike polynomials and their associated coefficients are commonly used to quantify the wavefront aberrations of the eye. When the aberrations of different eyes, pupil sizes, or corrections are compared or averaged, it is important that the Zernike coefficients have been calculated for the correct size, position, orientation, and shape of the pupil. We present the first complete theory to transform Zernike coefficients analytically with regard to concentric scaling, translation of pupil center, and rotation. The transformations are described both for circular and elliptical pupils. The algorithm has been implemented in MATLAB, for which the code is given in an appendix.

  • 148.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unwrapping Hartmann-Shack images from highly aberrated eyes using an iterative B-spline based extrapolation method2004Inngår i: Optometry and Vision Science, ISSN 1040-5488, E-ISSN 1538-9235, Vol. 81, nr 5, s. 383-388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose. When the wavefront aberrations of the eye are measured with a Hartmann-Shack (HS) sensor, the resulting spot pattern must be unwrapped, that is, for each lenslet the corresponding spot must be identified. This puts a limitation on the measurable amount of aberrations. To extend the range of an HS sensor, a powerful unwrapping algorithm has been developed. Methods. The unwrapping algorithm starts by connecting the central HS spots to the central lenslets. It then fits a B-spline function through a least squares estimate to the deviations of the central HS spots. This function is then extrapolated to find the expected locations of HS spots for the unconnected lenslets. The extrapolation is performed gradually in an iterative manner; the closest unconnected lenslets are extrapolated and connected, and then the B-spline function is least squares fitted to all connected HS spots and extrapolated again. Results. Wavefront aberrations from eyes with high aberrations can be successfully unwrapped with the developed algorithm. The dynamic range of a typical HS sensor increases 3.5 to 13 times compared with a simple unwrapping algorithm. Conclusions. The implemented algorithm is an efficient unwrapping tool and allows the use of lenslets with a low numerical aperture and thus gives a relatively higher accuracy of measurements of the ocular aberrations.

  • 149.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Tidigare Institutioner, Fysik. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, J
    Measuring peripheral wavefront aberrations in subjects with large central visual field loss2004Inngår i: OPHTHALMIC TECHNOLOGIES XIV / [ed] Manns, F; Soderberg, PG; Ho, A, BELLINGHAM: SPIE-INT SOC OPTICAL ENGINEERING , 2004, Vol. 5314, s. 209-219Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a previous study we have shown that correction of peripheral refractive errors can improve the remaining vision in the preferred retinal location (PRL) of subjects with large central visual field loss (CFL). Measuring peripheral refractive errors with traditional methods is often difficult due to the low visual acuity and large aberrations. Therefore a Hartmann-Shack (HS) sensor has been designed to measure peripheral wavefront aberrations in CFL subjects. Method: The HS sensor incorporates an eyetracker and analyzing software designed to handle large wavefront aberrations. To ensure that the measurement axis is aligned with the subject's PRL, a special fixation target has been developed. It consists of concentric rings surrounding the aperture of the HS together with a central fixation mark along the measurement axis. Results: Some initial measurements on subjects with CFL have been performed successfully. As a first step in improving the peripheral optics of the eye, the wavefront data have been used to calculate the subject's optimal eccentric refraction. Conclusion: Measuring the wavefront aberrations is a fast and easy way to assess the details of the optics in subjects with CFL. The wavefront data can then be used to better understand the problems of eccentric correction.

  • 150.
    Lundström, Linda
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Unsbo, Peter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Gustafsson, Jörgen
    Lund University, Certec, Rehabilitation Engineering Research, Department of Design Sciences, Lund.
    Off-axis wave front measurements for optical correction in eccentric viewing2005Inngår i: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 10, nr 3, s. 034002-1-034002-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a previous study we have shown that correction of peripheral refractive errors can improve the remaining vision of subjects with large central visual field loss. Measuring peripheral refractive errors with traditional methods is often difficult due to low visual acuity and large aberrations. Therefore a Hartmann-Shack sensor has been designed to measure peripheral wave front aberrations in subjects using eccentric viewing. The sensor incorporates an eye tracker and analyzing software designed to handle large wave front aberrations and elliptic pupils. To ensure that the measurement axis is aligned with the direction of the subject's preferred retinal location, a special fixation target has been developed. It consists of concentric rings surrounding the aperture of the sensor together with a central fixation mark along the measurement axis. Some initial measurements on subjects using eccentric viewing have been performed successfully. As a first step in improving the peripheral optics of the eye, the wave front has been used to calculate the eccentric refraction. This refraction has been compared to the refraction found with the Power-Refractor instrument. Measuring the off-axis wave front is a fast way to assess the optical errors in the subject's eccentric viewing angle and to better understand the problems of eccentric correction.

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