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  • 1.
    Abtahi, Farhad
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Aslamy, Benjamin
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Boujabir, Imaneh
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    An Affordable ECG and Respiration Monitoring System Based on Raspberry PI and ADAS1000: First Step towards Homecare Applications2015Ingår i: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, Springer, 2015, s. 5-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    Homecare is a potential solution for problems associated with an aging population. This may involve several physiological measurements, and hence a flexible but affordable measurement device is needed. In this work, we have designed an ADAS1000-based four-lead electrocardiogram (ECG) and respiration monitoring system. It has been implemented using Raspberry PI as a platform for homecare applications. ADuM chips based on iCoupler technology have been used to achieve electrical isolation as required by IEC 60601 and IEC 60950 for patient safety. The result proved the potential of Raspberry PI for the design of a compact, affordable, and medically safe measurement device. Further work involves developing a more flexible software for collecting measurements from different devices (measuring, e.g., blood pressure, weight, impedance spectroscopy, blood glucose) through Bluetooth or user input and integrating them into a cloud-based homecare system.

  • 2.
    Abtahi, Farhad
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Seoane, Fernando
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Lindecrantz, Kaj
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system.
    Electrical bioimpedance spectroscopy in time-variant systems: Is undersampling always a problem?2014Ingår i: Journal of Electrical Bioimpedance, ISSN 1891-5469, Vol. 5, nr 1, s. 28-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During the last decades, Electrical Bioimpedance Spectroscopy (EBIS) has been applied mainly by using the frequency-sweep technique, across a range of many different applications. Traditionally, the tissue under study is considered to be time-invariant and dynamic changes of tissue activity are ignored by treating the changes as a noise source. A new trend in EBIS is simultaneous electrical stimulation with several frequencies, through the application of a multi-sine, rectangular or other waveform. This method can provide measurements fast enough to sample dynamic changes of different tissues, such as cardiac muscle. This high sampling rate comes at a price of reduction in SNR and the increase in complexity of devices. Although the frequency-sweep technique is often inadequate for monitoring the dynamic changes in a variant system, it can be used successfully in applications focused on the time-invariant or slowly-variant part of a system. However, in order to successfully use frequency-sweep EBIS for monitoring time-variant systems, it is paramount to consider the effects of aliasing and especially the folding of higher frequencies, on the desired frequency e.g. DC level. This paper discusses sub-Nyquist sampling of thoracic EBIS measurements and its application in the case of monitoring pulmonary oedema. It is concluded that by considering aliasing, and with proper implementation of smoothing filters, as well as by using random sampling, frequency-sweep EBIS can be used for assessing time-invariant or slowly-variant properties of time-variant biological systems, even in the presence of aliasing. In general, undersampling is not always a problem, but does always require proper consideration.

  • 3.
    Ammendrup, Katrin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    Framework for Wireless Acquisition of Surface EMG and Real-Time Control2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Muscle driven devices are controlled or powered with muscle activation. These devices open up the possibility of offering patients with limited muscle function to automatically control assistive devices - for instance exoskeletons - with input from their own muscles. This solution would help a number of patient groups suffering from common conditions, such as spinal cord injuries, stroke and cerebral palsy.

    To use muscle activation as input it is necessary to have a way to communicate with the mus- cles. Electromyography (EMG) is a technology used to gain information about muscle function and activation. It is performed by measuring and analyzing electrical signals conducted by the muscles during activation. Activation and activation level can be seen from analyzed EMG signal. EMG signals are frequently measured and analyzed afterwards, however, to use it as a controlling an assistive devices, real time analysis is necessary. In this thesis real time acquisi- tion and analysis of EMG was performed. The measured signal was used as an input to control a simple MATLAB computer game.

    The EMG of a muscle of the forearm, Brachioradialis, was measured with Myon Aktos sys- tem. The measured signal was written to a server as soon as the measurements were acquired. MATLAB was used to connect to the server and performing the signal analysis. The analysis was kept simple in order to limit delay.

    The result showed that it was possible to acquire real time signal with this method. The delay was negligible, both for the testing and for the game play.

    Showing that it is possible to play a game with muscle activation supports the idea of a motor that can be controlled automatically with muscle input. Future work should focus on understanding movement intent with respect to EMG and on analyzing multiple signals from different muscles at the same time.

  • 4.
    Angelopoulos, Angelos
    et al.
    -.
    Apostolakis, A.
    -.
    Aslanides, E.
    -.
    Backenstoss, Gerhard
    -.
    Bargassa, P.
    -.
    Bee, C P.
    -.
    Behnke, O.
    -.
    Benelli, A.
    -.
    Bertin, V.
    -.
    Blanc, F.
    -.
    Danielsson, Mats
    KTH, Tidigare Institutioner, Fysik.
    Physics at CPLEAR2003Ingår i: Physics Reports, Vol. 374, nr 3, s. 165-270Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study of CP, T and CPT symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.

  • 5. Apostolakis, A
    et al.
    Aslanides, E.
    -.
    Backenstoss, G.
    -.
    Bargassa, P.
    -.
    Behnke, O.
    -.
    Benelli, A.
    -.
    Bertin, V.
    -.
    Blanc, F.
    -.
    Bloch, P.
    -.
    Carlson, P.
    KTH, Skolan för teknikvetenskap (SCI).
    Danielsson, Mats
    KTH, Tidigare Institutioner, Fysik.
    A determination of the CP violation parameter η+- from the decay of strangeness-tagged neutral kaons1999Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 458, nr 4, s. 545-552Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    LEAR offered unique opportunities to study the symmetries which exist between matter and antimatter. At variance with other approaches at this facility, CPLEAR was an experiment devoted to the study of CP, T and CPT symmetries in the neutral-kaon system. A variety of measurements allowed us to determine with high precision the parameters which describe the time evolution of the neutral kaons and their antiparticles, including decay amplitudes, and the related symmetry properties. Limits concerning quantum-mechanical predictions (EPR, coherence of the wave function) or the equivalence principle of general relativity have been obtained. An account of the main features of the experiment and its performances is given here, together with the results achieved.

  • 6.
    Borghäll, David
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Lundström, Mathilda
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Utveckling av handhållen prototyp för mätning av EKG och fingerpuls2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna rapport representerar ett kandidatexamensarbete vid Kungliga Tekniska Högskolan(KTH), där målet var att skapa en handhållen prototyp. Funktionerna för prototypen var mätning av puls i ett finger med optiska sensorn TCRT1010 och elektrokardiografi(EKG) med bipolära extremitetsavledningar. Prototypen är skapad med målet att vara användarvänlig, kostnadseffektiv och billig för att kunna appliceras i utvecklingsländer som finns i Afrika och Asien. Anledningen är då det finns brist på billig och lätthanterlig medicinsk teknik i de områden.

    Arbetet utfördes genom utveckling av två kretsar givna av uppdragsgivaren, för att sedan designas på ett kretskort som tillverkades av ett svenskt företag. Samtliga komponenter löddes fast på kretskortet och monterades i en behållare med uttag och batterier. Den slutgiltiga prototypen består av en plastlåda som innehåller kretskortet med funktionen att mäta antingen pulsen i ett finger eller EKG, som användaren väljer med hjälp av en switch. Prototypen är även utrustad med avtagbart lock, två BNC kontakter för signalutskick till oscilloskop, en för vardera krets, tre labbhylsor för extremiteterna och ett 4-polig kontakt för den optiska sensorn. Signalerna som fås är ej brusfria men innehåller respektive signals viktigaste parametrar för kontroll om vidare diagnostisk behövs.

    Den framtagna prototypens kostnad slutade på 1815,5 SEK, vilket ej ansågs uppfylla målet för kostnadeffektivet men som anses kunna användas i utvecklingsländer då prototypen har en simpel design, med avtagbart lock som möjliggör lätta batteribyten, endast en switch och är kompakt som gör den lätt att utföra undersökningar med. Signalhanteringen är testad för att ge tydlig signal som möjliggör att vårdpersonal kan identifiera om vidare diagnostik behövs. Många framtida förbättringar identifierades, så som att minska kostnaden med byte till billigare komponenter och massbeställning av kretskort, göra prototypen trådlöst kopplad till mätinstrument eller minska brus ytterligare.

  • 7.
    Callerström, Emma
    KTH, Skolan för teknik och hälsa (STH).
    Clinicians' demands on monitoring support in an Intensive Care Unit: A pilot study, at Capio S:t Görans Hospital2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Patienter som vårdas på intensivvårdsavdelningar har svikt i ett eller flera organ. Övervakning sker av patienterna för att kunna bidra till den vård som behövs för att upprätthålla ett meningsfullt liv. Idag hanterar sjukvårdpersonal en stor mängd data som genereras från övervakningsutrustning och system förknippade med övervakningsutrustning. Övervakningsparameterar kan antecknas förhand på ett övervakningspapper eller direkt sparas i digitalt format. Parameterarna sparas med syfte att vara ett lättillgängligt underlag under hela intensivvårdsprocessen. Patient data management systems (PDMSs) förenklar hämtning och integrering av data på exempelvis intensivvårdsavdelningar. Innan en ny konfiguration av ett patientdatasystem erhålls, är det eftersträvnadsvärt att intensivvårdsavdelningen analyserar vilken datasom skall hanteras. Detta examensarbete bidrog till kunskap om hur övervakning utförs på en intensivvårdsavdelning, på ett akutsjukhus i Stockholm. Målet med detta examensarbete var att insamla data om vad klinikerna behöver och vilken utrustning och system som de använder idag för att utföra övervakning. Behovsframkallning är en teknik som kan användas för att insamla krav. I detta projekt insamlades data genom aktivaobservationer och kvalitativa intervjuer. Mönster har hittats bland undersköterskornas, sjuksköterskornas och läkarnas behov av teknisksupport från system och utrustning som stödjer sjukvårdspersonalen under övervakningen av en patient. Undersköterskor uttrycker ett behov av att bli avlastade från uppgifter så som att manuellt skrivaner vitala parametervärden. De ifrågasätter behovet av automatiserad datahämtning eftersom de ständigt är närvarande bredvid patienten. Sjuksköterskor beskriver en hög vårdtyngd och önskaratt inte bli tillägnade fler aktiviteter som ökar den vårdtyngden. Läkare beskriver ett behov av ökat stöd för hur en interversion leder till resultat för individuella patienter. Resultaten visar attdet finns information om möjliga kliniska beslutsstöd utan givet sätt att applicera dessa, bättre än de sätt som används idag. Sjukvårdspersonalen hävdar att det det finns ett behov av att utvärdera det kliniska arbetet med hjälp av övervakningsparametrar. Resultaten utgör kunskap om vilka områden som sjukvårdpersonalens behov inte har stöd av nuvarnade verktyg. Resultaten visar att beroende på vilken profession och erfarenhet som sjukvårdspersonalen har, är behoven olika. På intensivvårdsavdelningen sker övervakning då enskilda patienter visuellt observeras såväl som övervakningsparametrar från medicintekniska produkter, resultat från medicinska tester och fysiska examinationer. Det finns behov att integrera och presenterainformation från dessa källor givet kunskap om att sjukvårdpersonalen fattar beslut på dessa som resulterar i behandling, diagnostik och/eller vård.

  • 8.
    Cederström, Björn
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Streubuehr, Ursula
    Comparison of photon-counting to storage phosphor plate mammography using contrast-detail phantom analysis2007Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 580, nr 2, s. 1101-1104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two digital mammography systems, one based on scanning photon counting silicon detectors and the other on storage phosphor plates (CR), have been compared in terms of image quality and dose. Sets of images of a contrast-detail phantom (CDMAM3.4) were acquired for each system and dose level. The images were evaluated in the disc diameter range 0.16-1 mm using a computer program (CDcom) and the results were fitted to a psychometric curve for each disc diameter. The contrast-detail curve was summarized into one single figure of merit, the image quality index, and the dose efficiency was calculated. The errors of the calculated parameters were assessed using statistical analysis. It was found that the scanning photon-counting system can achieve the same image quality as the storage phosphor plate (CR) system at 30-38% of the average glandular dose.

  • 9.
    Cederwall, Bo
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
    Development of a multimodality sensor for spectral photon counting CT, standard CT and PET2011Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 648, nr Suppl 1, s. S72-S74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A prototype sensor module for multimodality medical imaging applications requiring awide intensity range has been developed. It consists of a silicon photomultiplier (SiPM)-scintillator sensor connected to a 100 kHz bandwidth current amplifier integrated with afour stage energy discriminator and a charge sensitive preamplifier. The electronics design allows for simultaneous read out of current level and discriminatory information of single photon energy or, optionally, high-resolution energy information via the charge preamplifier. This single-channel device is a proof-of-principle system designed primarily for combined spectral photon counting computed tomography (CT)/standard CT or combined with positron emission tomography (PET).

  • 10.
    Fogelberg, Jonathan
    et al.
    KTH, Skolan för teknik och hälsa (STH).
    Nordbrøden, Mats
    KTH, Skolan för teknik och hälsa (STH).
    Infusionspumpar - en studie vid Astrid Lindgrens Barnsjukhus2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Bakgrunden till detta arbete är att det saknas riktlinjer från den tekniska avdelningen när vårdavdelningar på Astrid Lindgrens barnsjukhus skall köpa in infusionspumpar.

    Syftet med arbetet är att rekommendera ett antal pumpar vilka möter de krav och önskemål som ställs på dessa. Krav och önskemål kommer framförallt ifrån sjuksköterskorna men även ifrån rapportskrivarna.

    I resultatet presenteras sammanfattningar från de intervjuer som hållits med sjuksköterskor.

    I diskussionen kommenterar vi sjuksköterskornas önskemål och lyfter fram våra egna. Vi spekulerar även om infusionspumpens framtid.

    I slutsatsen anges vilka pumpmodeller som bäst möter de krav och önskemål som ställts på pumparna och varför vi rekommenderar Brauns pumpar före CareFusions. 

  • 11.
    Frank A, Flachskampf
    et al.
    Uppsala Universitet, Institutionen för Medicinska Vetenskaper, Akademiska sjukhuset.
    Mattias, Mårtensson
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    How should tissue Doppler tracings be measured?2014Ingår i: European Heart Journal Cardiovascular Imaging, ISSN 2047-2404, E-ISSN 2047-2412, Vol. 15, nr 7, s. 828-829Artikel i tidskrift (Refereegranskat)
  • 12.
    Frånberg, Oskar
    Swedish Defence Research Agency.
    Anordning och förfarande för att producera oxygen: Device and method for producing oxygen2005Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The invention relates to a medical device for producing oxygen, wherein the device comprises means for providing first conditions, and means for changing said first conditions to second conditions, the device being configured to during a charging phase extract oxygen from air by, under said first conditions, bringing said air (A) into contact with an agent (SfF) constituted by a reversibly oxygen-fixating agent, i.e. an oxygen selective material, such that the oxygen of the air is adsorbed by said agent, and to remove nitrogen under said first conditions, and configured to during a discharging phase release the oxygen from the agent by means of changing said first conditions to said second conditions. The invention also relates to a method for producing oxygen for individual medical purposes.

  • 13.
    Frånberg, Oskar
    Swedish Defence Research Agency.
    Breathing apparatus1999Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    A breathing apparatus is described, having a breathing circuit comprising a mouthpiece (8) and one or more gas carrying conduits (60), a compressed gas source (2) and a counterlung (5). The compressed gas source (2) is in communication with the counterlung (5) via the breathing circuit. The counterlung (5) has an expansion assisting means (3) and a contraction assisting means (20), and a control allows selective activation of the expansion assisting means (3) and the contraction assisting means (20). The counterlung has primary (12) and secondary (10) chambers, and inflation of the secondary chamber (10) causes inflation of the primary chamber (12). The expansion assisting means (3) is a flow of compressed gas to inflate the secondary chamber (10).

  • 14.
    Frånberg, Oskar
    Swedish Defence Research Agency.
    Rechargeable breathing apparatus particularly an apparatus for divers2000Patent (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    A rechargeable breathing apparatus with a closed breathing system, particularly for aqua-diver. It comprises a breathing bellows (28) for reception of the exhaled air, to which bellows a pressurised container (38) for a gas or a mixture of gases is connected through a hydrostatic valve (42). The breathing bellows is arranged, after adsorption of CO2 from the exhaled air, and oxygen supply, to deliver breathing air to the diver. An oxygen accumulator (12) containing a reversibly oxygen fixating agent is connected to the breathing bellows (28). The oxygen accumulator (12) is rechargeable by bringing said agent into reaction with oxygen gas or oxygen in the air whereby the oxygen is adsorbed to the same. An oxygen accumulator (12) upon heating gives off oxygen to the breathing bellows. The apparatus may also be used during smoke divin

  • 15. Fröberg, Asa
    et al.
    Mårtensson, Mattias
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Larsson, Matilda
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Janerot-Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    D'Hooge, Jan
    Arndt, Anton
    High variability in strain estimation errors when using a commercial ultrasound speckle tracking algorithm on tendon tissue2016Ingår i: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 57, nr 10, s. 1223-1229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Ultrasound speckle tracking offers a non-invasive way of studying strain in the free Achilles tendon where no anatomical landmarks are available for tracking. This provides new possibilities for studying injury mechanisms during sport activity and the effects of shoes, orthotic devices, and rehabilitation protocols on tendon biomechanics. Purpose: To investigate the feasibility of using a commercial ultrasound speckle tracking algorithm for assessing strain in tendon tissue. Material and Methods: A polyvinyl alcohol (PVA) phantom, three porcine tendons, and a human Achilles tendon were mounted in a materials testing machine and loaded to 4% peak strain. Ultrasound long-axis cine-loops of the samples were recorded. Speckle tracking analysis of axial strain was performed using a commercial speckle tracking software. Estimated strain was then compared to reference strain known from the materials testing machine. Two frame rates and two region of interest (ROI) sizes were evaluated. Results: Best agreement between estimated strain and reference strain was found in the PVA phantom (absolute error in peak strain: 0.21 +/- 0.08%). The absolute error in peak strain varied between 0.72 +/- 0.65% and 10.64 +/- 3.40% in the different tendon samples. Strain determined with a frame rate of 39.4Hz had lower errors than 78.6Hz as was the case with a 22mm compared to an 11mm ROI. Conclusion: Errors in peak strain estimation showed high variability between tendon samples and were large in relation to strain levels previously described in the Achilles tendon.

  • 16.
    Granqvist, Svante
    et al.
    KTH, Skolan för teknik och hälsa (STH), Naturvetenskap och biomedicin, Grundläggande naturvetenskap. Karolinska Institutet (KI), Sweden.
    Simberg, S.
    Hertegård, S.
    Holmqvist, S.
    Larsson, H.
    Lindestad, P. -Å
    Södersten, M.
    Hammarberg, B.
    Resonance tube phonation in water: High-speed imaging, electroglottographic and oral pressure observations of vocal fold vibrations - A pilot study2015Ingår i: Logopedics, Phoniatrics, Vocology, ISSN 1401-5439, E-ISSN 1651-2022, Vol. 40, nr 3, s. 113-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phonation into glass tubes (resonance tubes), keeping the free end of the tube in water, has been a frequently used voice therapy method in Finland and more recently also in other countries. The purpose of this exploratory study was to investigate what effects tube phonation with and without water has on the larynx. Two participants were included in the study. The methods used were high-speed imaging, electroglottographic observations of vocal fold vibrations, and measurements of oral pressure during tube phonation. Results showed that the fluctuation in the back pressure during tube phonation in water altered the vocal fold vibrations. In the high-speed imaging, effects were found in the open quotient and amplitude variation of the glottal opening. The open quotient increased with increasing water depth (from 2 cm to 6 cm). A modulation effect by the water bubbles on the vocal fold vibrations was seen both in the high-speed glottal area tracings and in the electroglottography signal. A second experiment revealed that the increased average oral pressure was largely determined by the water depth. The increased open quotient can possibly be explained by an increased abduction of the vocal folds and/or a reduced transglottal pressure. The back pressure of the bubbles also modulates glottal vibrations with a possible massage effect on the vocal folds. This effect and the well-defined average pressure increase due to the known water depth are different from those of other methods using a semi-occluded vocal tract.

  • 17.
    Grishenkov, Dmitry
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk avbildning. Karolinska Institute, Sweden.
    Adrian, Gonon
    Karolinska University Hospital, Sweden.
    Janerot Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk avbildning. Karolinska Institute, Sweden.
    In search of the optimal ultrasound heart perfusion imaging platform2015Ingår i: Journal of ultrasound in medicine, ISSN 0278-4297, E-ISSN 1550-9613, Vol. 34, nr 9, s. 1599-1605Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective

    Quantification of the myocardial perfusion by contrast echocardiography (CEC) remains a challenge. Existing imaging phantoms used to evaluate the performance of ultrasound scanners do not comply with perfusion basics in the myocardium, where perfusion and motion are inherently coupled.

    Methods

    To contribute towards an improvement, we developed a CEC perfusion imaging platform based on isolated rat heart coupled to the ultrasound scanner. Perfusion was assessed using three different types of contrast agent: dextran-based Promiten®, phospholipid-shelled SonoVue®, and polymer-shelled MB-pH5-RT. The myocardial video-intensity was monitored over time from contrast administration to peak and two characteristic constants were calculated using exponential fit (A representing capillary volume and b representing inflow velocity).

    Results

    Acquired experimental evidence demonstrates that the application of all three types of contrast agent allow ultrasonic estimation of myocardial perfusion in the isolated rat heart. Video-intensity maps show that an increase in contrast concentration increases the late plateau values, A, mimicking increased capillary volume. Estimated values of the flow, proportional to Axb, increase when the pressure of the perfusate column increases from 80 to 110 cm of water. This finding is in agreement with the true values of the coronary flow increase measured by the flowmeter attached to the aortic cannula.

    Conclusions

    The described CEC perfusion imaging platform holds promise for standardized evaluation and optimization of ultrasound contrast perfusion imaging where real time inflow curves at low acoustic power semi-quantitatively reflect coronary flow.

  • 18.
    Grishenkov, Dmitry
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk avbildning. Karolinska Institutet (KI), CLINTEC – Division of Medical Imaging and Technology.
    Adrian, Gonon
    Department of Clinical Physiology, Karolinska University Hospital.
    Weitzberg, Eddie
    Department of Physiology and Pharmacology, Karolinska Institutet.
    Lundberg, Jon
    Department of Physiology and Pharmacology, Karolinska Institutet, .
    Harmark, Johan
    KTH, Skolan för teknik och hälsa (STH), Naturvetenskap och biomedicin, Strukturell bioteknik.
    Cerroni, Barbara
    Department of Chemical Sciences and Technologies, University of Rome Tor Vergata.
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    Janerot Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk avbildning. CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Ultrasound contrast agent loaded with nitric oxide as a theranostic microdevice: Theranostic contrast agent loaded with nitric oxide2015Ingår i: Drug Design, Development and Therapy, ISSN 1177-8881, E-ISSN 1177-8881, Vol. 9, s. 2409-2419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current study describes novel multifunctional polymer-shelled microbubbles (MBs) loaded with nitric oxide (NO) for integrated therapeutic and diagnostic applications, i.e. theranostics, of myocardial ischemia. We used gas filled MBs with an average diameter of 4 µm stabilized by a biocompatible shell of poly(vinyl)alcohol. In vitro acoustic tests showed a sufficient enhancement of the backscattered power (20 dB) acquired from the MBs suspension. The values of attenuation coefficient (0.8 dB/cm MHz) and phase velocities (1517 m/s) were comparable to those reported for the soft tissue. Moreover, polymer MBs demonstrate increased stability compared to clinically approved contrast agents with fracture threshold of about 900 kPa. In vitro chemiluminescence measurements demonstrated that dry powder of NO-loaded MBs releases its gas content in about 2 hours following an exponential decay profile with an exponential time constant equal 36 min. The application of high power ultrasound pulse (MI=1.2) on the MBs resuspended in saline decreases the exponential time constant from 55 to 4 min in air saturated solution and from 17 to 10 min in degased solution. Thus, ultrasound-triggered release of NO is achieved. Cytotoxicity tests indicate that phagocytosis of the MBs by macrophages starts within 6 to 8 hours. This is suitable time for initial diagnostics, treatment and monitoring of the therapeutic effect using single injection of the proposed multifunctional MBs.

  • 19.
    Hamid Muhammed, Hamed
    et al.
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap.
    Raghavendra, Jammalamadaka
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    Optomyografi (OMG): Ny teknik för muskelaktivitets mätning2015Ingår i: Abstract Proceedings of Medicinteknik dagarna 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

    Introduktion / Mål

    Den nya tekniken är effektivare och har inte de brister som de existerande teknikerna (elektromyografi EMG och mekanomyografi MMG) lider av, exempelvis, lågt signal till brus förhållande (SNR), interferens med andra biosignaler, interferens med externa signaler från omgivningen, påverkas av hudegenskaperna, komplicerad installation och kalibrering, kan inte användas vid extrema förhållanden, kan inte användas i rymden eller under vatten. Den nya tekniken används av:

    *Idrottare: för att optimera träningen.

    *Patienter och handikappade personer som lider av rörelsestörningar, svaga händer, amputerade händer, rygg eller nackskador.

    *Astronauter: för människa-dator interaktion och robotstyrning.

    Metod

    Den nya tekniken använder fotoelektriska sensorer som mäter reflekterade närainfraröda strålar från hudytan. Den reflekterade signalen varierar då topografiska förändringar, på landskapet som formas av hudytan, sker. Nästan inga bio- eller omgivande signaler interfererar med närainfraröda strålar. Hudens kemiska och fysiska egenskaper påverkar inte heller mätsignalernas kvalitet. Därför registreras signaler av hög SNR. Ytterligare fördelar med den nya tekniken är att den är kostnadseffektiv, mobil, användarvänlig, icke-invasiv och riskfri. Ett armband med två sensorer används för att mäta kontinuerliga tidssignaler när försökspersonen utför ett antal handrörelser.

    Resultat

    Olika handrörelser producerar olika signaler som mäts med hjälp av ett oscilloskop. Varje rörelse ger två signaler eller ett signalpar som skiljer sig från de signalpar som produceras av andra handrörelser.

    Sammanfattning

    Fotoelektriska sensorer används för att mäta reflekterade närainfraröda strålar från huden. Olika muskelaktiviteter och rörelser förändrar topografin av landskapet som formas av hudytan. Miniatyr lysdiod-sensor par byggs in i kläder för att mäta och analysera muskelaktivitet och rörelse. Mätvärdena skickas trådlöst till mobilen för att analyseras och ge återkoppling i realtid för att varna och optimera tränings eller rehabiliterings aktiviteterna.

  • 20.
    Hamid Muhammed, Hamed
    et al.
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap.
    Raghavendra, Jammalamadaka
    KTH, Skolan för teknik och hälsa (STH), Hälso- och systemvetenskap, Systemsäkerhet och organisation.
    Optomyography (OMG): A Novel Technique for the Detection of Muscle Surface Displacement Using Photoelectric Sensors2015Ingår i: Measurements - Proceedings of the 10th International Conference on Bioelectromagnetism, International Society for Bioelectromagnetism, 2015, Vol. 10Konferensbidrag (Refereegranskat)
    Abstract [en]

    Several techniques have been introduced for detecting, measuring, processing and analyzing the signals generated during muscular activities. With the development of more advanced technical solutions, the measurement and analysis of these signals help not only to understand the medical abnormalities and characterization of muscle activities but also to develop human machine interfaces of higher efficiency. In this work, a novel technique to detect and measure the displacement caused on the surface of the skin due to muscle activities was introduced and developed using near-infrared photoelectric sensors. The new technique was coined as OptoMyoGraphy (OMG). In order to evaluate the new technique, real-time pairs of signals were registered using two photoelectric sensors measuring near-infrared rays reflected on the forearm while moving the hand to make a number of different gestures. Different pairs of signals, changing over time and showing repeated patterns while repeating the same hand gesture, were measured for different hand gesture. The signal to noise ratio (SNR) of these signals was good enough to be able to differentiate among the pairs of signals which correspond to different hand gestures using visual inspection.

  • 21.
    Iacobaeus, Christian
    et al.
    -.
    Brahme, Anders
    -.
    Danielsson, Mats
    KTH, Tidigare Institutioner, Fysik.
    Fonte, Paulo
    -.
    Ostling, Janina
    -.
    Peskov, Vladimir
    -.
    Wallmark, Monika
    -.
    A novel portal imaging device for advanced radiation therapy2001Ingår i: Nuclear Science, IEEE Transactions on, Vol. 48, nr 4, s. 1496-1502Artikel i tidskrift (Refereegranskat)
  • 22.
    Khan, Suleman
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Mekatronik.
    Design and optimization of parallel haptic devices: Design methodology and experimental evaluation2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The simulation of surgical procedures, in the case of hard tissues such as bone or teeth milling, using a haptic milling surgery simulator requires a haptic device which can provide high stiffness and transparency. To mimic a real milling process of hard tissue, such as for example creating a narrow channel or cavity, the simulator needs to provide force/torque feedback in 5–6 degrees of freedom (DOF). As described in this thesis, research has been performed to develop and optimize a haptic device that can provide high stiffness and force/torque capabilities to facilitate haptic interaction with stiff tissues. 

    The main contributions of this thesis are:

    (i) The use of a model-based design methodology for the design of haptic devices.  The proposed methodology is applied to a case study, i.e. the design and optimization of a haptic device based on parallel kinematics. Device requirements were elicited through dialogues with a prospective user from a neurosurgery clinic. In the conceptual design phase, different parallel concepts have been investigated and analyzed based on functional qualities such number of degrees of freedom, workspace size and force/torque capabilities. This analysis led to the selection of a specific 6 DOF kinematic structure for which dimension synthesis was performed including multi-objective optimization followed by control synthesis. Finally, a device prototype was realized and its performance verified.

    (ii) Optimization of the device for best kinematic and dynamic performance. For optimization, performance indices such as workspace-to-footprint ratio, kinematic isotropy and inertial indices were used. To cope with the problem of non-uniform units in the components of the Jacobian matrix, various normalization techniques were investigated. A new multi-objective optimization function is introduced to define the optimization problem, which is then resolved using multi-objective genetic algorithms. A sensitivity analysis of the performance indices against each design parameter is performed, as a basis for selecting a final set of design parameter values.

    (iii) A control strategy is investigated to achieve high transparency and stability of the device. The control strategy is based on careful analysis of the dynamics of the haptic device, computed torque feed-forward control and force control based on current feedback.

    (iv) Finally, experiments both separately in the lab and by using the device in a haptic milling surgery simulator were performed. Results from a face validity study performed in collaboration with orthopedists verify that the new haptic device enables high-performance force and torque feedback for stiff interactions.  

  • 23. Khosla, S.
    et al.
    Morris, D. R.
    Moxon, J. V.
    Walker, Philip J.
    Gasser, T. C.
    Golledge, Jonathan
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Meta-analysis of peak wall stress in ruptured, symptomatic and intact abdominal aortic aneurysms2014Ingår i: British Journal of Surgery, ISSN 0007-1323, E-ISSN 1365-2168, Vol. 101, nr 11, s. 1350-1357Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Background: Abdominal aortic aneurysm (AAA) is an important cause of sudden death; however, there are currently incomplete means to predict the risk of AAA rupture. AAA peak wall stress (PWS) can be estimated using finite element analysis (FEA) methods from computed tomography (CT) scans. The question is whether AAA PWS can predict AAA rupture. The aim of this systematic review was to compare PWS in patients with ruptured and intact AAA. Methods: The MEDLINE database was searched on 25 May 2013. Case-control studies assessing PWS in asymptomatic intact, and acutely symptomatic or ruptured AAA from CT scans using FEA were included. Data were extracted independently. A random-effects model was used to calculate standard mean differences (SMDs) for PWS measurements. Results: Nine studies assessing 348 individuals were identified and used in the meta-analysis. Results from 204 asymptomatic intact and 144 symptomatic or ruptured AAAs showed that PWS was significantly greater in the symptomatic/ruptured AAAs compared with the asymptomatic intact AAAs (SMD 0.95, 95 per cent confidence interval 0. 71 to 1.18; P < 0. 001). The findings remained significant after adjustment for mean systolic blood pressure, standardized at 120 mmHg(SMD 0.68, 0.39 to 0.96; P < 0. 001). Minimal heterogeneity between studies was noted (I-2 = 0 per cent). Conclusion: This study suggests that PWS is greater in symptomatic or ruptured AAA than in asymptomatic intact AAA.

  • 24.
    Kothapalli, Veera Venkata Satya Naray
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Daeichin, Verya
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC,.
    Mastik, Frits
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC.
    Brodin, Lars-Åke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Janerot Sjöberg, Birgitta
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Paradossi, Gaio
    Diapartimento di Chimica, Università di Roma Tor Vergata.
    de Jong, N.
    Department of Biomedical Engineering, Thoraxcenter, Erasmus MC.
    Grishenkov, Dmitry
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik. Karolinska Institutet, Sweden; Karolinska University Hospital, Sweden .
    Unique pumping-out fracturing mechanism of a polymer-shelled contrast agent: An acoustic characterization and optical visualization2014Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, ISSN 0885-3010, E-ISSN 1525-8955, Vol. 62, nr 3, s. 451-462, artikel-id 7055440Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work describes the fracturing mechanism of air-filled microbubbles (MBs) encapsulated by a cross-linked poly(vinyl alcohol) (PVA) shell. The radial oscillation and fracturing events following the ultrasound exposure were visualized with an ultrahigh-speed camera, and backscattered timedomain signals were acquired with the acoustic setup specific for harmonic detection. No evidence of gas emerging from defects in the shell with the arrival of the first insonation burst was found. In optical recordings, more than one shell defect was noted, and the gas core was drained without any sign of air extrusion when several consecutive bursts of 1 MPa amplitude were applied. In acoustic tests, the backscattered peak-to-peak voltage gradually reached its maximum and exponentially decreased when the PVA-based MB suspension was exposed to approximately 20 consecutive bursts arriving at pulse repetition frequencies of 100 and 500 Hz. Taking into account that the PVA shell is porous and possibly contains large air pockets between the cross-linked PVA chains, the aforementioned acoustic behavior might be attributed to pumping gas from these pockets in combination with gas release from the core through shell defects. We refer to this fracturing mechanism as pumping-out behavior, and this behavior could have potential use for the local delivery of therapeutic gases, such as nitric oxide.

  • 25.
    Kravchenko, Evgenija
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    Forsberg Trägårdh, Patrik
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    Flödesberoende avvikelser hos distributionen av läkemedel inom neonatalvården vid användning av infusionspumpar2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Volym- och sprutpumpar används inom neonatalvården tillsammans med en specialanpassad kateter. De prematurfödda barnen är mycket känsliga för feldoseringar men det finns minimalt med dokumenterade projekt som undersöker hur väl den distribuerade dosen stämmer överens med den angivna på infusionspumpen. Målet med denna studie var att kontrollera om det fettbaserade läkemedlet Clinoleic flyter tillbaka i det gemensamma blocket, avgöra tiden det tar för läkemedel att flyta fram samt mäta mängden av läkemedel som kommer till mynningen av katetern. Antalet pumpar begränsades till startuppsättningen inom intensivvården på neonatalavdelningen, vilket är fyra pumpar. Mängden av läkemedlet för fem olika flöden undersöktes endast för läkemedlet Peyona med koffeinbas. Projektet genomfördes på Karolinska Universitetssjukhuset och i samarbete med Nya Karolinska Solna förbättrades förståelse för uppsättningens användning. Samtliga sjuksköterskor och ingenjörer vi kom i kontakt med på sjukhusen ansåg att fler studier behöver göras inom distribution av läkemedlen. Tydliga kopplingar kan ses mellan resultat som presenteras i arbetet och misstankar och förväntningar efter samtal med de som jobbar med pumpar. Möjliga framtida experiment som kan ge tydligare riktlinjer inom neonatalvården diskuteras. Det är några anmärkningsvärda resultat som redovisas i studien. De är att Clinoleic flyter bakåt i blocket och att fylla backventilen tar mellan 16 och 25 minuter för de undersökta flödena. Dessutom framgår det att distributionen av Peyona avviker minst för de högre flödena.

  • 26.
    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 applications2011Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 82, nr 12, s. 123701-Artikel i tidskrift (Refereegranskat)
    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.

  • 27.
    Lindberg, Frida
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Mårtensson, Mattias
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Aesthetic ultrasound devices: Current state of knowledge and suggested measurement set-up for characterization of exposure2013Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report concerns the ultrasound devices used for the aesthetic purposes of body contouring and fat reduction (ablation of adipose tissue). Such devices have recently become more frequent on the Swedish market. These ultrasound devices are currently not medically regulated in Sweden and little is known about their safety and potentially harmful exposure when using them.

    This report aims to provide relevant information about present guidelines and scientific results in the area, a survey of the Swedish market and also recommendations on how to characterize the ultrasound emitted by these devices. This information provides an important basis for possible future regulatory actions.

    All aesthetic ultrasound devices found on the Swedish market use low-frequency non-thermal ultrasound. These types of devices (with one exception) have not yet been studied in peer-reviewed publications and the technical specifications from the suppliers are often incomplete. Consequently, there is a need to evaluate the devices in order to gain adequate knowledge about possible risks associated with their use.

    Ultrasound exposure should be characterized by its frequency and acoustic pressure. It has not been fully investigated whether the mathematical equation for the mechanical index is valid for the low frequencies used by aesthetic ultrasound equipment on the Swedish market. In this report, two different hydrophone measurement set-ups for characterization of ultrasound exposure are proposed. The most common reason behind adverse events or exposure of non-target tissue regions is most likely handling errors by the operator. Hence, only characterization of the ultrasound field does not necessarily imply the safe use of aesthetic ultrasound devices.

    It is recommended that the Swedish Radiation Safety Authority and the Swedish Medical Products Agency discuss their respective future responsibility and how aesthetic ultrasound devices should be regulated.

  • 28.
    Lindroth, Emma
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    Saljén, Lisa
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Medicinteknik och hälsosystem.
    3D-utskrifter inom Karolinska Universitetssjukhuset: Utredning av idag rådande riktlinjer samt framtagning av ett kvalitetssäkringsobjekt2018Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Användandet av 3D-skrivare har ökat inom sjukvården, och möjliggjort utskrift av anatomiska modeller. Karolinska Universitetssjukhuset i Solna planerar att starta ett 3D-laboratorium, med möjlighet till egen produktion av anatomiska modeller. För detta behövs kunskap kring vilka riktlinjer som ska följas, samt möjlighet till kvalitetssäkring av skrivare. I detta arbete undersöks regelverken kring 3D-printing, och ett kvalitetssäkringsobjekt för framtida kvalitetssäkring tas fram. Regelverket för medicintekniska produkter undersöktes bland dokument från EU, USA, och Australien. Tolkningen av EU:s publikationer görs via kontakt med Läkemedelsverket och Socialstyrelsen. Södertälje Sjukhus, jurister, samt professorer vid Stockholms Universitet och Kungliga Tekniska Högskolan kontaktas också med frågor kring riktlinjer. Resultatet visar på ett vagt och subjektivt tolkat regelverk inom EU, där 3D-printade anatomiska modeller kan tolkas som specialanpassade- eller egentillverkade produkter. Kvalitetssäkringsobjektet tas fram med grund i 13 kriterier. De kriterier som i detta arbete ej visar skillnad mellan utskrivna modeller, däribland negativa vinklar, spiral (form), kantighet och ömtålighet spiral, kan bytas ut eller specificeras på annat sätt. Kriterier som minsta hålbredd, kvalitetssäkringsobjektets bottenarea, släthet, självsprickor, spiral (kvalitet) och sprickor (hål) visade på kvalitetsskillnader hos utskrifterna.

  • 29.
    Liu, Xuejin
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Characterization and Energy Calibration of a Silicon-Strip Detector for Photon-Counting Spectral Computed Tomography2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Multibin photon-counting x-ray detectors are promising candidates to be applied in next generation computed tomography (CT), whereby energy information from a broad x-ray spectrum can be extracted and properly used for improving image quality and correspondingly reducing radiation dose. A silicon-strip detector has been developed for spectral CT, which operates in photon-counting mode and allows pulse-height discrimination with 8 adjustable energy bins.

    Critical characteristics, energy resolution and count-rate performance, of the detector are evaluated. An absolute energy resolution (E) from 1.5 keV to 1.9 keV with increasing x-ray energy from 40 keV to 120 keV is found. Pulse pileup degrades the energy resolution by 0.4 keV when increasing the input count rate from zero to 100 Mcps mm−2, while charge sharing shows negligible effect. A near linear relationship between the input and output count rates is observed up to 90 Mcps mm−2 in a clinical CT environment. In addition, no saturation effect appears for the maximally achieved photon flux of 485 Mphotons s−1 mm−2 with a count rate loss of 30%.

    The detector is energy calibrated in terms of gain and offset with the aid of monoenergetic x rays. The gain variation among channels is below 4%, whereas the variation of offsets is on the order of 1 keV. In order to do the energy calibration in a routinely available way, a method that makes use of the broad x-ray spectrum instead of using monoenergetic x rays is proposed. It is based on a regression analysis that adjusts a modelled spectrum of deposited energies to a measured pulse-height spectrum. Application of this method shows high potential to be applied in an existing CT scanner with an uncertainty of a calibrated threshold between 0.1 and 0.2 keV.

    The energy-calibration method is further used in the development of a spectral response model of the detector. This model is used to accurately bin-wise predict the response of each detector channel, which is validated by two application examples. First, the model is used in combination with the inhomogeneity compensation method to eliminate ring artefacts in CT images. Second, the spectral response model is used as the basis of the maximum likelihood approach for projection-based material decomposition. The reconstructed basis images show a good separation between the calcium-like material and the contrast agents, iodine and gadolinium. Additionally, the contrast agent concentrations are reconstructed with more than 94% accuracy.

  • 30.
    Maksuti, Elira
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Larsson, David
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Urban, M. W.
    Caidahl, K.
    Larsson, Matilda
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Strain and strain rate generated by shear wave elastography in ex vivo porcine aortas2017Ingår i: IEEE International Ultrasonics Symposium, IUS, IEEE Computer Society , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In shear wave elastography (SWE), acoustic radiation forces (ARF) are employed to generate shear waves within the tissue. Although the transmitted pulses are longer than those in conventional clinical ultrasound, they typically obey the mechanical and thermal regulatory limits. In arterial applications, specific safety concerns may arise, as ARF-induced stresses and strain rates could potentially affect the arterial wall. A previous simulation study (Doherty et al., J Biomech, 2013 Jan; 46(1):83-90) showed that stresses imposed by the ARF used in SWE are orders of magnitude lower than those caused by blood pressure. ARF-induced strain rates have not been investigated yet, therefore the aim of this study was to assess such strain rates in an ex vivo setup.

  • 31.
    Marquez Ruiz, Juan Carlos
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS) (Stängd 20130701).
    Sensor-Based Garments that Enable the Use of Bioimpedance Technology: Towards PersonalizedHealthcare Monitoring.2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Functional garments for physiological sensing purposes have been utilized in several disciplinesi.e. sports, firefighting, military and medical. In most of the cases textile electrodes (Textrodes)embedded in the garment are employed to monitor vital signs and other physiologicalmeasurements. Electrical Bioimpedance (EBI) is a non-invasive and effective technology that canbe used for detection and supervision of different health conditions. In some specific applicationssuch as body composition assessment EBIS has shown encouraging results proving good degreeof effectiveness and reliability. In a similar way Impedance Cardiography (ICG) is anothermodality of EBI primarily concerned with the determination of Stroke Volume SV, indices ofcontractility, and other aspects of hemodynamics.EBI technology in the previously mentioned modalities can benefit from a integration with agarment; however, a successful implementation of EBI technology depends on the goodperformance of textile electrodes. The main weakness of Textrodes is a deficient skin-electrodeinterface which produces a high degree of sensitivity to signal disturbances. This sensitivity canbe reduced with a suitable selection of the electrode material and an intelligent and ergonomicgarment design that ensures an effective skin-electrode contact area.This research work studies the performance of textile electrodes and garments for EBIspectroscopy for Total Body Assessment and Transthoracic Electrical Bioimpedance (TEB) forcardio monitoring. Their performance is analyzed based on impedance spectra, estimation ofparameters, influence of electrode polarization impedance Zep and quality of the signals using asreference Ag/AgCl electrodes. The study includes the analysis of some characteristics of thetextile electrodes such as conductive material, skin-electrode contact area size and fabricconstruction.The results obtained in this research work present evidence that textile garments with a dry skinelectrodeinterface like the ones used in research produce reliable EBI measurements in bothmodalities: BIS for Total Body Assessment and TEB for Impedance Cardiography. Textiletechnology, if successfully integrated, may enable the utilization of EBI in both modalities andconsequently implementing wearable applications for home and personal health monitoring.

  • 32.
    Mi, Wujun
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Nillius, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Pearce, Mark
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. The Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, Stockholm, Sweden.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    A stacked prism lens concept for next-generation hard X-ray telescopes2019Ingår i: Nature Astronomy, E-ISSN 2397-3366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effective collecting area, angular resolution, field of view and energy response are fundamental attributes of X-ray telescopes. The performance of state-of-the-art telescopes is currently restricted by Wolter optics, especially for hard X-rays. Here we report the development of a stacked prism lens (SPL), which is lightweight and modular and has the potential for a significant improvement in effective area, while retaining high angular resolution. The proposed optics are built by stacking disks embedded with prismatic rings, created with photoresist by focused ultraviolet lithography. We demonstrate the SPL approach using a prototype lens that was manufactured and characterized at a synchrotron radiation facility. The design of a potential satellite-borne X-ray telescope is outlined and the performance is compared with contemporary missions.

  • 33.
    Mårtensson, Mattias
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Bjällmark, Anna
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Brodin, Lars-Åke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Evaluation of tissue Doppler-based velocity and deformation imaging: a phantom study of ultrasound systems.2011Ingår i: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 12, nr 6, s. 467-476Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    AIMS: The objective of this study was to test the accuracy and diagnostic interchangeability of tissue Doppler-based displacement, velocity, strain, and strain rate measurements in commercially used ultrasound (US) systems. METHODS AND RESULTS: Using an in-house made phantom, four different US scanner models were evaluated. Two different scanners of the same model were tested, and one scanner acquisition was tested twice with two generations of the same workstation giving six test results in total. The scanners were in active clinical use and are subject to regular maintenance checks. There were three displacement and four velocity results that stood out from the rest and could be regarded as accurate and interchangeable. Among the deformation measurements, three acceptable strain results were found while there were no acceptable strain rate results. Furthermore, the study showed that measurements from scanners of the same model, same acquisition post-processed on different workstations and repeated measurements from the same scanner, can yield disparate results. CONCLUSION: Measurements that are accurate and of interchangeable use can be found for displacement and velocity measurements, but are less likely to be found for strain and strain rate measurements. It is strongly recommended that the ability of each individual US scanner to measure displacement, velocity, strain, and strain rate is evaluated before it is introduced into clinical practice, and it must always be evaluated together with the workstation the scanner is intended to be used in conjunction with.

  • 34.
    Mårtensson, Mattias
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Olsson, Mats
    Brodin, Lars-Åke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Ultrasound transducer function: annual testing is not sufficient2010Ingår i: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 11, nr 9, s. 801-805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective was to follow-up the study 'High incidence of defective ultrasound transducers in use in routine clinical practice' and evaluate if annual testing is good enough to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level. A total of 299 transducers were tested in 13 clinics at five hospitals in the Stockholm area. Approximately 7000-15 000 ultrasound examinations are carried out at these clinics every year. The transducers tested in the study had been tested and classified as fully operational 1 year before and since then been in normal use in the routine clinical practice. The transducers were tested with the Sonora FirstCall Test System. There were 81 (27.1%) defective transducers found; giving a 95% confidence interval ranging from 22.1 to 32.1%. The most common transducer errors were 'delamination' of the ultrasound lens and 'break in the cable' which together constituted 82.7% of all transducer errors found. The highest error rate was found at the radiological clinics with a mean error rate of 36.0%. There was a significant difference in error rate between two observed ways the clinics handled the transducers. There was no significant difference in the error rates of the transducer brands or the transducers models. Annual testing is not sufficient to reduce the incidence of defective ultrasound transducers in routine clinical practice to an acceptable level and it is strongly advisable to create a user routine that minimizes the handling of the transducers.

  • 35.
    Mårtensson, Mattias
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Olsson, Mats
    Segall, Björn
    Fraser, Alan G.
    Winter, Reidar
    Brodin, Lars-Åke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    High incidence of defective ultrasound transducers in use in routine clinical practice2009Ingår i: European Journal of Echocardiography, ISSN 1525-2167, E-ISSN 1532-2114, Vol. 10, nr 3, s. 389-394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective was to evaluate the function of ultrasound transducers in use in routine clinical practice and thereby estimating the incidence of defective transducers. The study comprised a one-time test of 676 transducers from 7 manufacturers which were in daily use in clinical departments at 32 hospitals. They were tested with the Sonora FirstCall Test System; 39.8% exhibited a transducer error. Delamination was detected in 26.5% and break in the cable was detected in 8.4% of the tested transducers. Errors originating from the piezoelectrical elements were unusual. Delamination and short circuit occurred without significant differences between transducers from all tested manufacturers, but the errors break in the cable, weak and dead element showed a statistically significant higher frequency in transducers from certain manufacturers. The high error frequency and the risk for incorrect medical decisions when using a defective transducer indicate an urgent need for increased testing of the transducers in clinical departments.

  • 36.
    Mårtensson, Mattias
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinsk bildteknik.
    Winter, Reidar
    Cederlund, Kerstin
    Ripsweden, Jonaz
    Mir-Akbari, Habib
    Nowak, Jacek
    Brodin, Lars-Åke
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Assessment of left ventricular volumes using simplified 3-D echocardiography and computed tomography - a phantom and clinical study2008Ingår i: Cardiovascular Ultrasound, ISSN 1476-7120, E-ISSN 1476-7120, Vol. 6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: To compare the accuracy of simplified 3-dimensional (3-D) echocardiography vs. multi-slice computed tomography (MSCT) software for the quantification of left ventricular (LV) volumes. Design: Three-D echocardiography (3-planes approach) and MSCT-CardIQ software were calibrated by measuring known volumes of 10 phantoms designed to closely mimic blood-endocardium interface. Subsequently, LV volumes were measured with both the methods in 9 patients referred routinely for coronary angiography and the agreement between the measurements was evaluated. Results: Simplified 3D-echocardiography provided higher degree of agreement between the measured and true phantom volumes (mean difference 0 +/- 1 ml, variation range + 4 to -4 ml) than MSCT software (mean difference 6 +/- 5 ml; variation range + 22 to -10 ml). The agreement between LV measurements in the patients was considerably poorer, with significantly larger volumes produced by MSCT (mean difference - 23 +/- 40 ml, variation between + 93 and -138 ml). Conclusion: Simplified 3-D echocardiography provides more accurate assessment of phantom volumes than MSCT-CardIQ software. The discrepancy between the results of LV measurements with the two methods is even greater and does not warrant their interchangeable diagnostic use.

  • 37.
    Najar, salwan
    KTH, Skolan för teknik och hälsa (STH).
    Simulering av 1-Wire sensorer2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The 1-wire bus is a communication bus system which is designed to provide data, signals and power over a single signal with low data rates, a high resolution and a long range. It is typically used to communicate with small inexpensive devices, as temperature sensors, which is worked as a slave with the master computer (PC).

    The 1-wire bus system provides the sufficient control and operation signal, a unique ID serial number of each sensor and it supports multiple temperature sensors by a driving power (Parasite Power) on single line.

    On the 1-Wire bus system, temperature sensors are supplied by two types of power supplies, external Power supply and Parasitic Power.

    The aim of this project is to program the microprocessor (Arduino) by using Arduino programming language to work as a temperature sensor type DS18B20 and also as a slave on the 1-Wire bus system.

    This report explains the 1-Wire bus system techniques and how the communication is achieved between the master and the slave (sensors) to measure the temperature values.

    The measured temperature values are collected from the output of each active sensor on the 1-Wire bus. These data are displayed by the personal computer (PC) which is worked as a master on the 1-Wire bus, and the data are represent the measured temperature values from twelve active sensors on the bus system.

    In this thesis, the temperature values from the 12 active sensors can be read and displayed on the master (PC) by using the following programs: Open Logger One Wire (OLOW) program, One Wire Viewer, DigiTemp and OWFS and I validated all the temperature values from these active sensors which are read and monitored by the drive bus programs. The comparison is done among the measured temperature values to see if the active sensors are given accurate temperature values with different drive bus programs.

    The project shows that the sensors can be connected in a network with the master, by using 1-Wire bus techniques. This thesis will be used by Karolinska University Hospital, and it can also be developed for different requirements in the future.

  • 38.
    Ottonello Briano, Floria
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    Mid-infrared photonic devices for on-chip optical gas sensing2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Gas detection is crucial in a wide range of fields and applications, such as safety and process control in the industry, atmospheric sciences, and breath diagnostics. Optical gas sensing offers some key advantages, compared to other sensing methods such as electrochemical and semiconductor sensing: high specificity, fast response, and minimal drift.

    Wavelengths between 3 and 10 μm are of particular interest for gas sensing. This spectral range, called the mid-infrared (mid-IR), is also known as the fingerprint region, because several gas species can be identified by their sharp absorption lines in this region. The most relevant mid-IR-active gases are the trace gases carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), ammonia (NH3), and nitrous oxide (N2O). They are greenhouse gases, contributing to global warming. They are waste products of human activities and widely used in agriculture and industry. Therefore, it is crucial to accurately and extensively monitor them. However, traditional optical gas sensors with a free-space optical path configuration, are too bulky, power-hungry, and expensive to be widely adopted.

    This thesis presents mid-IR integrated photonic devices that enable the on-chip integration of optical gas sensors, with a focus on CO2 sensing. The reported technologies address the fundamental sensor functionalities: light-gas interaction, infrared light generation, and infrared light detection. The thesis introduces a novel mid-IR silicon photonic waveguide that allows a light path as long as tens of centimeters to fit in a volume smaller than a few cubic millimeters. Mid-IR CO2 spectroscopy demonstrates the high sensing performance of the waveguide. The thesis also explores the refractive index sensing of CO2 with a mid-IR silicon photonic micro-ring resonator.

    Furthermore, the thesis proposes platinum nanowires as low-cost infrared light sources and detectors that can be easily integrated on photonic waveguides. Finally, the thesis presents a large-area infrared emitter fabricated by highs-peed wire bonding and integrated in a non-dispersive infrared sensor for the detection of alcohol in breath.

    The technologies presented in this thesis are suited for cost-effective mass production and large-scale adoption. Miniaturized integrated optical gas sensors have the potential to become the main choice for an increasingly broad range of existing and new applications, such as portable, distributed, and networked environmental monitoring, and high-volume medical and consumer applications.

  • 39.
    Persson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Spectral Computed Tomography with a Photon-Counting Silicon-Strip Detector2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Computed tomography (CT) is a widely used medical imaging modality. By rotating an x-ray tube and an x-ray detector around the patient, a CT scanner is able to measure the x-ray transmission from all directions and form an image of the patient’s interior. CT scanners in clinical use today all use energy-integrating detectors, which measure the total incident energy for each measurement interval. A photon-counting detector, on the other hand, counts the number of incoming photons and can in addition measure the energy of each photon by comparing it to a number of energy thresholds. Using photon- counting detectors in computed tomography could lead to improved signal-to-noise ratio, higher spatial resolution and improved spectral imaging which allows better visualization of contrast agents and more reliable quantitative measurements. In this Thesis, the feasibility of using a photon-counting silicon-strip detector for CT is investigated. In the first part of the Thesis, the necessary performance requirements on such a detector is investigated in two different areas: the detector element homogeneity and the capability of handling high photon fluence rates. A metric of inhomogeneity is proposed and used in a simulation study to evaluate different inhomogeneity compensation methods. Also, the photon fluence rate incident on the detector in a scanner in clinical use today is investigated for different patient sizes through dose rate measurements together with simulations of transmission through patient im- ages. In the second part, a prototype detector module is used to demonstrate new applications enabled by the energy resolution of the detector. The ability to generate material-specific images of contrast agents with iodine and gadolinium is demonstrated. Furthermore, it is shown theoretically and ex- perimentally that interfaces in the image can be visualized by imaging the so-called nonlinear partial volume effect. The results suggest that the studied silicon-strip detector is a promising candidate for photon-counting CT.  

  • 40.
    Persson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Bujila, Robert
    Unit of X-ray Physics, Section of Imaging Physics Solna, Department of Medical Physics,Karolinska University Hospital.
    Nowik, Patrik
    Unit of X-ray Physics, Section of Imaging Physics Solna, Department of Medical Physics,Karolinska University Hospital.
    Andersson, Henrik
    Unit of X-ray Physics, Section of Imaging Physics Solna, Department of Medical Physics, Karolinska University Hospital.
    Kull, Love
    Medical Radiation Physics, Sunderby Hospital.
    Andersson, Jonas
    Department of Radiation Sciences, Radiation Physics, Umeå University.
    Bornefalk, Hans
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Upper limits of the photon fluence rate on CT detectors: case study on a commercial scannerIngår i: Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Purpose: The highest photon fluence rate that a CT detector must be able to measure is animportant parameter. We calculate the maximum transmitted fluence rate in a commercial CT scanner as a function of patient size for standard head, chest and abdomen protocols.Method: We scanned an anthropomorphic phantom (Kyoto Kagaku PBU-60) with the reference CT protocols provided by AAPM on a GE LightSpeed VCT scanner and noted the tube currentapplied with the tube current modulation (TCM) system. By rescaling this tube current usingpublished measurements on the tube current modulation of a GE scanner we could estimate the tube current that these protocols would have resulted in for other patient sizes. An ECG gatedchest protocol was also simulated. Using measured dose rate profiles along the bowtie filters, wesimulated imaging of anonymized patient images with a range of sizes on a GE VCT scanner andcalculated the maximum transmitted fluence rate. In addition, the 99th and the 95th percentilesof the transmitted fluence rate distribution behind the patient are calculated and the effect of omitting projection lines passing just below the skin line is investigated.Results: The highest transmitted fluence rates on the detector for the AAPM reference protocolswith centered patients are found for head and chest images of small patients, with a maximumof 7.1 · 107 mm−2 s−1 for head and 9.6 · 107 mm−2 s−1 for chest. Miscentering the head by 50 mm downwards increases the maximum transmitted fluence rate to 3.9 · 108 mm−2 s−1 . The ECG gatedchest protocol gives fluence rates up to 2.3 · 108 − 2.4 · 108 mm−2 s−1 depending on miscentering.Conclusion: The fluence rate on a CT detector reaches 1 · 108 − 4 · 108 mm−2 s−1 in standardimaging protocols, with the highest rates occurring for ECG gated chest and miscentered headscans. These results will be useful to developers of CT detectors, in particular photon countingdetectors.

  • 41.
    Persson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik. Royal Inst Technol, Dept Phys, SE-10691 Stockholm, Sweden..
    Bujila, Robert
    Karolinska Univ Hosp, Unit Xray Phys, Sect Imaging Phys Solna, Dept Med Phys, SE-17176 Stockholm, Sweden..
    Nowik, Patrik
    Karolinska Univ Hosp, Unit Xray Phys, Sect Imaging Phys Solna, Dept Med Phys, SE-17176 Stockholm, Sweden..
    Andersson, Henrik
    Karolinska Univ Hosp, Unit Xray Phys, Sect Imaging Phys Solna, Dept Med Phys, SE-17176 Stockholm, Sweden..
    Kull, Love
    Sunderby Hosp, Med Radiat Phys, SE-97180 Lulea, Sweden..
    Andersson, Jonas
    Umea Univ, Radiat Phys, Dept Radiat Sci, SE-90185 Umea, Sweden..
    Bornefalk, Hans
    KTH, Skolan för teknikvetenskap (SCI), Fysik. Royal Inst Technol, Dept Phys, SE-10691 Stockholm, Sweden..
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik. Royal Inst Technol, Dept Phys, SE-10691 Stockholm, Sweden..
    Upper limits of the photon fluence rate on CT detectors: Case study on a commercial scanner2016Ingår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 43, nr 7, s. 4398-4411Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: The highest photon fluence rate that a computed tomography (CT) detector must be able to measure is an important parameter. The authors calculate the maximum transmitted fluence rate in a commercial CT scanner as a function of patient size for standard head, chest, and abdomen protocols. Methods: The authors scanned an anthropomorphic phantom (Kyoto Kagaku PBU-60) with the reference CT protocols provided by AAPM on a GE LightSpeed VCT scanner and noted the tube current applied with the tube current modulation (TCM) system. By rescaling this tube current using published measurements on the tube current modulation of a GE scanner [N. Keat, "CT scanner automatic exposure control systems," MHRA Evaluation Report 05016, ImPACT, London, UK, 2005], the authors could estimate the tube current that these protocols would have resulted in for other patient sizes. An ECG gated chest protocol was also simulated. Using measured dose rate profiles along the bowtie filters, the authors simulated imaging of anonymized patient images with a range of sizes on a GE VCT scanner and calculated the maximum transmitted fluence rate. In addition, the 99th and the 95th percentiles of the transmitted fluence rate distribution behind the patient are calculated and the effect of omitting projection lines passing just below the skin line is investigated. Results: The highest transmitted fluence rates on the detector for the AAPM reference protocols with centered patients are found for head images and for intermediate-sized chest images, both with a maximum of 3.4 . 10(8) mm(-2) s-1, at 949 mm distance from the source. Miscentering the head by 50 mm downward increases the maximum transmitted fluence rate to 5.7 . 10(8) mm(-2) s(-1). The ECG gated chest protocol gives fluence rates up to 2.3 . 10(8)-3.6 . 10(8) mm(-2) s(-1) depending on miscentering. Conclusions: The fluence rate on a CT detector reaches 3 . 10(8)-6 . 10(8) mm(-2) s(-1) in standard imaging protocols, with the highest rates occurring for ECG gated chest and miscentered head scans. These results will be useful to developers of CT detectors, in particular photon counting detectors. (C) 2016 American Association of Physicists in Medicine.

  • 42.
    Persson, Mats
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Holmin, Staffan
    Department of Clinical Neuroscience, Karolinska Institutet, SE-17177 Stockholm, Sweden and Department of Neuroradiology, Karolinska University Hospital Solna, SE-17176 Stockholm, Sweden.
    Karlsson, Staffan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Sub-pixel information retrieval from spectral x-ray imagesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The detector pixel size can be a severe limitation in projection x-ray imaging of fine details inthe human body, but developing higher resolution detectors is technically challenging. Wedemonstrate a novel method of using spectral x-ray measurements, from an energy-resolvingdetector or from multiple acquisitions with different beam quality, to obtain information aboutthe spatial distribution of the linear attenuation coefficient on a length scale smaller than onepixel. The method builds on the fact that the linear attenuation coefficient of all materials inthe human body can be expressed as linear combinations of a small number of basis functions.However, an interface parallel to the x-ray beam has a unique spectral responose which makesit distinguishable from homogeneous materials.To demonstrate the method experimentally, a 120 mm polyethylene phantom with a 6 mmiodine-filled hole in its centre was imaged in a projection geometry using a photon-countingsilicon-strip detector with eight energy bins. X-ray transmission measurements of differentthicknesses of polyethylene and iodine were used to calibrate a forward model describing thedetector response for different objects in the beam. Using the proposed method, an imagespecific to the spectral response of an iodine-polyethylene interface was generated. Theresults show that the borders of the iodine insert are highlighted in the resulting image, ingood agreement with simulations.Our study demonstrates that spectral x-ray measurements can be used to distinguish betweensharp and gradual transitions in an x-ray image. The method may potentially be used forimproving visualization of blood vessel boundaries in stroke care.

  • 43.
    Peskov, Vladimir
    et al.
    -.
    Fonte, P.
    -.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Iacobaeus, C.
    -.
    Östling, J.
    -.
    Wallmark, M.
    -.
    Fundamentals of gas micropattern detectors2001Ingår i: arXiv preprint physics/0106016Artikel i tidskrift (Refereegranskat)
  • 44.
    Rodriguez, Saul
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Tao, Sha
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Rusu, Ana
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Advances in Technologies for Implantable Bioelectronics2016Ingår i: Wireless Medical Systems and Algorithms: Design and Applications / [ed] Pietro Salvo and Miguel Hernandez-Silveira, CRC Press, 2016, s. 3-20Kapitel i bok, del av antologi (Refereegranskat)
  • 45. Schröder, Stephan
    et al.
    Ottonello Briano, Floria
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    Rödjegård, Henrik
    Bryzgalov, Maksym
    Orelund, Jonas
    Gylfason, Kristinn
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    Stemme, Göran
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system. KTH, Tidigare Institutioner (före 2005), Bioteknologi. KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    Niklaus, Frank
    KTH, Tidigare Institutioner (före 2005), Signaler, sensorer och system. KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    A large-area single-filament infrared emitter and its application in a spectroscopic ethanol gas sensing systemManuskript (preprint) (Övrigt vetenskapligt)
  • 46.
    Seoane, Fernando
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinska sensorer, signaler och system (MSSS).
    Bouwstra, Sibrecht
    Technical University of Eindovhen.
    Marquez, Juan Carlos
    löfhede, johan
    Högskolan i Borås.
    Lindecrantz, Kaj
    Smart Textiles in Neonatal Monitoring: Enabling Unobtrusive Monitoring at the NICU2012Ingår i: Neonatal Monitoring Technologies: : Design for Integrated Solutions / [ed] W. Chen, S. Oetomo, & L. Feijs, IGI Global, 2012, s. -55Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 47. Simon, A.
    et al.
    Balkay, L.
    Kalinka, G.
    Kerek, Andras
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Novak, D.
    Sipos, A.
    Vegh, J.
    Tron, L.
    Molnar, J.
    High spatial resolution measurement of depth-of-interaction of a PET LSO crystal2005Ingår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 546, nr 1-2, s. 33-36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new type of experimental technique to investigate the depth- of-interaction (DOI) dependence in small scintillator elements designed for high-resolution animal PET is tested. An Oxford-type nuclear microprobe was used to irradiate a lutetium oxyorthosilicate (LSO) crystal (2 x 2 x 10 mm) with a highly focused, (few micrometers diam.), 2 MeV He+ beam. Pulse height spectra from a PMT attached to one end of the LSO crystal were collected in list mode. By scanning the beam over the crystal high-resolution 2D-images are generated and thus the DOI effect in the scintillator could be investigated. The obtained results of the overall DOI dependence confirm previous findings using gamma-rays. Since the present experimental setup allows obtaining data with several orders of magnitude better spatial resolution than with collimated gamma-beam, the method can be applied for variety of problems where high spatial resolution is required.

  • 48.
    Sjölin, Martin
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Methods of image acquisition and calibration for x-ray computed tomography2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Datortomografi (CT) är en vanligt förekommande medicinsk avbildningsteknik som används för att ta högupplösta 3D bilder av människans inre. Bilderna rekonstrueras matematiskt från hundratals 2D röntgenbilder som har tagits under mindre än en sekund.

    Introduktionen av spektrala fotonräknande röntgendetektorer anses vara nästa stora steg i utvecklingen av medicinsk CT. De potentiella fördelarna innefattar: kvantitativ CT, avbildning vid ultra-låg dos och optimalt kontrast-brus förhållande. Målet för det arbete som utförs av gruppen för Medicinsk Bildfysik på KTH är att utveckla och kommersialisera en spektral fotonräknande detektor baserad på kiselskivor som är monterade ”edge-on” (med kanten pekandes mot röntgenkällan). Den här avhandlingen adresserar några utav de utmaningar som följer införandet av denna nya typ av detektor.

    Tillgången till effektiva kalibreringstekniker kommer att vara nödvändig för realisationen av spektrala fotonräknande detektorer i medicinsk CT. I den första delen av avhandlingen presenteras tre kalibreringsmetoder, varav två relaterar till kalibrering av energitrösklarna på spektrala röntgendetektorer och en relaterar till geometrisk kalibrering av ”edge-on” detektorer monterade i en CT scanner.

    Bildtagningen i CT producerar stora mängder data som måste transporteras ut ur systemet, gärna i realtid. Redan idag tvingas man ofta ha färre mätpunkter när man använder höga rotationshastigheter på grund av begränsningar i utläsningens bandbredd eller mätelektronikens hastighet. För spektrala fotonräknande detektorer kommer mängden data att öka på grund av den extra energiinformationen och de generellt mindre pixlarna. Därför är det önskvärt att minimera antalet mätpunkter i vinkelled per varv. I den andra delen av avhandlingen presenteras två metoder som minskar kravet på antalet mätpunkter per varv. Den första metoden använder den inbyggda redundansen hos detektorer med flera lager för att ökan antalet mätpunkter i vinkelled genom att förskjuta mätpunkterna för dom olika lagerna i tiden. Den andra metoden använder decimering i vinkelled för att komprimera CT data. Kompressionen kan utföras på CT scannern och kan användas för att minska kravet på datautläsningens bandbredd.

    Det övergripande målet för arbetet som utgör avhandling har varit att utveckla metoder som möjliggör introduktionen av spektrala fotonräknande detektorer för medicinsk CT. De presenterade metoderna är emellertid även användbara i den mer generella kontexten av kalibrering av röntgendetektorer och bildtagning i CT.

  • 49.
    Sjölin, Martin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Danielsson, Mats
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    A method for geometric calibration of edge-on detectors in a CT-gantry2016Ingår i: Medical physics (Lancaster), ISSN 0094-2405, Vol. 43, nr 11, s. 6165-6174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: Photon-counting edge-on detectors are currently being considered for use

    in clinical computed tomography (CT) systems. A method for geometric calibration

    of edge-on detectors mounted in a CT gantry has been developed and evaluated.

    The method is complementary to the geometrical calibration methods developed for

    CT systems using flat-panel detectors and takes the extra dimension of the edge-on

    detectors (along the direction of the x-rays) into account.

    Methods: The method uses projection images of a simple phantom together with

    geometrical arguments to accurately estimate the orientation and relative position of

    the edge-on detectors. Both computer simulations and experimental measurements

    were used to verify the method.

    Results: It is experimentally demonstrated that the method can determine the orientation

    of the detector with an accuracy of 0.08 degrees. The method is also shown

    to be insensitive to errors in the modeled parameters used in the algorithm.

    Conclusions: The presented method can accurately determine the orientation and

    relative position of edge-on detectors mounted in a CT-gantry and can be used to

    evaluate the detector mounting and to produce an accurate forward model of the

    imaging system. Also, the method has potential to reduce the dimensionality of the

    geometric calibration of the full CT system since the direction of the x-rays with

    respect to the detector is measured.

  • 50.
    Sjölin, Martin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Medicinsk bildfysik.
    Danielsson, Mats
    Compression of CT sinogram data by decimation in the view directionArtikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Purpose: In clinical computed tomography (CT), the image data is acquired during continuous

    rotation. If the time during which the signal is integrated (the frame time) is too long, the data

    is blurred in the view direction. This can be overcome by having a high angular sampling rate,

    but for systems with limited bandwidth, the increased amount of data can be a problem. In this

    paper, we evaluate the benefit of maintaining a high angular sampling rate on the CT gantry

    and performing a decimation (digital low-pass filtration followed by a downsampling) in the view

    direction before the bottleneck of the data transfer chain.

    Methods: A theoretical evaluation of the effects of the decimation is presented and the

    implementation of the digital filter is discussed. The compression scheme is evaluated on image

    data of a CATPHANR 504 phantom.

    Results: From a resolution point-of-view, it is beneficial to sample at more than twice the

    Nyquist frequency (the minimum rate required for not introducing aliasing). At this sampling

    rate, a decimation step can reduce the amount of data by a factor of two without loosing any of

    the signal. It is demonstrated that a 2:1 compression can be achieved without compromising the

    spatial resolution or increasing the noise.

    Conclusions: In continuous rotation CT, the angular sampling rate must be high in order

    not to suffer from blur in the view direction. From a sampling point-of-view, the sampling rate

    is higher than necessary and the signal can be decimated (low-pass filtered and downsampled)

    without losing any signal. The proposed compression scheme can be implemented on the CT

    gantry and thus reduce the bandwidth requirements on the data transfer.

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