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  • 201.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments, KTH Syd.
    Carlsson, Camilla
    Brodin, Lars-Åke
    Conductance measurements in the left ventricle: a pressure-flow approach2002In: IFMBE proc., 2002, p. 1012-3Conference paper (Refereed)
  • 202.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments, KTH Syd.
    Carlsson, Camilla
    Brodin, Lars-Åke
    Elmqvist, Håkan
    Kronander, Håkan
    Ericsson, Anders B.
    Design of a single segment conductance catheter for measurement of left ventricular volume2001In: Annual Reports of the Research Reactor Institute, Kyoto University, 2001, p. 151-154Conference paper (Refereed)
    Abstract [en]

    The objective of this paper is to investigate how to best position the sensing electrodes on a single segment conductance catheter, and to calculate the expected performance. Using electrode potential data, obtained with the present five segment conductance catheter in pig experiments, we have interpolated the electrical field at any given point of time, and calculated what volume curve to expect with only two sensing electrodes. Comparison shows that the deviation between our calculated method and the present one is stable and small. Mean deviation with optimized electrode positions was 0.05% per sample, and the maximum deviation found for a single time sample was 2.57%. This indicates that it is possible to build a thin single segment catheter with as good performance as for the present five segment conductance catheter.

  • 203.
    Söderqvist, Emil
    et al.
    Department of Medical Engineering, Karolinska Institutet, Stockholm, Sweden.
    Hultman, Jan
    Källner, Göran
    Nowak, Jacek
    Brodin, Lars-Åke
    Department of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden.
    The assessment of acute load and contractility changes by left ventricular pressure measurements2006In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 27, no 12, p. 1281-1292Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to establish whether analysis of the left ventricular pressure waveform provides indicative information about cardiac load and contractility and to develop an algorithm for computer-based assessment of changes in these variables. In eight healthy standard breed anaesthetized open-chest pigs, a high frequency response guide-wire mounted pressure sensor was introduced into the left ventricle. Preload reduction was induced by vena cava occlusion, afterload increase by an i.v. injection of phenylephrine and increased contractility by an i.v. injection of adrenalin. Left ventricular pressure waveform analysis was performed by plotting the slope of the pressure curve during the systolic ejection period versus maximal systolic pressure. The analysis revealed characteristic changes in left ventricular pressure and pressure waveform and identified easily discernible reaction patterns in the slope versus maximal pressure plot, specific for each provocation. Analysis of the left ventricular waveform provides indicative information about loading conditions and contractility. The proposed algorithm can easily be implemented in pressure monitoring systems allowing real-time assessment and discrimination of acute changes in preload, afterload and myocardial performance.

  • 204.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments, KTH Syd.
    Lang, Helmuth
    Källner, Göran
    Hultman, Jan
    Lind, Britta
    KTH, Superseded Departments, KTH Syd. KTH, School of Technology and Health (STH).
    Brodin, Lars-Åke
    Left ventricular pressure indicies help to evaluate loading conditions and contractility2002In: IFMBE proc, ISSN 1680-0737, p. 1014-5Article in journal (Refereed)
  • 205.
    Söderqvist, Emil
    et al.
    KTH, Superseded Departments, KTH Syd.
    Storaa, Camilla
    KTH, School of Engineering Sciences (SCI), Physics.
    Ericsson, Anders B.
    Brodin, Lars-Åke
    Ultrasound tissue doppler measurements imply that conductance changes in the left ventricle during isovolumic phases are due to tissue motion.2002In: IFMBE proc.,, 2002, p. 1016-7Conference paper (Refereed)
  • 206.
    Ternström, Sten
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Does the acoustic waveform mirror the voice?2005In: Logopedics, Phoniatrics, Vocology, ISSN 1401-5439, E-ISSN 1651-2022, Vol. 30, no 3-4, p. 100-107Article in journal (Refereed)
    Abstract [en]

    Over recent decades, much effort has been invested in the search for acoustic correlates of vocal function and dysfunction. The convenience of non-invasive voice measurements has been a major incentive for this effort. The acoustic signal is a rich but also very diversified source of information. Computer literacy and technical curiosity in the voice care and voice performance communities are now higher than ever, and tools for voice analysis are proliferating. On such a busy scene, a review may be useful of some basic principles for what we can and cannot hope to determine from non-invasive acoustic analysis. One way of doing this is to consider communication by voice as though it were engineered, with layered protocols. This results in a scheme for systematizing the many sources of variation that are present in the acoustic signal, that can complement other strategies for extracting information.

  • 207.
    Thaning, Elin M.
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Asplund, Maria
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Inganäs, Olle W.
    Biomolecular and Organic Electronics, IFM, Linköping University.
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Stability of Poly(3,4-ethylene dioxythiophene) Materials Intended for Implants2010In: Journal of Biomedical Materials Research - Part B Applied Biomaterials, ISSN 1552-4973, Vol. 93B, no 2, p. 407-415Article in journal (Refereed)
    Abstract [en]

    This study presents experiments designed to study the stability of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions using phosphate-buffered saline (PBS) and hydrogen peroxide (H2O2) (0 01M) at 37 degrees C over a 5- to 6-week period Voltage pulsing in PBS was used as an additional test environment The influence of switching the counter ion used in electropolymerization from polystyrene sulphonate (PSS) to heparin was investigated Absorbance spectroscopy and cyclic voltammetry were used to evaluate the material properties Most of the samples in H2O2 lost both electroactivity and optical absorbance within the study period, but PEDOT.PSS was found slightly more stable than PEDOT heparin. Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after 5 weeks, disregarding delamination, which was a significant problem especially for polymer on indium tin oxide substrates Voltage pulsing in PBS did not increase degradation. The counter ion influenced the time course of degradation in Oxidizing agents.

  • 208.
    Turco, Anna
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Valastyán, Iván
    KTH, School of Technology and Health (STH), Medical Engineering.
    Colarieti-Tosti, Massimiliano
    KTH, School of Technology and Health (STH), Medical Engineering.
    Modular miniPET: A comparison between 10 and 12 detector modules2012In: 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC), IEEE , 2012, p. 2598-2602Conference paper (Refereed)
    Abstract [en]

    By means of computer simulations, scatter fraction, spatial resolution and sensitivity of two 10-detector-module small-animal PET (r77-miniPET and r106-miniPET), are analyzed and compared to the performance of the 12-detector-module PET scanner miniPET II [1]. All simulations have been performed with the well validated Geant4 Application for Emission Tomography (GATE) [2]. Sensitivity and scatter fraction speak in favor of the 10-module scanner: a clear improvement in count rate and scatter fraction was found. Moreover, steeper slopes of noise equivalent count rate curves at low levels of activity was found. Spatial resolution instead was found to be better in the 12-module scanner.

  • 209.
    Töpfer, Fritzi
    KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.
    Micromachined Microwave Sensors for Non-Invasive Skin Cancer Diagnostics2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Malignant melanoma is one of the cancers with the highest incident rates. It is also the most dangerous skin cancer type and an early diagnosis is crucial for the successful treatment of malignant melanoma patients. If it is diagnosed and treated at an early stage, the survival rate for patients is 99%, however, this is reduced to only 25% if diagnosed at a later stage. The work in this thesis combines microsystem technology, microwave engineering and biomedical engineering to develop a sensing tool for early-stage malignant melanoma diagnostics. Such a tool could not only increase the clinical accuracy of malignant melanoma diagnosis, but also reduce the time needed for examination, and lower the number of unnecessary biopsies. Furthermore, a reliable and easy-to-use tool can enable non-specialist healthcare personnel, including primary care physicians or nurses, to perform a prescreening for malignant melanoma with a high sensitivity. Consequently, a large number of patients could receive a timely examination despite the shortage of dermatologists, which exists in many healthcare systems. The dielectric properties of tumor tissue differ from healthy tissue, which is mainly accounted to a difference in the water content. This difference can be measured by a microwave-based sensing technique called microwave reflectometry. Previously reported microwave-based skin measurements largely relied on standard open-ended waveguide probes that are not suitable for early-stage skin tumor diagnosis. Thus, alternative near-field probe designs based on micromachined dielectric-rod waveguides are presented here. The thesis focuses on a broadband microwave probe that operates in the W-band (75 to 110 GHz), with a sensing depth and resolution tailored to small and shallow skin tumors, allowing a high sensitivity to early-stage malignant melanoma. Prototypes of the probe were fabricated by micromachining and characterized. For the characterization, a novel type of silicon-based heterogeneous sample with tailor-made permittivity was introduced. Furthermore, the performance of the probe was evaluated in vivo. First, through measurements on human volunteers, it was shown that the probe is sensitive to artificially induced changes of the skin hydration. Then, measurements on murine skin melanoma models were performed and small early-stage skin tumors were successfully distinguished from healthy skin. Additionally, a resonant probe for microwave skin sensing was designed and micromachined protoypes were tested on phantom materials. However, the resonant probe was found less suitable than the broadband probe for the measurements on skin. The broadband probe presented in this thesis is the first microwave nearfield probe specifically designed for early-stage malignant melanoma diagnostics and successfully evaluated in vivo.

  • 210.
    Töpfer, Fritzi
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Emtestam, L.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Diagnosis of malignant melanoma by micromachined near-field millimeter-wave probe2016In: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    A micromachined millimeter-wave probe, optimized for early-stage skin tumor diagnosis has been verified using a murine skin cancer model. Malignant melanoma tumors are clearly distinguishable from surrounding healthy tissue, since the difference in S11 between a malignant melanoma skin tumor and surrounding healthy tissue is 6.7 times larger than typical standard deviations of measurements on the same spot. Furthermore, the probe has an 8 times higher selectivity to a tumor growing in the skin close to the surface as compared to a subcutaneous tumor buried beneath a thick healthy tissue layer. This confirms the optimized sensitivity of the probe to the targeted upper portion of the skin, in which skin tumor growth starts in malignant melanoma patients.

  • 211.
    Töpfer, Fritzi
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Emtestam, Lennart
    Oberhammer, Joachim
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Long-Term Monitoring of Skin Recovery by Micromachined Microwave Near-Field Probe2017In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 27, no 6, p. 605-607Article in journal (Refereed)
    Abstract [en]

    The water content in the epidermis correlates with different pathologic states of the skin; thus its assessment can aid the diagnosis and monitoring of conditions such as inflammation, edema, burns, and skin cancer. A micromachined microwave near-field probe, operating from 90 to 106 GHz, which, in contrast to earlier used microwave probes, has a minimized sensing area of 0.6 mm x 0.5 mm and an optimized sensing depth of 400 mu m in tissue, has been developed and technically characterized by the authors earlier. This letter reports on the long-term monitoring of sodium lauryl sulfate (SLS)-induced skin irritations with the micromachined microwave probe. Aqueous solutions with 1%, 2%, 5%, and 10% SLS were applied to the forearm of a volunteer for 24 h and microwave reflection measurements were taken before and during 11 days after the SLS application. For all SLS-treated spots the microwave absorption reached the highest levels of 4 to 7 days after SLS application and afterward converged toward baseline levels again. The observed biphasic progression of the microwave reflection signal agrees well with trends from the literature for capacitance measurements and for epidermal thickness and signal attenuation in optical coherence tomography after SLS exposure. The measurements indicate that the microwave probe is very suitable to determine changes in the water content in the epidermis and can aid in the diagnosis of pathologic conditions including skin cancer.

  • 212.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Imrek, J.
    Hegyesi, G.
    Kalinka, G.
    Molnar, J.
    Novak, D.
    LSO based dual slice helical CT and PET demonstrators2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 633, p. S300-S302Article in journal (Refereed)
    Abstract [en]

    Two demonstrators, a spiralCT and a miniPET, have been designed and constructed for educational purposes. Computed tomographs (CTs) and positron emission tomographs (PETs) are some of the most commonly used structural and functional imaging devices in medicine, respectively. There is a need for transparent demonstrators where the principles of the different modalities and their functions are presented. The aim of the developments of these systems was to present the major building blocks of CT and PET for undergraduate students. Photon detection in both systems is based on small pixelised scintillation crystals with position sensitive PMT readout. Similar analogue and digital data processing based on FPGA technique is applied for the demonstrators and common image reconstruction and presentation software components are used.

  • 213.
    Valastyán, Iván
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Kerek, Andras
    KTH, School of Technology and Health (STH), Medical Engineering.
    Molnar, J.
    Novak, D.
    Vegh, J.
    Emri, M.
    Tron, L.
    A SPECT demonstrator - revival of a gamma camera2006In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 563, no 1, p. 274-277Article in journal (Refereed)
    Abstract [en]

    A gamma camera has been updated and converted to serve as a demonstrator for educational purposes. The gantry and the camera head were the only part of the system that remained untouched. The main reason for this modernization was to increase the transparency of the gamma camera by partitioning the different logical building blocks of the system and thus providing access for inspection and improvements throughout the chain. New data acquisition and reconstruction software has been installed. By taking these measures, the camera is now used in education and also serves as a platform for tests of new hardware and software solutions. The camera is also used to demonstrate 3D (SPECT) imaging by collecting 2D projections from a rotatable cylindrical phantom. Since the camera head is not attached mechanically to the phantom, the effect of misalignment between the head and the rotation axis of the phantom can be studied. (c) 2006 Elsevier B.V. All rights reserved.

  • 214. Valentín, A.
    et al.
    Holzapfel, Gerhard A.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Constrained mixture models as tools for testing competing hypotheses in arterial biomechanics: A brief survey2012In: Mechanics research communications, ISSN 0093-6413, E-ISSN 1873-3972, Vol. 42, p. 126-133Article, review/survey (Refereed)
    Abstract [en]

    Hypothesis testing via numerical models has emerged as a powerful tool which permits the verification of theoretical frameworks against canonical experimental and clinical observations. Cleverly designed computational experiments also inspire new methodologies by elucidating important biological processes and restricting parametric spaces. Constrained mixture models of arterial growth and remodeling (G&R) can facilitate the design of computational experiments which can bypass technical limitations in the laboratory, by considering illustrative special cases. The resulting data may then inform the design of focused experimental techniques and the development of improved theories. This work is a survey of computational hypothesis-testing studies, which exploit the unique abilities offered by the constrained mixture theory of arterial G&R. Specifically, we explore the core hypotheses integrated in these models, review their basic mathematical conceptualizations, and recapitulate their most salient and illuminating findings. We then assess how a decade's worth of constrained mixture models have contributed to a lucid, emerging picture of G&R mechanisms.

  • 215.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, BioMEx. KTH, School of Engineering Sciences (SCI), Mechanics. Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
    Gäverth, J.
    Herman, Pawel
    KTH, School of Electrical Engineering and Computer Science (EECS), Computational Science and Technology (CST).
    Changes in the neural and non-neural related properties of the spastic wrist flexors after treatment with botulinum toxin a in post-stroke subjects: An optimization study2018In: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 9, no June, article id 73Article in journal (Refereed)
    Abstract [en]

    Quantifying neural and non-neural contributions to the joint resistance in spasticity is essential for a better evaluation of different intervention strategies such as botulinum toxin A (BoTN-A). However, direct measurement of muscle mechanical properties and spasticity-related parameters in humans is extremely challenging. The aim of this study was to use a previously developed musculoskeletal model and optimization scheme to evaluate the changes of neural and non-neural related properties of the spastic wrist flexors during passive wrist extension after BoTN-A injection. Data of joint angle and resistant torque were collected from 21 chronic stroke patients before, and 4 and 12 weeks post BoTN-A injection using NeuroFlexor, which is a motorized force measurement device to passively stretch wrist flexors. The model was optimized by tuning the passive and stretch-related parameters to fit the measured torque in each participant. It was found that stroke survivors exhibited decreased neural components at 4 weeks post BoNT-A injection, which returned to baseline levels after 12 weeks. The decreased neural component was mainly due to the increased motoneuron pool threshold, which is interpreted as a net excitatory and inhibitory inputs to the motoneuron pool. Though the linear stiffness and viscosity properties of wrist flexors were similar before and after treatment, increased exponential stiffness was observed over time which may indicate a decreased range of motion of the wrist joint. Using a combination of modeling and experimental measurement, valuable insights into the treatment responses, i.e., transmission of motoneurons, are provided by investigating potential parameter changes along the stretch reflex pathway in persons with chronic stroke.

  • 216.
    Wiklund, Urban
    et al.
    Department of Biomedcal Engineering and Informatics, Univeristy Hospital of Umeå.
    Karlsson, Marcus
    Department of Biomedcal Engineering and Informatics, Univeristy Hospital of Umeå.
    Ostlund, Nils
    Department of Biomedcal Engineering and Informatics, Univeristy Hospital of Umeå.
    Berglin, Lena
    School of Textiles, University of Borås.
    Lindecrantz, Kaj
    School of Engineering, University of Borås.
    Karlsson, Stefan
    Engineering and Informatics, Univeristy Hospital of Umeå.
    Sandsjö, Leif
    National Institute of Working Life, Gothenburg.
    Adaptive spatio-temporal filtering of disturbed ECGs: a multi-channel approach to heartbeat detection in smart clothing2007In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 45, no 6, p. 515-523Article in journal (Refereed)
    Abstract [en]

    Intermittent disturbances are common in ECG signals recorded with smart clothing: this is mainly because of displacement of the electrodes over the skin. We evaluated a novel adaptive method for spatio-temporal filtering for heartbeat detection in noisy multi-channel ECGs including short signal interruptions in single channels. Using multi-channel database recordings (12-channel ECGs from 10 healthy subjects), the results showed that multi-channel spatio-temporal filtering outperformed regular independent component analysis. We also recorded seven channels of ECG using a T-shirt with textile electrodes. Ten healthy subjects performed different sequences during a 10-min recording: resting, standing, flexing breast muscles, walking and pushups. Using adaptive multi-channel filtering, the sensitivity and precision was above 97% in nine subjects. Adaptive multi-channel spatio-temporal filtering can be used to detect heartbeats in ECGs with high noise levels. One application is heartbeat detection in noisy ECG recordings obtained by integrated textile electrodes in smart clothing.

  • 217.
    Williams, Cecilia
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Pontén, F
    Moberg, C
    Söderkvist, P
    Uhlén, M
    Pontén, J
    Sitbon, G
    Lundeberg, J
    A high frequency of sequence alterations is due to formalin fixation of archival specimens.1999In: American Journal of Pathology, ISSN 0002-9440, E-ISSN 1525-2191, Vol. 155, no 5Article in journal (Refereed)
    Abstract [en]

    Genomic analysis of archival tissues fixed in formalin is of fundamental importance in biomedical research, and numerous studies have used such material. Although the possibility of polymerase chain reaction (PCR)-introduced artifacts is known, the use of direct sequencing has been thought to overcome such problems. Here we report the results from a controlled study, performed in parallel on frozen and formalin-fixed material, where a high frequency of nonreproducible sequence alterations was detected with the use of formalin-fixed tissues. Defined numbers of well-characterized tumor cells were amplified and analyzed by direct DNA sequencing. No nonreproducible sequence alterations were found in frozen tissues. In formalin-fixed material up to one mutation artifact per 500 bases was recorded. The chance of such artificial mutations in formalin-fixed material was inversely correlated with the number of cells used in the PCR-the fewer cells, the more artifacts. A total of 28 artificial mutations were recorded, of which 27 were C-T or G-A transitions. Through confirmational sequencing of independent amplification products artifacts can be distinguished from true mutations. However, because this problem was not acknowledged earlier, the presence of artifacts may have profoundly influenced previously reported mutations in formalin-fixed material, including those inserted into mutation databases.

  • 218.
    Wåhslén, Jonas
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Orhan, Ibrahim
    KTH, School of Technology and Health (STH), Data- och elektroteknik (Closed 20130701).
    Lindh, Thomas
    KTH, School of Technology and Health (STH).
    Local Time Synchronization in Bluetooth Piconets for Data Fusion Using Mobile Phones2011In: BSN 2011: 8th International Conference on Body Sensor Networks, 2011, p. 113-138Conference paper (Refereed)
    Abstract [en]

    This paper presents a method to synchronize the clocks in a Bluetooth piconet from the application layer in a mobile phone. It adapts algorithms for time synchronization of distributed systems and the Internet to Bluetooth networks. The performance issues that cause problems for data synchronization between master and slaves in Bluetooth are highlighted. The tests show that the synchronization error is limited to one sampling time.

  • 219. Xing, Zhe
    et al.
    Xue, Ying
    Dånmark, Staffan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Arvidson, Kristina
    Hellem, Solve
    Yang, Zhuang-Qun
    Mustafa, Kamal
    Comparison of short-run cell seeding methods for poly(L-lactide-co-1,5-dioxepan-2-one) scaffold intended for bone tissue engineering2011In: International Journal of Artificial Organs, ISSN 0391-3988, E-ISSN 1724-6040, Vol. 34, no 5, p. 432-441Article in journal (Refereed)
    Abstract [en]

    Constructs intended for bone tissue engineering are influenced by the initial cell seeding procedure. The seeding method should be rapid, convenient, improve cell spatial distribution, and have no negative effects on cellular viability and differentiation. This study aimed to compare the effect of short-run seeding methods (centrifuge and vortex) with a static method on the scaffolds prepared from poly(L-lactide-co-1,5-dioxepan-2-one) by solvent-casting particulate-leaching (SCPL) technique. Human osteoblast-like cells (HOB) were seeded by the three methods described above. The seeding efficiency was determined by attached cell numbers. Cellular proliferation was analyzed by WST-1 and dsDNA assay. Cell distribution was examined by scanning electron (SEM) and fluorescence microscopy. Expression of Alkaline Phosphatase (ALP), Collagen type I (Col I), Osteocalcin (OC) and Proliferating Cell Nuclear Antigen (PCNA) were determined by real time RT-PCR. Results indicated that centrifuge and vortex increased seeding efficiency and had no negative effects on cellular viability. The data obtained by the fluorescence microscope confirmed the SEM results that the vortex method improved cell distribution through the scaffolds more than the other two methods (p<0.05). The RT-PCR results showed no significant differences on the expression of mRNA between the three methods of the above markers. The vortex method was found to be a simple and feasible seeding method for the poly(L-lactide-co-1,5-dioxepan-2-one) scaffolds.

  • 220.
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    A Segmented Silicon Strip Detector for Photon-Counting Spectral Computed Tomography2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Spectral computed tomography with energy-resolving detectors has a potential to improve the detectability of images and correspondingly reduce the radiation dose to patients by extracting and properly using the energy information in the broad x-ray spectrum. A silicon photon-counting detector has been developed for spectral CT and it has successfully solved the problem of high photon flux in clinical CT applications by adopting the segmented detector structure and operating the detector in edge-on geometry. The detector was evaluated by both the simulation and measurements.

    The effects of energy loss and charge sharing on the energy response of this segmented silicon strip detector with different pixel sizes were investigated by Monte Carlo simulation and a comparison to pixelated CdTe detectors is presented. The validity of spherical approximations of initial charge cloud shape in silicon detectors was evaluated and a more accurate statistical model has been proposed.

    A photon-counting energy-resolving application specific integrated circuit (ASIC) developed for spectral CT was characterized extensively by electrical pulses, pulsed laser and real x-ray photons from both the synchrotron and an x-ray tube. It has been demonstrated that the ASIC performs as designed. A noise level of 1.09 keV RMS has been measured and a threshold dispersion of 0.89 keV RMS has been determined. The count rate performance of the ASIC in terms of count loss and energy resolution was evaluated by real x-rays and promising results have been obtained.

    The segmented silicon strip detector was evaluated using synchrotron radiation. An energy resolution of 16.1% has been determined with 22 keV photons in the lowest flux limit, which deteriorates to 21.5% at an input count rate of 100 Mcps mm−2. The fraction of charge shared events has been estimated and found to be 11.1% for 22 keV and 15.3% for 30 keV. A lower fraction of charge shared events and an improved energy resolution can be expected by applying a higher bias voltage to the detector.

  • 221.
    Zheng, Miaomiao
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering.
    Härmark, Johan
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Structural Biotechnology.
    Grishenkov, Dmitry
    KTH, School of Technology and Health (STH), Medical Engineering.
    Janerot Sjöberg, Birgitta
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Polymer-Shelled Ultrasound Contrast Agents with controlled size and polydispersity.2011In: Nanomedicine: Nanotechnology, Biology & Medicine, 2011Conference paper (Refereed)
    Abstract [en]

    Ultrasound imaging techniques can be greatly improved by the use of ultrasound contrast agents (UCAs). Gas bubbles encapsulated into biocompatible polymer shell are of particular interest of this work. Shell of the bubbles produced from Poly-Vinyl-Alcohol (PVA) offers considerable chemical versatility and stability. However, questions regarding the size and polydispersity of the microbubbles must be further investigated. The ideal UCAs should not obstruct the blood flow in pulmonary capillaries which diameter is less than 10 μm. From the technical perspective UCAs should modify the acoustic properties of a region of interest, by increasing backscattered efficiency. In order to enhance the ultrasound response UCAs should be engineered with narrow size distribution. In the present work PVA-shelled UCAs with controlled size and polydispersity is manufactured under varied parameters of the manufacturing protocol. It was observed that temperature of the surrounding atmosphere has major effect on the size of the UCAs, while polydispersity is regulated by geometry and speed of the disperser. Finally, the acoustic response of these microbubbles is tested using developed ultrasound test rig. The enhancement of the backscattered power of about 25 dB from a suspension of the microbubbles is observed at 5 MHz ultrasound frequency. Keeping in mind that in clinical practice ultrasound scatter from the blood is of about 30 dB weaker than scatter from surrounding tissue, introduction of novel PVA microbubbles will potentially improve diagnosis of the cardiovascular patients.

  • 222.
    Zhou, Jing
    et al.
    University of Tampere.
    Zhang, Weikai
    University of Tampere.
    Poe, Dennis
    University of Tampere.
    Qin, Jian
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Fornara, Andrea
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Zhang, Ya
    University of Tampere.
    Ramadan, Usama
    University of Helsinki.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Functional Materials, FNM.
    Pyykkö, Ilmari
    University of Tampere.
    MRI manifestation of novel superparamagnetic iron oxide nanoparticles in the rat inner ear2010In: Nanomedicine, ISSN 1743-5889, Vol. 5, no 5, p. 739-754Article in journal (Refereed)
    Abstract [en]

    Aim: Superparamagnetic iron oxide nanoparticles hierarchically coated with oleic acid and Pluronic F127 copolymers (POA@SPION) have shown exceptional 12 contrast enhancement. The aim of the present work was to investigate the MRI manifestation of POA@SPION in the inner ear. Materials & methods: A total of 26 male Wister rats were selected for testing POA@SPION administered through intracochlear, intratympanic and intravenous routes. MRI was performed with a 4.7 T MR scanner. Results & conclusion: POA@SPION can be introduced into the perilymph space, after which it becomes widely distributed and can demonstrate the integrity of the perilymph-endolymph barrier. Positive highlighting of the endolymph compartment against the darkened perilymph was visualized for the first time. POA@SPION passed through the middle-inner ear barriers in only small amounts, but stayed in the perilymph for 3 days. They did not traverse the blood-perilymph barrier or blood-endolymph barrier. The inner ear distribution of POA@SPION was confirmed by histology. POA@SPION is a promising T2 negative contrast agent.

  • 223.
    Åslund, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederström, Björn
    KTH, School of Engineering Sciences (SCI), Physics.
    Lundqvist, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    AEC for scanning digital mammography based on variation of scan velocity2005In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 32, no 11, p. 3367-3374Article in journal (Refereed)
    Abstract [en]

    A theoretical evaluation of nonuniform x-ray field distributions in mammography was conducted. An automatic exposure control (AEC) is proposed for a scanning full field digital mammography system. It uses information from the leading part of the detector to vary the scan velocity dynamically, thus creating a nonuniform x-ray field in the scan direction. Nonuniform radiation fields were also created by numerically optimizing the scan velocity profile to each breast's transmission distribution, with constraints on velocity and acceleration. The goal of the proposed AEC is to produce constant pixel signal-to-noise ratio throughout the image. The target pixel SNR for each image could be set based on the breast thickness, breast composition, and the beam quality as to achieve the same contrast-to-noise ratio between images for structures of interest. The results are quantified in terms of reduction in entrance surface air kerma (ESAK) and scan time relative to a uniform x-ray field. The theoretical evaluation was performed on a set of 266 mammograms. The performance of the different methods to create nonuniform fields decreased with increased detector width, from 18% to 11% in terms of ESAK reduction and from 30% to 25% in terms of scan time reduction for the proposed AEC and detector widths from 10 to 60 mm. Some correlation was found between compressed breast thickness and the projected breast area onto the image field. This translated into an increase of the ESAK and decrease of the scan time reduction with breast thickness. Ideally a nonuniform field in two dimensions could reduce the entrance dose by 39% on average, whereas a field nonuniform in only the scanning dimension ideally yields a 20% reduction. A benefit with the proposed AEC is that the risk of underexposing the densest region of the breast can be virtually eliminated.

  • 224.
    Åslund, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederström, Björn
    KTH, School of Engineering Sciences (SCI), Physics.
    Lundqvist, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Evaluation of an AEC system for scanning photon counting mammography based on variation of scan velocityIn: Medical physics (Lancaster), ISSN 0094-2405Article in journal (Other academic)
  • 225.
    Åslund, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederström, Björn
    KTH, School of Engineering Sciences (SCI), Physics.
    Lundqvist, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Physical characterization of a scanning photon counting digital mammography system based on Si-strip detectors2007In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 34, no 6, p. 1918-1925Article in journal (Refereed)
    Abstract [en]

    The physical performance of a scanning multislit full field digital mammography system was determined using basic image quality parameters. The system employs a direct detection detector comprised of linear silicon strip sensors in an edge-on geometry connected to photon counting electronics. The pixel size is 50 mu m and the field of view 24 x 26 cm(2). The performance was quantified using the presampled modulation transfer function, the normalized noise power spectrum and the detective quantum efficiency (DQE). Compared to conventional DQE methods, the scanning geometry with its intrinsic scatter rejection poses additional requirements on the measurement setup, which are investigated in this work. The DQE of the photon counting system was found to be independent of the dose level to the detector in the 7.6-206 mu Gy range. The peak DQE was 72% and 73% in the scan and slit direction, respectively, measured with a 28 kV W-0.5 mm Al anodefilter combination with an added 2 mm Al filtration.

  • 226.
    Åslund, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederström, Björn
    KTH, School of Engineering Sciences (SCI), Physics.
    Lundqvist, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Scatter rejection in multislit digital mammography2006In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 33, no 4, p. 933-940Article in journal (Refereed)
    Abstract [en]

    The scatter to primary ratio (SPR) was measured on a scanning multislit full-field digital mammography system for different thickness of breast equivalent material and different tube voltages. Scatter within the detector was measured separately and was found to be the major source of scatter in the assembly. Measured total SPRs below 6% are reported for breast range 3-7 cm. The performance of the multislit assembly is compared to other imaging geometries with different scatter rejection schemes by using the scatter detective quantum efficiency.

  • 227.
    Åslund, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Fredenberg, Erik
    KTH, School of Engineering Sciences (SCI), Physics.
    Cederström, Björn
    KTH, School of Engineering Sciences (SCI), Physics.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics.
    Spectral shaping for photon counting digital mammography2007In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 580, no 2, p. 1046-1049Article in journal (Refereed)
    Abstract [en]

    The spectral shaping properties of conventional filters have been evaluated for a photon counting digital mammography system, and the result has been compared with the theoretical spectrum from a multi-prism X-ray lens (MPL). The absorption filters and the MPL were evaluated using a theoretical model of the system which has been verified experimentally. The spectral shaping performance is quantified with the spectral quantum efficiency (SQE), calculated as the polychromatic signal-difference-to-noise ratio (SDNR) squared over the optimal monochromatic SDNR squared at the same average glandular dose. The MPL increases the SQE by 25% compared to the investigated absorption filter when compared with a Tungsten anode. This translates into a potential dose reduction of 20% at maintained SDNR.

2345 201 - 227 of 227
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