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Adolfsson E.,Linkoping University | Karlsson M.,Linkoping University | Alm Carlsson G.,Linkoping University | Carlsson Tedgren A.,Linkoping University | And 3 more authors.
Physics in Medicine and Biology | Year: 2012

The aim of this study was to investigate signal fading in lithium formate electron paramagnetic resonance (EPR) dosimeters used for clinical applications in radiotherapy. A new experimental method for determination of signal fading, designed to resolve small changes in signal from slowly decaying unstable radicals, was used. Possible signal fading in lithium formate due to different storage temperatures was also tested. Air humidity was kept at a constant level of 33% throughout the experiments. The conclusion drawn from the investigations was that the EPR signal from lithium formate is stable during at least 1 month after irradiation and is not sensitive to variations in storage temperature <40°C when kept at a relative air humidity of 33%. This makes lithium formate a suitable dosimeter for transfer dosimetry in clinical audits. © 2012 Institute of Physics and Engineering in Medicine. Source

Adolfsson E.,Linkoping University | Gustafsson H.,Linkoping University | Lund E.,Linkoping University | Alm Carlsson G.,Linkoping University | And 2 more authors.
Radiotherapy and Oncology | Year: 2014

The aim of this work was to develop and test a remote end-to-end audit system using lithium formate EPR dosimeters. Four clinics were included in a pilot study, absorbed doses determined in the PTV agreed with TPS calculated doses within ±5% for 3D-CRT and ±7% (k = 1) for IMRT/VMAT dose plans. © 2014 Elsevier Ireland Ltd. Source

Dams F.E.,Albert Schweitzer Hospital | Esther Leung K.Y.,Medical Physics and Technology | van der Valk P.H.,Albert Schweitzer Hospital | Kock M.C.,Albert Schweitzer Hospital | And 2 more authors.
Medical Devices: Evidence and Research | Year: 2014

Methods: We recruited 1 9 radiologists and residents to compare the image quality of four liquid crystal displays, including 3-megapixel Barco®, Eizo®, and NEC® displays and a 6-megapixel Barco display. The evaluators were blinded to the manufacturers’ names. Technical assessments were based on acceptance criteria and test patterns proposed by the American Association of Physicists in Medicine. Radiological assessments were performed on images from the American Association of Physicists in Medicine Task Group 1 8. They included X-ray images of the thorax, knee, and breast, a computed tomographic image of the thorax, and a magnetic resonance image of the brain. Image quality was scored on an analog scale (range 0–10). Statistical analysis was performed with repeated-measures analysis of variance.Results: The Barco 3-megapixel display passed all acceptance criteria. The Eizo and NEC displays passed the acceptance criteria, except for the darkest pixel value in the grayscale display function. The Barco 6-megapixel display failed criteria for the maximum luminance response and the veiling glare. Mean radiological assessment scores were 7.8±1.1 (Barco 3-megapixel), 7.8±1.2 (Eizo), 8.1±1.0 (NEC), and 8.1±1.0 (Barco 6-megapixel). No signifcant differences were found between displays.Conclusion: According to the tested criteria, all the displays had comparable image quality; however, there was a three-fold difference in price between the most and least expensive displays.Background: To inform cost-effective decisions in purchasing new medical liquid crystal displays, we compared the image quality in displays made by three manufacturers. © 2014 Dams et al. Source

Meijer E.J.,Maxima Medical Center | Hermans K.H.M.,Maxima Medical Center | Hermans K.H.M.,TU Eindhoven | Zwanenburg A.,Maastricht University | And 8 more authors.
European Journal of Paediatric Neurology | Year: 2014

Objective To quantify the neuronal connectivity in preterm infants between homologous channels of both hemispheres.Methods EEG coherence analysis was performed on serial EEG recordings collected from preterm infants with normal neurological follow-up. The coherence spectrum was divided in frequency bands: δnewborn(0-2 Hz), θnewborn(2-6 Hz), αnewborn(6-13 Hz), βnewborn(13-30 Hz). Coherence values were evaluated as a function of gestational age (GA) and postnatal maturation.Results All spectra show two clear peaks in the δnewborn and θnewborn-band, corresponding to the delta and theta EEG waves observed in preterm infants. In the δnewborn-band the peak magnitude coherence decreases with GA and postnatal maturation for all channels. In the θnewborn-band, the peak magnitude coherence decreases with GA for all channels, but increases with postnatal maturation for the frontal polar channels. In the βnewborn-band a modest magnitude coherence peak was observed in the occipital channels, which decreases with GA. Conclusions Interhemispherical connectivity develops analogously with electrocortical maturation: signal intensities at low frequencies decrease with GA and postnatal maturation, but increase at high frequencies with postnatal maturation. In addition, peak magnitude coherence is a clear trend indicator for brain maturation.Significance Coherence analysis can aid in the clinical assessment of the functional connectivity of the infant brain with maturation. © 2014 European Paediatric Neurology Society. Source

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