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Zeitschrift Für Medizinische Physik

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https://www.readbyqxmd.com/read/28807441/whole-body-dose-and-energy-measurements-in-radiotherapy-by-a-combination-of-lif-mg-cu-p-and-lif-mg-ti
#1
Pascal Hauri, Uwe Schneider
PURPOSE: Long-term survivors of cancer who were treated with radiotherapy are at risk of a radiation-induced tumor. Hence, it is important to model the out-of-field dose resulting from a cancer treatment. These models have to be verified with measurements, due to the small size, the high sensitivity to ionizing radiation and the tissue-equivalent composition, LiF thermoluminescence dosimeters (TLD) are well-suited for out-of-field dose measurements. However, the photon energy variation of the stray dose leads to systematic dose errors caused by the variation in response with radiation energy of the TLDs...
August 11, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28802623/an-analytical-model-which-determines-the-apparent-t1-for-modified-look-locker-inversion-recovery-analysis-of-the-longitudinal-relaxation-under-the-influence-of-discontinuous-balanced-classical-molli-and-spoiled-gradient-echo-readouts
#2
Thomas Kampf, Theresa Reiter, Wolfgang Rudolf Bauer
Quantitative nuclear magnetic resonance imaging (MRI) shifts more and more into the focus of clinical research. Especially determination of relaxation times without/and with contrast agents becomes the foundation of tissue characterization, e.g. in cardiac MRI for myocardial fibrosis. Techniques which assess longitudinal relaxation times rely on repetitive application of readout modules, which are interrupted by free relaxation periods, e.g. the Modified Look-Locker Inversion Recovery = MOLLI sequence. These discontinuous sequences reveal an apparent relaxation time, and, by techniques extrapolated from continuous readout sequences, a putative real T1 is determined...
August 9, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28801204/improved-post-processing-strategy-for-molli-based-tissue-characterization-allows-application-in-patients-with-dyspnoe-and-impaired-left-ventricular-function
#3
Thomas Kampf, Wolfgang Rudolf Bauer, Theresa Reiter
Contrast and non-contrast MRI based characterization of myocardium by T1-mapping will be of paramount importance to obtain biomarkers, e.g. fibrosis, which determines the risk of heart failure patients. T1-mapping by the standard post-processing of the modified look-locker inversion recovery (MOLLI) lacks of accuracy when trying to reduce its duration, which on the other hand, is highly desirable in patients with heart failure. The recently suggested inversion group fitting (IGF) technique, which considers more parameters for fitting, has a superior accuracy for long T1 times despite a shorter duration...
August 8, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28676372/computerized-modeling-of-the-human-heart
#4
EDITORIAL
Olaf Dössel, Axel Loewe
No abstract text is available yet for this article.
July 1, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28676371/modeling-tumor-control-probability-for-spatially-inhomogeneous-risk-of-failure-based-on-clinical-outcome-data
#5
Armin Lühr, Steffen Löck, Annika Jakobi, Kristin Stützer, Anna Bandurska-Luque, Ivan Richter Vogelius, Wolfgang Enghardt, Michael Baumann, Mechthild Krause
PURPOSE: Objectives of this work are (1) to derive a general clinically relevant approach to model tumor control probability (TCP) for spatially variable risk of failure and (2) to demonstrate its applicability by estimating TCP for patients planned for photon and proton irradiation. METHODS AND MATERIALS: The approach divides the target volume into sub-volumes according to retrospectively observed spatial failure patterns. The product of all sub-volume TCPi values reproduces the observed TCP for the total tumor...
July 1, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28647226/inhalation-of-nanoplatelets-theoretical-deposition-simulations
#6
Robert Sturm
Primary objective of the contribution was the theoretical prediction of nanoplatelet deposition in the human respiratory tract. Modeling was founded on the hypothetical inhalation of graphene nanoplatelets (GNP) measuring 0.01 and 0.1μm in thickness and adopting a projected area diameter of 1-30μm. Particle uptake was assumed to take place with inhalation flow rates of 250, 500, 750, and 1000cm(3)s(-1), respectively. For an appropriate description of pulmonary particle behavior, transport of GNP in a stochastic lung structure and deposition formulae based on analytical and numerical studies were presupposed...
June 21, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28601374/quantitative-susceptibility-mapping-qsm-and-r2-in-the-human-brain-at-3t-evaluation-of-intra-scanner-repeatability
#7
Xiang Feng, Andreas Deistung, Jürgen R Reichenbach
Quantitative susceptibility mapping (QSM) and the effective transverse relaxation rate (R2*) can be used to monitor iron and myelin content in brain tissue, which are both subject to changes in many neurological diseases but also during healthy aging. In this study, we quantitatively assessed the repeatability of QSM and R2* by applying four independent scans in eight young healthy, female subjects on a 3T MRI scanner. Since QSM does not yield absolute values for bulk magnetic susceptibilities, we additionally investigated the influence of the choice of a reference brain region for susceptibility by computing susceptibility differences with respect to five different brain structures (whole brain, frontal white matter (fWM), internal capsule (IC), cerebrospinal fluid (CSF) in the lateral ventricle, cortical gray matter (cGM))...
June 7, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28595775/surface-dose-measurements-in-and-out-of-field-implications-for-breast-radiotherapy-with-megavoltage-photon-beams
#8
Peta Lonski, Prabhakar Ramachandran, Rick Franich, Tomas Kron
This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6MV, 6MV FFF, 10MV, 10MV FFF and 18MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams...
June 5, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28595774/feasibility-of-using-single-photon-counting-x-ray-for-lung-tumor-position-estimation-based-on-4d-ct
#9
Katharina P Aschenbrenner, Christian V Guthier, Yulia Lyatskaya, Judit Boda-Heggemann, Frederik Wenz, Jürgen W Hesser
PURPOSE: In stereotactic body radiation therapy of lung tumors, reliable position estimation of the tumor is necessary in order to minimize normal tissue complication rate. While kV X-ray imaging is frequently used, continuous application during radiotherapy sessions is often not possible due to concerns about the additional dose. Thus, ultra low-dose (ULD) kV X-ray imaging based on a single photon counting detector is suggested. This paper addresses the lower limit of photons to locate the tumor reliably with an accuracy in the range of state-of-the-art methods, i...
June 5, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28554547/the-influence-of-cardiac-triggering-time-and-an-optimization-strategy-for-improved-cardiac-mr-spectroscopy
#10
Åsa Carlsson, Maja C Sohlin, Kerstin M Lagerstrand, Eva Forsell Aronsson, Maria Ljungberg
PURPOSE: To study how cardiac motion affects the spectral quality in cardiac MR spectroscopy and to establish an optimization strategy for the cardiac triggering time for improved quality and success rate of cardiac MRS. METHOD: Water spectra were acquired while the cardiac triggering time was varied over the cardiac cycle, and five different spectral quality parameters were studied (frequency, phase, linewidth, amplitude and noise). Furthermore, three different optimization strategies for the cardiac triggering time were tested, and finally, a comparison was made between water suppressed lipid spectra acquired in systole and diastole...
May 26, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28546005/fast-epithermal-and-thermal-photoneutron-dosimetry-in-air-and-in-tissue-equivalent-phantom-for-a-high-energy-x-ray-medical-accelerator
#11
Mehdi Sohrabi, Amir Hakimi
Photoneutron (PN) dosimetry in fast, epithermal and thermal energy ranges originated from the beam and albedo neutrons in high-energy X-ray medical accelerators is highly important from scientific, technical, radiation protection and medical physics points of view. Detailed dose equivalents in the fast, epithermal and thermal PN energy ranges in air up to 2m as well as at 35 positions from the central axis of 12 cross sections of the phantom at different depths were determined in 18MV X-ray beams of a Siemens ONCOR accelerator...
May 22, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28532604/validation-of-dwi-pre-processing-procedures-for-reliable-differentiation-between-human-brain-gliomas
#12
Sebastian Vellmer, Aram S Tonoyan, Dieter Suter, Igor N Pronin, Ivan I Maximov
Diffusion magnetic resonance imaging (dMRI) is a powerful tool in clinical applications, in particular, in oncology screening. dMRI demonstrated its benefit and efficiency in the localisation and detection of different types of human brain tumours. Clinical dMRI data suffer from multiple artefacts such as motion and eddy-current distortions, contamination by noise, outliers etc. In order to increase the image quality of the derived diffusion scalar metrics and the accuracy of the subsequent data analysis, various pre-processing approaches are actively developed and used...
May 19, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28522170/optimization-of-the-alpha-image-reconstruction-an-iterative-ct-image-reconstruction-with-well-defined-image-quality-metrics
#13
Sergej Lebedev, Stefan Sawall, Michael Knaup, Marc Kachelrieß
PURPOSE: Optimization of the AIR-algorithm for improved convergence and performance. METHODS: The AIR method is an iterative algorithm for CT image reconstruction. As a result of its linearity with respect to the basis images, the AIR algorithm possesses well defined, regular image quality metrics, e.g. point spread function (PSF) or modulation transfer function (MTF), unlike other iterative reconstruction algorithms. The AIR algorithm computes weighting images α to blend between a set of basis images that preferably have mutually exclusive properties, e...
May 15, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28506858/accuracy-of-1h-magnetic-resonance-spectroscopy-for-quantification-of-2-hydroxyglutarate-using-linear-combination-and-j-difference-editing-at-9-4t
#14
Ulf Neuberger, Philipp Kickingereder, Xavier Helluy, Manuel Fischer, Martin Bendszus, Sabine Heiland
Non-invasive detection of 2-hydroxyglutarate (2HG) by magnetic resonance spectroscopy is attractive since it is related to tumor metabolism. Here, we compare the detection accuracy of 2HG in a controlled phantom setting via widely used localized spectroscopy sequences quantified by linear combination of metabolite signals vs. a more complex approach applying a J-difference editing technique at 9.4T. Different phantoms, comprised out of a concentration series of 2HG and overlapping brain metabolites, were measured with an optimized point-resolved-spectroscopy sequence (PRESS) and an in-house developed J-difference editing sequence...
May 12, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28476316/aberration-free-intraocular-lenses-what-does-this-really-mean
#15
Achim Langenbucher, Simon Schröder, Alan Cayless, Timo Eppig
BACKGROUND: So-called aberration-free intraocular lenses (IOLs) are well established in modern cataract surgery. Usually, they are designed to perfectly refract a collimated light beam onto the focal point. METHODS: We show how much aberration can be expected with such an IOL in a convergent light beam such as that found anterior to the human cornea. Additionally, the aberration in a collimated beam is estimated for an IOL that has no aberrations in the convergent beam...
May 3, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28457676/higher-order-chromatin-structures-are-taking-shape
#16
EDITORIAL
Thomas Schalch
No abstract text is available yet for this article.
April 27, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28431859/mri-based-quantification-of-renal-perfusion-in-mice-improving-sensitivity-and-stability-in-fair-asl
#17
Fabian Tobias Gutjahr, Stephan Michael Günster, Thomas Kampf, Patrick Winter, Volker Herold, Wolfgang Rudolf Bauer, Peter Michael Jakob
PURPOSE: The importance of the orientation of the selective inversion slice in relation to the anatomy in flow-sensitive alternating inversion recovery arterial spin labeling (FAIR ASL) kidney perfusion measurements is demonstrated by comparing the standard FAIR scheme to a scheme with an improved slice selective control experiment. METHODS: A FAIR ASL method is used. The selective inversion preparation slice is set perpendicular to the measurement slice to decrease the unintended labeling of arterial spins in the control experiment...
April 18, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28412013/investigation-of-the-imaging-characteristics-of-the-albira-ii-small-animal-pet-system-for-18-f-68-ga-and-64-cu
#18
Ali Asgar Attarwala, Yvonne Wanjiku Karanja, Deni Hardiansyah, Chiara Romanó, Mareike Roscher, Björn Wängler, Gerhard Glatting
AIM: In this study the performance characteristics of the Albira II PET sub-system and the response of the system for the following radionuclides (18)F, (68)Ga and (64)Cu was analyzed. MATERIALS AND METHODS: The Albira II tri-modal system (Bruker BioSpin MRI GmbH, Ettlingen, Germany) is a pre-clinical device for PET, SPECT and CT. The PET sub-system uses single continuous crystal detectors of lutetium yttrium orthosilicate (LYSO). The detector assembly consists of three rings of 8 detector modules...
April 12, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28410964/comparison-of-turbo-spin-echo-and-echo-planar-imaging-for-intravoxel-incoherent-motion-and-diffusion-tensor-imaging-of-the-kidney-at-3tesla
#19
Fabian Hilbert, Tobias Wech, Henning Neubauer, Simon Veldhoen, Thorsten Alexander Bley, Herbert Köstler
Echo Planar Imaging (EPI) is most commonly applied to acquire diffusion-weighted MR-images. EPI is able to capture an entire image in very short time, but is prone to distortions and artifacts. In diffusion-weighted EPI of the kidney severe distortions may occur due to intestinal gas. Turbo Spin Echo (TSE) is robust against distortions and artifacts, but needs more time to acquire an entire image compared to EPI. Therefore, TSE is more sensitive to motion during the readout. In this study we compare diffusion-weighted TSE and EPI of the human kidney with regard to intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI)...
April 12, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28342596/the-practical-application-of-scintillation-dosimetry-in-small-field-photon-beam-radiotherapy
#20
Elisa Burke, Daniela Poppinga, Andreas A Schönfeld, Dietrich Harder, Björn Poppe, Hui Khee Looe
Plastic scintillation detectors are a new instrument of stereotactic photon-beam dosimetry. The clinical application of the plastic scintillation detector Exradin W1 at the Siemens Artiste and Elekta Synergy accelerators is a matter of current interest. In order to reduce the measurement uncertainty, precautions have to be taken with regard to the geometrical arrangement of the scintillator, the light-guide fiber and the photodiode in the radiation field. To determine the "Cerenkov light ratio" CLR with a type A uncertainty below 1%, the Cerenkov calibration procedure for small-field measurements based on the two-channel spectral method was used...
March 22, 2017: Zeitschrift Für Medizinische Physik
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