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Zeitschrift Für Medizinische Physik

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
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
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
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
Thomas Schalch
No abstract text is available yet for this article.
April 27, 2017: Zeitschrift Für Medizinische Physik
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
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
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
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
Bozidar Casar, Marlies Pasler, Sonja Wegener, David Hoffman, Cinzia Talamonti, Jianguo Qian, Ignasi Mendez, Denis Brojan, Bruce Perrin, Martijn Kusters, Richard Canters, Stefania Pallotta, Primoz Peterlin
PURPOSE: The influence of the Integral Quality Monitor (IQM) transmission detector on photon beam properties was evaluated in a preclinical phase, using data from nine participating centres: (i) the change of beam quality (beam hardening), (ii) the influence on surface dose, and (iii) the attenuation of the IQM detector. METHODS: For 6 different nominal photon energies (4 standard, 2 FFF) and square field sizes from 1×1cm(2) to 20×20cm(2), the effect of IQM on beam quality was assessed from the PDD20,10 values obtained from the percentage dose depth (PDD) curves, measured with and without IQM in the beam path...
March 20, 2017: Zeitschrift Für Medizinische Physik
Fritz Schick
No abstract text is available yet for this article.
March 2017: Zeitschrift Für Medizinische Physik
Alexander Solle, Carsten Wanke, Lilli Geworski
Ga-68-labeled radiotracers, particularly used for the detection of neuroendocrine tumors by means of Ga-68-DOTA-TATE or -DOTA-TOC or for the diagnosis of prostate cancer by means of Ga-68-labeled antigens (Ga 68-PSMA), become increasingly important. In addition to the high sensitivity and specificity of these radiopharmaceuticals, the short-lived radionuclide Ga-68 offers almost ideal nuclear characteristics for use in PET. Ga-68 is obtained from a germanium-gallium-generator system, so that the availability of Ga-68-labeled radiotracers is independent of an on-site-cyclotron regardless of the short half-life of Ga-68 of about 68minutes...
March 2017: Zeitschrift Für Medizinische Physik
Manuela C Felix, Gerhard Glatting, Frank A Giordano, Marc A Brockmann, Frederik Wenz, Jens Fleckenstein
PURPOSE: In radiation therapy of small animals treatment depths range from a few millimetres to several centimetres. In order to spare surrounding organs at risk steep dose gradients are necessary. To minimize the treatment time, and therefore the strain to the animals, a high dose rate is required. A description how these parameters can be optimized through an appropriate choice of collimators with different source surface distances (SSD) as well as different materials and geometries is presented...
March 2017: Zeitschrift Für Medizinische Physik
Thorsten Frenzel, Michael Gerhard Kaul, Thomas Michael Ernst, Johannes Salamon, Maria Jäckel, Udo Schumacher, Andreas Krüll
AIMS: Radiotherapy of small laboratory animals (SLA) is often not as precisely applied as in humans. Here we describe the use of a dedicated SLA magnetic resonance imaging (MRI) scanner for precise tumor volumetry, radiotherapy treatment planning, and diagnostic imaging in order to make the experiments more accurate. METHODS AND MATERIALS: Different human cancer cells were injected at the lower trunk of pfp/rag2 and SCID mice to allow for local tumor growth. Data from cross sectional MRI scans were transferred to a clinical treatment planning system (TPS) for humans...
March 2017: Zeitschrift Für Medizinische Physik
Martin Kupper, Wolfgang Sprengel, Peter Winkler, Brigitte Zurl
In four-dimensional time-dependent computed tomography (4D-CT) of the lungs, irregularities in breathing movements can cause errors in data acquisition, or even data loss. We present a method based on sending a synthetic, regular breathing signal to the CT instead of the real signal, which ensures 4D-CT data sets without data loss. Subsequent correction of the signal based on the real breathing curve enables an accurate reconstruction of the size and movement of the target volume. This makes it possible to plan radiation treatment based on the obtained data...
March 2017: Zeitschrift Für Medizinische Physik
Fabian Zimmer, Sarah Klotz, Simone Hoeger, Benito A Yard, Bernhard K Krämer, Lothar R Schad, Frank G Zöllner
OBJECTIVES: To employ ASL for the measurement of renal cortical perfusion in particular renal disorders typically associated with graft loss and to investigate its potential to detect and differentiate the related functional deterioration i.e., in a setting of acute kidney injury (AKI) as well as in renal grafts showing acute and chronic transplant rejection. MATERIALS AND METHODS: 14 Lewis rats with unilateral ischaemic AKI and 43 Lewis rats with renal grafts showing acute or chronic rejections were used...
March 2017: Zeitschrift Für Medizinische Physik
Andrea Schwahofer, Harald Feist, Holger Georg, Peter Häring, Wolfgang Schlegel
The aim of this study has been the experimental determination of the energy dependent dose-to-water response of TLD600 and TLD700 thermoluminescent detectors (Harshaw) in X-ray beams with mean photon energies from about 20 to 200keV in comparison with (60)Co gamma rays and 6MV X-rays. Experiments were carried out in collaboration with the German secondary standard laboratory PTW Freiburg. The energy dependent relative responses of TLD600 and TLD700 thermoluminescence detectors were determined at radiation qualities between 30kVp and 280kVp...
March 2017: Zeitschrift Für Medizinische Physik
Daniela Thorwarth, Mike Notohamiprodjo, Daniel Zips, Arndt-Christan Müller
BACKGROUND: To increase tumour control probability (TCP) in prostate cancer a method was developed integrating multi-parametric functional and biological information into a dose painting treatment plan aiming focal dose-escalation to tumour sub-volumes. A dose-escalation map was derived considering individual, multi-parametric estimated tumour aggressiveness. METHODS AND MATERIALS: Multi-parametric functional imaging (MRI, Choline-/PSMA-/FMISO-PET/CT) was acquired for a high risk prostate cancer patient with a high level of tumour load (cT3b cN0 cM0) indicated by subtotal involvement of prostate including the right seminal vesicle and by PSA-level >100...
March 2017: Zeitschrift Für Medizinische Physik
Marius Treutwein, Lothar Schad
No abstract text is available yet for this article.
December 2016: Zeitschrift Für Medizinische Physik
Reinhard Rzanny, Norman Stutzig, Patrick Hiepe, Alexander Gussew, Hans-Alexander Thorhauer, Jürgen R Reichenbach
PURPOSE: The objective of the study was to investigate the reproducibility of exercise induced pH-heterogeneity by splitting of the inorganic phosphate (Pi) signal in the corresponding (31)P-MRS spectra and to compare results of this approach with other fiber-type related markers, like phosphocreatine/adenosine triphosphate (PCr/ATP) ratio, and PCr-recovery parameters. MATERIAL AND METHODS: Subjects (N=3) with different sportive background were tested in 10 test sessions separated by at least 3 days...
December 2016: Zeitschrift Für Medizinische Physik
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