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Zeitschrift Für Medizinische Physik

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https://www.readbyqxmd.com/read/29631759/dose-calculation-of-dynamic-trajectory-radiotherapy-using-monte-carlo
#1
P Manser, D Frauchiger, D Frei, W Volken, D Terribilini, M K Fix
PURPOSE: Using volumetric modulated arc therapy (VMAT) delivery technique gantry position, multi-leaf collimator (MLC) as well as dose rate change dynamically during the application. However, additional components can be dynamically altered throughout the dose delivery such as the collimator or the couch. Thus, the degrees of freedom increase allowing almost arbitrary dynamic trajectories for the beam. While the dose delivery of such dynamic trajectories for linear accelerators is technically possible, there is currently no dose calculation and validation tool available...
April 6, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29602589/adaptive-radiation-therapy
#2
EDITORIAL
Di Yan
No abstract text is available yet for this article.
March 27, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29580616/increasing-robustness-of-radial-grase-acquisition-for-sar-reduced-brain-imaging
#3
Melisa Okanovic, Michael Völker, Robert Trampel, Felix Breuer, Peter Jakob, Martin Blaimer
PURPOSE: To improve a radial multi-slice 2D gradient- and spin-echo (GRASE) sequence and provide an appropriate image reconstruction technique for SAR-reduced high-resolution neuroimaging. METHODS: Additional readout gradients per radio-frequency (RF) refocusing allow for a reduced number of RF pulses. In this way, a specific absorption rate (SAR) reduction is achieved and the application at high-field systems becomes more feasible. A phase insensitive image reconstruction is proposed to reduce signal dropout artifacts originating from opposite readout polarities...
March 23, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29550014/a-practical-implementation-of-physics-quality-assurance-for-photon-adaptive-radiotherapy
#4
Bin Cai, Olga L Green, Rojano Kashani, Vivian L Rodriguez, Sasa Mutic, Deshan Yang
The fast evolution of technology in radiotherapy (RT) enabled the realization of adaptive radiotherapy (ART). However, the new characteristics of ART pose unique challenges for efficiencies and effectiveness of quality assurance (QA) strategies. In this paper, we discuss the necessary QAs for ART and introduce a practical implementation. A previously published work on failure modes and effects analysis (FMEA) of ART is introduced first to explain the risks associated with ART sub-processes. After a brief discussion of QA challenges, we review the existing QA strategies and tools that might be suitable for each ART step...
March 14, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29548595/range-resolution-and-reproducibility-of-a-dedicated-phantom-for-proton-pbs-daily-quality-assurance
#5
Lorenzo Placidi, Michele Togno, Damien C Weber, Antony J Lomax, Jan Hrbacek
PURPOSE: Wedge phantoms coupled with a CCD camera are suggested as a simple means to improve the efficiency of quality assurance for pencil beam scanning (PBS) proton therapy, in particular to verify energy/range consistency on a daily basis. The method is based on the analysis of an integral image created by a pencil beam (PB) pattern delivered through a wedge. We have investigated the reproducibility of this method and its dependence on setup and positional beam errors for a commercially available phantom (Sphinx® , IBA Dosimetry) and CCD camera (Lynx® , IBA Dosimetry) system...
March 13, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29463428/swiss-survey-on-hybrid-imaging-cts-doses-in-nuclear-medicine-and-proposed-national-dose-reference-levels
#6
REVIEW
Thiago V M Lima, Silvano Gnesin, Nick Ryckx, Klaus Strobel, Nicolas Stritt, Reto Linder
A multidisciplinary working group led by the Swiss Federal Office of Public Health was formed to plan and perform a nationwide survey of patient radiation exposure from computed tomography (CT) in hybrid devices across Nuclear Medicine departments. The survey included 16 departments (of which 5 were university hospitals) and the submitted responses included 10,673 entries for the 33 different protocols proposed (11 in PET and 22 in SPECT). The working group determined the selection and exclusion criteria applied to the analysis...
February 17, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29439849/potential-of-metric-homotopy-between-intensity-and-geometry-information-for-multi-modal-3d-registration
#7
Daniel Glodeck, Jürgen Hesser, Lei Zheng
This paper focuses on a novel strategy increasing robustness with respect to local optima when using Mutual Information (MI) in multi-modal image registration. This is realized by integrating additional geometry information in the cost function. Hereby, the main innovation is a generalization of multi-metric registration approaches by means of a metric homotopy. Particularly we realize a method which automatically determines the parameters of the metric homotopy. To construct the cost function independent of the choice of the optimizer, the weighting is defined as a function of one of the metrics instead of optimizer steps...
February 10, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29429610/automated-ultrafast-kilovoltage-megavoltage-cone-beam-ct-for-image-guided-radiotherapy-of-lung-cancer-system-description-and-real-time-results
#8
Manuel Blessing, Anna Arns, Hansjoerg Wertz, Dzmitry Stsepankou, Judit Boda-Heggemann, Juergen Hesser, Frederik Wenz, Frank Lohr
PURPOSE: To establish a fully automated kV-MV CBCT imaging method on a clinical linear accelerator that allows image acquisition of thoracic targets for patient positioning within one breath-hold (∼15s) under realistic clinical conditions. METHODS AND MATERIALS: Our previously developed FPGA-based hardware unit which allows synchronized kV-MV CBCT projection acquisition is connected to a clinical linear accelerator system via a multi-pin switch; i.e. either kV-MV imaging or conventional clinical mode can be selected...
February 9, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29426589/determination-of-the-effective-dose-delivered-by-image-guided-radiotherapy-in-head-neck-and-breast-treatments
#9
Mireille Conrad, Grégory Bolard, Marie Nowak, Berardino De Bari, Wendy Jeanneret-Sozzi, Jean Bourhis, Jean-François Germond, François Bochud, Raphaël Moeckli
PURPOSE: Image guided radiotherapy (IGRT) improves patient positioning for treatment delivery at the cost of an additional dose. This work aimed to calculate the effective dose (as an indicator of dose) for head & neck (H&N) and breast IGRT treatments by implementing dose calculation models to determine the dose distributions. METHODS: The kV dose-models were created for the IGRT systems of Elekta Synergy (XVI) and Varian Clinac (OBI) linear accelerators within Philips Pinnacle TPS...
February 6, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29426588/-magnetic-resonance-imaging-beyond-the-proton-what-does-oxygen-17-mri-have-to-offer
#10
EDITORIAL
Michael Bock
No abstract text is available yet for this article.
February 6, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29373177/the-quest-for-higher-sensitivity-in-mri-through-higher-magnetic-fields
#11
EDITORIAL
Mark E Ladd
No abstract text is available yet for this article.
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29054678/excitation-characteristic-of-a-bipolar-stimulus-for-broadband-stimulation-in-measurements-of-electrically-evoked-auditory-potentials
#12
Oliver C Dziemba, Thomas Hocke, Alexander Müller, Holger Kaftan
OBJECTIVE: The aim of this study was to determine the optimum electrical stimulation mode for the measurement of electrically evoked potentials. To quantify the broadband excitation electrically evoked compound action potentials were recorded in cochlear implant recipients. The full width half maximum was determined for spread of excitation along the electrode array. DESIGN: Prospective clinical study. STUDY SAMPLE: The study sample consisted of 20 adult cochlear implant users...
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29033293/ct-and-mri-slice-separation-evaluation-by-labview-developed-software
#13
Giuseppe Acri, Barbara Testagrossa, Angela Sestito, Lilla Bonanno, Giuseppe Vermiglio
The efficient use of Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) equipment necessitates establishing adequate quality-control (QC) procedures. In particular, the accuracy of slice separation, during multislices acquisition, requires scan exploration of phantoms containing test objects. To simplify such procedures, a novel phantom and a computerised LabView-based procedure have been devised, enabling determination the midpoint of full width at half maximum (FWHM) in real time while the distance from the profile midpoint of two progressive images is evaluated and measured...
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28869162/a-novel-method-for-t2-quantification-in-presence-of-b1-inhomogeneities
#14
David Milford, Martin Bendszus, Sabine Heiland
INTRODUCTION: T2 relaxometry as a quantitative MRI technique offers a more precise characterization of tissue, compared with qualitative T2 weighted imaging. The issue, however, is that in typically used T2 relaxometry sequences such as a multi-spin echo sequences, incorrect refocussing flip angles and B1 inhomogeneities cause inaccuracies in T2 determination. The work presented here within presents a new technique for modelling T2 decay curves and thereby correcting T2 times altered by inhomogeneities...
February 2018: 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
#15
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...
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28601374/quantitative-susceptibility-mapping-qsm-and-r-2-in-the-human-brain-at-3t-evaluation-of-intra-scanner-repeatability
#16
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))...
February 2018: 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
#17
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...
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28532604/validation-of-dwi-pre-processing-procedures-for-reliable-differentiation-between-human-brain-gliomas
#18
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...
February 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29338903/clinical-workflow-optimization-to-improve-4dct-reconstruction-for-toshiba-aquilion-ct-scanners
#19
P Freislederer, C Heinz, H von Zimmermann, S Gerum, F Roeder, M Reiner, M Söhn, C Belka, K Parodi
Respiratory motion remains a source of major uncertainties in radiotherapy. Respiratory correlated computed tomography (referred to as 4DCT) serves as one way of reducing breathing artifacts in 3D-CTs and allows the investigation of tumor motion over time. The quality of the 4DCT images depends on the data acquisition scheme, which in turn is dependent on the vendor. Specifically, the only way Toshiba Aquilion LB CT scanners can reconstruct 4DCTs is a cycle-based reconstruction using triggers provided by an external surrogate signal...
January 12, 2018: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29336934/determination-of-recombination-and-polarity-correction-factors-k-s-and-k-p-for-small-cylindrical-ionization-chambers-ptw-31021-and-ptw-31022-in-pulsed-filtered-and-unfiltered-beams
#20
Gregor Bruggmoser, Rainer Saum, Rafael Kranzer
The aim of this technical communication is to provide correction factors for recombination and polarity effect for two new ionization chambers PTW PinPoint 3D (type 31022) and PTW Semiflex 3D (type 31021). The correction factors provided are for the (based on the) German DIN 6800-2 dosimetry protocol and the AAPM TG51 protocol. The measurements were made in filtered and unfiltered high-energy photon beams in a water equivalent phantom at maximum depth of the PDD and a field size on the surface of 10cm×10cm...
January 12, 2018: Zeitschrift Für Medizinische Physik
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