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Zeitschrift Für Medizinische Physik

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https://www.readbyqxmd.com/read/29033293/ct-and-mri-slice-separation-evaluation-by-labview-developed-software
#1
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...
October 13, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29033292/-dosimetric-verification-of-mammosite-treatment-plans-using-monte-carlo-simulations-and-measurements-with-a-2d-ionization-chamber-array
#2
Moritz Budde, Irenäus A Adamietz, Holger Sommer, Horst Hermani
The surgical removal of a breast tumour is often followed by postoperative irradiation of the surrounding tissue with a radioactive source (brachytherapy). When performing the MammoSite procedure, a spherical silicone balloon is inserted and filled with a NaCl solution. In a period of about five days in several sessions an iridium-192 source with high activity travels through a catheter into the balloon (afterloading) to irradiate the tumour cells remaining in the cavity. In this study, dose distributions of a MammoSite applicator are investigated based on measurements with a 2D detector array, Monte Carlo simulations and calculations with BrachyVision...
October 12, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29031916/image-guided-adaptive-external-beam-radiation-therapy-for-cervix-cancer-evaluation-of-a-clinically-implemented-plan-of-the-day-technique
#3
Martin Buschmann, Katarina Majercakova, Alina Sturdza, Stephanie Smet, Dina Najjari, Michaela Daniel, Richard Pötter, Dietmar Georg, Yvette Seppenwoolde
BACKGROUND: Radiotherapy for cervix cancer is challenging in patients exhibiting large daily changes in the pelvic anatomy, therefore adaptive treatments (ART) have been proposed. The aim of this study was the clinical implementation and subsequent evaluation of plan-of-the-day (POTD)-ART for cervix cancer in supine positioning. The described workflow was based on standard commercial equipment and current quality assurance (QA) methods. MATERIALS AND METHODS: A POTD strategy, which employs a VMAT plan library consisting of an empty bladder plan, a full bladder plan and a motion robust backup plan, was developed...
October 11, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29031915/experimental-and-monte-carlo-based-determination-of-the-beam-quality-specifier-for-tomotherapyhd-treatment-units
#4
S Howitz, M Schwedas, T Wiezorek, K Zink
Reference dosimetry by means of clinical linear accelerators in high-energy photon fields requires the determination of the beam quality specifier TPR20,10, which characterizes the relative particle flux density of the photon beam. The measurement of TPR20,10 has to be performed in homogenous photon beams of size 10×10cm(2) with a focus-detector distance of 100cm. These requirements cannot be fulfilled by TomoTherapy treatment units from Accuray. The TomoTherapy unit provides a flattening-filter-free photon fan beam with a maximum field width of 40cm and field lengths of 1...
October 11, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/29030203/characterization-and-clinical-evaluation-of-a-novel-2d-detector-array-for-conventional-and-flattening-filter-free-fff-imrt-pre-treatment-verification
#5
Yuvaraj Sekar, Johannes Thoelking, Miriam Eckl, Irakli Kalichava, Dwi Seno Kuncoro Sihono, Frank Lohr, Frederik Wenz, Hansjoerg Wertz
BACKGROUND AND PURPOSE: The novel MatriXX(FFF) (IBA Dosimetry, Germany) detector is a new 2D ionization chamber detector array designed for patient specific IMRT-plan verification including flattening-filter-free (FFF) beams. This study provides a detailed analysis of the characterization and clinical evaluation of the new detector array. MATERIAL AND METHODS: The verification of the MatriXX(FFF) was subdivided into (i) physical dosimetric tests including dose linearity, dose rate dependency and output factor measurements and (ii) patient specific IMRT pre-treatment plan verifications...
October 10, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28969957/reference-conditions-for-ion-chamber-based-hdr-brachytherapy-dosimetry-and-for-the-calibration-of-high-resolution-solid-detectors
#6
Andreas A Schoenfeld, Katrin Büsing, Björn Delfs, Ndimofor Chofor, Ping Jiang, Dietrich Harder, Björn Poppe, Kay C Willborn
The aim of this study has been to develop a two-step method of in-phantom dosimetry around a brachytherapy (192)Ir photon source. The first step is to measure the absorbed dose rate to water with a calibrated ionization chamber under reference conditions, the second to cross-calibrate, under these conditions, small solid-state detectors such as silicon diodes, synthetic diamond or scintillation detectors suited for spatially resolved dose rate measurements at other, particularly at smaller source axis distances in the water phantom...
September 29, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28939288/pet-mr-hybrid-imaging
#7
EDITORIAL
Harald H Quick
No abstract text is available yet for this article.
September 19, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28869164/the-output-factor-correction-as-function-of-the-photon-beam-field-size-direct-measurement-and-calculation-from-the-lateral-dose-response-functions-of-gas-filled-and-solid-detectors
#8
Daniela Poppinga, Björn Delfs, Jutta Meyners, Dietrich Harder, Björn Poppe, Hui Khee Looe
The first aim of this study has been to extend the systematic experimental study of the field size dependence of the output factor correction for three micro-ionization chambers (PTW 31014, PTW 31022 and IBA Razor chamber), two silicon diodes (PTW 60017 and IBA Razor Diode) and the synthetic diamond detector microDiamond (PTW 60019) in a 6 MV photon beam down to an effective field side length of 2.6mm, and to summarize the present knowledge of this factor by treating it as a function of the dosimetric field size...
August 28, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28869163/biologically-adapted-radiation-therapy
#9
Daniela Thorwarth
The aim of biologically adapted radiotherapy (RT) is to shape or paint the prescribed radiation dose according to biological properties of the tumor in order to increase local control rates in the future. Human tumors are known to present with an extremely heterogeneous tissue architecture leading to highly variable local cell densities and chaotic vascular structures leading to tumor hypoxia and regions of increased radiation resistance. The goal of biologically adapted RT or dose painting is to individually adapt the radiation dose to biological features of the tumor as non-invasively assessed with functional imaging in order to overcome increased radiation resistance...
August 28, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28869162/a-novel-method-for-t2-quantification-in-presence-of-b1-inhomogeneities
#10
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...
August 28, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28843397/experimental-validation-of-a-4d-dose-calculation-routine-for-pencil-beam-scanning-proton-therapy
#11
T Pfeiler, C Bäumer, E Engwall, D Geismar, B Spaan, B Timmermann
Respiratory induced organ motion poses a major challenge for high-precision radiotherapy such as pencil beam scanning proton therapy (PBS). In order to employ PBS for target regions affected by respiratory motion, the implementation of dedicated motion mitigation techniques should be considered and residual uncertainties need to be assessed. For the latter purpose, a routine simulating the delivery of a scanned proton beam to a moving target was developed and implemented in the commercial treatment planning system RayStation...
August 23, 2017: Zeitschrift Für Medizinische Physik
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
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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