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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
Sarah Ghandour, Adrien Cosinschi, Zohra Mazouni, Marc Pachoud, Oscar Matzinger
PURPOSE: To provide high-quality and efficient dosimetric planning for various types of stereotactic body radiotherapy (SBRT) for tumor treatment using a multicriteria optimization (MCO) technique fine-tuned with direct machine parameter optimization (DMPO). METHODS AND MATERIALS: Eighteen patients with lung (n=11), liver (n=5) or adrenal cell cancer (n=2) were treated using SBRT in our clinic between December 2014 and June 2015. Plans were generated using the RayStation™ Treatment Planning System (TPS) with the VMAT technique...
December 2016: Zeitschrift Für Medizinische Physik
Yvonne Dzierma, Frank Nuesken, Norbert Licht, Christian Rübe
PURPOSE: The mARC technique is a hybrid rotational IMRT modality operating in "burst mode". While it is generally assumed that it will be slower than VMAT, the real limits of operation have not been defined so far. We here present the first systematic study of the technical limits on mARC treatment. METHODS: The following scenarios are considered: 18, 30, 36 or 45 arclets per rotation (spacing between 20° and 8°), flat and flattening-filter-free (FFF) energy, arclet width 4° or 2°, from 1 MU/arclet to 1000 MU/plan...
December 2016: Zeitschrift Für Medizinische Physik
Willem Grootjans, Antoi P W Meeuwis, Cornelis H Slump, Lioe-Fee de Geus-Oei, Martin Gotthardt, Eric P Visser
PURPOSE: Low count single photon emission computed tomography (SPECT) is becoming more important in view of whole body SPECT and reduction of radiation dose. In this study, we investigated the performance of several 3D ordered subset expectation maximization (3DOSEM) and maximum a posteriori (MAP) algorithms for reconstructing low count SPECT images. MATERIALS AND METHODS: Phantom experiments were conducted using the National Electrical Manufacturers Association (NEMA) NU2 image quality (IQ) phantom...
December 2016: Zeitschrift Für Medizinische Physik
Claudia Hagelstein, Thomas Henzler, Holger Haubenreisser, Mathias Meyer, Sonja Sudarski, Stefan O Schoenberg, K Wolfgang Neff, Meike Weis
PURPOSE: Minimizing radiation dose while at the same time preserving image quality is of particular importance in pediatric chest CT. Very recently, CT imaging with a tube voltage of 70 kVp has become clinically available. However, image noise is inversely proportional to the tube voltage. We aimed to investigate radiation dose and image quality of pediatric chest CT performed at 70 kVp in an anthropomorphic pediatric phantom as well as in clinical patients. METHODS AND MATERIALS: An anthropomorphic pediatric phantom, which resembles a one-year-old child in physiognomy, was scanned on the 3(rd) generation dual-source CT (DSCT) system at 70 kVp and 80 kVp and a fixed ultra low tube-current of 8 mAs to solely evaluate the impact of lowering tube voltage...
December 2016: Zeitschrift Für Medizinische Physik
Bastian Szermerski, Iris Bruchmann, Rolf Behrens, Lilli Geworski
According to recent studies, the human eye lens is more sensitive to ionising radiation than previously assumed. Therefore, the dose limit for personnel occupationally exposed to ionising radiation will be lowered from currently 150 mSv to 20 mSv per year. Currently, no data base for a reliable estimation of the dose to the lens of the eye is available for nuclear medicine. Furthermore, the dose is usually not monitored. The aim of this work was to determine dose rate constants for the quantity Hp(3), which is supposed to estimate the dose to the lens of the eye...
December 2016: Zeitschrift Für Medizinische Physik
Iris Bruchmann, Bastian Szermerski, Rolf Behrens, Lilli Geworski
The human eye lens appears to be more radiosensitive than previously assumed. The reduction of the limit for the dose to the lens of the eye to 20 mSv per year has been passed in the current Euratom Directives (2013). Therefore, in this work the impact of laboratory glasses and X-ray protective goggles was investigated and reciprocal attenuation factors (i.e. transmission factors) for different nuclides (Tc-99m, I-131, Y-90, F-18 and Ga-68) were determined. The radionuclides in typical geometry (syringe, applicator) were positioned at a distance of 50 cm to the eyes of four Alderson-Head-Phantoms...
December 2016: Zeitschrift Für Medizinische Physik
Evelyn Bohrer, Stefan Schäfer, Ulf Mäder, Peter B Noël, Gabriele A Krombach, Martin Fiebich
INTRODUCTION: The trend towards submillisievert CT scans leads to a higher dose fraction of localizer radiographs in CT examinations. The already existing technical capabilities make dose optimization of localizer radiographs worthwhile. Modern CT scanners apply automatic exposure control (AEC) based on attenuation data in such a localizer. Therefore not only this aspect but also the detectability of anatomical landmarks in the localizer for the desired CT scan range adjustment needs to be considered...
October 6, 2016: Zeitschrift Für Medizinische Physik
Wiebke Neumann, Florian Lietzmann, Lothar R Schad, Frank G Zöllner
OBJECTIVES: This work proposes a modular, anthropomorphic MR and CT thorax phantom that enables the comparison of experimental studies for quantitative evaluation of deformable, multimodal image registration algorithms and realistic multi-nuclear MR imaging techniques. METHODS: A human thorax phantom was developed with insertable modules representing lung, liver, ribs and additional tracking spheres. The quality of human tissue mimicking characteristics was evaluated for (1)H and (23)Na MR as well as CT imaging...
September 2, 2016: Zeitschrift Für Medizinische Physik
Thomas Flohr
No abstract text is available yet for this article.
September 2016: Zeitschrift Für Medizinische Physik
Michael Schwerter, Florian Lietzmann, Lothar R Schad
Minimally invasive interventions are frequently aided by 2D projective image guidance. To facilitate the navigation of medical tools within the patient, information from preoperative 3D images can supplement interventional data. This work describes a novel approach to perform a 3D CT data registration to a single interventional native fluoroscopic frame. The goal of this procedure is to recover and visualize a current 2D interventional tool position in its corresponding 3D dataset. A dedicated routine was developed and tested on a phantom...
September 2016: Zeitschrift Für Medizinische Physik
Alexander Gerbershagen, David Meer, Jacobus Maarten Schippers, Mike Seidel
PURPOSE: A first order design of the beam optics of a superconducting proton therapy gantry beam is presented. The possibilities of superconducting magnets with respect to the beam optics such as strong fields, large apertures and superposition of different multipole fields have been exploited for novel concepts in a gantry. Since various techniques used in existing gantries have been used in our first design steps, some examples of the existing superconducting gantry designs are described and the necessary requirements of such a gantry are explained...
September 2016: Zeitschrift Für Medizinische Physik
Eckhart Fröhlich, Juliane Hofmann, Ines Debove, Christoph F Dietrich, Hans Kaarmann, Jan Pauluschke-Fröhlich, Stefan Schmidt, Reinhold Muller
AIM: To replace pictograms with pictocam pictures: A prospective blinded quality improvement study in documenting image orientation and localisation in abdominal ultrasound imaging. MATERIALS AND METHODS: A minicam was mounted on the ultrasound scanhead to record pictocam pictures. The primary examiner produced an ultrasound image together with the routinely embedded pictogram. Subsequently the pictogram was covered by the synchronically taken pictocam picture. Subsequently, the primary examiner assessed the pictograms and the second examiner the pictocam pictures (blinded to the pictogram findings of the primary examiner)...
September 2016: Zeitschrift Für Medizinische Physik
Joachim H X Schrauth, Gunthard Lykowsky, Kathrin Hemberger, Jakob Kreutner, Daniel Weber, Lars Rackwitz, Ulrich Nöth, Peter M Jakob, Daniel Haddad
RATIONALE AND OBJECTIVES: Osteoarthritis (OA) is a degenerative joint disease leading to cartilage deterioration by loss of matrix, fibrillation, formation of fissures, and ultimately complete loss of the cartilage surface. Here, three magnetic resonance imaging (MRI) techniques, dGEMRIC (delayed Gadolinium enhanced MRI of cartilage; dG1=T1,post; dG2=1/T1,post-1/T1,pre), T1ρ,and sodium MRI, are compared in a preclinical in vivo study to evaluate the differences in their potential for cartilage characterization and to establish an examination protocol for a following clinical study...
September 2016: Zeitschrift Für Medizinische Physik
Franziska Renner
Monte Carlo simulations are regarded as the most accurate method of solving complex problems in the field of dosimetry and radiation transport. In (external) radiation therapy they are increasingly used for the calculation of dose distributions during treatment planning. In comparison to other algorithms for the calculation of dose distributions, Monte Carlo methods have the capability of improving the accuracy of dose calculations - especially under complex circumstances (e.g. consideration of inhomogeneities)...
September 2016: Zeitschrift Für Medizinische Physik
Ndimofor Chofor, Dietrich Harder, Hans-Joachim Selbach, Björn Poppe
The application of various radiation detectors for brachytherapy dosimetry has motivated this study of the energy dependence of radiation quality correction factor kQ,M, the quotient of the detector responses under calibration conditions at a (60)Co unit and under the given non-reference conditions at the point of measurement, M, occurring in photon brachytherapy. The investigated detectors comprise TLD, radiochromic film, ESR, Si diode, plastic scintillator and diamond crystal detectors as well as ionization chambers of various sizes, whose measured response-energy relationships, taken from the literature, served as input data...
September 2016: Zeitschrift Für Medizinische Physik
Johannes Thoelking, Yuvaraj Sekar, Jens Fleckenstein, Frank Lohr, Frederik Wenz, Hansjoerg Wertz
PURPOSE: Online verification and 3D dose reconstruction on daily patient anatomy have the potential to improve treatment delivery, accuracy and safety. One possible implementation is to recalculate dose based on online fluence measurements with a transmission detector (TD) attached to the linac. This study provides a detailed analysis of the influence of a new TD on treatment beam characteristics. METHODS: The influence of the new TD on surface dose was evaluated by measurements with an Advanced Markus Chamber (Adv-MC) in the build-up region...
September 2016: Zeitschrift Für Medizinische Physik
Verónica García-Vázquez, Eugenio Marinetto, Pedro Guerra, Manlio Fabio Valdivieso-Casique, Felipe Ángel Calvo, Eduardo Alvarado-Vásquez, Claudio Vicente Sole, Kirby Gannett Vosburgh, Manuel Desco, Javier Pascau
Intraoperative electron radiation therapy (IOERT) involves irradiation of an unresected tumour or a post-resection tumour bed. The dose distribution is calculated from a preoperative computed tomography (CT) study acquired using a CT simulator. However, differences between the actual IOERT field and that calculated from the preoperative study arise as a result of patient position, surgical access, tumour resection and the IOERT set-up. Intraoperative CT imaging may then enable a more accurate estimation of dose distribution...
August 23, 2016: Zeitschrift Für Medizinische Physik
Stephan Helmbrecht, Wolfgang Enghardt, Fine Fiedler, Marc Iltzsche, Guntram Pausch, Carlo Tintori, Thomas Kormoll
Positron emission tomography (PET) is a means of imaging the β(+)-activity produced by the radiation field in ion beam therapy and therefore for treatment verification. Prompt γ-rays that are emitted during beam application challenge the detectors and electronics of PET systems, since those are designed for low and medium count rates. Typical PET detectors operated according to a modified Anger principle suffer from multiple events at high rates. Therefore, in-beam PET systems using such detectors rely on a synchronization of beam status and measurement to reject deteriorated data...
August 20, 2016: Zeitschrift Für Medizinische Physik
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