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MV and KV dose

Dennis N Stanley, Karl Rasmussen, Neil Kirby, Nikos Papanikolaou, Alonso N Gutiérrez
INTRODUCTION: A robust image quality assurance and analysis methodology for image-guided localization systems is crucial to ensure the accurate localization and visualization of target tumors. In this study, the long-term stability of selected image parameters was assessed and evaluated for the cone-beam computed tomography (CBCT) mode, planar radiographic kV mode, and the radiographic MV mode of an Elekta VersaHD. MATERIALS AND METHODS: The CATPHAN, QckV-1, and QC-3 phantoms were used to evaluate the image quality parameters...
March 9, 2018: Journal of Applied Clinical Medical Physics
C Noblet, G Delpon, S Supiot, V Potiron, F Paris, S Chiavassa
BACKGROUND: In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Zeff ) affect the dose distribution...
February 26, 2018: Radiation Oncology
Suphalak Khachonkham, Ralf Dreindl, Gerd Heilemann, Wolfgang Lechner, Hermann Fuchs, Hugo Palmans, Dietmar Georg, Peter Kuess
Recently, a new type of radiochromic film, the EBT XD film, has been introduced for high dose radiotherapy. The EBT XD film contains the same structure as the EBT3 film but has a slightly different composition and a thinner active layer. This study benchmarks the EBT XD against EBT3 film for 6 MV and 10 MV photon beams, as well as for 97.4 MeV and 148.2 MeV proton beams and 15¬ 100 kV x-rays. Dosimetric and film reading characteristics, such as post irradiation darkening, film orientation effect, lateral response artifact (LRA), film sensitivity, energy and beam quality dependency were investigated...
February 23, 2018: Physics in Medicine and Biology
Christoph Straube, Markus Oechsner, Severin Kampfer, Sophia Scharl, Friederike Schmidt-Graf, Jan J Wilkens, Stephanie E Combs
BACKGROUND: Tumor-Treating Fields (TTFields) are a novel treatment strategy for glioblastoma (GBM) that is approved for the use concomitantly to adjuvant chemotherapy. Preclinical data suggest a synergistic interaction of TTFields and radiotherapy (RT). However, the dosimetric uncertainties caused by the highly dense arrays have led to caution of applying the TTF setup during RT. METHODS: In a RW3 slab phantom we compared the MV- and kV-CT based planned dose with the measured dose...
February 23, 2018: Radiation Oncology
George X Ding, Parham Alaei, Bruce Curran, Ryan Flynn, Michael Gossman, T Rock Mackie, Moyed Miften, Richard Morin, X George Xu, Timothy C Zhu
With radiotherapy having entered the era of image guidance, or image-guided radiation therapy (IGRT), imaging procedures are routinely performed for patient positioning and target localization. The imaging dose delivered may result in excessive dose to sensitive organs and potentially increase the chance of secondary cancers and, therefore, needs to be managed. This task group was charged with: a) providing an overview on imaging dose, including megavoltage electronic portal imaging (MV EPI), kilovoltage digital radiography (kV DR), Tomotherapy MV-CT, megavoltage cone-beam CT (MV-CBCT) and kilovoltage cone-beam CT (kV-CBCT), and b) providing general guidelines for commissioning dose calculation methods and managing imaging dose to patients...
February 22, 2018: Medical Physics
Eric Schnarr, Matt Beneke, Dylan Casey, Edward Chao, Jonathan Chappelow, Andrea Cox, Doug Henderson, Petr Jordan, Etienne Lessard, Dan Lucas, Andriy Myronenko, Calvin Maurer
PURPOSE: This study investigates the potential application of image-based motion tracking and real-time motion correction to a helical tomotherapy system. METHODS: A kV X ray imaging system was added to a helical tomotherapy system, mounted 90 degrees offset from the MV treatment beam, and an optical camera system was mounted above the foot of the couch. This experimental system tracks target motion by acquiring an X ray image every few seconds during gantry rotation...
February 5, 2018: Medical Physics
James A Swinscoe, Colleen I Dickie, Rob H Ireland
Radiation therapy for limb-extremity soft tissue sarcoma (STS) requires accurate, reproducible dose delivery. However, patient positioning is challenging and there is a lack of existing guidelines to assist institutional standardization. Therefore, we conducted a multi-institutional international survey of STS immobilization, image guidance methods, and treatment protocols to investigate current practice. Seventy-three UK radiotherapy centers and 15 hospitals in 7 other countries completed a questionnaire on STS immobilization and image-guidance procedures...
January 17, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
Yue-Houng Hu, Joerg Rottmann, Rony Fueglistaller, Marios Myronakis, Adam Wang, Pascal Huber, Daniel Shedlock, Daniel Morf, Paul Baturin, Josh Star-Lack, Ross Berbeco
While megavoltage cone-beam computed tomography (CBCT) using an electronic portal imaging device (EPID) provides many advantages over kilovoltage (kV) CBCT, clinical adoption is limited by its high doses. Multi-layer imager (MLI) EPIDs increase DQE(0) while maintaining high resolution. However, even well-designed, high-performance MLIs suffer from increased electronic noise from each readout, degrading low-dose image quality. To improve low-dose performance, shift-and-bin addition (ShiBA) imaging is proposed, leveraging the unique architecture of the MLI...
January 30, 2018: Physics in Medicine and Biology
Héctor Mauricio Garnica-Garza
PURPOSE: To demonstrate, via Monte Carlo simulation, that an image obtained from the patient-generated scattered radiation forced to impinge on the detector from a known direction by means of parallel-focused grids, can be used to complement the information conveyed by the primary image, such that accurate stereoscopic three-dimensional localization of fiducial markers can be achieved in a single kV x-ray exposure. METHODS: A voxelized Zubal phantom was used to model the process of fiducial marker localization...
February 2018: Medical Physics
Yannick Poirier, Svetlana Kuznetsova, Jose Eduardo Villarreal-Barajas
PURPOSE: To investigate empirically the energy dependence of the detector response of two in-vivo luminescence detectors, LiF:Mg,Cu,P (MCP-N) high-sensitivity TLDs and Al2 O3 :C OSLDs, in the 40-300-kVp energy range in the context of in-vivo surface dose measurement. As these detectors become more prevalent in clinical and pre-clinical in-vivo measurements, knowledge of the variation of the empirical dependence of the measured response of these detectors across a wide spectrum of beam qualities is important...
November 22, 2017: Medical Physics
Anna Arns, Manuel Blessing, Jens Fleckenstein, Dzmitry Stsepankou, Judit Boda-Heggemann, Juergen Hesser, Frank Lohr, Frederik Wenz, Hansjoerg Wertz
PURPOSE: Combined ultrafast 90°+90° kV-MV-CBCT within single breath-hold of 15s has high clinical potential for accelerating imaging for lung cancer patients treated with deep inspiration breath-hold (DIBH). For clinical feasibility of kV-MV-CBCT, dose exposure has to be small compared to prescribed dose. In this study, kV-MV dose output is evaluated and compared to clinically-established kV-CBCT. METHODS: Accurate dose calibration was performed for kV and MV energy; beam quality was determined...
2017: PloS One
Yawei Zhang, Xinchen Deng, Fang-Fang Yin, Lei Ren
PURPOSE: Limited-angle intrafraction verification (LIVE) has been previously developed for four-dimensional (4D) intrafraction target verification either during arc delivery or between three-dimensional (3D)/IMRT beams. Preliminary studies showed that LIVE can accurately estimate the target volume using kV/MV projections acquired over orthogonal view 30° scan angles. Currently, the LIVE imaging acquisition requires slow gantry rotation and is not clinically optimized. The goal of this study is to optimize the image acquisition parameters of LIVE for different patient respiratory periods and gantry rotation speeds for the effective clinical implementation of the system...
January 2018: Medical Physics
Dylan Y Breitkreutz, Michael D Weil, Sergei Zavgorodni, Magdalena Bazalova-Carter
PURPOSE: To determine the most suitable lesion size and depth for radiotherapy treatments with a prototype kilovoltage x-ray arc therapy (KVAT) system through Monte Carlo simulations of the dose delivered to lesion, dose homogeneity, and lesion-to-skin ratio. METHODS: Monte Carlo simulations were used to calculate dose distributions generated by a novel low-energy kilovoltage x-ray system to a variety of clinically relevant lesion sizes and depths in phantoms and for hypothetical partial breast irradiations of patients in supine and prone positions...
December 2017: Medical Physics
Bo Liu, Piotr Zygmanski, Erno Sajo
PURPOSE: We investigate the potential of the recently introduced high-energy current (HEC) thin-film detector as an alternative design to existing electronic portal imaging devices (EPID). The HEC radiation detectors employ multiple nano-/micrometer layers made of disparate atomic number (Z) conductors separated by solid or gaseous (e.g., air) dielectrics. The HEC detector may be designed as an external structure or an auxiliary device integrated into the existing EPID. METHOD: Using Geant4 Monte Carlo simulations, we compare the image contrast of a HEC detector to that of a commercial EPID device (AS500) for a 2...
December 2017: Medical Physics
Brita Singers Sørensen, Niels Bassler, Steffen Nielsen, Michael R Horsman, Leszek Grzanka, Harald Spejlborg, Jan Swakoń, Paweł Olko, Jens Overgaard
INTRODUCTION: The aim of the present study was to examine the RBE for early damage in an in vivo mouse model, and the effect of the increased linear energy transfer (LET) towards the distal edge of the spread-out Bragg peak (SOBP). METHOD: The lower part of the right hind limb of CDF1 mice was irradiated with single fractions of either 6 MV photons, 240 kV photons or scanning beam protons and graded doses were applied. For the proton irradiation, the leg was either placed in the middle of a 30-mm SOBP, or to assess the effect in different positions, irradiated in 4 mm intervals from the middle of the SOBP to behind the distal dose fall-off...
November 2017: Acta Oncologica
Dousatsu Sakata, Akihiro Haga, Satoshi Kida, Toshikazu Imae, Shigeharu Takenaka, Keiichi Nakagawa
Dual-energy computed tomography (DECT) imaging can measure the effective atomic number (EAN) as well as the electron density, and thus its adoption may improve dose calculations in brachytherapy and external photon/particle therapy. An expanded energy gap in dual-energy sources is expected to yield more accurate EAN estimations than conventional DECT systems, which typically span less than 100kV. The aim of this paper is to assess a larger energy gap DECT by using a linear accelerator (LINAC) radiotherapy system with a kV X-ray imaging device, which are combined to provide X-rays in both the kV- and MV-energy ranges...
July 2017: Physica Medica: PM
Michael Martyn, Tuathan P O'Shea, Emma Harris, Jeffrey Bamber, Stephen Gilroy, Mark J Foley
PURPOSE: The aim of this study was to estimate changes in surface dose due to the presence of the Clarity Autoscan™ ultrasound (US) probe during prostate radiotherapy using Monte Carlo (MC) methods. METHODS: MC models of the Autoscan US probe were developed using the BEAMnrc/DOSXYZnrc code based on kV and MV CT images. CT datasets were converted to voxelized mass density phantoms using a CT number-to-mass density calibration. The dosimetric effect of the probe, in the contact region (an 8 mm × 12 mm single layer of voxels), was investigated using a phantom set-up mimicking two scenarios (a) a transperineal imaging configuration (radiation beam perpendicular to the central US axial direction), and (b) a transabdominal imaging configuration (radiation beam parallel to the central US axial direction)...
October 2017: Medical Physics
Yan-Fei Qian, Yang Wang, Wei-Wei Tian, Sheng Wang, Lei Zhao, Li Li, Ke-Tao Ma, Jun-Qiang Si
The current study observed the effects and investigated the mechanism of remifentanil (RMF) on the isolated cerebral basilar arteries of spontaneously hypertensive rats (SHR) and Wistar‑Kyoto (WKY) rats. A pressure myograph system was used to observe and compare the effects of different concentrations of RMF (10‑10‑10‑5 mol/l) on the diameter changes of freshly isolated cerebral basilar arteries, which have been pre‑shrunk by phenylephrine (PE), an endothelium‑independent vasoconstrictor. Vascular smooth‑muscle cells of the cerebral basilar artery (BASMCs) were freshly obtained via enzymolysis...
September 2017: Molecular Medicine Reports
Malak Soueid, Martinus C F Dobbelaar, Sabrina Bentouati, Sylvia M Bardet, Rodney P O'Connor, Delphine Bessières, Jean Paillol, Philippe Leveque, Delia Arnaud-Cormos
In this paper, delivery devices for nanosecond pulsed electric field exposure of biological samples in direct contact with electrodes or isolated are presented and characterized. They are based on a modified electroporation cuvette and two transverse electromagnetic cells (TEM cells). The devices were used to apply pulses with high intensity (4.5 kV) and short durations (3 and 13 ns). The delivery devices were electromagnetically characterized in the frequency and time domains. Field intensities of around 5, 0...
July 4, 2017: Medical & Biological Engineering & Computing
J-H Kim, D T Nguyen, C-Y Huang, T Fuangrod, V Caillet, R O'Brien, P Poulsen, J Booth, P Keall
Target rotation can considerably impact the delivered radiotherapy dose depending on the tumour shape. More accurate tumour pose during radiotherapy treatment can be acquired through tracking in 6 degrees-of-freedom (6 DoF) rather than in translation only. A novel real-time 6 DoF kilovoltage intrafraction monitoring (KIM) target tracking system has recently been developed. In this study, we experimentally evaluated the accuracy and precision of the 6 DoF KIM implementation. Real-time 6 DoF KIM motion measurements were compared against the ground truth motion retrospectively derived from kV/MV triangulation for a range of lung and prostate tumour motion trajectories as well as for various static poses using a phantom...
June 23, 2017: Physics in Medicine and Biology
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