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https://www.readbyqxmd.com/read/28212708/development-and-performance-evaluation-of-a-three-dimensional-clinostat-synchronized-heavy-ion-irradiation-system
#1
Hiroko Ikeda, Hikaru Souda, Anggraeini Puspitasari, Kathryn D Held, Jun Hidema, Takeshi Nikawa, Yukari Yoshida, Tatsuaki Kanai, Akihisa Takahashi
Outer space is an environment characterized by microgravity and space radiation, including high-energy charged particles. Astronauts are constantly exposed to both microgravity and radiation during long-term stays in space. However, many aspects of the biological effects of combined microgravity and space radiation remain unclear. We developed a new three-dimensional (3D) clinostat synchronized heavy-ion irradiation system for use in ground-based studies of the combined exposures. Our new system uses a particle accelerator and a respiratory gating system from heavy-ion radiotherapy to irradiate samples being rotated in the 3D clinostat with carbon-ion beams only when the samples are in the horizontal position...
February 2017: Life Sciences in Space Research
https://www.readbyqxmd.com/read/28196271/dose-distribution-at-the-bragg-peak-dose-measurements-using-ebt-and-rtqa-gafchromic-film-set-at-two-positions-to-the-central-beam-axis
#2
Borowicz Dorota Maria, Malicki Julian, Mytsin Gennady, Shipulin Konstantin
AIM: To evaluate the impact of radiochromic film positioning relative to the central beam axis (CAX) in proton beam therapy. Secondarily, to compare the dosimetric measurements obtained by RTQA and EBT film and to compare these to the doses calculated by the treatment planning system (TPS). METHODS: EBT and RTQA dosimetric radiochromic films were immersed in a water phantom and irradiated with a proton beam. The films were placed parallel to the CAX and at a 5º angle on the horizontal plane to assess the effect of film inclination on Bragg peak profiles...
February 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28144120/simplified-method-for-creating-a-density-absorbed-dose-calibration-curve-for-the-low-dose-range-from-gafchromic-ebt3-film
#3
Tatsuhiro Gotanda, Toshizo Katsuda, Rumi Gotanda, Tadao Kuwano, Takuya Akagawa, Nobuyoshi Tanki, Akihiko Tabuchi, Tetsunori Shimono, Yasuyuki Kawaji
Radiochromic film dosimeters have a disadvantage in comparison with an ionization chamber in that the dosimetry process is time-consuming for creating a density-absorbed dose calibration curve. The purpose of this study was the development of a simplified method of creating a density-absorbed dose calibration curve from radiochromic film within a short time. This simplified method was performed using Gafchromic EBT3 film with a low energy dependence and step-shaped Al filter. The simplified method was compared with the standard method...
October 2016: Journal of Medical Physics
https://www.readbyqxmd.com/read/28102956/experimental-verification-of-4d-monte-carlo-simulations-of-dose-delivery-to-a-moving-anatomy
#4
Sara Gholampourkashi, Miro Vujicic, Jason Belec, Joanna E Cygler, Emily Heath
PURPOSE: To evaluate a novel 4D Monte Carlo simulation tool by comparing calculations to physical measurements using a respiratory motion phantom. METHODS: We used a dynamic Quasar phantom in both stationary and breathing states (sinusoidal motion of amplitude of 1.8 cm and period of 3.3 s) for dose measurements on an Elekta Agility linear accelerator. Gafchromic EBT3 film and the RADPOS 4D dosimetry system were placed inside the lung insert of the phantom to measure dose profiles and point-dose values at the center of the spherical tumor inside the insert...
January 2017: Medical Physics
https://www.readbyqxmd.com/read/28102944/a-simple-and-robust-trajectory-based-stereotactic-radiosurgery-treatment
#5
Byron Wilson, Karl Otto, Ermias Gete
INTRODUCTION: We present a Trajectory-based Volumetric Modulated Arc Therapy (TVMAT) technique for Stereotactic Radiosurgery (SRS) that takes advantage of a modern linacs ability to modulate dose rate and move the couch dynamically. In addition, we investigate the quality of the developed TVMAT method and the dosimetric accuracy of the technique. METHODS: The main feature of the TVMAT technique is a standard beam trajectory formed by dynamic motion of the treatment couch and the linac gantry...
January 2017: Medical Physics
https://www.readbyqxmd.com/read/28094853/high-dose-per-pulse-electron-beam-dosimetry-a-model-to-correct-for-the-ion-recombination-in-the-advanced-markus-ionization-chamber
#6
Kristoffer Petersson, Maud Jaccard, Jean-François Germond, Thierry Buchillier, François Bochud, Jean Bourhis, Marie-Catherine Vozenin, Claude Bailat
PURPOSE: The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semi-empirical general equation presented by Burns and McEwen. METHODS: Two independent methods were used to investigate the ion recombination: 1) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD)...
January 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28048877/su-g-brb-08-investigation-on-the-magnetic-field-effect-on-tlds-oslds-and-gafchromic-films-using-an-mr-linac
#7
Z Wen, J Wang, W Jiang, D O'Brien, G Sawakuchi, G Ibbott
PURPOSE: To investigate whether a strong magnetic field (B=1.5 T) can affect dose responses of thermoluminescent dosimeters (TLDs), optically stimulated luminescence dosimeters (OSLDs) and Gafchromic films using an MR-Linac (Elekta) before and after the magnet was ramped down from 1.5 T to 0 T. METHODS: Three types of dosimeters (TLDs, OSLDs, EBT3 films) were divided into two groups. Group 1 was first irradiated in a phantom of Solid Water slabs (Standard Imaging) inside a B=1...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048873/su-f-t-32-evaluation-of-the-performance-of-a-multiple-array-diode-detector-for-quality-assurance-tests-in-high-dose-rate-brachytherapy-with-ir-192-source
#8
K Harpool, T De La Fuente Herman, S Ahmad, I Ali
PURPOSE: To evaluate the performance of a two-dimensional (2D) array-diode- detector for geometric and dosimetric quality assurance (QA) tests of high-dose-rate (HDR) brachytherapy with an Ir-192-source. METHODS: A phantom setup was designed that encapsulated a two-dimensional (2D) array-diode-detector (MapCheck2) and a catheter for the HDR brachytherapy Ir-192 source. This setup was used to perform both geometric and dosimetric quality assurance for the HDR-Ir192 source...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048811/su-g-tep4-15-the-roucoulette-a-set-of-quality-control-tests-for-dynamic-trajectory-4pi-treatment-delivery-techniques
#9
T Teke
PURPOSE: To present and validate a set of quality control tests for trajectory treatment delivery using synchronized dynamic couch (translation and rotation), MLC and collimator motion. METHODS: The quality control tests are based on the Picket fence test, which consist of 5 narrow band 2mm width spaced at 2.5cm intervals, and adds progressively synchronized dynamic motions. The tests were exposed on GafChromic EBT3 films. The first test is a regular (no motion and MLC static while beam is on) Picket Fence test used as baseline...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048740/su-f-t-07-dosimetric-impact-of-the-dwell-position-inaccuracy-in-hdr-ring-and-tandem-treatments-with-varisourceix-afterloader
#10
I Veltchev, R Price, P Anderson, C Ma
PURPOSE: The dwell positions in the VariSourceIX HDR ring applicator are known to be somewhat inaccurate with observed deviations from the planned position of up to 5mm. The details of how to correct this issue are suggested by the vendor and the dosimetric impact on volumetric HDR plans varies from patient to patient. In this study we present our experience with correcting this issue, and discuss the impact on plan quality if the planned dwell positions were left unchanged. METHODS: A 60 degree ring was characterized using gafchromic film with the applicator in treatment orientation...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048729/su-f-t-219-verification-of-the-accuracy-of-a-relative-stopping-power-rsp-to-hounsfield-unit-hu-calibration-curve-produced-for-proton-treatment-planning-using-ebt3-gafchromic-film-dosimetry
#11
E Schnell, C Ferreira, S Ahmad, T De La Fuente Herman
PURPOSE: Accuracy of a RSP-HU calibration curve produced for proton treatment planning is tested by comparing the treatment planning system dose grid to physical doses delivered on film by a Mevion S250 double-scattering proton unit. METHODS: A single batch of EBT3 Gafchromic film was used for calibration and measurements. The film calibration curve was obtained using Mevion proton beam reference option 20 (15cm range, 10cm modulation). Paired films were positioned at the center of the spread out Bragg peak (SOBP) in solid water...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048695/su-f-t-86-electron-dosimetric-effects-of-bolus-and-lens-shielding-in-treating-superficial-eye-lesions
#12
L Young, L Wootton, O Gopan, J Liao
PURPOSE: Electron therapy for the treatment of ocular lymphomas requires the lens to be shielded to prevent secondary cataracts. This work evaluates the dosimetry under a suspended eyeshield with and without bolus for low energy electron fields. METHODS: Film (GafChromic EBT3) dosimetry and relative output factors were measured for 6, 8, and 10 MeV electron energies. A customized 5 cm diameter circle electron orbital cutout was constructed for a 6×6 cm applicator with a lens shield, 1 cm diameter Cerrobend cylinder with 2...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048645/su-f-t-404-dosimetric-advantages-of-flattening-free-beams-to-prone-accelerated-partial-breast-irradiation
#13
P Galavis, D Barbee, G Jozsef
PURPOSE: Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk. METHODS: Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re-planned in Eclipse-TPS using FFF beams...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048622/su-f-t-173-one-scan-protocol-verifying-the-delivery-of-spot-scanning-proton-beam
#14
M Chan, C Chen, J Li, X Tang, X Li, G Tang, D Mah
PURPOSE: Radiochromic film for spot-scanning QA provides high spatial resolution and efficiency gains from one-shot irradiation for multiple depths. However, calibration can be a tedious procedure which may limit widespread use. Moreover, since there may be an energy dependence, which manifests as a depth dependence, this may require additional measurements for each patient. We present a one-scan protocol to simplify the procedure. METHODS: We performed the calibration using an EBT3 film at depths of 18, 20, 24cm of Plastic Water exposed by a 6-level step-wedge plan on a Proteus Plus proton system (IBA, Belgium)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048481/su-f-t-562-validation-of-epid-based-dosimetry-for-fsrs-commissioning
#15
Y Song, Z Saleh, C Obcemea, M Chan, X Tang, S Lim, D Lovelock, A Ballangrud, B Mueller, M Zinovoy, D Gelblum, B Mychalczak, S Both
PURPOSE: The prevailing approach to frameless SRS (fSRS) small field dosimetry is Gafchromic film. Though providing continuous information, its intrinsic uncertainties in fabrication, response, scan, and calibration often make film dosimetry subject to different interpretations. In this study, we explored the feasibility of using EPID portal dosimetry as a viable alternative to film for small field dosimetry. METHODS: Plans prescribed a dose of 21 Gy were created on a flat solid water phantom with Eclipse V11 and iPlan for small static square fields (1...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048443/su-g-201-06-directional-low-dose-rate-brachytherapy-determination-of-the-tg-43-dose-rate-constant-analog-for-a-new-pd-103-source
#16
M Aima, W Culberson, C Hammer, J Micka, L DeWerd
PURPOSE: The aim of this work is to determine the TG-43 dose-rate constant analog for a new directional low-dose rate brachytherapy source based on experimental methods and comparison to Monte Carlo simulations. The CivaSheet™ is a new commercially available planar source array comprised of a variable number of discrete directional source elements called "CivaDots". Given the directional nature and non-conventional design of the source, modifications to the AAPM TG-43 protocol for dosimetry are required...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048441/su-f-t-506-development-and-commissioning-of-the-effective-and-efficient-grid-therapy-using-high-dose-rate-flattening-filter-free-beam-and-multileaf-collimator
#17
M Liu, N Wen, C Beyer, F Siddiqui, I Chetty, B Zhao
PURPOSE: Treating bulky tumors with grid therapy (GT) has demonstrated high response rates. Long delivery time (∼15min), with consequent increased risk of intrafraction motion, is a major disadvantage of conventional MLC-based GT (MLC-GT). The goal of this study was to develop and commission a MLC-GT technique with similar dosimetric characteristics, but more efficient delivery. METHODS: Grid plan was designed with 10X-FFF (2400MU/min) beam and MLC in a commercial treatment planning system (TPS)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048402/su-f-t-569-implementation-of-a-patient-specific-qa-method-using-ebt-xd-for-cyberknife-srs-sbrt-plans
#18
K Zerouali, J Aubry, R Doucet
PURPOSE: To implement the new EBT-XD Gafchromic films for accurate dosimetric and geometric validation of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) CyberKnife (CK) patient specific QA. METHODS: Film calibration was performed using a triplechannel film analysis on an Epson 10000XL scanner. Calibration films were irradiated using a Varian Clinac 21EX flattened beam (0 to 20 Gy), to ensure sufficient dose homogeneity. Films were scanned to a resolution of 0...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048385/su-g-brc-07-evaluation-of-aaa-focal-spot-size-for-srs-planning-using-end-to-end-dosimetric-data
#19
S Gardner, A Doemer, B Miller, N Wen, I Chetty
PURPOSE: To use end-to-end dosimetric measurements with Gafchromic film to evaluate the effects of focal spot size parameter for small-field dose calculations using AAA for SRS lesions. METHODS: A total of 13 plans, corresponding to 7 patients previously treated with cranial SRS, were analyzed in this study (target volume range:[0.67cc,13.9cc]). The plans included DCA delivery (4 plans total) and VMAT delivery (9 plans total). All plans were mapped to a solid water phantom (15 cm thickness; isocenter and film plane at 7...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048359/su-f-j-121-dosimetric-evaluation-of-active-breathing-coordinator-response-gating-system-linked-to-linear-accelerator-in-volumetric-modulated-arc-therapy
#20
S Lee, Y Zheng, D Albani, V Colussi, J Dorth, J Sohn
PURPOSE: To reduce internal target volume (ITV), respiratory management is a must in imaging and treatment for lung, liver, and breast cancers. We investigated the dosimetric accuracy of VMAT treatment delivery with a Response™ gating system linked to linear accelerator. METHODS: The Response™ gating module designed to directly control radiation beam by breath-holding with a ABC system (Elekta AB, Stockholm, Sweden) was tested for VMAT treatments. Seven VMAT plans including three conventional and four stereotactic body radiotherapy (SBRT) cases were evaluated...
June 2016: Medical Physics
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