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https://www.readbyqxmd.com/read/29204169/independent-assessment-of-source-position-for-gynecological-applicator-in-high-dose-rate-brachytherapy
#1
Hiroyuki Okamoto, Satoshi Nakamura, Shie Nishioka, Kotaro Iijima, Akihisa Wakita, Yukinao Abe, Naoki Tohyama, Shinji Kawamura, Toshiyuki Minemura, Jun Itami
Purpose: The aim of this study is to describe a phantom designed for independent examination of a source position in brachytherapy that is suitable for inclusion in an external auditing program. Material and methods: We developed a phantom that has a special design and a simple mechanism, capable of firmly fixing a radiochromic film and tandem-ovoid applicators to assess discrepancies in source positions between the measurements and treatment planning system (TPS)...
October 2017: Journal of Contemporary Brachytherapy
https://www.readbyqxmd.com/read/29176074/validation-and-uncertainty-analysis-of-a-pre-treatment-2d-dose-prediction-model
#2
Jose A Baeza, Cecile J A Wolfs, Sebastiaan M J J G Nijsten, Frank Verhaegen
Independent verification of complex treatment delivery with megavolt photon beam radiotherapy (RT) has been effectively used to detect and prevent errors. This work presents the validation and uncertainty analysis of a model that predicts 2D portal dose images without a patient or phantom in the beam. The prediction model is based on an exponential point dose model with separable primary and secondary photon fluence components. The model includes a scatter kernel, off-axis ratio map, transmission values and penumbra kernels for beam-delimiting components...
November 26, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29173922/on-the-re-calibration-process-in-radiochromic-film-dosimetry
#3
Carmen Ruiz-Morales, Juan Antonio Vera-Sánchez, Antonio González-López
PURPOSE: The accuracy and precision of the dose estimates obtained with radiochromic film dosimetry are investigated in a clinical environment. The improvement in the accuracy of dose estimates reached with corrective methods is analyzed. Two novel re-calibration algorithms for radiochromic film dosimetry are presented. METHODS: Two different EBT3 lots are evaluated in two different centres. They are calibrated in Varian linacs and read in two different EPSON scaners...
October 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/29173920/evaluation-and-clinical-implementation-of-in-vivo-dosimetry-for-kv-radiotherapy-using-radiochromic-film-and-micro-silica-bead-thermoluminescent-detectors
#4
Antony L Palmer, Shakardokht M Jafari, Ioanna Mone, Sarah Muscat
PURPOSE: kV radiotherapy treatment calculations are based on flat, homogenous, full-scatter reference conditions. However, clinical treatments often include surface irregularities and inhomogeneities, causing uncertainty. Therefore, confirmation of actual delivered doses in vivo is valuable. The current study evaluates, and implements, radiochromic film and micro silica bead TLD for in vivo kV dosimetry. METHODS: The kV energy and dose response of EBT3 film and silica bead TLD was established and uncertainty budgets determined...
October 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/29164628/technical-note-response-time-evolution-of-xr-qa2-gafchromic-tm-film-models
#5
Saad Aldelaijan, Nada Tomic, Pavlos Papaconstadopoulos, James Schneider, Jan Seuntjens, Shelley Shih, David Lewis, Slobodan Devic
PURPOSE: To evaluate the response of the newest XR-QA2 GafChromic(™) film model in terms of post-exposure signal growth and energy response in comparison with the older XR-QA (Version 2) model. METHODS: Pieces of film were irradiated to air kerma in air values up to 12 cGy with several beam qualities (5.3-8.25 mm Al) commonly used for CT scanning. Film response was scored in terms of net reflectance from scanned film images at various points in time post-irradiation ranging from 1 to 7 days and 5 months post exposure...
November 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/29159807/experimental-investigation-of-gafchromic-%C3%A2-ebt3-intrinsic-energy-dependence-with-kilovoltage-x-rays-137-cs-and-60-co
#6
Cliff G Hammer, Benjamin Saul Rosen, Jessica M Fagerstrom, Wesley S Culberson, Larry A DeWerd
PURPOSE: To determine experimentally the intrinsic energy response, kbq , of EBT3 GafChromic(®) radiochromic film with kilovoltage x-rays,(137) Cs, and (60) Co in therapeutic and diagnostic dose ranges through direct measurement with an accompanying mathematical approach to describe the physical processes involved. METHODS: EBT3 film was irradiated to known doses using (60) Co, (137) Cs, and 13 NIST-matched kilovoltage x-ray beams. Seven dose levels, ranging from 57 to 7002 mGy, were chosen for this work...
November 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/29155691/magnetic-fields-are-causing-small-but-significant-changes-of-the-radiochromic-ebt3-film-response-to-6-mv-photons
#7
Bjoern Delfs, Andreas Alexander Schoenfeld, Daniela Poppinga, Ralf-Peter Kapsch, Ping Jiang, Dietrich Harder, Bjoern Poppe, Hui Khee Looe
The optical density (OD) of EBT3 radiochromic exposed to absorbed doses to water up to D = 20 Gy in magnetic fields of B = 0.35 and 1.42 T was measured in three colour channels. A 7 cm wide water phantom with fixed film holder was placed in magnetic fields and was irradiated by a 6 MV photon beam whose axis was directed at right angles with the field lines. The doses at the film position at water depth 5 cm were measured with a calibrated ionization chamber when the magnet was switched off and were converted to the doses in presence of the magnetic field via the monitor units and by a Monte Carlo-calculated correction accounting for the slight change of the depth dose curves in magnetic fields...
November 20, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29125832/minibeam-radiotherapy-with-small-animal-irradiators-in-vitro-and-in-vivo-feasibility-studies
#8
Soha Bazyar, Christina R Inscoe, E Timothy O'Brian, Otto Zhou, Yueh Z Lee
Minibeam radiation therapy (MBRT) delivers an ultrahigh dose of x-ray (⩾100 Gy) in 200-1000 µm beams (peaks), separated by wider non-irradiated regions (valleys) usually as a single temporal fraction. Preclinical studies performed at synchrotron facilities revealed that MBRT is able to ablate tumors while maintaining normal tissue integrity. The main purpose of the present study was to develop an efficient and accessible method to perform MBRT using a conventional x-ray irradiator. We then tested this new method both in vitro and in vivo...
November 10, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29102741/physics-aspects-of-the-papillon-technique-five-decades-later
#9
Li Heng Liang, Nada Tomic, Te Vuong, Saad Aldelaijan, Hamed Bekerat, Francois DeBlois, Jan Seuntjens, Slobodan Devic
PURPOSE: The Papillon technique using 50-kVp soft X-rays to treat rectal adenocarcinomas was developed and clinically implemented in the 1960s. We describe differences between accurate dosimetry and clinical implementation of this technique that is extending from its very inception to date. METHODS AND MATERIALS: A renaissance of the Papillon technique occurred with two recently introduced 50-kVp systems: Papillon+ by Ariane and a custom-made rectal applicator (consisting of a surface applicator inserted into a proctoscope) by iCAD's Xoft Axxent Electronic Brachytherapy (eBT) System (iCad, Inc...
November 1, 2017: Brachytherapy
https://www.readbyqxmd.com/read/29091588/the-incidence-of-the-different-sources-of-noise-on-the-uncertainty-in-radiochromic-film-dosimetry-using-single-channel-and-multichannel-methods
#10
Antonio González-López, Juan Antonio Vera-Sánchez, Carmen Ruiz-Morales
The influence of the various sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Pieces of an RCF were each irradiated to different uniform doses, ranging from 0 to 1092 cGy. Then, the pieces were read at two resolutions (72 and 150 ppp) with two flatbed scanners: Epson 10000XL and Epson V800, representing two states of technology...
November 1, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/29037776/a-multicentre-end-to-end-dosimetry-audit-of-motion-management-4dct-defined-motion-envelope-in-radiotherapy
#11
Antony L Palmer, David Nash, John R Kearton, Shakardokht M Jafari, Sarah Muscat
PURPOSE: External dosimetry audit is valuable for the assurance of radiotherapy quality. However, motion management has not been rigorously audited, despite its complexity and importance for accuracy. We describe the first end-to-end dosimetry audit for non-SABR (stereotactic ablative body radiotherapy) lung treatments, measuring dose accumulation in a moving target, and assessing adequacy of target dose coverage. MATERIALS AND METHODS: A respiratory motion lung-phantom with custom-designed insert was used...
October 13, 2017: Radiotherapy and Oncology: Journal of the European Society for Therapeutic Radiology and Oncology
https://www.readbyqxmd.com/read/29033210/measurements-of-air-kerma-index-in-computed-tomography-a-comparison-among-methodologies
#12
Thêssa C Alonso, Arnaldo P Mourão Filho, Teógenes A Da Silva
As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. In this work, dosimetry in CT beams was carried out in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber, thermoluminescent (TL) detectors and radiochromic film. Calibration results showed the low energy dependence of all three dosimetric systems for the 100-120kV range, the very high uncertainty of the TL dosimeters in comparison to the other systems and high nonlinearity response in terms of air kerma of the radiochromic film...
October 5, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28994669/minibeam-radiotherapy-with-small-animal-irradiators-i-in-vitro-i-and-i-in-vivo-i-feasibility-studies
#13
Soha Bazyar, Christina R Inscoe, E Timothy O'Brien Iii, Otto Z Zhou, Yueh Z Lee
Minibeam radiation therapy (MBRT) delivers ultrahigh dose of X-ray (≥100 Gy) in 200-1000 μm beams (peaks), separated by wider non-irradiated regions (valleys) usually as a single temporal fraction. Preclinical studies performed at synchrotron facilities revealed that MBRT is able to ablate tumors while maintaining normal tissue integrity. The main purpose of present study was to develop an efficient and accessible method to perform MBRT using a conventional X-ray irradiator. We then tested this new method both in-vitro and in-vivo...
October 10, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28974858/volumetric-modulated-arc-therapy-lung-stereotactic-body-radiation-therapy-dosimetric-quality-assurance-a-comparison-between-radiochromic-film-and-chamber-array
#14
Juan Fernando Mata Colodro, Alfredo Serna Berná, Vicente Puchades Puchades, David Ramos Amores, Miguel Alcaraz Baños
INTRODUCTION: The aim of this work is to verify the use of radiochromic film in the quality assurance (QA) of volumetric-modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT) plans and compare the results with those obtained using an ion chamber array. MATERIALS AND METHODS: QA was performed for 14 plans using a two-dimensional-array seven29 and EBT3 film. Dose values per session ranged between 7.5 Gy and 18 Gy. The multichannel method was used to obtain a dose map for film...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28952964/incidence-of-the-different-sources-of-noise-on-the-uncertainty-in-radiochromic-film-dosimetry-using-single-channel-and-multichannel-methods
#15
Antonio Gonzalez-Lopez, Juan Antonio Vera-Sánchez, Carmen Ruiz-Morales
The incidence of the different sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Different pieces of a RCF were irradiated to uniform doses ranging from 0 to 1092 cGy. Then, the pieces were read at two resolutions (72 and 150 ppp) with two flatbed scanners: Epson 10000XL and Epson V800, representing two states of technology...
September 27, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28916952/air-electron-stream-interactions-during-magnetic-resonance-igrt-skin-irradiation-outside-the-treatment-field-during-accelerated-partial-breast-irradiation
#16
Jong Min Park, Kyung Hwan Shin, Jung-In Kim, So-Yeon Park, Seung Hyuck Jeon, Noorie Choi, Jin Ho Kim, Hong-Gyun Wu
PURPOSE: To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). MATERIALS AND METHODS: In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system)...
September 15, 2017: Strahlentherapie und Onkologie: Organ der Deutschen Röntgengesellschaft ... [et Al]
https://www.readbyqxmd.com/read/28915893/dosimetric-comparison-of-different-treatment-modalities-for-stereotactic-radiotherapy
#17
Shih-Ming Hsu, Yuan-Chun Lai, Chien-Chung Jeng, Chia-Ying Tseng
BACKGROUND: The modalities for performing stereotactic radiotherapy (SRT) on the brain include the cone-based linear accelerator (linac), the flattening filter-free (FFF) volumetric modulated arc therapy (VMAT) linac, and tomotherapy. In this study, the cone-based linac, FFF-VMAT linac, and tomotherapy modalities were evaluated by measuring the differences in doses delivered during brain SRT and experimentally assessing the accuracy of the output radiation doses through clinical measurements...
September 16, 2017: Radiation Oncology
https://www.readbyqxmd.com/read/28887825/performance-of-a-multi-leaf-collimator-system-for-mr-guided-radiation-therapy
#18
Bin Cai, Harold Li, Deshan Yang, Vivian Rodriguez, Austen Curcuru, Yuhe Wang, Jie Wen, Rojano Kashani, Sasa Mutic, Olga Green
PURPOSE: The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. METHODS: The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films...
September 9, 2017: Medical Physics
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
#19
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/28827006/intraoperative-implantation-of-a-mesh-of-directional-palladium-sources-civasheet-dosimetry-verification-clinical-commissioning-dose-specification-and-preliminary-experience
#20
Gil'ad N Cohen, Karen Episcopia, Seng-Boh Lim, Thomas J LoSasso, Mark J Rivard, Amandeep S Taggar, Neil K Taunk, Abraham J Wu, Antonio L Damato
PURPOSE: To present the clinical commissioning of a novel (103)Pd directional brachytherapy device (CivaSheet) for intraoperative radiation therapy. METHODS AND MATERIALS: Clinical commissioning for the CivaSheet consisted of establishing: (1) source strength calibration capabilities, (2) experimental verification of TG-43 dosimetry parameters, (3) treatment planning system validation, and (4) departmental practice for dose specification and source ordering. Experimental verification was performed in water with radiochromic film calibrated with a 37 kVp X-ray beam...
August 18, 2017: Brachytherapy
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