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Khan AU, Simiele EA, Lotey R, DeWerd LA, Yadav P. Development and evaluation of a GEANT4-based Monte Carlo Model of a 0.35 T MR-guided radiation therapy (MRgRT) linear accelerator. Med Phys 2021; 48:1967-1982. [PMID: 33555052 PMCID: PMC8251819 DOI: 10.1002/mp.14761] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 01/05/2021] [Accepted: 02/02/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The aim of this work was to develop and benchmark a magnetic resonance (MR)-guided linear accelerator head model using the GEANT4 Monte Carlo (MC) code. The validated model was compared to the treatment planning system (TPS) and was also used to quantify the electron return effect (ERE) at a lung-water interface. METHODS The average energy, including the spread in the energy distribution, and the radial intensity distribution of the incident electron beam were iteratively optimized in order to match the simulated beam profiles and percent depth dose (PDD) data to measured data. The GEANT4 MC model was then compared to the TPS model using several photon beam tests including oblique beams, an off-axis aperture, and heterogeneous phantoms. The benchmarked MC model was utilized to compute output factors (OFs) with the 0.35 T magnetic field turned on and off. The ERE was quantified at a lung-water interface by simulating PDD curves with and without the magnetic field for 6.6 × 6.6 cm 2 and 2.5 × 2.5 cm 2 field sizes. A 2%/2 mm gamma criterion was used to compare the MC model with the TPS data throughout this study. RESULTS The final incident electron beam parameters were 6.0 MeV average energy with a 1.5 MeV full width at half maximum (FWHM) Gaussian energy spread and a 1.0 mm FWHM Gaussian radial intensity distribution. The MC-simulated OFs were found to be in agreement with the TPS-calculated and measured OFs, and no statistical difference was observed between the 0.35 T and 0.0 T OFs. Good agreement was observed between the TPS-calculated and MC-simulated data for the photon beam tests with gamma pass rates ranging from 96% to 100%. An increase of 4.3% in the ERE was observed for the 6.6 × 6.6 cm 2 field size relative to the 2.5 × 2.5 cm 2 field size. The ratio of the 0.35 T PDD to the 0.0 T PDD was found to be up to 1.098 near lung-water interfaces for the 6.6 × 6.6 cm 2 field size using the MC model. CONCLUSIONS A vendor-independent Monte Carlo model has been developed and benchmarked for a 0.35 T/6 MV MR-linac. Good agreement was obtained between the GEANT4 and TPS models except near heterogeneity interfaces.
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Khan AU, DeWerd LA. A Monte Carlo Investigation of Dose Point Kernel Scaling for α-Emitting Radionuclides. Cancer Biother Radiopharm 2020; 36:252-259. [PMID: 33337280 DOI: 10.1089/cbr.2020.4542] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Background: Density-based dose point kernel (DPK) scaling accuracy was investigated in various homogeneous tissue media. Methods: Using GEometry ANd Tracking 4 Monte Carlo code, DPKs were generated for 5, 8 MeV monoenergetic α particles and 223Ra, 225Ac, and 227Th. Dose was scored in 1 μm thick concentric shells and DPKs were scaled based on the tissue's mass density and compared with the water DPK. Results: Scaled kernels agreed within ±5% except near the Bragg peaks, where they differed up to 25%. Conclusions: The authors conclude that kernel scaling based on mass density of the transport medium can be utilized accurately up to 5%, excluding Bragg peak regions.
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Walter AE, Hansen JB, DeWerd LA. Evaluation of ionization chamber stability checks using various sources. Phys Med 2020; 80:327-334. [DOI: 10.1016/j.ejmp.2020.11.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 09/30/2020] [Accepted: 11/07/2020] [Indexed: 10/22/2022] Open
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Khan AU, Culberson WS, DeWerd LA. Characterizing a PTW microDiamond detector in kilovoltage radiation beams. Med Phys 2020; 47:4553-4562. [DOI: 10.1002/mp.14330] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 05/12/2020] [Accepted: 06/08/2020] [Indexed: 12/16/2022] Open
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Smith BR, DeWerd LA, Culberson WS. On the stability of well‐type ionization chamber source strength calibration coefficients. Med Phys 2020; 47:4491-4501. [DOI: 10.1002/mp.14247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 04/26/2020] [Accepted: 05/06/2020] [Indexed: 11/09/2022] Open
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Desai VK, Labby ZE, DeWerd LA, Culberson WS. On the implementation of the plan‐class specific reference field using multidimensional clustering of plan features and alternative strategies for improved dosimetry in modulated clinical linear accelerator treatments. Med Phys 2020; 47:3621-3635. [DOI: 10.1002/mp.14207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/14/2020] [Accepted: 04/20/2020] [Indexed: 11/08/2022] Open
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DiMaso LD, Miller JR, Lawless MJ, Bassetti MF, DeWerd LA, Huang J. Investigating split-filter dual-energy CT for improving liver tumor visibility for radiation therapy. J Appl Clin Med Phys 2020; 21:249-255. [PMID: 32410336 PMCID: PMC7484851 DOI: 10.1002/acm2.12904] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 01/20/2020] [Accepted: 04/16/2020] [Indexed: 11/17/2022] Open
Abstract
Purpose Accurate liver tumor delineation is crucial for radiation therapy, but liver tumor volumes are difficult to visualize with conventional single‐energy CT. This work investigates the use of split‐filter dual‐energy CT (DECT) for liver tumor visibility by quantifying contrast and contrast‐to‐noise ratio (CNR). Methods Split‐filter DECT contrast‐enhanced scans of 20 liver tumors including cholangiocarcinomas, hepatocellular carcinomas, and liver metastases were acquired. Analysis was performed on the arterial and venous phases of mixed 120 kVp‐equivalent images and VMIs at 57 keV and 40 keV gross target volume (GTV) contrast and CNR were calculated. Results For the arterial phase, liver GTV contrast was 12.1 ± 10.0 HU and 43.1 ± 32.3 HU (P < 0.001) for the mixed images and 40 keV VMIs. Image noise increased on average by 116% for the 40 keV VMIs compared to the mixed images. The average CNR did not change significantly (1.6 ± 1.5, 1.7 ± 1.4, 2.4 ± 1.7 for the mixed, 57 keV and 40 keV VMIs (P > 0.141)). For individual cases, however, CNR increases of up to 607% were measured for the 40 keV VMIs compared to the mixed image. Venous phase 40 keV VMIs demonstrated an average increase of 35.4 HU in GTV contrast and 121% increase in image noise. Average CNR values were also not statistically different, but for individual cases CNR increases of up to 554% were measured for the 40 keV VMIs compared to the mixed image. Conclusions Liver tumor contrast was significantly improved using split‐filter DECT 40 keV VMIs compared to mixed images. On average, there was no statistical difference in CNR between the mixed images and VMIs, but for individual cases, CNR was greatly increased for the 57 keV and 40 keV VMIs. Therefore, although not universally successful for our patient cohort, split‐filter DECT VMIs may provide substantial gains in tumor visibility of certain liver cases for radiation therapy treatment planning.
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Fru LC, Jacques SL, Nickel KP, Varghese T, Kissick MW, DeWerd LA, Kimple RJ. Interstitial diffuse optical probe with spectral fitting to measure dynamic tumor hypoxia. Biomed Phys Eng Express 2020; 6. [PMID: 32095273 DOI: 10.1088/2057-1976/ab6e16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Understanding the dynamic nature of tumor hypoxia is vital for cancer therapy. The presence of oxygen within a tumor during radiation therapy increases the likelihood of local control. We used a novel interstitial diffuse optical probe to make real-time measurements of blood volume fraction and hemoglobin oxygen saturation within a tumor at a high temporal resolution. This device was initially characterized and benchmarked using a customized vessel designed to control hemoglobin oxygen saturation and blood volume in a solution of blood with different concentrations of an oxygen scavenger, tetrakis (hydroxymethyl) phosphonium chloride. The optical device was found to consistently monitor the changes in oxygen saturation and these changes correlated to the concentration of the oxygen scavenger added. In near-simultaneous measurements of blood volume and oxygen saturation in tumor-bearing mice, the changes in blood volume fraction and oxygen saturation measured with the interstitial diffuse optical probe were benchmarked against photoacoustic imaging system to track and compare temporal dynamics of oxygen saturation and blood volume in a patient-derived xenograft model of hypopharyngeal carcinoma. Positive correlations between our device and photoacoustic imaging in measuring blood volume and oxygen saturation were observed.
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Kry SF, Alvarez P, Cygler JE, DeWerd LA, Howell RM, Meeks S, O'Daniel J, Reft C, Sawakuchi G, Yukihara EG, Mihailidis D. AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs. Med Phys 2019; 47:e19-e51. [DOI: 10.1002/mp.13839] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 12/20/2022] Open
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Smith BR, Pankuch M, Hammer CG, DeWerd LA, Culberson WS. LET response variability of Gafchromic TM EBT3 film from a 60 Co calibration in clinical proton beam qualities. Med Phys 2019; 46:2716-2728. [PMID: 30740699 DOI: 10.1002/mp.13442] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 11/01/2019] [Accepted: 02/02/2019] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To establish a method of accurate dosimetry required to quantify the expected linear energy transfer (LET) quenching effect of EBT3 film used to benchmark the dose distribution for a given treatment field and specified measurement depth. In order to facilitate this technique, a full analysis of film calibration which considers LET variability at the plane of measurement and as a function of proton beam quality is demonstrated. Additionally, the corresponding uncertainty from the process was quantified for several measurement scenarios. MATERIALS AND METHODS The net change in optical density (OD) from a single version of Gafchromic TM EBT3 film was measured using an Epson flatbed scanner and NIST-traceable OD filters. Film OD response was characterized with respect to the known dose to water at the point of measurement for both a NIST-traceable 60 Co beam at the UWADCL and several clinical single-energy and spread-out Bragg peak (SOBP) proton beam qualities at the Northwestern Medicine Chicago Proton Center. Increasing proton LET environments were acquired by placing film at increasing depths of Gammex HE Solid Water® whose water-equivalent thickness was characterized prior to measurement. RESULTS A strong LET dependence was observed near the Bragg peak (BP) consistent with previous studies performed with earlier versions of EBT3 film. The influence of range straggling on the film's LET response appears to have a uniform effect toward the BP regardless of the nominal beam energy. Proximal to this depth, the film's response decreased with decreasing energy at the same dose-average LET. The opposite trend was observed for depths past the BP. Changes in the SOBP energy modulation showed a linear relationship between the film's relative response and dose-averaged LET. Relative effectiveness factors (RE) were observed to range between 2%-7% depending on the width of the SOBP and depth of the film. Using the field-specific calibration technique, a total k = 1 uncertainty in the absorbed dose to water was estimated to range from 4.68%-5.21%. CONCLUSION While EBT3 film's strong LET dependence is a common problem in proton beam dosimetry, this work has shown that the LET dependence can be taken into account by carefully considering the depth and energy modulation across the film using field-specific corrections. RE factors were determined with a combined k = 1 uncertainty of 3.57% for SOBP environments and between 3.17%-4.69% for uniform, monoenergetic fields proximal to the distal 80% of the BP.
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Hansen JB, Culberson WS, DeWerd LA. A convex windowless extrapolation chamber to measure surface dose rate from 106 Ru/ 106 Rh episcleral plaques. Med Phys 2019; 46:2430-2443. [PMID: 30873611 DOI: 10.1002/mp.13488] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/19/2019] [Accepted: 02/28/2019] [Indexed: 11/08/2022] Open
Abstract
PURPOSE A convex windowless extrapolation chamber was developed as a primary measurement device to determine surface dose rate from curved 106 Ru/106 Rh episcleral plaques. METHODS A convex extrapolation chamber without an entrance window was constructed for this work, and surface dose rate measurements were performed with two curved CCB-type 106 Ru/106 Rh plaques (S/N 2545 and 2596) manufactured by Eckert & Ziegler BEBIG. FARO ® Gage measurements were performed to verify the radius of curvature for the convex electrode and the concave plaque surface. Furthermore, the collecting electrode area was verified through capacitance measurements. Chamber correction factors for divergence and backscatter were generated using the EGSnrc cavity user code. For each source, surface dose rate was measured with the convex extrapolation chamber and compared with on-contact measurements made with curved un-laminated EBT3 film strips. A Monte Carlo correction was generated for radiochromic film measurements to account for volume averaging within the active layer and effects of phantom scatter. Additionally, extrapolation chamber results for each plaque were compared with scintillation detector measurements performed by the manufacturer. For the second source (S/N 2596), a comparison was also made with the Monte Carlo-corrected surface dose rate measured at the National Physical Laboratory (NPL) using cylindrical alanine pellets. Finally, source measurements were performed using conventional ionization chambers (Exradin A26, A1SL, and A20) within a custom fixture to investigate the transfer of extrapolation chamber surface dose rate to clinics. RESULTS For the first 106 Ru/106 Rh plaque (S/N 2545), average surface dose rate from the convex windowless extrapolation chamber was found to be 1.5% higher than the corresponding value from curved un-laminated EBT3 film measurements and 5.6% lower than the manufacturer value. For the second source (S/N 2596), the extrapolation chamber surface dose rate was 2.5% higher than the un-laminated EBT3 film result, 4.5% lower than the manufacturer value, and 3.9% higher compared to corrected alanine measurements made at NPL. Total uncertainty in the extrapolation chamber measurement was estimated to be approximately ± 7.0% (k = 2). For the plaque measurements made using conventional ionization chambers with a custom fixture, surface dose rate from the transfer technique was found to agree within 3.8% with the expected convex extrapolation chamber result for S/N 2596. CONCLUSIONS A convex windowless extrapolation chamber was developed as a primary measurement device for 106 Ru/106 Rh plaques. Through comparison with the extrapolation chamber, the accuracy of surface dose rate measurements from current dosimetry techniques was assessed and agreement was seen within 5.6%. Finally, it was found that conventional ionization chambers could be calibrated with a reference 106 Ru/106 Rh plaque in order to transfer the extrapolation chamber result for surface dose rate to clinics.
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Hansen JB, Culberson WS, DeWerd LA. Surface dose rate from a flat 106Ru/106Rh episcleral plaque measured with a planar windowless extrapolation chamber and un-laminated EBT3 film. RADIAT MEAS 2019. [DOI: 10.1016/j.radmeas.2018.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Desai VK, Labby ZE, Hyun MA, DeWerd LA, Culberson WS. VMAT and IMRT plan‐specific correction factors for linac‐based ionization chamber dosimetry. Med Phys 2018; 46:913-924. [DOI: 10.1002/mp.13293] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 11/07/2022] Open
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Fagerstrom JM, DeWerd LA, Palmer B, Culberson WS. Prototype modulated orthovoltage stereotactic radiosurgery cones. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2018.09.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Lawless MJ, Dimaso L, Palmer B, Micka J, Culberson WS, DeWerd LA. Monte Carlo and60Co‐based kilovoltage x‐ray dosimetry methods. Med Phys 2018; 45:5564-5576. [DOI: 10.1002/mp.13213] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 09/07/2018] [Accepted: 09/07/2018] [Indexed: 11/08/2022] Open
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Di Maso LD, Huang J, Bassetti MF, DeWerd LA, Miller JR. Investigating a novel split-filter dual-energy CT technique for improving pancreas tumor visibility for radiation therapy. J Appl Clin Med Phys 2018; 19:676-683. [PMID: 30117641 PMCID: PMC6123148 DOI: 10.1002/acm2.12435] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 07/17/2018] [Accepted: 07/21/2018] [Indexed: 12/17/2022] Open
Abstract
Purpose Tumor delineation using conventional CT images can be a challenge for pancreatic adenocarcinoma where contrast between the tumor and surrounding healthy tissue is low. This work investigates the ability of a split‐filter dual‐energy CT (DECT) system to improve pancreatic tumor contrast and contrast‐to‐noise ratio (CNR) for radiation therapy treatment planning. Materials and methods Multiphasic scans of 20 pancreatic tumors were acquired using a split‐filter DECT technique with iodinated contrast medium, OMNIPAQUETM. Analysis was performed on the pancreatic and portal venous phases for several types of DECT images. Pancreatic gross target volume (GTV) contrast and CNR were calculated and analyzed from mixed 120 kVp‐equivalent images and virtual monoenergetic images (VMI) at 57 and 40 keV. The role of iterative reconstruction on DECT images was also investigated. Paired t‐tests were used to assess the difference in GTV contrast and CNR among the different images. Results The VMIs at 40 keV had a 110% greater image noise compared to the mixed 120 kVp‐equivalent images (P < 0.0001). VMIs at 40 keV increased GTV contrast from 15.9 ± 19.9 HU to 93.7 ± 49.6 HU and CNR from 1.37 ± 2.05 to 3.86 ± 2.78 in comparison to the mixed 120 kVp‐equivalent images. The iterative reconstruction algorithm investigated decreased noise in the VMIs by about 20% and improved CNR by about 30%. Conclusions Pancreatic tumor contrast and CNR were significantly improved using VMIs reconstructed from the split‐filter DECT technique, and the use of iterative reconstruction further improved CNR. This gain in tumor contrast may lead to more accurate tumor delineation for radiation therapy treatment planning.
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Hansen JB, Culberson WS, DeWerd LA. Surface Dose Rate from a 106 Ru Episcleral Plaque Measured with a Convex Windowless Extrapolation Chamber and EBT3 Film. Brachytherapy 2018. [DOI: 10.1016/j.brachy.2018.04.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Simiele EA, DeWerd LA. Characterization of spectral and intensity changes with measurement geometry in various light guides used in scintillation dosimetry. Med Phys 2018; 45:3417-3428. [DOI: 10.1002/mp.12992] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/02/2018] [Accepted: 05/15/2018] [Indexed: 11/09/2022] Open
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Aima M, DeWerd LA, Mitch MG, Hammer CG, Culberson WS. Dosimetric characterization of a new directional low-dose rate brachytherapy source. Med Phys 2018; 45:10.1002/mp.12994. [PMID: 29797517 PMCID: PMC6548702 DOI: 10.1002/mp.12994] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 03/27/2018] [Accepted: 04/04/2018] [Indexed: 12/28/2022] Open
Abstract
PURPOSE CivaTech Oncology Inc. (Durham, NC) has developed a novel low-dose rate (LDR) brachytherapy source called the CivaSheet.TM The source is a planar array of discrete elements ("CivaDots") which are directional in nature. The CivaDot geometry and design are considerably different than conventional LDR cylindrically symmetric sources. Thus, a thorough investigation is required to ascertain the dosimetric characteristics of the source. This work investigates the repeatability and reproducibility of a primary source strength standard for the CivaDot and characterizes the CivaDot dose distribution by performing in-phantom measurements and Monte Carlo (MC) simulations. Existing dosimetric formalisms were adapted to accommodate a directional source, and other distinguishing characteristics including the presence of gold shield x-ray fluorescence were addressed in this investigation. METHODS Primary air-kerma strength (SK ) measurements of the CivaDots were performed using two free-air chambers namely, the Variable-Aperture Free-Air Chamber (VAFAC) at the University of Wisconsin Medical Radiation Research Center (UWMRRC) and the National Institute of Standards and Technology (NIST) Wide-Angle Free-Air Chamber (WAFAC). An intercomparison of the two free-air chamber measurements was performed along with a comparison of the different assumed CivaDot energy spectra and associated correction factors. Dose distribution measurements of the source were performed in a custom polymethylmethacrylate (PMMA) phantom using GafchromicTM EBT3 film and thermoluminescent dosimeter (TLD) microcubes. Monte Carlo simulations of the source and the measurement setup were performed using MCNP6 radiation transport code. RESULTS The CivaDot SK was determined using the two free-air chambers for eight sources with an agreement of better than 1.1% for all sources. The NIST measured CivaDot energy spectrum intensity peaks were within 1.8% of the MC-predicted spectrum intensity peaks. The difference in the net source-specific correction factor determined for the CivaDot free-air chamber measurements for the NIST WAFAC and UW VAFAC was 0.7%. The dose-rate constant analog was determined to be 0.555 cGy h-1 U-1 . The average difference observed in the estimated CivaDot dose-rate constant analog using measurements and MCNP6-predicted value (0.558 cGy h-1 U-1 ) was 0.6% ± 2.3% for eight CivaDot sources using EBT3 film, and -2.6% ± 1.7% using TLD microcube measurements. The CivaDot two-dimensional dose-to-water distribution measured in phantom was compared to the corresponding MC predictions at six depths. The observed difference using a pixel-by-pixel subtraction map of the measured and the predicted dose-to-water distribution was generally within 2-3%, with maximum differences up to 5% of the dose prescribed at the depth of 1 cm. CONCLUSION Primary SK measurements of the CivaDot demonstrated good repeatability and reproducibility of the free-air chamber measurements. Measurements of the CivaDot dose distribution using the EBT3 film stack phantom and its subsequent comparison to Monte Carlo-predicted dose distributions were encouraging, given the overall uncertainties. This work will aid in the eventual realization of a clinically viable dosimetric framework for the CivaSheet based on the CivaDot dose distribution.
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Trichter S, Soares CG, Zaider M, DeWyngaert JK, DeWerd LA, Kleiman NJ. 15 years of
106
Ru eye plaque dosimetry at Memorial Sloan-Kettering Cancer Center and Weill Cornell Medical Center using radiochromic film in a Solid Water phantom. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aab674] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Rivard MJ, Ballester F, Butler WM, DeWerd LA, Ibbott GS, Meigooni AS, Melhus CS, Mitch MG, Nath R, Papagiannis P. Erratum: “Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO” [Med. Phys. Vol 44 (9), e297-e338 (2017)]. Med Phys 2018; 45:971-974. [DOI: 10.1002/mp.12728] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 11/20/2017] [Accepted: 11/30/2017] [Indexed: 12/23/2022] Open
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Hansen JB, Culberson WS, DeWerd LA. Windowless extrapolation chamber measurement of surface dose rate from a 90 Sr/ 90 Y ophthalmic applicator. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2017.11.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hammer CG, Rosen BS, Fagerstrom JM, Culberson WS, DeWerd LA. Experimental investigation of GafChromic®
EBT3 intrinsic energy dependence with kilovoltage x rays, 137
Cs, and 60
Co. Med Phys 2017; 45:448-459. [DOI: 10.1002/mp.12682] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/13/2017] [Accepted: 11/07/2017] [Indexed: 11/10/2022] Open
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Rivard MJ, Ballester F, Butler WM, DeWerd LA, Ibbott GS, Meigooni AS, Melhus CS, Mitch MG, Nath R, Papagiannis P. Supplement 2 for the 2004 update of the AAPM Task Group No. 43 Report: Joint recommendations by the AAPM and GEC-ESTRO. Med Phys 2017. [DOI: 10.1002/mp.12430] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Ellefson ST, Culberson WS, Bednarz BP, DeWerd LA, Bayouth JE. An analysis of the ArcCHECK-MR diode array's performance for ViewRay quality assurance. J Appl Clin Med Phys 2017; 18:161-171. [PMID: 28681448 PMCID: PMC5874930 DOI: 10.1002/acm2.12107] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 04/11/2017] [Accepted: 04/18/2017] [Indexed: 11/06/2022] Open
Abstract
The ArcCHECK-MR diode array utilizes a correction system with a virtual inclinometer to correct the angular response dependencies of the diodes. However, this correction system cannot be applied to measurements on the ViewRay MR-IGRT system due to the virtual inclinometer's incompatibility with the ViewRay's multiple simultaneous beams. Additionally, the ArcCHECK's current correction factors were determined without magnetic field effects taken into account. In the course of performing ViewRay IMRT quality assurance with the ArcCHECK, measurements were observed to be consistently higher than the ViewRay TPS predictions. The goals of this study were to quantify the observed discrepancies and test whether applying the current factors improves the ArcCHECK's accuracy for measurements on the ViewRay. Gamma and frequency analysis were performed on 19 ViewRay patient plans. Ion chamber measurements were performed at a subset of diode locations using a PMMA phantom with the same dimensions as the ArcCHECK. A new method for applying directionally dependent factors utilizing beam information from the ViewRay TPS was developed in order to analyze the current ArcCHECK correction factors. To test the current factors, nine ViewRay plans were altered to be delivered with only a single simultaneous beam and were measured with the ArcCHECK. The current correction factors were applied using both the new and current methods. The new method was also used to apply corrections to the original 19 ViewRay plans. It was found the ArcCHECK systematically reports doses higher than those actually delivered by the ViewRay. Application of the current correction factors by either method did not consistently improve measurement accuracy. As dose deposition and diode response have both been shown to change under the influence of a magnetic field, it can be concluded the current ArcCHECK correction factors are invalid and/or inadequate to correct measurements on the ViewRay system.
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