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Hu Y, Hickling SV, Qian J, Blackwell CR, McLemore LB, Tryggestad EJ. Characterization and commissioning of a Leksell Gamma Knife ICON system for framed and frameless stereotactic radiosurgery. J Appl Clin Med Phys 2022; 23:e13475. [PMID: 35064749 PMCID: PMC8906202 DOI: 10.1002/acm2.13475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 10/08/2021] [Accepted: 10/28/2021] [Indexed: 11/11/2022] Open
Affiliation(s)
- Yue‐Houng Hu
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
| | - Susannah V. Hickling
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
| | - Jing Qian
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
| | - C. Robert Blackwell
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
| | - Luke B. McLemore
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
| | - Erik J. Tryggestad
- Department of Radiation Oncology Division of Medical Physics Mayo Clinic Rochester Minnesota
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Kim TH, Yang HJ, Jeong JY, Schaarschmidt T, Kim YK, Chung HT. Feasibility of Isodose-shaped scintillation detectors for the measurement of gamma Knife ® output factors. Med Phys 2022; 49:1944-1954. [PMID: 35050516 DOI: 10.1002/mp.15469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 12/20/2021] [Accepted: 01/06/2022] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Scintillation detectors were 3D printed based on a gamma knife (GK) dose distribution to calculate the volume averaging effect. The collimator output factors were measured using isodose-shaped scintillators (ISSs) and compared with those of a micro-diamond detector and previous reports. METHODS An absorbed dose distribution in a spherical dosimetry phantom with a radius of 8 cm was obtained from GK treatment planning software (Leksell GammaPlan (LGP), Elekta AB, Stockholm, Sweden). Two types of ISSs were fabricated to fit the 97.2% (ISS-1) and 95.6% (ISS-2) isodose surfaces. The volume averaging correction factors were obtained by dividing the absorbed dose to water in the central voxel (CV) by that in the ISS. The correction effect due to the difference between the ISS and water was calculated by Monte Carlo simulations. Ten ISS detectors, five of each type, were used to measure the output factors of the 4 and 8 mm collimators of a GK IconTM to assess system consistency. The output factors of seven GKs were measured using two ISS detectors, one of each type, and a PTW T60019 (PTW, Freiburg, Germany) micro-diamond detector. RESULTS The detector output ratios (DORs) measured using the five ISSs of each type were consistent, with standard uncertainties less than 0.2%. In the 4 mm field, the volume averaging correction factor ratios were 1.018 and 1.026, and the output factors after all corrections were 0.827 (0.006) and 0.825 (0.006) for ISS-1 and ISS-2, respectively. In the 8 mm field, the volume averaging correction factor ratios were 1.000 for both ISS types, and the output factors were 0.898 (0.003) and 0.900 (0.003) for ISS-1 and ISS-2, respectively. The ISS detectors could measure the output factors of a GK with uncertainties comparable to that of the PTW 60019 detector. The output factors of all detectors decreased with the dose rate. CONCLUSION The volume averaging effect of an ISS developed in-house could be calculated using known dose distributions. The collimator output factors of the GK Perfexion/Icon™ models measured using ISS detectors were consistent with those of a commercial synthetic micro-diamond detector and recent studies. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Tae Hoon Kim
- Department of Nuclear Engineering, Hanyang University College of Engineering, Seoul, Republic of Korea
| | - Hye Jeong Yang
- Department of Biomedical Engineering, College of Medicine, Catholic University of Korea, Seoul, Republic of Korea
| | - Jae Young Jeong
- Department of Nuclear Engineering, Hanyang University College of Engineering, Seoul, Republic of Korea
| | - Thomas Schaarschmidt
- Department of Nuclear Engineering, Hanyang University College of Engineering, Seoul, Republic of Korea
| | - Yong Kyun Kim
- Department of Nuclear Engineering, Hanyang University College of Engineering, Seoul, Republic of Korea
| | - Hyun-Tai Chung
- Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Republic of Korea
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Rudek B, Bernstein K, Osterman S, Qu T. Replacing gamma knife beam-profiles on film with point-detector scans. J Appl Clin Med Phys 2022; 23:e13522. [PMID: 35001499 DOI: 10.1002/acm2.13522] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 12/02/2021] [Accepted: 12/15/2021] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Detector arrays and profile-scans have widely replaced film-measurements for quality assurance (QA) on linear accelerators. Film is still used for relative output factor (ROF) measurements, positioning, and dose-profile verification for annual Leksell Gamma Knife (LGK) QA. This study shows that small-field active detector measurements can be performed in the easily accessed clinical mode and that they are an effective replacement to time-consuming and exacting film measurements. METHODS Beam profiles and positioning scans for 4-mm, 8-mm, and 16-mm-collimated fields were collected along the x-, y-, and z-axes. The Exradin W2-scintillator and the PTW microdiamond-detector were placed in custom inserts centered in the Elekta solid-water phantom for these scans. GafChromic EBT3-film was irradiated with single uniformly collimated exposures as the clinical-standard reference, using the same solid-water phantom for profile tests and the Elekta film holder for radiation focal point (RFP)/patient-positioning system (PPS) coincidence. All experimental data were compared to the tissue-maximum-ratio-based (TMR10) dose calculation. RESULTS The detector-measured beam profiles and film-based profiles showed excellent agreement with TMR10-predicted full-width, half-maximum (FWHM) values. Absolute differences between the measured FWHM and FWHM from the treatment-planning system were on average 0.13 mm, 0.08 mm, and 0.04 mm for film, microdiamond, and scintillator, respectively. The coincidence between the RFP and the PPS was measured to be ≤0.5 mm with microdiamond, ≤0.41 mm with the W2-1 × 1 scintillator, and ≤0.22 mm using the film-technique. CONCLUSIONS Small-volume field detectors, used in conjunction with a clinically available phantom, an electrometer with data-logging, and treatment plans created in clinical mode offer an efficient and viable alternative for film-based profile tests. Position verification can be accurately performed when CBCT-imaging is available to correct for residual detector-position uncertainty. Scans are easily set up within the treatment-planning-system and, when coupled with an automated analysis, can provide accurate measurements within minutes.
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Affiliation(s)
- Benedikt Rudek
- Department of Radiation Oncology, Laura and Isaac Perlmutter Cancer Center, NYU Langone Health, New York, New York, USA
| | - Kenneth Bernstein
- Department of Radiation Oncology, Laura and Isaac Perlmutter Cancer Center, NYU Langone Health, New York, New York, USA
| | - Sunshine Osterman
- Department of Radiation Oncology, NYU Grossman School of Medicine, New York University, New York, New York, USA
| | - Tanxia Qu
- Department of Radiation Oncology, NYU Grossman School of Medicine, New York University, New York, New York, USA
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Petti PL, Rivard MJ, Alvarez PE, Bednarz G, Daniel Bourland J, DeWerd LA, Drzymala RE, Johansson J, Kunugi K, Ma L, Meltsner SG, Neyman G, Seuntjens JP, Shiu AS, Goetsch SJ. Recommendations on the practice of calibration, dosimetry, and quality assurance for gamma stereotactic radiosurgery: Report of AAPM Task Group 178. Med Phys 2021; 48:e733-e770. [DOI: 10.1002/mp.14831] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 02/21/2021] [Accepted: 02/24/2021] [Indexed: 12/25/2022] Open
Affiliation(s)
- Paula L. Petti
- Gamma Knife Center Washington Hospital Fremont CA 94538 USA
| | - Mark J. Rivard
- Department of Radiation Oncology Alpert Medical School of Brown University Providence RI 02903 USA
| | - Paola E. Alvarez
- Radiological Physics Center University of Texas MD Anderson Cancer Center Houston TX 77054 USA
| | - Greg Bednarz
- Department of Radiation Oncology University of Pittsburgh Medical Center Pittsburgh PA 15232 USA
| | - J. Daniel Bourland
- Department of Radiation Oncology Wake Forest University Winston‐Salem NC 27157 USA
| | - Larry A. DeWerd
- Accredited Dosimetry and Calibration Laboratory University of Wisconsin Madison WI 53705 USA
| | - Robert E. Drzymala
- Department of Radiation Oncology Washington University Saint Louis MO 63119 USA
| | | | - Keith Kunugi
- Accredited Dosimetry and Calibration Laboratory University of Wisconsin Madison WI 53705 USA
| | - Lijun Ma
- Department of Radiation Oncology University California–San Francisco San Francisco CA 94143 USA
| | - Sheridan G. Meltsner
- Department of Radiation Oncology Duke University Medical Center Durham NC 27713 USA
| | - Gennady Neyman
- Department of Radiation Oncology The Cleveland Clinic Cleveland OH 44195 USA
| | - Jan P. Seuntjens
- Department of Medical Physics McGill University Montreal QC H4A3J1 Canada
| | - Almon S. Shiu
- Department of Radiation Oncology University of Southern California Los Angeles CA 90033 USA
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Rani AR, Ayyangar K, Reddy AR, Kumar AA, Reddy PRY. Estimation of Skin doses for Retrofit Prototype Multileaf Collimators Designed for Telecobalt Therapy Machine. J Med Phys 2021; 45:215-220. [PMID: 33953496 PMCID: PMC8074722 DOI: 10.4103/jmp.jmp_25_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 10/12/2020] [Accepted: 10/13/2020] [Indexed: 11/04/2022] Open
Abstract
Aim The objective of this study was to evaluate skin dose based on retrofit prototype multileaf collimators (MLCs), designed for cobalt-60 teletherapy machine. Since patient's skin is sensitive to radiation, evaluation of skin dose is of utmost importance for investigating the risk of late effects. Materials and Methods Measurements were performed with a Phoenix cobalt-60 teletherapy machine and the detector used was EBT3 radiochromic film. The experiments were performed in a solid water phantom with two prototype MLCs mounted to the machine. Dose readings were taken by placing the films at source-to-surface distance (SSD) of 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, and 90 cm for various MLC-generated field sizes starting from 2 cm × 2 cm to 14 cm × 14 cm. The films were analyzed using custom made programs. The measured doses were normalized to the dose at dmax for that particular measurement of SSD. Results The skin dose is expressed as a percentage of dose at dose maximum. In general, the skin dose increases with field size and decreases with SSD. The measurements indicate surface doses within 20%-60% for the investigated SSD range. Furthermore, there is no significant difference between the surface doses of two prototype MLCs studied. Conclusions From the measurements, it can be concluded that there is good skin sparing even at close distance to the MLCs. The skin dose is <50% for SSDs >65 cm. A minimum gap of 5 cm is required to produce acceptable skin dose.
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Affiliation(s)
- Akula Roopa Rani
- Department of Physics, Osmania University, Hyderabad, Telangana, India.,Department of Radiation Oncology, MNJ Institute of Oncology and Regional Cancer Center, Hyderabad, Telangana, India.,Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - Komanduri Ayyangar
- Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - A R Reddy
- Department of Radiation Oncology, International Cancer Centre, MGMMT, Bhimavaram, Andhra Pradesh, India
| | - Ayyalasomayajula Anil Kumar
- Department of Radiation Oncology, Mahatma Gandhi Cancer Hospital and Research Institute, Visakhapatnam, Andhra Pradesh, India
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Srivastava SP, Jani SS, Pinnaduwage DS, Yan X, Rogers L, Barranco FD, Barani IJ, Sorensen S. Treatment planning system and beam data validation for the ZAP-X: A novel self-shielded stereotactic radiosurgery system. Med Phys 2021; 48:2494-2510. [PMID: 33506520 DOI: 10.1002/mp.14740] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 12/04/2020] [Accepted: 01/16/2021] [Indexed: 12/16/2022] Open
Abstract
PURPOSE To evaluate the treatment planning system (TPS) performance of the ZAP-X stereotactic radiosurgery (SRS) system through nondosimetric, dosimetric, and end-to-end (E2E) tests. METHODS A comprehensive set of TPS commissioning and validation tests was developed using published guidelines. Nondosimetric validation tests included information transfer, computed tomography-magnetic resonance (CT-MR) image registration, structure/contouring, geometry, dose tools, and CT density. Dosimetric validation included comparisons between TPS and water tank/Solid Water measurements for various geometries and beam arrangements and end-to-end (E2E) tests. Patient-specific quality assurance was performed with an ion chamber in the Lucy phantom and with Gafchromic EBT3 film in the CyberKnife head phantom. RadCalc was used for independent verification of monitor units. Additional E2E tests were performed using the RPC Gamma Knife thermoluminescent dosimeter (TLD) phantom, MD Anderson SRS head phantom, and PseudoPatient gel phantom for independent absolute dose verification. RESULTS CT-MR image registrations with known translational and rotational offsets were within tolerance (<0.5 × maximum voxel dimension). Slice thickness and distance accuracy were within 0.1 mm, and volume accuracy was within 0 to 0.11 cm3 . Treatment planning system volume measurement uncertainty was within 0.1 to 0.4 cm3 . Ion chamber point-dose measurements for a single beam in a water phantom agreed to TPS-calculated values within ±4% for collimator diameters 10 to 25 mm, and ±6% for 7.5 mm, for all measured depths (7, 50, 100, 150, and 200 mm). In homogeneous Solid Water, point-dose measurements agreed to within ±4% for cones sizes 7.5 to 25 mm. With 1-cm high/low density inserts, measurements were within ±4.2% for cone sizes 10 to 25 mm. Film-based E2E using 4/5-mm cones resulted in a gamma passing rate (%GP) of 99.8% (2%/1.5 mm). Point-dose measurements in a Lucy phantom with an ion chamber using 36 beams distributed along three noncoplanar arcs agreed to within ±4% for cone sizes 10 to 25 mm. The RPC Gamma Knife TLD phantom yielded passing results with a measured-to-expected TLD dose ratio of 1.02. The MD Anderson SRS head phantom yielded passing results, with 4% TLD agreement and %GP of 95%/93% (5%/3 mm) for coronal/sagittal film planes. The RTsafe gel phantom gave %GP of >95% (5%/2 mm) for all four targets. For our first 58 patients, film-based patient-specific quality assurance has resulted in an average %GP of 98.7% (range, 94-100%) at 2%/2 mm. CONCLUSIONS Core ZAP-X features were found to be functional. On the basis of our results, point-dose and planar measurements were in agreement with TPS calculations using multiple phantoms and setup geometries, validating the ZAP-X TPS beam model for clinical use.
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Affiliation(s)
- Shiv P Srivastava
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Shyam S Jani
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Dilini S Pinnaduwage
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Xiangsheng Yan
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Leland Rogers
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - F David Barranco
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Igor J Barani
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
| | - Stephen Sorensen
- Department of Radiation Oncology, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ, USA
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Cyriac SL, Liu J, Calugaru E, Chang J. A novel and effective method for validation and measurement of output factors for Leksell Gamma Knife® Icon™ using TRS 483 protocol. J Appl Clin Med Phys 2020; 21:80-88. [PMID: 32892452 PMCID: PMC7592982 DOI: 10.1002/acm2.13011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 05/12/2020] [Accepted: 07/26/2020] [Indexed: 11/16/2022] Open
Abstract
The objective of this work was to identify the exact location of the effective point of measurement (EPM) of four different active detectors to compare the relative collimator output factors (ROF) of Leksell Gamma Knife (LGK) according to IAEA TRS-483 recommendations. ROF was measured at the center of the spherical LGK-Solid Water (LGK-SW) Phantom for three (4-, 8-, and 16-mm in diameter) collimators using four (PTW-TN60008, PTW-TN60016, PTW-TN60017, and PTW-60019 diode/diamond) detectors. Since diode detectors have a much smaller sensitive volume than the PTW-31010 ion chamber used for reference dosimetry, its EPM might not be at the center of the phantom, or (100, 100, 100) of the Leksell Coordinate System, particularly in the z-direction. Hence for each diode detector, a CBCT image was acquired after it was inserted into the phantom, from which the z-Leksell coordinate of EPM was determined. Relative collimator output factors was then measured by focusing GK beams on the determined EPM of each diode. Measured ROFs were compared with the vendor-provided values in GK treatment planning system. For validation, a plan was generated to measure the output of 4-mm collimator for PTW-TN60017 at various couch locations along the z-axis. For PTW-TN60008, the percentage variations were 0.6 ± 0.4%, and -0.8 ± 0.2% for 4 and 8-mm collimators, respectively. For PTW-TN60016, the percentage variations were 0.8 ± 0.0%, and 0.2 ± 0.1%, respectively. The percentage variations were -3.3 ± 0.0% and -0.9 ± 0.1%, respectively, for PTW-TN60017, and -0.5 ± 0.0% and -0.8 ± 0.2%, respectively, for PTW-TN60019. Center of the measured profile for PTW-TN60017 was only 0.1 mm different from that identified using the CBCT. In conclusion, we have developed a simple and effective method to determine the EPMs of diode detectors when inserted into the existing LGK-SW phantom. With the acquired positional information and using TRS-483 protocol, good agreements were obtained between the measured ROFs and manufacturer recommended values.
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Affiliation(s)
- Swapna Lilly Cyriac
- Department of Radiation OncologyKIMS Cancer Care and Research Center Pvt LtdThiruvananthapuramKeralaIndia
| | - Jian Liu
- Department of Radiation MedicineNorthwell HealthLake SuccessNYUSA
| | - Emel Calugaru
- Department of Radiation MedicineNorthwell HealthLake SuccessNYUSA
| | - Jenghwa Chang
- Department of Radiation MedicineDonald and Barbara Zucker School of Medicine at Hofstra/NorthwellLake SuccessNYUSA
- Department of Physics and AstronomyHofstra UniversityHempsteadNYUSA
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Logothetis A, Pantelis E, Zoros E, Pappas EP, Dimitriadis A, Paddick I, Garding J, Johansson J, Kollias G, Karaiskos P. Dosimetric evaluation of the Leksell GammaPlan ™ Convolution dose calculation algorithm. Phys Med Biol 2020; 65:045011. [PMID: 31860889 DOI: 10.1088/1361-6560/ab64b7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The dosimetric accuracy of the Leksell GammaPlan Convolution calculation algorithm was evaluated through comparison with corresponding Monte Carlo (MC) dosimetric results. MC simulations were based on generated sector phase space files for the 4 mm, 8 mm and 16 mm collimator sizes, using a previous comprehensive Gamma Knife Perfexion™ source model and validated using film dosimetry. Test cases were designed for the evaluation of the Convolution algorithm involving irradiation of homogeneous and inhomogeneous phantom geometries mimicking clinical cases, with radiation fields created using one sector (single sector), all sectors with the same (single shot) or different (composite shot) collimator sizes. Dose calculations using the Convolution algorithm were found to be in excellent agreement (gamma pass rate greater than 98%, applying 1%/1 mm local dose difference and distance agreement criteria), with corresponding MC calculations, indicating the accuracy of the Convolution algorithm in homogeneous and heterogeneous model geometries. While of minor clinical importance, large deviations were observed for the voxels laying inside air media. The calculated beam on times using the Convolution algorithm were found to increase (up to 7%) relative to the TMR 10 algorithm currently used in clinical practice, especially in a test case mimicking a brain metastasis close to the skull, in excellent agreement with corresponding MC calculations.
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Affiliation(s)
- A Logothetis
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, Athens, Greece
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Chagas Saraiva CW, Cardoso SC, Groppo DP, De Salles AAF, de Ávila LF, Ribeiro da Rosa LA. Gamma Knife radiosurgery for vestibular schwannomas: Evaluation of planning using the sphericity degree of the target volume. PLoS One 2020; 15:e0225638. [PMID: 31923229 PMCID: PMC6953829 DOI: 10.1371/journal.pone.0225638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 11/08/2019] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION This study explores the possibility of a relationship between the sphericity degree of a target volume with the dose distribution. This relationship is evaluated based on the ratio isodose volume / target volume (IV/TV) and the metrics coverage, i.e., selectivity, gradient index, conformity index and mean dose when planning radiosurgery for vestibular schwannoma. METHODS Sphericity degree (φ) was calculated for each target volume (TV) of 64 patients who underwent stereotactic radiosurgery (SRS) for vestibular schwannoma. The calculation of this parameter was developed using the theoretical definition for operational sphericity φ = VP/VCS. The values found are evaluated considering the following metrics:-Coverage (C), selectivity (S), gradient index (GI), Paddick conformity index (CIPaddick) and dose distribution (IV/TV). The planning was also carried out considering a spherical target volume defined in a spherical phantom. The spherical volume is the same as the target used in the treatment plan. The planning of the spherical target was considered as a reference plan to evaluate the dose distribution inside and outside the volume. RESULTS It was possible to observe that the majority of target volumes has (ϕ) around 0,66-0,77, corresponding to 54,7% of the total. Considering the mean values for metrics, the results are: C = 0,98, S = 0,78, GI = 3,11 and CI = 0,81. The dose distribution was equivalent for treatment plans and reference plans. Quantitative analysis for IV/TV shows that these values are higher than 30% for treatment plans where shot density is large. CONCLUSION This study demonstrates that de sphericity degree (φ) can be related to the dose distribution (IV/TV). Therefore the sphericity degree is a good parameter to evaluate the dose distribution of a plan for vestibular schwannoma treatment, considering the reference plan as being a spherical target using a leksell gamma knife® perfexion (LGKP). This study shows that the sphericity degree offers important information of the dose distribution outside and inside the target volume. This is not evaluated by the other parameters already implemented as metric to analyzing the GKP plans.
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Affiliation(s)
- Crystian Wilian Chagas Saraiva
- Instituto de Radioproteção e Dosimetria / Comissão Nacional de Energia Nuclear–IRD / CNEN, Rio de Janeiro, Brazil
- Associação do Sanatório Sírio—Hospital do Coração–HCor, São Paulo, Brazil
| | | | - Daniela Piai Groppo
- Instituto de Pesquisa Energéticas e Nucleares–IPEN / CNEN, São Paulo, Brazil
| | | | | | - Luiz Antonio Ribeiro da Rosa
- Instituto de Radioproteção e Dosimetria / Comissão Nacional de Energia Nuclear–IRD / CNEN, Rio de Janeiro, Brazil
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Therriault-Proulx F, Pino R, Yang JN, Beddar AS. Quality assurance for Gamma Knife Perfexion using the Exradin W1 plastic scintillation detector and Lucy phantom. Phys Med Biol 2019; 64:225007. [PMID: 31581139 DOI: 10.1088/1361-6560/ab4ac3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The goal of this work is to validate the use of the Exradin W1 plastic scintillation detector (PSD) to measure profiles and output factors from Gamma Knife Perfexion collimators in a Lucy phantom. The Exradin W1 PSD has a small-volume, near-water-equivalent, energy-independent sensitive element. Output measurements were performed for all 3 collimators (4 mm, 8 mm, and 16 mm) of the Gamma Knife Perfexion system, and these measurements were compared to measurements made with an A16 ion chamber and an EBT3 film and to the nominal values. We showed that a configuration in which the focus or 'shot' moves while the detector remains fixed is essentially equivalent to a configuration in which the focus is fixed while the detector moves. A Lucy phantom containing a PSD was moved in small steps to acquire profiles in all three dimensions. EBT3 film was inserted in the Lucy phantom and exposed to a single shot for each collimator. The relative values for output factors measured with the PSD were 1.000, 0.892, and 0.795, for the 16 mm, 8 mm, and 4 mm collimators, respectively. The values measured with EBT3 film were 1.000, 0.881, and 0.793, and the values measured with the A16 ion chamber were 1.000, 0.883, and 0.727. The nominal output factors for the Gamma Knife Perfexion are 1.000, 0.900, and 0.814, respectively. There was excellent agreement between all profiles measured with the PSD and EBT3 as well as with the treatment planning system data provided by the vendor. In light of our results, the Exradin W1 PSD is well suited for beam quality assurance of a Gamma Knife Perfexion irradiator.
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Affiliation(s)
- Francois Therriault-Proulx
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, United States of America
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Alhakeem E, Zavgorodni S. Output and ($k_{{{Q}_{{\rm clin},}}{{Q}_{{\rm msr}}}}^{{{\,f}_{{\rm clin},}}{{f}_{{\rm msr}}}}$ ) correction factors measured and calculated in very small circular fields for microDiamond and EFD-3G detectors. ACTA ACUST UNITED AC 2018; 63:155002. [DOI: 10.1088/1361-6560/aacfb2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Zoros E, Moutsatsos A, Pappas EP, Georgiou E, Kollias G, Karaiskos P, Pantelis E. Monte Carlo and experimental determination of correction factors for gamma knife perfexion small field dosimetry measurements. Phys Med Biol 2017; 62:7532-7555. [PMID: 28796643 DOI: 10.1088/1361-6560/aa8590] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detector-, field size- and machine-specific correction factors are required for precise dosimetry measurements in small and non-standard photon fields. In this work, Monte Carlo (MC) simulation techniques were used to calculate the [Formula: see text] and [Formula: see text] correction factors for a series of ionization chambers, a synthetic microDiamond and diode dosimeters, used for reference and/or output factor (OF) measurements in the Gamma Knife Perfexion photon fields. Calculations were performed for the solid water (SW) and ABS plastic phantoms, as well as for a water phantom of the same geometry. MC calculations for the [Formula: see text] correction factors in SW were compared against corresponding experimental results for a subset of ionization chambers and diode detectors. Reference experimental OF data were obtained through the weighted average of corresponding measurements using TLDs, EBT-2 films and alanine pellets. [Formula: see text] values close to unity (within 1%) were calculated for most of ionization chambers in water. Greater corrections of up to 6.0% were observed for chambers with relatively large air-cavity dimensions and steel central electrode. A phantom correction of 1.006 and 1.024 (breaking down to 1.014 from the ABS sphere and 1.010 from the accompanying ABS phantom adapter) were calculated for the SW and ABS phantoms, respectively, adding up to [Formula: see text] corrections in water. Both measurements and MC calculations for the diode and microDiamond detectors resulted in lower than unit [Formula: see text] correction factors, due to their denser sensitive volume and encapsulation materials. In comparison, higher than unit [Formula: see text] results for the ionization chambers suggested field size depended dose underestimations (being significant for the 4 mm field), with magnitude depending on the combination of contradicting phenomena associated with volume averaging and electron fluence perturbations. Finally, the presence of 0.5 mm air-gap between the diodes' frontal surface and their phantom-inserts may considerably influence OF measurements, reaching 4.6% for the Razor diode.
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Affiliation(s)
- E Zoros
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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Sahgal A, Ruschin M, Ma L, Verbakel W, Larson D, Brown PD. Stereotactic radiosurgery alone for multiple brain metastases? A review of clinical and technical issues. Neuro Oncol 2017; 19:ii2-ii15. [PMID: 28380635 DOI: 10.1093/neuonc/nox001] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Over the past three decades several randomized trials have enabled evidence-based practice for patients presenting with limited brain metastases. These trials have focused on the role of surgery or stereotactic radiosurgery (SRS) with or without whole brain radiation therapy (WBRT). As a result, it is clear that local control should be optimized with surgery or SRS in patients with optimal prognostic factors presenting with up to 4 brain metastases. The routine use of adjuvant WBRT remains debatable, as although greater distant brain control rates are observed, there is no impact on survival, and modern outcomes suggest adverse effects from WBRT on patient cognition and quality of life. With dramatic technologic advances in radiation oncology facilitating the adoption of SRS into mainstream practice, the optimal management of patients with multiple brain metastases is now being put forward. Practice is evolving to SRS alone in these patients despite a lack of level 1 evidence to support a clinical departure from WBRT. The purpose of this review is to summarize the current state of the evidence for patients presenting with limited and multiple metastases, and to present an in-depth analysis of the technology and dosimetric issues specific to the treatment of multiple metastases.
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Affiliation(s)
- Arjun Sahgal
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Mark Ruschin
- Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, Ontario, Canada
| | - Lijun Ma
- Department of Radiation Oncology, University of California San Francisco, San Francisco, California, USA
| | - Wilko Verbakel
- Department of Radiation Oncology, VU University Medical Center, Amsterdam,The Netherlands
| | - David Larson
- Department of Radiation Oncology, University of California San Francisco, San Francisco, California, USA
| | - Paul D Brown
- Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota, USA
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Zeverino M, Jaccard M, Patin D, Ryckx N, Marguet M, Tuleasca C, Schiappacasse L, Bourhis J, Levivier M, Bochud FO, Moeckli R. Commissioning of the Leksell Gamma Knife®
Icon™. Med Phys 2017; 44:355-363. [DOI: 10.1002/mp.12052] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 11/29/2016] [Accepted: 12/01/2016] [Indexed: 01/08/2023] Open
Affiliation(s)
- Michele Zeverino
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - Maud Jaccard
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - David Patin
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - Nick Ryckx
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - Maud Marguet
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - Constantin Tuleasca
- Department of Neurosurgery and Gamma Knife Center; Lausanne University Hospital; Lausanne Switzerland
| | - Luis Schiappacasse
- Department of Radiation Oncology; Lausanne University Hospital; Lausanne Switzerland
| | - Jean Bourhis
- Department of Radiation Oncology; Lausanne University Hospital; Lausanne Switzerland
| | - Marc Levivier
- Department of Neurosurgery and Gamma Knife Center; Lausanne University Hospital; Lausanne Switzerland
| | - Francois O. Bochud
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
| | - Raphaël Moeckli
- Institute of Radiation Physics; Lausanne University Hospital; Lausanne Switzerland
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Tian Y, Wang H, Xu Y, Yan H, Song Y, Men K, Ma P, Ren X, Li M, Zhang K, Dai J. Comparison of dosimetric characteristics between stationary and rotational gamma ray stereotactic radiosurgery systems based on Monte Carlo simulation. Biomed Phys Eng Express 2016. [DOI: 10.1088/2057-1976/2/4/045014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Pappas EP, Moutsatsos A, Pantelis E, Zoros E, Georgiou E, Torrens M, Karaiskos P. On the development of a comprehensive MC simulation model for the Gamma Knife Perfexion radiosurgery unit. Phys Med Biol 2016; 61:1182-203. [PMID: 26788618 DOI: 10.1088/0031-9155/61/3/1182] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This work presents a comprehensive Monte Carlo (MC) simulation model for the Gamma Knife Perfexion (PFX) radiosurgery unit. Model-based dosimetry calculations were benchmarked in terms of relative dose profiles (RDPs) and output factors (OFs), against corresponding EBT2 measurements. To reduce the rather prolonged computational time associated with the comprehensive PFX model MC simulations, two approximations were explored and evaluated on the grounds of dosimetric accuracy. The first consists in directional biasing of the (60)Co photon emission while the second refers to the implementation of simplified source geometric models. The effect of the dose scoring volume dimensions in OF calculations accuracy was also explored. RDP calculations for the comprehensive PFX model were found to be in agreement with corresponding EBT2 measurements. Output factors of 0.819 ± 0.004 and 0.8941 ± 0.0013 were calculated for the 4 mm and 8 mm collimator, respectively, which agree, within uncertainties, with corresponding EBT2 measurements and published experimental data. Volume averaging was found to affect OF results by more than 0.3% for scoring volume radii greater than 0.5 mm and 1.4 mm for the 4 mm and 8 mm collimators, respectively. Directional biasing of photon emission resulted in a time efficiency gain factor of up to 210 with respect to the isotropic photon emission. Although no considerable effect on relative dose profiles was detected, directional biasing led to OF overestimations which were more pronounced for the 4 mm collimator and increased with decreasing emission cone half-angle, reaching up to 6% for a 5° angle. Implementation of simplified source models revealed that omitting the sources' stainless steel capsule significantly affects both OF results and relative dose profiles, while the aluminum-based bushing did not exhibit considerable dosimetric effect. In conclusion, the results of this work suggest that any PFX simulation model should be benchmarked in terms of both RDP and OF results.
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Affiliation(s)
- E P Pappas
- Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 75 Mikras Asias, 115 27 Athens, Greece
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Pipek J, Novotný J, Novotný J, Kozubíková P. A modular Geant4 model of Leksell Gamma Knife Perfexion™. Phys Med Biol 2016; 59:7609-23. [PMID: 25415510 DOI: 10.1088/0031-9155/59/24/7609] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This work presents a Monte Carlo model of Leksell Gamma Knife Perfexion as well as the main parameters of the dose distribution in the standard phantom obtained using this model. The model is developed in the Geant4 simulation toolkit in a modular way which enables its reuse in other Perfexion studies. Large phase space files were created, containing particles that are entering the inner machine cavity after being transported through the collimation system. All 14 output factors of the machine and effective output factors for both the 4 mm (0.830 ± 0.009) and 8 mm (0.921 ± 0.004) collimators were calculated. Dose profiles along the main axes are also included for each collimator size. All results are compared to the values obtained from the treatment planning system, from experiments, and from other Monte Carlo models.
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Affiliation(s)
- J Pipek
- Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Prague 1, Czech Republic
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18
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Mancosu P, Reggiori G, Stravato A, Gaudino A, Lobefalo F, Palumbo V, Navarria P, Ascolese A, Picozzi P, Marinelli M, Verona-Rinati G, Tomatis S, Scorsetti M. Evaluation of a synthetic single-crystal diamond detector for relative dosimetry on the Leksell Gamma Knife Perfexion radiosurgery system. Med Phys 2015; 42:5035-41. [DOI: 10.1118/1.4927569] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Benmakhlouf H, Johansson J, Paddick I, Andreo P. Monte Carlo calculated and experimentally determined output correction factors for small field detectors in Leksell Gamma Knife Perfexion beams. Phys Med Biol 2015; 60:3959-73. [DOI: 10.1088/0031-9155/60/10/3959] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber. Phys Med 2014; 30:914-9. [DOI: 10.1016/j.ejmp.2014.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 08/28/2014] [Accepted: 09/04/2014] [Indexed: 11/18/2022] Open
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Novotny J, Bhatnagar JP, Xu Y, Huq MS. Long-term stability of the Leksell Gamma Knife® Perfexion™ patient positioning system (PPS). Med Phys 2014; 41:031711. [PMID: 24593715 DOI: 10.1118/1.4866225] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To assess the long-term mechanical stability and accuracy of the patient positioning system (PPS) of the Leksell Gamma Knife(®) Perfexion™ (LGK PFX). METHODS The mechanical stability of the PPS of the LGK PFX was evaluated using measurements obtained between September 2007 and June 2011. Three methods were employed to measure the deviation of the coincidence of the radiological focus point (RFP) and the PPS calibration center point (CCP). In the first method, the onsite diode test tool with single diode detector was used together with the 4 mm collimator on a daily basis. In the second method, a service diode test tool with three diode detectors was used biannually at the time of the routine preventive maintenance. The test performed with the service diode test tool measured the deviations for all three collimators 4, 8, and 16 mm and also for three different positions of the PPS. The third method employed the conventional film pin-prick method. This test was performed annually for the 4 mm collimator at the time of the routine annual QA. To estimate the effect of the patient weight on the performance of the PPS, the focus precision tests were also conducted with varying weights on the PPS using a set of lead bricks. RESULTS The average deviations measured from the 641 daily focus precision tests were 0.1 ± 0.1, 0.0 ± 0.0, and 0.0 ± 0.0 mm, respectively, for the 4 mm collimator in the X (left/right of the patient), Y (anterior/posterior of the patient), and Z (superior/inferior of the patient) directions. The average of the total radial deviations as measured during ten semiannual measurements with the service diode test tool were 0.070 ± 0.029, 0.060 ± 0.022, and 0.103 ± 0.028 mm, respectively for the central, long, and short diodes for the 4 mm collimator. Similarly, the average total radial deviations measured during the semiannual measurements for the 4, 8, and 16 mm collimators and using the central diode were 0.070 ± 0.029, 0.097 ± 0.025, 0.159 ± 0.028 mm, respectively. The average values of the deviations as obtained from the five annual film pin-prick tests for the 4 mm collimator were 0.10 ± 0.06, 0.06 ± 0.09, and 0.03 ± 0.03 mm for the X, Y, Z stereotactic directions, respectively. Only a minor change was observed in the total radial deviations of the PPS as a function of the simulated patient weight up to 202 kg on the PPS. CONCLUSIONS Excellent long-term mechanical stability and high accuracy was observed for the PPS of the LGK PFX. No PPS recalibration or any adjustment in the PPS was needed during the monitored period of time. Similarly, the weight on the PPS did not cause any significant disturbance in the performance of the PPS for up to 202 kg simulated patient weight.
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Affiliation(s)
- J Novotny
- Department of Radiation Oncology, Medical Physics Division, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213; Department of Medical Physics, Na Homolce Hospital, Prague 150 30, Czech Republic; Institute of Biophysics and Informatics, First Faculty of Medicine, Charles University in Prague, Prague 120 00, Czech Republic; Department of Dosimetry and Application of Ionizing Radiation, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Prague 115 19, Czech Republic; and Department of Radiation Oncology, University Hospital Motol, Prague 150 06, Czech Republic
| | - J P Bhatnagar
- Department of Radiation Oncology, Medical Physics Division, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - Y Xu
- Department of Radiation Oncology, Medical Physics Division, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
| | - M S Huq
- Department of Radiation Oncology, Medical Physics Division, University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213
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Chan MF, Lewis D, Yu X. Is It Possible to Publish a Calibration Function for Radiochromic Film? INTERNATIONAL JOURNAL OF MEDICAL PHYSICS, CLINICAL ENGINEERING AND RADIATION ONCOLOGY 2014; 3:25-30. [PMID: 27642545 PMCID: PMC5023153 DOI: 10.4236/ijmpcero.2014.31005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To assess the possibility of using a public calibration function for radiochromic film dosimetry in dose QA of highly conformal treatment plans. METHODS EBT3 film calibration strips (3.5 × 20 cm2 from lots A101212 and A011713) were exposed on a Varian Trilogy at a facility to a 10 × 10 cm2 open field at doses of 80, 160, 320 cGy using 6MV photons. Together with a strip of unexposed film from the same lot the exposed films were digitized in a single scan using different Epson 10,000 XL scanners at two different facilities. The dose-response data for each color-channel from each facility were generated using the same calibration function X(D) = a + b/(D - c), where X(D) is the response at dose D and a, b and c are the coefficients. Different batches of EBT3 film were exposed to a VMAT beam. These films, plus two reference strips exposed to doses of zero and 160 cGy, were digitized on the scanners at the two facilities. Using the multi-channel dosimetry method and One-scan protocol (Med Phys, 39:6339-49, 2012) the recorded doses on the VMAT films were calculated and the results were compared with the VMAT plan using a Gamma index of 3%/3 mm. RESULTS The passing rates obtained for dose maps calculated for all combinations of VMAT images and calibration functions were nearly unchanged, using the One-scan protocol. Also, in all cases a passing rate of >99% was obtained for Gamma index of 3%/3 mm. On the other hand, if the One-scan protocol was not employed, the dose maps for VMAT images and calibration functions from different scanners showed poor correlation with the treatment plan. This is probably due to the scan-to-scan variability. CONCLUSIONS The authors have found that it is feasible to use a public calibration function for a given radiochromic film lot using the same methodology, One-scan protocol, for patient-specific QA.
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Affiliation(s)
- Maria F. Chan
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, Basking Ridge, USA
| | - David Lewis
- Advanced Materials Group, Ashland, Inc., Bridgewater, USA
| | - Xiang Yu
- Advanced Materials Group, Ashland, Inc., Bridgewater, USA
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Natanasabapathi G, Bisht RK. Verification of Gamma Knife extend system based fractionated treatment planning using EBT2 film. Med Phys 2013; 40:122104. [DOI: 10.1118/1.4832138] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Massillon-J L G, Cueva-Prócel D, Díaz-Aguirre P, Rodríguez-Ponce M, Herrera-Martínez F. Dosimetry for small fields in stereotactic radiosurgery using gafchromic MD-V2-55 film, TLD-100 and alanine dosimeters. PLoS One 2013; 8:e63418. [PMID: 23671677 PMCID: PMC3650064 DOI: 10.1371/journal.pone.0063418] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 04/03/2013] [Indexed: 11/29/2022] Open
Abstract
This work investigated the suitability of passive dosimeters for reference dosimetry in small fields with acceptable accuracy. Absorbed dose to water rate was determined in nine small radiation fields with diameters between 4 and 35 mm in a Leksell Gamma Knife (LGK) and a modified linear accelerator (linac) for stereotactic radiosurgery treatments. Measurements were made using Gafchromic film (MD-V2-55), alanine and thermoluminescent (TLD-100) dosimeters and compared with conventional dosimetry systems. Detectors were calibrated in terms of absorbed dose to water in 60Co gamma-ray and 6 MV x-ray reference (10×10 cm2) fields using an ionization chamber calibrated at a standards laboratory. Absorbed dose to water rate computed with MD-V2-55 was higher than that obtained with the others dosimeters, possibly due to a smaller volume averaging effect. Ratio between the dose-rates determined with each dosimeter and those obtained with the film was evaluated for both treatment modalities. For the LGK, the ratio decreased as the dosimeter size increased and remained constant for collimator diameters larger than 8 mm. The same behaviour was observed for the linac and the ratio increased with field size, independent of the dosimeter used. These behaviours could be explained as an averaging volume effect due to dose gradient and lack of electronic equilibrium. Evaluation of the output factors for the LGK collimators indicated that, even when agreement was observed between Monte Carlo simulation and measurements with different dosimeters, this does not warrant that the absorbed dose to water rate in the field was properly known and thus, investigation of the reference dosimetry should be an important issue. These results indicated that alanine dosimeter provides a high degree of accuracy but cannot be used in fields smaller than 20 mm diameter. Gafchromic film can be considered as a suitable methodology for reference dosimetry. TLD dosimeters are not appropriate in fields smaller than 10 mm diameters.
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Chan MF, Chiu-Tsao ST, Li J, Schupak K, Parhar P, Burman C. Confirmation of Skin Doses Resulting from Bolus Effect of Intervening Alpha-cradle and Carbon Fiber Couch in Radiotherapy. Technol Cancer Res Treat 2012; 11:571-81. [PMID: 22712603 DOI: 10.7785/tcrt.2012.500269] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we verified the treatment planning calculations of skin doses with the incorporation of the bolus effect due to the intervening alpha-cradle (AC) and carbon fiber couch (CFC) using radiochromic EBT2 films. A polystyrene phantom (25 × 25 × 15 cm3) with six EBT2 films separated by polystyrene slabs, at depths of 0, 0.1, 0.2, 0.5, 1, 1.4 cm, was positioned above an AC, which was ~1 cm thick. The phantom and AC assembly were CT scanned and the CT-images were transferred to the treatment planning system (TPS) for calculations in three scenarios: (A) ignoring AC and CFC, (B) accounting for AC only, (C) accounting for both AC and CFC. A single posterior 10 × 10 cm2 field, a pair of posterior-oblique 10 × 10 cm2 fields, and a posterior IMRT field (6 MV photons from a Varian Trilogy linac) were planned. For each radiation field configuration, the same MU were used in all three scenarios in the TPS. Each plan for scenario C was delivered to expose a stack of EBT2 films in the phantom through AC and CFC. In addition, in vivo EBT2 film measurement on a lung cancer patient immobilized with AC undergoing IMRT was also included in this study. Point doses and planar distributions generated from the TPS for the three scenarios were compared with the data from the EBT2 film measurements. For all the field arrangements, the EBT2 film data including the in vivo measurement agreed with the doses calculated for scenario (C), within the uncertainty of the EBT2 measurements (~4%). For the single posterior field (a pair of posterior-oblique fields), the TPS generated doses were lower than the EBT2 doses by 34%, 33%, 31%, 13% (34%, 31%, 31%, 11%) for scenario A and by 27%, 25%, 22%, 8% (25%, 21%, 21%, 6%) for scenario B at the depths of 0, 0.1, 0.2, 0.5 cm, respectively. For the IMRT field, the 2D dose distributions at each depth calculated in scenario C agree with those measured data. When comparing the central axis doses for the IMRT field, we found the TPS generated doses for scenario A (B) were lower than the EBT2 data by 35%, 34%, 31%, 16% (29%, 26%, 23%, 10%) at the depths of 0, 0.1, 0.2, 0.5 cm, respectively. There were no significant differences for the depths of 1.0 and 1.4 cm for all the radiation fields studied. TPS calculation of doses in the skin layers accounting for AC and CFC was verified by EBT2 film data. Ignoring the presence of AC and/or CFC in TPS calculation would significantly underestimate the doses in the skin layers. For the clinicians, as more hypofractionated regimens and stereotactic regimens are being used, this information will be useful to avoid potential serious skin toxicities, and also assist in clinical decisions and report these doses accurately to relevant clinical trials/cooperative groups, such as RTOG.
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Affiliation(s)
- Maria F. Chan
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 136 Mountain View Blvd., Basking Ridge, NJ 07920, USA
| | | | - Jingdong Li
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 136 Mountain View Blvd., Basking Ridge, NJ 07920, USA
| | - Karen Schupak
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 136 Mountain View Blvd., Basking Ridge, NJ 07920, USA
| | - Preeti Parhar
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 136 Mountain View Blvd., Basking Ridge, NJ 07920, USA
| | - Chandra Burman
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 136 Mountain View Blvd., Basking Ridge, NJ 07920, USA
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Kim J, Wen N, Jin JY, Walls N, Kim S, Li H, Ren L, Huang Y, Doemer A, Faber K, Kunkel T, Balawi A, Garbarino K, Levin K, Patel S, Ajlouni M, Miller B, Nurushev T, Huntzinger C, Schulz R, Chetty IJ, Movsas B, Ryu S. Clinical commissioning and use of the Novalis Tx linear accelerator for SRS and SBRT. J Appl Clin Med Phys 2012; 13:3729. [PMID: 22584170 PMCID: PMC5716565 DOI: 10.1120/jacmp.v13i3.3729] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 11/14/2011] [Accepted: 01/25/2012] [Indexed: 12/31/2022] Open
Abstract
The purpose of this study was to perform comprehensive measurements and testing of a Novalis Tx linear accelerator, and to develop technical guidelines for com-missioning from the time of acceptance testing to the first clinical treatment. The Novalis Tx (NTX) linear accelerator is equipped with, among other features, a high-definition MLC (HD120 MLC) with 2.5 mm central leaves, a 6D robotic couch, an optical guidance positioning system, as well as X-ray-based image guidance tools to provide high accuracy radiation delivery for stereotactic radiosurgery and stereotactic body radiation therapy procedures. We have performed extensive tests for each of the components, and analyzed the clinical data collected in our clinic. We present technical guidelines in this report focusing on methods for: (1) efficient and accurate beam data collection for commissioning treatment planning systems, including small field output measurements conducted using a wide range of detectors; (2) commissioning tests for the HD120 MLC; (3) data collection for the baseline characteristics of the on-board imager (OBI) and ExacTrac X-ray (ETX) image guidance systems in conjunction with the 6D robotic couch; and (4) end-to-end testing of the entire clinical process. Established from our clinical experience thus far, recommendations are provided for accurate and efficient use of the OBI and ETX localization systems for intra- and extracranial treatment sites. Four results are presented. (1) Basic beam data measurements: Our measurements confirmed the necessity of using small detectors for small fields. Total scatter factors varied significantly (30% to approximately 62%) for small field measurements among detectors. Unshielded stereotactic field diode (SFD) overestimated dose by ~ 2% for large field sizes. Ion chambers with active diameters of 6 mm suffered from significant volume averaging. The sharpest profile penumbra was observed for the SFD because of its small active diameter (0.6 mm). (2) MLC commissioning: Winston Lutz test, light/radiation field congruence, and Picket Fence tests were performed and were within criteria established by the relevant task group reports. The measured mean MLC transmission and dynamic leaf gap of 6 MV SRS beam were 1.17% and 0.36 mm, respectively. (3) Baseline characteristics of OBI and ETX: The isocenter localization errors in the left/right, posterior/anterior, and superior/inferior directions were, respectively, -0.2 ± 0.2 mm, -0.8 ± 0.2 mm, and -0.8 ± 0.4 mm for ETX, and 0.5 ± 0.7 mm, 0.6 ± 0.5 mm, and 0.0 ± 0.5 mm for OBI cone-beam computed tomography. The registration angular discrepancy was 0.1 ± 0.2°, and the maximum robotic couch error was 0.2°. (4) End-to-end tests: The measured isocenter dose differences from the planned values were 0.8% and 0.4%, measured respectively by an ion chamber and film. The gamma pass rate, measured by EBT2 film, was 95% (3% DD and 1 mm DTA). Through a systematic series of quantitative commissioning experiments and end-to-end tests and our initial clinical experience, described in this report, we demonstrate that the NTX is a robust system, with the image guidance and MLC requirements to treat a wide variety of sites - in particular for highly accurate delivery of SRS and SBRT-based treatments.
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Affiliation(s)
- Jinkoo Kim
- Department of Radiation Oncology, Henry Ford Health System, Detroit, MI, USA.
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Arjomandy B, Tailor R, Zhao L, Devic S. EBT2 film as a depth-dose measurement tool for radiotherapy beams over a wide range of energies and modalities. Med Phys 2012; 39:912-21. [DOI: 10.1118/1.3678989] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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28
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Chan MF, Zhang Q, Li J, Parhar P, Schupak K, Burman C. The Verification of iPlan Commissioning by Radiochromic EBT2 Films. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ijmpcero.2012.11001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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29
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Park JH, Han JH, Kim CY, Oh CW, Lee DH, Suh TS, Gyu Kim D, Chung HT. Application of the gamma evaluation method in Gamma Knife film dosimetry. Med Phys 2011; 38:5778-87. [DOI: 10.1118/1.3641644] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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30
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Target and peripheral dose from radiation sector motions accompanying couch repositioning of patient coordinates with the Gamma Knife(®) Perfexion(™). Radiol Oncol 2011; 45:132-42. [PMID: 22933947 PMCID: PMC3423725 DOI: 10.2478/v10019-011-0012-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 03/13/2011] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The GammaPlan(™) treatment planning system (TPS) does not fully account for shutter dose when multiple shots are required to deliver a patient's treatment. The unaccounted exposures to the target site and its periphery are measured in this study. The collected data are compared to a similar effect from the Gamma Knife(®) model 4C. MATERIALS AND METHODS.: A stereotactic head frame was attached to a Leksell(®) 16 cm diameter spherical phantom; using a fiducial-box, CT images of the phantom were acquired and registered in the TPS. Measurements give the relationship of measured dose to the number of repositions with the patient positioning system (PPS) and to the collimator size. An absorbed dose of 10 Gy to the 50% isodose line was prescribed to the target site and all measurements were acquired with an ionization chamber. RESULTS Measured dose increases with frequency of repositioning and with collimator size. As the radiation sectors transition between the beam on and beam off states, the target receives more shutter dose than the periphery. Shutter doses of 3.53±0.04 and 1.59±0.04 cGy/reposition to the target site are observed for the 16 and 8 mm collimators, respectively. The target periphery receives additional dose that varies depending on its position relative to the target. CONCLUSIONS The radiation sector motions for the Gamma Knife(®) Perfexion(™) result in an additional dose due to the shutter effect. The magnitude of this exposure is comparable to that measured for the model 4C.
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31
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McDonald D, Yount C, Koch N, Ashenafi M, Peng J, Vanek K. Calibration of the Gamma Knife Perfexion using TG-21 and the solid water Leksell dosimetry phantom. Med Phys 2011; 38:1685-93. [DOI: 10.1118/1.3557884] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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32
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Novotny J, Bhatnagar JP, Chung HT, Johansson J, Bednarz G, Ma L, Saiful Huq M. Assessment of variation in Elekta ®
plastic spherical-calibration phantom and its impact on the Leksell Gamma Knife ®
calibration. Med Phys 2010; 37:5066-5071. [DOI: 10.1118/1.3481508] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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33
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Massillon-JL G, Zúñiga-Meneses L. The response of the new MD-V2-55 radiochromic film exposed to60Co gamma rays. Phys Med Biol 2010; 55:5437-49. [DOI: 10.1088/0031-9155/55/18/011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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34
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Lindsay P, Rink A, Ruschin M, Jaffray D. Investigation of energy dependence of EBT and EBT-2 Gafchromic film. Med Phys 2010; 37:571-6. [PMID: 20229865 DOI: 10.1118/1.3291622] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Patricia Lindsay
- Department of Radiation Oncology, Radiation Physics, and Princess Margaret Hospital, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
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