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Bassiri N, Bayouth JE, Mittauer KE. Characterization of mechanical and radiation isocenter on an MR-guided radiotherapy (MRgRT) Linac. J Appl Clin Med Phys 2023; 24:e14111. [PMID: 37535938 PMCID: PMC10647948 DOI: 10.1002/acm2.14111] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 07/06/2023] [Accepted: 07/18/2023] [Indexed: 08/05/2023] Open
Abstract
BACKGROUND AND PURPOSE In the emerging paradigm of stereotactic radiosurgery being proposed for MR-guided radiotherapy (MRgRT), assessment of mechanical geometric accuracy is critical for the implementation of stereotactic delivery. We benchmarked the mechanical accuracy of an MR Linac system that lacks an onboard detector/array. Our mechanical tests utilize a half beam block (HBB) geometry that takes advantage of the sensitivity of a partially occluded detector. MATERIALS AND METHODS Mechanical tests benchmarked the couch, MLC, and gantry geometric accuracy for an MR-Linac system. An HBB technique was used to irradiate an ionization chamber profiler (ICP) array with partial occlusion of individual detectors for characterization of MLC skew, beam divergence displacement, and RT isocenter localization. The sensitivity of the partially occluded detector's ICP-X (detector width) and ICP-Y (detector length) was characterized by displacing the detector relative to radiation isocenter by 0.2 mm increments, introduced through couch motion. The accuracy of the HBB ICP technique was verified with a starshot using radiochromic film, and the reproducibility was verified on a conventional C-arm Linac and compared to Winston-Lutz. RESULTS The sensitivity of the HBB technique as quantified through the dose difference normalized to open field as a function of displacement from RT isocenter was 6.4%/mm and 13.0%/mm for the ICP-X and ICP-Y orientation, respectively, due to the oblong detector orientation. Couch positional accuracy and sag was within ±0.1 mm. Maximum MLC positional displacement was 0.7 mm with mean MLC skew at 0.07°. The maximum beam divergence displacement was 0.03 mm. The gantry angle was within 0.1°. Independent verification of the RT isocenter localization procedure produced repeatable results. CONCLUSION This work serves for characterizing the mechanical and geometric radiation accuracy for the foundation of an MR-guided stereotactic radiosurgery program, as demonstrated with high sensitivity and independent validation.
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Affiliation(s)
- Nema Bassiri
- Department of Radiation OncologyMiami Cancer InstituteBaptist Health South FloridaMiamiFloridaUSA
- Herbert Wertheim College of MedicineFlorida International UniversityMiamiFloridaUSA
| | - John E. Bayouth
- Department of Radiation MedicineOregon Health and Science UniversityPortlandOregonUSA
| | - Kathryn E. Mittauer
- Department of Radiation OncologyMiami Cancer InstituteBaptist Health South FloridaMiamiFloridaUSA
- Herbert Wertheim College of MedicineFlorida International UniversityMiamiFloridaUSA
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Rippke C, Renkamp CK, Attieh C, Schlüter F, Buchele C, Debus J, Alber M, Klüter S. Leaf-individual calibration for a double stack multileaf collimator in photon radiotherapy. Phys Imaging Radiat Oncol 2023; 27:100477. [PMID: 37635846 PMCID: PMC10457557 DOI: 10.1016/j.phro.2023.100477] [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: 01/08/2023] [Revised: 07/20/2023] [Accepted: 07/22/2023] [Indexed: 08/29/2023] Open
Abstract
Background and Purpose In online adaptive stereotactic body radiotherapy treatments, linear accelerator delivery accuracy is essential. Recently introduced double stack multileaf collimators (MLCs) have new facets in their calibration. We established a radiation-based leaf-individual calibration (LIMCA) method for double stack MLCs. Materials and Methods MLC leaf positions were evaluated from four cardinal angles with test patterns at measurement positions throughout the radiation field on EBT3 radiochromic film for each single stack. The accuracy of the method and repeatability of the results were assessed. The effect of MLC positioning errors was characterized for a measured output factor curve and a clinical patient plan. Results All positions in the motor step - position calibration file were optimized in the established LIMCA method. The resulting double stack mean accuracy for all angles was 0.2 ± 0.1 mm for X1 (left bank) and 0.2 ± 0.2 mm for X2 (right bank). The accuracy of the leaf position evaluation was 0.2 mm (95% confidence level). The MLC calibration remained stable over four months. Small MLC leaf position errors (e.g. 1.2 mm field size reduction) resulted in important dose errors (-5.8 %) for small quadratic fields of 0.83 × 0.83 cm2. Single stack position accuracy was essential for highly modulated treatment plans. Conclusions LIMCA is a new double stack MLC calibration method that increases treatment accuracy from four angles and for all moving leaves.
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Affiliation(s)
- Carolin Rippke
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
- Medical Faculty, University of Heidelberg, Heidelberg, Baden-Württemberg, Germany
| | - C. Katharina Renkamp
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
| | | | - Fabian Schlüter
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
| | - Carolin Buchele
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
- Medical Faculty, University of Heidelberg, Heidelberg, Baden-Württemberg, Germany
| | - Jürgen Debus
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
- Medical Faculty, University of Heidelberg, Heidelberg, Baden-Württemberg, Germany
- National Center for Tumor Diseases (NCT), Heidelberg, Baden-Württemberg, Germany
- Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Baden-Württemberg, Germany
- German Cancer Consortium (DKTK), Core-center Heidelberg, Heidelberg, Baden-Württemberg, Germany
- Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany
| | - Markus Alber
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
- Medical Faculty, University of Heidelberg, Heidelberg, Baden-Württemberg, Germany
| | - Sebastian Klüter
- Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Baden-Württemberg, Germany
- Heidelberg Institute of Radiation Oncology (HIRO), National Center for Radiation Oncology (NCRO), Heidelberg, Baden-Württemberg, Germany
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Ma Y, Mou X, Beeraka NM, Guo Y, Liu J, Dai J, Fan R. Machine Log File and Calibration Errors-based Patient-specific Quality Assurance (QA) for Volumetric Modulated Arc Therapy (VMAT). Curr Pharm Des 2023; 29:2738-2751. [PMID: 37916622 DOI: 10.2174/0113816128226519231017050459] [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: 09/14/2022] [Revised: 05/19/2023] [Accepted: 06/05/2023] [Indexed: 11/03/2023]
Abstract
INTRODUCTION Dose reconstructed based on linear accelerator (linac) log-files is one of the widely used solutions to perform patient-specific quality assurance (QA). However, it has a drawback that the accuracy of log-file is highly dependent on the linac calibration. The objective of the current study is to represent a new practical approach for a patient-specific QA during Volumetric modulated arc therapy (VMAT) using both log-file and calibration errors of linac. METHODS A total of six cases, including two head and neck neoplasms, two lung cancers, and two rectal carcinomas, were selected. The VMAT-based delivery was optimized by the TPS of Pinnacle^3 subsequently, using Elekta Synergy VMAT linac (Elekta Oncology Systems, Crawley, UK), which was equipped with 80 Multi-leaf collimators (MLCs) and the energy of the ray selected at 6 MV. Clinical mode log-file of this linac was used in this study. A series of test fields validate the accuracy of log-file. Then, six plans of test cases were delivered and log-file of each was obtained. The log-file errors were added to the corresponding plans through the house script and the first reconstructed plan was obtained. Later, a series of tests were performed to evaluate the major calibration errors of the linac (dose-rate, gantry angle, MLC leaf position) and the errors were added to the first reconstruction plan to generate the second reconstruction plan. At last, all plans were imported to Pinnacle and recalculated dose distribution on patient CT and ArcCheck phantom (SUN Nuclear). For the former, both target and OAR dose differences between them were compared. For the latter, γ was evaluated by ArcCheck, and subsequently, the surface dose differences between them were performed. RESULTS Accuracy of log-file was validated. If error recordings in the log file were only considered, there were four arcs whose proportion of control points with gantry angle errors more than ± 1°larger than 35%. Errors of leaves within ± 0.5 mm were 95% for all arcs. The distinctness of a single control point MU was bigger, but the distinctness of cumulative MU was smaller. The maximum, minimum, and mean doses for all targets were distributed between -6.79E-02-0.42%, -0.38-0.4%, 2.69E-02-8.54E-02% respectively, whereas for all OAR, the maximum and mean dose were distributed between -1.16-2.51%, -1.21-3.12% respectively. For the second reconstructed dose: the maximum, minimum, and mean dose for all targets was distributed between 0.0995~5.7145%, 0.6892~4.4727%, 0.5829~1.8931% separately. Due to OAR, maximum and mean dose distribution was observed between -3.1462~6.8920%, -6.9899~1.9316%, respectively. CONCLUSION Patient-specific QA based on the log-file could reflect the accuracy of the linac execution plan, which usually has a small influence on dose delivery. When the linac calibration errors were considered, the reconstructed dose was closer to the actual delivery and the developed method was accurate and practical.
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Affiliation(s)
- Yangguang Ma
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
- School of Information and Communications Engineering, Xi'AN Jiaotong University, Xi'an 710049, China
| | - Xuanqin Mou
- School of Information and Communications Engineering, Xi'AN Jiaotong University, Xi'an 710049, China
| | - Narasimha M Beeraka
- Raghavendra Institute of Pharmaceutical Education and Research (RIPER), Anantapuramu, Chiyyedu, Andhra Pradesh 515721, India
- Department of Human Anatomy, I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), 8/2 Trubetskaya Str., Moscow 119991, Russia
| | - Yuexin Guo
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Junqi Liu
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Jianrong Dai
- Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100021, China
| | - Ruitai Fan
- Department of Radiation Oncology, First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
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Rosenfeld AB, Biasi G, Petasecca M, Lerch MLF, Villani G, Feygelman V. Semiconductor dosimetry in modern external-beam radiation therapy. Phys Med Biol 2020; 65:16TR01. [PMID: 32604077 DOI: 10.1088/1361-6560/aba163] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Mittauer KE, Yadav P, Paliwal B, Bayouth JE. Characterization of positional accuracy of a double‐focused and double‐stack multileaf collimator on an MR‐guided radiotherapy (MRgRT) Linac using an IC‐profiler array. Med Phys 2019; 47:317-330. [DOI: 10.1002/mp.13902] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 10/23/2019] [Accepted: 10/24/2019] [Indexed: 11/07/2022] Open
Affiliation(s)
- Kathryn E. Mittauer
- Department of Radiation Oncology Miami Cancer Institute Baptist Health South Florida Miami FL USA
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - Poonam Yadav
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - Bhudatt Paliwal
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
| | - John E. Bayouth
- Department of Human Oncology School of Medicine and Public Health University of Wisconsin‐Madison Madison WI USA
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Katsuta Y, Kadoya N, Fujita Y, Shimizu E, Matsunaga K, Matsushita H, Majima K, Jingu K. Quantification of residual dose estimation error on log file-based patient dose calculation. Phys Med 2016; 32:701-5. [PMID: 27162084 DOI: 10.1016/j.ejmp.2016.04.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 04/02/2016] [Accepted: 04/29/2016] [Indexed: 11/30/2022] Open
Abstract
PURPOSE The log file-based patient dose estimation includes a residual dose estimation error caused by leaf miscalibration, which cannot be reflected on the estimated dose. The purpose of this study is to determine this residual dose estimation error. METHODS AND MATERIALS Modified log files for seven head-and-neck and prostate volumetric modulated arc therapy (VMAT) plans simulating leaf miscalibration were generated by shifting both leaf banks (systematic leaf gap errors: ±2.0, ±1.0, and ±0.5mm in opposite directions and systematic leaf shifts: ±1.0mm in the same direction) using MATLAB-based (MathWorks, Natick, MA) in-house software. The generated modified and non-modified log files were imported back into the treatment planning system and recalculated. Subsequently, the generalized equivalent uniform dose (gEUD) was quantified for the definition of the planning target volume (PTV) and organs at risks. RESULTS For MLC leaves calibrated within ±0.5mm, the quantified residual dose estimation errors that obtained from the slope of the linear regression of gEUD changes between non- and modified log file doses per leaf gap are in head-and-neck plans 1.32±0.27% and 0.82±0.17Gy for PTV and spinal cord, respectively, and in prostate plans 1.22±0.36%, 0.95±0.14Gy, and 0.45±0.08Gy for PTV, rectum, and bladder, respectively. CONCLUSIONS In this work, we determine the residual dose estimation errors for VMAT delivery using the log file-based patient dose calculation according to the MLC calibration accuracy.
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Affiliation(s)
- Yoshiyuki Katsuta
- Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan; Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Noriyuki Kadoya
- Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan.
| | - Yukio Fujita
- Department of Radiation Oncology, Tokai University Graduate School of Medicine, Isehara, Japan
| | - Eiji Shimizu
- Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan
| | - Kenichi Matsunaga
- Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan
| | - Haruo Matsushita
- Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Kazuhiro Majima
- Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan
| | - Keiichi Jingu
- Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan
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Park JC, Li JG, Arhjoul L, Yan G, Lu B, Fan Q, Liu C. Adaptive beamlet-based finite-size pencil beam dose calculation for independent verification of IMRT and VMAT. Med Phys 2015; 42:1836-50. [PMID: 25832074 DOI: 10.1118/1.4914858] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The use of sophisticated dose calculation procedure in modern radiation therapy treatment planning is inevitable in order to account for complex treatment fields created by multileaf collimators (MLCs). As a consequence, independent volumetric dose verification is time consuming, which affects the efficiency of clinical workflow. In this study, the authors present an efficient adaptive beamlet-based finite-size pencil beam (AB-FSPB) dose calculation algorithm that minimizes the computational procedure while preserving the accuracy. METHODS The computational time of finite-size pencil beam (FSPB) algorithm is proportional to the number of infinitesimal and identical beamlets that constitute an arbitrary field shape. In AB-FSPB, dose distribution from each beamlet is mathematically modeled such that the sizes of beamlets to represent an arbitrary field shape no longer need to be infinitesimal nor identical. As a result, it is possible to represent an arbitrary field shape with combinations of different sized and minimal number of beamlets. In addition, the authors included the model parameters to consider MLC for its rounded edge and transmission. RESULTS Root mean square error (RMSE) between treatment planning system and conventional FSPB on a 10 × 10 cm(2) square field using 10 × 10, 2.5 × 2.5, and 0.5 × 0.5 cm(2) beamlet sizes were 4.90%, 3.19%, and 2.87%, respectively, compared with RMSE of 1.10%, 1.11%, and 1.14% for AB-FSPB. This finding holds true for a larger square field size of 25 × 25 cm(2), where RMSE for 25 × 25, 2.5 × 2.5, and 0.5 × 0.5 cm(2) beamlet sizes were 5.41%, 4.76%, and 3.54% in FSPB, respectively, compared with RMSE of 0.86%, 0.83%, and 0.88% for AB-FSPB. It was found that AB-FSPB could successfully account for the MLC transmissions without major discrepancy. The algorithm was also graphical processing unit (GPU) compatible to maximize its computational speed. For an intensity modulated radiation therapy (∼12 segments) and a volumetric modulated arc therapy fields (∼90 control points) with a 3D grid size of 2.0 × 2.0 × 2.0 mm(3), dose was computed within 3-5 and 10-15 s timeframe, respectively. CONCLUSIONS The authors have developed an efficient adaptive beamlet-based pencil beam dose calculation algorithm. The fast computation nature along with GPU compatibility has shown better performance than conventional FSPB. This enables the implementation of AB-FSPB in the clinical environment for independent volumetric dose verification.
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Affiliation(s)
- Justin C Park
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Jonathan G Li
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Lahcen Arhjoul
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Guanghua Yan
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Bo Lu
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Qiyong Fan
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
| | - Chihray Liu
- Department of Radiation Oncology, University of Florida, Gainesville, Florida 32610-0385
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Denton TR, Shields LBE, Howe JN, Spalding AC. Quantifying isocenter measurements to establish clinically meaningful thresholds. J Appl Clin Med Phys 2015; 16:5183. [PMID: 26103187 PMCID: PMC5690087 DOI: 10.1120/jacmp.v16i2.5183] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 11/23/2014] [Accepted: 11/23/2014] [Indexed: 11/23/2022] Open
Abstract
A dataset range of isocenter congruency verification tests have been examined from a statistical perspective for the purpose of establishing tolerance levels that are meaningful, based on the fundamental limitation of linear accelerator isocentricity and the demands of a high-precision stereotactic radiosurgery program. Using a laser-defined isocenter, a total of 149 individual isocenter congruency tests were examined with recorded values for ideal spatial corrections to the isocenter test tool. These spatial corrections were determined from radiation exposures recorded on an electronic portal imaging device (EPID) at various gantry, collimator, and treatment couch combinations. The limitations of establishing an ideal isocenter were quantified from each variable which contributed to uncertainty in isocenter definition. Individual contributors to uncertainty, specifically, daily positioning setup errors, gantry sag, multileaf collimator (MLC) offset, and couch walkout, were isolated from isocenter congruency measurements to determine a clinically meaningful isocenter measurement. Variations in positioning of the test tool constituted, on average, 0.38 mm magnitude of correction. Gantry sag and MLC offset contributed 0.4 and 0.16 mm, respectively. Couch walkout had an average degrading effect to isocenter of 0.72 mm. Considering the magnitude of uncertainty contributed by each uncertainty variable and the nature of their combination, an appropriate schedule action and immediate action level were determined for use in analyzing daily isocenter congruency test results in a stereotactic radiosurgery (SRS) program. The recommendations of this study for this linear accelerator include a schedule action level of 1.25 mm and an immediate action level of 1.50mm, requiring prompt correction response from clinical medical physicists before SRS or stereotactic body radiosurgery (SBRT) is administered. These absolute values were derived from considering relative data from a specific linear accelerator and, therefore, represent a means by which a numerical quantity can be used as a test threshold with relative specificity to a particular linear accelerator.
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Affiliation(s)
- Travis R Denton
- The Norton Cancer Institute Radiation Center, Louisville, KY and Associates in Medical Physics, LLC, Greenbelt, MD.
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A quality assurance technique for the static multileaf collimator mode based on intrinsic base lines. JOURNAL OF RADIATION RESEARCH AND APPLIED SCIENCES 2014. [DOI: 10.1016/j.jrras.2014.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Mittauer K, Lu B, Yan G, Kahler D, Gopal A, Amdur R, Liu C. A study of IMRT planning parameters on planning efficiency, delivery efficiency, and plan quality. Med Phys 2013; 40:061704. [DOI: 10.1118/1.4803460] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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Mohammadi M, Bezak E. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device. J Med Phys 2012; 37:14-26. [PMID: 22363108 PMCID: PMC3283912 DOI: 10.4103/0971-6203.92716] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 09/29/2011] [Accepted: 10/06/2011] [Indexed: 11/13/2022] Open
Abstract
The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle3 treatment planning system (TPS). Using gamma evaluation with the ΔDmax and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.
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Devic S, McEwen MR, Orton CG. Radiochromic film is superior to ion chamber arrays for IMRT quality assurance. Med Phys 2010; 37:959-61. [DOI: 10.1118/1.3298377] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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