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Price AT, Knutson NC, Kim T, Green OL. Commissioning a secondary dose calculation software for a 0.35 T MR-linac. J Appl Clin Med Phys 2022; 23:e13452. [PMID: 35166011 PMCID: PMC8906210 DOI: 10.1002/acm2.13452] [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: 12/21/2020] [Revised: 08/09/2021] [Accepted: 08/28/2021] [Indexed: 11/09/2022] Open
Abstract
Secondary external dose calculations for a 0.35 T magnetic resonance image-guided radiation therapy (MRgRT) are needed within the radiation oncology community to follow safety standards set forth within the field. We evaluate the commercially available software, RadCalc, in its ability to accurately perform monitor unit dose calculations within a magnetic field. We also evaluate the potential effects of a 0.35 T magnetic field upon point dose calculations. Monitor unit calculations were evaluated with (wMag) and without (noMag) a magnetic field considerations in RadCalc for the ViewRay MRIdian. The magnetic field is indirectly accounted for by using asymmetric profiles for calculation. The introduction of double-stacked multi-leaf collimator leaves was also included in the monitor unit calculations and a single transmission value was determined. A suite of simple and complex geometries with a variety field arrangements were calculated for each method to demonstrate the effect of the 0.35 T magnetic field on monitor unit calculations. Finally, 25 patient-specific treatment plans were calculated using each method for comparison. All simple geometries calculated in RadCalc were within 2% of treatment planning system (TPS) values for both methods, except for a single noMag off-axis comparison. All complex muilt-leaf collimator (MLC) pattern calculations were within 5%. All complex phantom geometry calculations were within 5% except for a single field within a lung phantom at a distal point. For the patient calculations, the noMag method average percentage difference was 0.09 ± 2.5% and the wMag average percentage difference was 0.08 ± 2.5%. All results were within 5% for the wMag method. We performed monitor unit calculations for a 0.35 T MRgRT system using a commercially available secondary monitor unit dose calculation software and demonstrated minimal impact of the 0.35 T magnetic field on monitor unit dose calculations. This is the first investigation demonstrating successful calculations of dose using RadCalc in the low-field 0.35 T ViewRay MRIdian system.
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Affiliation(s)
- Alex T Price
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Nels C Knutson
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Taeho Kim
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Olga L Green
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri, USA
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Knutson NC, Schmidt MC, Reynoso FJ, Hao Y, Mazur TR, Laugeman E, Hugo G, Mutic S, Li HH, Ngwa W, Cai B, Sajo E. Automated and robust beam data validation of a preconfigured ring gantry linear accelerator using a 1D tank with synchronized beam delivery and couch motions. J Appl Clin Med Phys 2020; 21:200-207. [PMID: 32614511 PMCID: PMC7484825 DOI: 10.1002/acm2.12946] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 04/25/2020] [Accepted: 05/12/2020] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To develop an efficient and automated methodology for beam data validation for a preconfigured ring gantry linear accelerator using scripting and a one-dimensional (1D) tank with automated couch motions. MATERIALS AND METHODS Using an application programming interface, a program was developed to allow the user to choose a set of beam data to validate with measurement. Once selected the program generates a set of instructions for radiation delivery with synchronized couch motions for the linear accelerator in the form of an extensible markup language (XML) file to be delivered on the ring gantry linear accelerator. The user then delivers these beams while measuring with the 1D tank and data logging electrometer. The program also automatically calculates this set of beams on the measurement geometry within the treatment planning system (TPS) and extracts the corresponding calculated dosimetric data for comparison to measurement. Once completed the program then returns a comparison of the measurement to the predicted result from the TPS to the user and prints a report. In this work lateral, longitudinal, and diagonal profiles were taken for fields sizes of 6 × 6, 8 × 8, 10 × 10, 20 × 20, and 28 × 28 cm2 at depths of 1.3, 5, 10, 20, and 30 cm. Depth dose profiles were taken for all field sizes. RESULTS Using this methodology, the TPS was validated to agree with measurement. All compared points yielded a gamma value less than 1 for a 1.5%/1.5 mm criteria (100% passing rate). Off axis profiles had >98.5% of data points producing a gamma value <1 with a 1%/1 mm criteria. All depth profiles produced 100% of data points with a gamma value <1 with a 1%/1 mm criteria. All data points measured were within 1.5% or 2 mm distance to agreement. CONCLUSIONS This methodology allows for an increase in automation in the beam data validation process. Leveraging the application program interface allows the user to use a single system to create the measurement files, predict the result, and then compare to actual measurement increasing efficiency and reducing the chance for user input errors.
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Affiliation(s)
- Nels C Knutson
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA.,Department of Physics, University of Massachusetts Lowell, Lowell, MA, USA
| | - Matthew C Schmidt
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA.,Department of Physics, University of Massachusetts Lowell, Lowell, MA, USA
| | - Francisco J Reynoso
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Yao Hao
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Thomas R Mazur
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Eric Laugeman
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Geoffrey Hugo
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Sasa Mutic
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - H Harold Li
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Wilfred Ngwa
- Department of Physics, University of Massachusetts Lowell, Lowell, MA, USA
| | - Bin Cai
- Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO, USA
| | - Erno Sajo
- Department of Physics, University of Massachusetts Lowell, Lowell, MA, USA
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