TY - JOUR

T1 - A practical method to optimize quality assurance results of arc therapy plans in beam modeling

AU - Xue, Jinyu

AU - Wang, Hesheng

AU - Barbee, David

AU - Schmidt, Matthew

AU - Das, Indra J.

N1 - Publisher Copyright:
© 2018 Journal of Medical Physics | Published by Wolters Kluwer - Medknow.

PY - 2018/4/1

Y1 - 2018/4/1

N2 - Dosimetric accuracy of a volumetric modulated arc therapy (VMAT) plan is directly related to the beam model, particularly with multileaf collimator characterization. Inappropriate dosimetric leaf gap (DLG) value can lead to a suboptimal beam model, with significant failure in patient-specific quality assurance (PSQA) of VMAT plans. This study addressed the systematic issue of beam modeling and developed a practical method to determine the optimal DLG value for a beam model. Several complex VMAT plans were selected for the quality assurance analysis using the variable DLG values. The results of three-dimensional (3D) Gamma analysis as a function of the DLG at 3%/3 mm, 2%/2 mm, and 1%/1 mm criteria were fitted by a polynomial curve. The DLG value corresponding to the maximum Gamma passing rate for each polynomial fitting function was derived, and the average was calculated to be the optimal DLG value for each model. The 3D Gamma analysis was repeated with the optimal DLG value to verify the dosimetric accuracy of each VMAT case by PSQA. Gamma passing rates are seen to vary considerably with the DLG values and different analysis criteria (3%/3 mm, 2%/2 mm, and 1%/1 mm) for each case. The optimal DLG derived for each model was 1.16 mm and 1.10 mm, much larger than the measured value (about 0.3 mm). The beam models with the optimal DLG was able to produce an average Gamma passing rate of 97.1% (range, 94.6%- 99.1%) at 3%/3 mm and 93.5% (range, 89.0%- 96.5%) at 2%/2 mm for one beam model, and 97.1% (range, 94.8%- 99.1%) at 3%/3 mm, and 93.3% (range, 88.8%- 96.7%) at 2%/2 mm for another. The overall accuracy of dose calculation for VMAT plans should be optimized with a compromise of varied modulation complexities in a beam model. We have developed a practical method to derive the optimal DLG value for each beam model based on the Gamma passing criterion. This technique should be applicable in general for all beam energies and patient cases.

AB - Dosimetric accuracy of a volumetric modulated arc therapy (VMAT) plan is directly related to the beam model, particularly with multileaf collimator characterization. Inappropriate dosimetric leaf gap (DLG) value can lead to a suboptimal beam model, with significant failure in patient-specific quality assurance (PSQA) of VMAT plans. This study addressed the systematic issue of beam modeling and developed a practical method to determine the optimal DLG value for a beam model. Several complex VMAT plans were selected for the quality assurance analysis using the variable DLG values. The results of three-dimensional (3D) Gamma analysis as a function of the DLG at 3%/3 mm, 2%/2 mm, and 1%/1 mm criteria were fitted by a polynomial curve. The DLG value corresponding to the maximum Gamma passing rate for each polynomial fitting function was derived, and the average was calculated to be the optimal DLG value for each model. The 3D Gamma analysis was repeated with the optimal DLG value to verify the dosimetric accuracy of each VMAT case by PSQA. Gamma passing rates are seen to vary considerably with the DLG values and different analysis criteria (3%/3 mm, 2%/2 mm, and 1%/1 mm) for each case. The optimal DLG derived for each model was 1.16 mm and 1.10 mm, much larger than the measured value (about 0.3 mm). The beam models with the optimal DLG was able to produce an average Gamma passing rate of 97.1% (range, 94.6%- 99.1%) at 3%/3 mm and 93.5% (range, 89.0%- 96.5%) at 2%/2 mm for one beam model, and 97.1% (range, 94.8%- 99.1%) at 3%/3 mm, and 93.3% (range, 88.8%- 96.7%) at 2%/2 mm for another. The overall accuracy of dose calculation for VMAT plans should be optimized with a compromise of varied modulation complexities in a beam model. We have developed a practical method to derive the optimal DLG value for each beam model based on the Gamma passing criterion. This technique should be applicable in general for all beam energies and patient cases.

KW - Beam model

KW - dosimetric leaf gap

KW - quality assurance

KW - treatment planning system

KW - volumetric modulated arc therapy

UR - http://www.scopus.com/inward/record.url?scp=85049197170&partnerID=8YFLogxK

U2 - 10.4103/jmp.JMP_144_17

DO - 10.4103/jmp.JMP_144_17

M3 - Article

AN - SCOPUS:85049197170

SN - 0971-6203

VL - 43

SP - 106

EP - 111

JO - Journal of Medical Physics

JF - Journal of Medical Physics

IS - 2

ER -