Program Information
A Computer Program for Physics Second Manual Calculation for Low-Dose-Rate Brachytherapy
W Taylor*, A Ayan , J Woollard , N Gupta , Ohio State Univ, Columbus, OH
Presentations
SU-I-GPD-T-36 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: A pre-treatment and commissioning recommendation for low-dose-rate (LDR) brachytherapy treatments is that a secondary calculation check be performed of the treatment planning system. The purpose of this study is to create and implement a calculation tool utilizing the TG-43U1 formalism to perform second check dose calculations for LDR brachytherapy treatment plans.
Methods: Using DICOM generated radiation therapy treatments plans can decrease the number of possible transcription errors that may occur during entry of secondary calculation parameters. We have developed a MATLAB(TM) code, which extracts the necessary information for calculation. The dose is calculated using the TG-43U1 parameters. Prior to implementation, the program was benchmarked against a manual calculation spreadsheet. Both of these secondary calculation check methods were compared to BrachyVision(TM). All calculations were performed with eye plaque plans utilizing the Best(R) I-125 Model 2301 source. Dose calculation to the sclera and prescription points were evaluated for 5 patients. The prescription point is ~1 cm from the centroid of the seed collection. The sclera point is off-axis with respect to the prescription point.
Results: The average percent differences between the manual spreadsheet calculation and MATLAB(TM) program for the prescription and sclera points were 0.04% ± 0.22% and -0.86% ± 0.58%, respectively. The average percent differences between the manual spreadsheet and BrachyVision(TM) for the prescription and sclera points were -0.04% ± 0.23% and -0.25% ± 1.23%, respectively. The average percent differences between the MATLAB(TM) program and BrachyVision(TM) for the prescription and sclera points were -0.03% ± 0.15% and -0.95% ± 1.04%, respectively. Differences between the secondary check calculations were greater for the off-axis sclera point because both calculations use the point-source approximation and the anisotropic factor was assumed to be 1.
Conclusion: The developed program was implemented clinically and streamlined the manual second calculation process for LDR brachytherapy treatment plans.
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