Online dose reconstruction for tracked volumetric arc therapy: Real‐time implementation and offline quality assurance for prostate SBRT

• Published in: Medical physics (Lancaster) Vol. 44; no. 11; pp. 5997 - 6007
• Main Authors: Kamerling, Cornelis Ph, Fast, Martin F., Ziegenhein, Peter, Menten, Martin J., Nill, Simeon, Oelfke, Uwe
• Format: Journal Article
• Language: English
• Published: United States 01.11.2017
• Subjects: Humans; Male; MLC tracking; online dose reconstruction; online quality assurance; Online Systems; Prostatic Neoplasms - radiotherapy; Quality Control; Radiation Dosage; Radiometry; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated; Time Factors; volumetric arc therapy; online dose reconstruction; online quality assurance; volumetric arc therapy; MLC tracking
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1002/mp.12522

Purpose Firstly, this study provides a real‐time implementation of online dose reconstruction for tracked volumetric arc therapy (VMAT). Secondly, this study describes a novel offline quality assurance tool, based on commercial dose calculation algorithms. Methods Online dose reconstruction for VMAT is a computationally challenging task in terms of computer memory usage and calculation speed. To potentially reduce the amount of memory used, we analyzed the impact of beam angle sampling for dose calculation on the accuracy of the dose distribution. To establish the performance of the method, we planned two single‐arc VMAT prostate stereotactic body radiation therapy cases for delivery with dynamic MLC tracking. For quality assurance of our online dose reconstruction method we have also developed a stand‐alone offline dose reconstruction tool, which utilizes the RayStation treatment planning system to calculate dose. Results For the online reconstructed dose distributions of the tracked deliveries, we could establish strong resemblance for 72 and 36 beam co‐planar equidistant beam samples with less than 1.2% deviation for the assessed dose‐volume indicators (clinical target volume D98 and D2, and rectum D2). We could achieve average runtimes of 28–31 ms per reported MLC aperture for both dose computation and accumulation, meeting our real‐time requirement. To cross‐validate the offline tool, we have compared the planned dose to the offline reconstructed dose for static deliveries and found excellent agreement (3%/3 mm global gamma passing rates of 99.8%–100%). Conclusion Being able to reconstruct dose during delivery enables online quality assurance and online replanning strategies for VMAT. The offline quality assurance tool provides the means to validate novel online dose reconstruction applications using a commercial dose calculation engine.