Beam-commissioning methodology for a three-dimensional convolution/superposition photon dose algorithm.

George Starkschall,Roy E Steadham,Richard A Popple,Isaac I Rosen,Salahuddin Ahmad

doi:10.1120/jacmp.v1i1.2651

George Starkschall, Roy E Steadham + Show 3 more

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https://doi.org/10.1120/jacmp.v1i1.2651

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Abstract

Commissioning beam data for the convolution/superposition dose‐calculation algorithm used in a commercial three‐dimensional radiation treatment planning (3D RTP) system (PINNACLE3, ADAC Laboratories, Milpitas, CA) can be difficult and time consuming. Sixteen adjustable parameters, as well as spectral weights representing a discrete energy spectrum, must be fit to sets of central‐axis depth doses and off‐axis profiles for a large number of field sizes. This paper presents the beam‐commissioning methodology that we used to generate accurate beam models. The methodology is relatively rapid and provides physically reasonable values for beam parameters. The methodology was initiated by using vendor‐provided automodeling software to generate a single set of beam parameters that gives an approximate fit to relative dose distributions for all beams, open and wedged, in a data set. A limited number of beam parameters were adjusted by small amounts to give accurate beam models for four open‐beam field sizes and three wedged‐beam field sizes. Beam parameters for other field sizes were interpolated and validated against measured beam data. Using this methodology, a complete set of beam parameters for a single energy can be generated and validated in approximately 40 h. The resulting parameter values yielded calculated relative doses that matched measured relative doses in a water phantom to within 0.5–1.0% along the central axis and 2% along off‐axis beam profiles for field sizes from 4cm×4cm to the largest field size available. While the methodology presented is specific to the ADAC PINNACLE3 treatment planning system, the approach should apply to other implementations of the dose model in other treatment planning system.PACS number(s): 87.53.–j, 87.66.–a

Highlights

Radiation treatment planning systems that support three-dimensional3Dvisualization and dose computation are becoming more prevalent in radiation oncology clinics
Users realize that 3D radiation treatment planning3D RTPprovides increased capabilities over the more conventional two-dimensional radiation treatment planning2D RTP, they are discovering that the 3D RTP process and its treatment planning systems require significantly more quality assurance support.[1]
Acquire the appropriate parameters for a sophisticated beam model used in a 3D RTP system than for data-driven beam models such as those commonly used in 2D RTP systems

Summary

Introduction

Radiation treatment planning systems that support three-dimensional3Dvisualization and dose computation are becoming more prevalent in radiation oncology clinics. Users realize that 3D radiation treatment planning3D RTPprovides increased capabilities over the more conventional two-dimensional radiation treatment planning2D RTP, they are discovering that the 3D RTP process and its treatment planning systems require significantly more quality assurance support.[1] The simulation of radiation beams in 3D RTP systems is more complex than that in 2D RTP systems, relying more on beam models rather than on tabulations and modifications of measured data.[2,3,4] The commissioning of a clinical treatment beam, i.e., acquiring the appropriate parameters to support the dose-calculation model for the particular beam configuration, is a task of major significance for a model-based dose-calculation algorithm. Papers have been presented to assist the physicist in this task,[5,6,7,8] illustrating the difficulty of the procedure

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