SU‐E‐T‐334: A Rapid Method for Testing the Accuracy of Heterogeneity Correction Algorithms Using a 2‐D Detector‐Array QA Tool

• Published in: Medical Physics Vol. 38; no. 6; p. 3564
• Main Authors: Chu, A, Feng, W, Liu, W, Chen, Z, Nath, R
• Format: Conference Proceeding Journal Article
• Language: English
• Published: American Association of Physicists in Medicine 01.06.2011
• Subjects: Electrodeposition; Electronic transport; Foams; Particle beam detectors; Photons; Quality assurance; Solid surfaces; Testing procedures; Thin films; Transport properties
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3612288

Purpose: To demonstrate an efficient quality assurance (QA) method using a 2‐D diode array to verify the absolute dose distribution generated by heterogeneity corrected treatment plans. Methods: The AAA, ETAR, and modified Batho heterogeneity corrected Eclipse treatment plans were compared against the measured data obtained with 6 and 18MV (Varian 2100CD) photon irradiation with the following two geometric setups: (1) Reference setup: An inhomogeneous phantom was sandwiched by a solid water slab (Gammex) and the 22×22cm2 MapCHECK detector (Sun Nuclear) under the incident photon beam that was perpendicular to the slabs. The sandwiched slab material consisted of low‐density foam occupying half of the detector area (11×22cm2), and another solid‐water slab on the other half. (2) Tested setup: two blocks of solid‐water separated by another slab of low‐density foam were erected vertically on the surface of the 2‐D array. A slightly oblique beam angle (<30o) allows primary photon field to pass through each slab of solid water and foam to project the field onto the array. Results: The measured 2‐D dose profiles from the first configuration (Reference setup) were reasonably predicted by all three algorithms, but only AAA among the three taking into account the electron transport shows the best results for the second setup. Conclusions: The geometric design of the second setup with oblique beam angle can enhance the characteristics of the complicated dose profile projected onto a 2‐D array as the transversal and longitudinal electron transports carry out non‐local dose deposit throughout inhomogeneous slabs by oblique primary photons. The combination of build‐up and build‐down profiles is usually illustrated by film dosimetry with much a more time‐consuming procedure.