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SU‐E‐T‐223: Investigation of the Accuracy of Two‐Dimensional Dose Distributions Measurement From High‐Dose‐Rate Brachytherapy Ir‐192 Source Using Multiple‐Diode‐Array Detector (MapCheck2)
Author(s) -
Taguenang J,
De La Fuente T Herman,
Ahmad S,
Ali I
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4888553
Subject(s) - imaging phantom , materials science , diode , brachytherapy , detector , calibration , optics , dosimetry , range (aeronautics) , physics , nuclear medicine , optoelectronics , medicine , radiation therapy , quantum mechanics , composite material
Purpose: To investigate the dosimetric accuracy of multiple‐diode‐array detector (Mapcheck2) for high‐dose‐rate brachytherapy Ir‐192 source. The two‐dimensional (2D) dose distributions measured with MapCheck2 were validated with EBT2 Gafchromic film measurement and AAPM task‐group‐ 43 (TG‐43) modeling. Methods: 2D‐dose distributions from Ir‐192 source were measured with MapCheck2 and EBT2‐films. MapCheck2 response was corrected for effects: directional dependence, diode and phantom heterogeneity. Optical density growth of the film was controlled by synchronized scanning of the film exposed to Ir‐192 and calibration films exposed to 6 MV linac beams. Similarly, MapCheck2 response was calibrated to dose using 6 MV beams. An empirical model was developed for the dose distributions measured with Mapcheck2 that considered directional, diode and phantom heterogeneity corrections. The dose deposited in solid‐state‐detectors was modeled using a cavity theory model for the diode. This model was then validated with measurements using EBT2‐films and calculations with TG‐43. Results: The response of MapCheck2 has been corrected for different effects including: (a) directional dependence of 0–20% over angular range 0o–90o, (b) phantom heterogeneity (3%) and (c) diode heterogeneity (9%). The corrected dose distributions measured with MapCheck2 agreed well with the measured dose distributions from EBT2‐film and with calculations using TG‐43 within 5% over a wide range of dose levels and rates. The advantages of MapCheck2 include less noisy, linear and stable response compared with film. The response of MapCheck2 exposed to 192Ir‐source showed no energy dependence similar to its response to MV energy beam. Detection spatial‐resolution of individual diodes was 0.8×0.8 mm2, however, 2DMapCheck2 resolution is limited by distance between diodes (7.07 mm). Conclusion: The dose distribution measured with MapCheck2 agreed well within 5% with that measured using EBT2‐films; and calculations with TG‐ 43. Considering correction of artifacts, MapCheck2 provides a compact, practical and accurate dosimetric tool for measurement of 2D‐dose distributions for brachytherapy Ir‐192.