Validation of accordance of ArcCHECK diode detector output with Monte Carlo simulation in brachytherapy

There are several accepted methods to verify External Beam Radiation Therapy (EBRT) treatment plans, but there is no standard way to check the quality of a brachytherapy treatment plan.

This feasibility study assesses whether the ArcCHECK EBRT radiation detector can also be used to verify Treatment Planning System software quality check procedures for brachytherapy.

ArcCHECK is a three-dimensional matrix of 1386 semiconductor diodes, arranged spirally around an internal cylindrical space that is 32 cm long and 15 cm in diameter. The detector makes it possible to reproduce the distribution of sources in a planned EBRT procedure (energy range 6-22 MeV) using an appropriate phantom. Detector responses are displayed as a two-dimensional dose distribution map on the diode surface. In this pilot brachytherapy study, we determined values that characterized the output of the detectors to a simulated Ir-192 radiation source with an energy range of approximately 9-1378 keV, and compared this to the actual signal recorded by an ArcCHECK detector. Experimental treatment plan measurement was performed using a standard Elekta micro-Selectron-v2 unit equipped with an iridium-192 source. To avoid unit inconsistencies, the signal from each of the diodes and the simulation results were normalized to the maximum value, with similar statistical parameters.

The difference between diode indications in the simulation and the actual measurement was analyzed statistically to show the degree of general inconsistency between them. The average difference for diode pairs here is equal 1,07%, with standard deviation 3, 95%.

The results obtained represent the first quantitative evidence of potential usefulness of the ArcCHECK detector in brachytherapy Treatment Planning System software QC verification.