Monte Carlo-based beam quality and phantom scatter corrections for solid-state detectors in 60Co and 192Ir brachytherapy dosimetry.

Beam quality correction, kQQ0(r), for solid-state detectors diamond, LiF, Li2B4O7, Al2O3, and plastic scintillator are calculated as a function of distance, r, along the transverse axis of the 60Co and 192Ir brachytherapy sources using the Monte Carlo- based EGSnrc code system. This study also includes calculation of detector-specific phantom scatter correction, kphan(r), for solid phantoms such as PMMA, polysty- rene, solid water, virtual water, plastic water, RW1, RW3, A150, and WE210. For 60Co source, kQQ0(r) is about unity and distance-independent for diamond, plastic scintillator, Li2B4O7 and LiF detectors. For this source, kQQ0(r) decreases gradually with r for Al2O3 detector (about 6% smaller than unity at 15 cm). For 192Ir source, kQQ0(r) is about unity and distance-independent for Li2B4O7 detector (overall variation is about 1% in the distance range of 1-15 cm). For this source, kQQ0(r) increases with r for diamond and plastic scintillator (about 6% and 8% larger than unity at 15 cm, respectively). Whereas kQQ0(r) decreases with r gradually for LiF (about 4% smaller than unity at 15 cm) and steeply for Al2O3 (about 25% smaller than unity at 15 cm). For 60Co source, solid water, virtual water, RW1, RW3, and WE210 phantoms are water-equivalent for all the investigated solid-state detectors. Whereas polystyrene and plastic water phantoms are water-equivalent for diamond, plastic scintillator, Li2B4O7 and LiF detectors, but show distance-dependent kphan(r) values for Al2O3 detector. PMMA phantom is water-equivalent at all distances for Al2O3 detector, but shows distance-dependent kphan(r) values for remaining detec- tors. A150 phantom shows distance-dependent kphan(r) values for all the investigated detector materials. For 192Ir source, solid water, virtual water, RW3, and WE210 phantoms are water-equivalent for diamond, plastic scintillator, Li2B4O7 and LiF detectors, but show distance-dependent kphan(r) values for Al2O3 detector. All other phantoms show distance-dependent kphan(r) values for all the detector materials.