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

摘要

Beam quality correction, k QQ 0 ( r ) , for solid-state detectors diamond, LiF, Li 2 B 4 O 7 , Al 2 O 3 , and plastic scintillator are calculated as a function of distance, r, along the transverse axis of the 60 Co and 192 Ir brachytherapy sources using the Monte Carlo-based EGSnrc code system. This study also includes calculation of detector-specific phantom scatter correction, k phan ( r ) , for solid phantoms such as PMMA, polystyrene, solid water, virtual water, plastic water, RW1, RW3, A150, and WE210. For 60 Co source, k QQ 0 ( r ) is about unity and distance-independent for diamond, plastic scintillator, Li 2 B 4 O 7 and LiF detectors. For this source, k QQ 0 ( r ) decreases gradually with r for Al 2 O 3 detector (about 6% smaller than unity at 15 cm). For 192 Ir source, k QQ 0 ( r ) is about unity and distance-independent for Li 2 B 4 O 7 detector (overall variation is about 1% in the distance range of 1–15 cm). For this source, k QQ 0 ( r ) increases with r for diamond and plastic scintillator (about 6% and 8% larger than unity at 15 cm, respectively). Whereas k QQ 0 ( r ) decreases with r gradually for LiF (about 4% smaller than unity at 15 cm) and steeply for Al 2 O 3 (about 25% smaller than unity at 15 cm). For 60 Co 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, Li 2 B 4 O 7 and LiF detectors, but show distance-dependent k phan ( r ) values for Al 2 O 3 detector. PMMA phantom is water-equivalent at all distances for Al 2 O 3 detector, but shows distance-dependent k phan ( r ) values for remaining detectors. A150 phantom shows distance-dependent k phan ( r ) values for all the investigated detector materials. For 192 Ir source, solid water, virtual water, RW3, and WE210 phantoms are water-equivalent for diamond, plastic scintillator, Li 2 B 4 O 7 and LiF detectors, but show distance-dependent k phan ( r ) values for Al 2 O 3 detector. All other phantoms show distance-dependent k phan ( r ) values for all the detector materials.PACS numbers: 87.10.Rt, 87.53.Bn, 87.53.Jw