Monte Carlo calculation of beam quality correction for solid-state detectors and phantom scatter correction at 137Cs energy.

Beam quality correction kQQo (r), which reflects the absorbed energy dependence of the detector, is calculated for solid state detector materials diamond, LiF, Li2B4O7 and Al2O3 for the 137Cs RTR brachytherapy source using the Monte Carlo-based EGSnrc code system. The study also includes calculation of detector-specific phantom scatter corrections kphant (r) for solid phantoms such as PMMA, polystyrene, RW1, solid water, virtual water and plastic water. Above corrections are calculated as a function of distance r along the transverse axis of the source. kQQo (r) is about unity for the Li2B4O7 detector. LiF detector shows a gradual decrease in kQQo (r) with r (decrease is about 2% over the distance range of 1 - 15 cm). Diamond detector shows a gradual increase in kQQo (r)with r (about 3% larger than unity at 15 cm). In the case of Al2O3 detector, kQQo (r)decreases with r steeply (about 14% over the distance range of 1 - 15 cm). The study shows that some solid state detectors demonstrate distance-dependent kphant (r)values, but the degree deviation from unity depends on the type of solid phantom and the detector.