EGSnrc-based depth-dependent photon energy response and phantom scatter corrections for low-energy brachytherapy...

In the present study, beam quality correction, [Formula: see text], and phantom scatter correction, k_phan(r), for low-energy brachytherapy sources, ¹³¹Cs, ¹²⁵I, and ¹⁰³Pd, are calculated using the Monte Carlo-based EGSnrc code system as a function of the distance along the transverse axis of the source. The solid-state detectors investigated are diamond, LiF, Li₂B₄O₇, Al₂O₃, and radiochromic films, such as HS, EBT, EBT2, EBT3, RTQA, XRT, and XRQA. The solid phantoms investigated are polystyrene, PMMA, virtual water, solid water, plastic water (LR), A150, RW1, RW3, and WE210. For a given detector and brachytherapy source, [Formula: see text] is independent of distance in the water phantom. Meanwhile, for a given detector, k_phan(r) depends on the distance from the source for the investigated solid phantoms. Moreover, the k_phan(r) values do not change with the detector type for sources ¹³¹Cs, ¹²⁵I, and ¹⁰³Pd at all distances. The LR and A150 phantoms are water equivalent for the investigated distances of 1-5 cm. The phantoms including solid water, virtual water, and WE210 are not water-equivalent for distances beyond 1 cm. Furthermore, PMMA, polystyrene, RW1, and RW3 are not water equivalent.