Monte Carlo-based dose calculation for 32 P patch source for superficial brachytherapy applications

Skin cancer treatment involving (32) P source is an easy, less expensive method of treatment limited to small and superficial lesions of approximately 1 mm deep. Bhabha Atomic Research Centre (BARC) has indigenously developed (32) P nafion-based patch source (1 cm 1 cm) for treating skin cancer. For this source, the values of dose per unit activity at different depths including dose profiles in water are calculated using the EGSnrc-based Monte Carlo code system. For an initial activity of 1 Bq distributed in 1 cm (2) surface area of the source, the calculated central axis depth dose values are 3.62 10 (-10) GyBq (-1) and 8.41 10 (-11) GyBq (-1) at 0.0125 and 1 mm depths in water, respectively. Hence, the treatment time calculated for delivering therapeutic dose of 30 Gy at 1 mm depth along the central axis of the source involving 37 MBq activity is about 2.7 hrs.