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.