Monte Carlo calculation of the dose distributions across a plane bone-marrow interface during diagnostic X-ray...

The distribution of dose across a plane bone-marrow interface on irradiation with various diagnostic X-ray beams at a representative site have been determined using the Monte Carlo method. The site was in a dorsal vertebra near its surface and situated at a depth of 70 mm under the skin. The X-ray beams studied were generated at 100, 90, 80 and 70 kV with 2 mm aluminium added filter and at 55 kV with 1 mm aluminium added filter. It was found that the dose to bone marrow due to excess photoelectrons produced in bone falls off rapidly as the distance from the bone-marrow interface increases. Consequently, the percentage excess dose to a plane bone-marrow cavity, which is almost constant for the range of kV studied, is significant only if the cavity size is small.