Comparison of treatment planning dose calculations with measurements and Monte Carlo calculations in a RANDO phantom

Solid tumours are often treated with external beams of photons generated by Bremsstrahlung radiation. These beams are shaped and filtered to optimise the dose to specific regions defined by the treatment plans, which may involve irradiations from multiple angles. It is important that doses to healthy tissue do not exceed tolerance doses and that the dose to the tumour is maximised. To accomplish these objectives, commercially available 3-D treatment planning software is used to calculate doses to healthy tissue and to the tumour. It is generally believed that these commercial software packages calculate doses through the patient to within a few per cent. In order to examine this claim, dose calculations obtained from ADAC software for external beam treatment to the pelvic region of a RANDO phantom are compared with 37 thermoluminescence dosemeters placed into several slices of a RANDO phantom. The phantom was irradiated to obtain a prescription dose of 180 cGy at the tumour location. Data from homogeneous regions agree within several per cent with results obtained from ADAC software, whereas this comparison is less favourable in regions of heterogeneity. Results from Monte Carlo calculations in a homogeneous phantom are comparable to results from ADAC treatment planning software.