Type of publication:
*Maryke Fox, *Mike Alexander
IPEM Medical Physics & Engineering Conference & Biennial Radiotherapy Meeting Proceedings, York, UK. September 2018
An increasing number of patients presenting for prostate radiotherapy have prosthetic hips. It is well known
that modern treatment planning systems are unable to accurately model dose in the vicinity of high density
prostheses. This work sought to characterise how dose is modelled by the Eclipse TPS around a hip prosthesis in a water phantom by comparing the modelled dose with dose measured by a Farmer chamber and find estimate dose due to scatter. Transmission, lateral scatter and back scatter were measured at a range of distances from the prosthesis and compared to the Eclipse modelled dose. It was found that dose distal to the prosthesis was underestimated by over 20%, backscatter was not modelled at all by Eclipse but lateral scatter was adequately modelled. The dose due to backscatter and lateral scatter from the prosthesis were not significant contributors to dose. These results indicate that planners should avoid treating through prosthetic hips, and that dose due to scatter was unlikely to cause ill effects.