Movement inaccuracies of up to two centimetres may occur in prostate radiation. “During the radiation treatment, patients have to lie on a table for some 20 minutes without moving. Over time, the muscles relax and the pelvis drops. As a consequence, the radiation may focus on the bladder or other organs. In our calculations, we concentrated on the precision of localising the prostate and on improvement potentials in treatment,” explained Karin Poljanc, Assistant Professor at the Atomic Institute of Austrian Universities.
In the study, Poljanc and her team used a number of ultrasound examinations that allowed for a precise localisation of the patients’ organs from the outside. In a next step, the scientists analysed the positioning of 60 patients, and evaluated the deviation of radiation in various spatial directions, such as to the right or left, and upward or downward (using 420 radiation plans for thirty patients).
While it takes more time, an ultrasound system makes the shifts in position visible and traceable. If the deviation exceeds 0.8 cm, the radiology technicians are responsible for returning the patient to the correct position to ensure that the radiation only targets the specified area.
In the subsequent study phase, Poljanc and her group calculated normal tissue compensation rates and the probability of tumour control. These approaches serve as forecasts and provide clues for the likelihood of healing. After a study period of some 2.5 years, the scientists were able to implement the calculated average positioning inaccuracies in a radiation planning system.
As part of their study of different radiation sources, the scientists found that localisation aids, such as ultrasound systems, are indispensable for accurate proton therapy of prostate carcinomas. In most cases, this combination leads to therapy results with a high level of tissue preservation.
MEDICA.de; Source: Technische Universität Wien