Effect of immobilization in treatment planning of pelvic malignancies

ABSTRACT

This study was carried out on 14 adult patients treated by radiotherapy from different types of pelvic malignancies. Most of the recorded craniocaudal and lateral set up deviations were less in immobilized patients than those in non immobilized patients. Difference in lateral deviations was found to be statistically significant with no significant difference in the craniocaudal deviations. Concerning the effect of treatment position on the set up variation, there was a significant difference between craniocaudal deviations in non immobilized and mobilized patients treated in the supine and prone positions, while for the lateral set up deviations, there was no statistically significant difference between supine and prone positions. The effect of different deviations on the dose distribution to the target volume was calculated using the computerized planning unit. A deviation above 15 mm was noted to affect the mean dose by more than 5%, which is less than the accuracy level recommended by the ICRU