Purpose: To reduce errors in the positioning of patients treated with external conformal radiotherapy for prostate cancer, we evaluated both the use of an immobilization device and new fiducial markers.
Materials and methods: The immobilization device consisted of an individual mold made of polyurethan foam. Two sets of skin markers located on the anterior tibial surfaces were used to identify the pelvic isocenter. The patient's position was evaluated by orthogonal port films which were then compared with the original simulation film.
Results: Results are presented with respect to orthogonal axes. Comparison with classic procedures without immobilization showed that use of the mold and new fiducial markers led to a decrease in set-up errors which were less than 5 mm.
Conclusion: With the use of an immobilization device and optimized techniques for patients' positioning, conformal radiotherapy of prostate cancer is more accurate.