Ultrasound guided percutaneous radiotherapy of prostate cancer

The number of patients treated by radiation therapy of localized prostate cancer (PC) increases significantly because of the high incidence and detection of PC due to an increasing mean age of men as well as an increasing use of laboratory tests (PSA). Different clinical studies could demonstrate a better local tumor control with higher total doses. Because the risk of severe side effects decreases with decreasing the volume irradiated with high doses of these organs the margin between the CTV and the PTV should be as small as possible. It is well known, that the prostate shifts with different filling of both the rectum and the bladder. In most cases the definition of the target volume is based on one initial CT-scan. The expected movement of the prostate during the next 7 to 8 weeks of treatment is taken into account by determining the planning target volume (PTV) in such a manner that the clinical target volume (CTV) is enclosed by the 95% isodose in at least 95% of the treatment sessions. A safety margin of 8 to 15 millimeters around the CTV (e.g. the prostate) is usually included when defining the PTV. This margin can only be reduced if the exact shape and position of the CTV is known during or directly before the radiation treatment. In this paper we investigate the use of ultrasound (US) to increase the accuracy of patient setup for prostate cancer[1].