Target localization and real-time tracking using the Calypso 4D localization system in patients with localized prostate cancer.

Purpose: The Calypso 4D Localization System is being developed to provide accurate, precise, objective, and continuous target localization during radiotherapy. This study involves the first human use of the system, to evaluate the localization accuracy of this technique compared with radiographic localization and to assess its ability to obtain real-time prostate-motion information.

Methods And Materials: Three transponders were implanted in each of 20 patients.