Novel methods of analyzing radio-frequency echo signals for the purpose of imaging brachytherapy seeds used to treat prostate cancer

Brachytherapy using small implanted radioactive seeds is becoming an increasingly popular method for treating prostate cancer. Seeds are inserted into the prostate transperineally using ultrasound guidance. Dosimetry software determines the optimal placement of seeds for achieving the prescribed dose based on ultrasonic determination of the gland boundaries. However, because of prostate movement after planning images are acquired and during the implantation procedure, seeds commonly are not placed in the desired locations and the delivered dose may differ from the prescribed dose. Current methods of ultrasonic imaging do not adequately display implanted seeds for the purpose of correcting the delivered dose. We are investigating new methods of ultrasonic imaging that overcome limitations of conventional ultrasound. These methods include resonance, modified elastographic, and signature techniques. Each method shows promise for enhancing the visibility of seeds in ultrasound images. Combining the information provided by each method may reduce ambiguities in determining where seeds are present or absent. If successful, these novel imaging methods will enable correction of seed-misplacement errors during the implantation procedure, and hence will improve the therapeutic radiation dose delivered to target tissues.