NOVEL ULTRASONIC IMAGING OF BRACHYTHERAPY SEEDS

Riverside Research Institute, New York NY

Investigators

Abstract

DESCRIPTION: (Applicant's Description) Current methods of implanting radioactive seeds for brachytherapy of prostate cancer rely upon B-mode imaging for planning the dose and monitoring implantation in the operating room. However, insertion of seed-implanting needles causes hemorrhage, edema, and other tissue changes in the prostate; these changes create clutter that interferes with visualization of actual seed locations. For a variety of reasons, the actual locations of seeds often differ from the planned locations; these differences may result in a considerable local reduction in the actually delivered radiation dose below the prescribed dose. However, because of the limited ability of current imaging methods to visualize seeds in the operating room, on-line correction for inadequate dosage cannot be made during the procedure. We propose to develop novel methods of ultrasonic imaging that can more effectively image seeds in the operating room during brachytherapy in a manner compatible with current dose-planning software so that corrections for misplaced seeds can be made while the implantation procedure is in progress. In the feasibility-assessment phase of our proposed study, we will evaluate and select an optimal combination of methods for visualizing seeds in the presence of tissue-caused clutter. These methods include spectrum analysis of radio-frequency ultrasonic echo signals, elastographic analysis, and harmonic-signal analysis; all can provide results that can be displayed in seed-depicting images. In the developmental phase of our proposed study, we will incorporate the selected method or combination of methods into a real-time imaging prototype based upon the ultrasonic scanner now used in the Department of Radiation Oncology (DRO) at the New York Presbyterian Medical Center for brachytherapy planning and guidance of seed implantation. DRO oncologists will use the seed images generated by the prototype to detect misplacements of seeds that cause underdosing. The oncologist then will add seeds to the seed-deprived region to assure that the delivered dose reaches the prescription level while not exceeding limits for other regions, such as the urethra, that are to be spared. These studies will be undertaken by Riverside Research Institute (a private not-for-profit research organization); Columbia University (a major medical research institution); and Spectrasonics Imaging, Inc. (a small, commercial technology corporation).