Registration of Prostate Brachytherapy Seeds with Prostate Anatomy for Improved Patient Dosimetry

摘要

Brachytherapy of prostate cancer involves permanent implantation of radioactive seeds in the prostate gland under transrectal ultrasound (TRUS) and fluoroscopic guidance with the goal to treat the entire gland to a prescribed tumoricidal dose. The seed coordinates are calculated prior to the procedure. However, due to uncertainties associated with the seed insertion process and changes in the anatomy, it is difficult to faithfully reproduce the planned dose distribution. The procedure can be improved substantially by identifying the underdosed regions via real-time dosimetry before the completion of implantation. The physician can then insert additional seeds to achieve clinically needed dose distribution. One possible method of performing such dosimetry is to fuse TRUS (which images the prostate gland very well but not the metallic seeds) and fluoroscopy (which images metallic seeds well but not soft tissue) data. We have developed a technique to register the 3D seed positions reconstructed from multiple fluoroscopic images with the prostate TRUS images. The technique utilizes a set of fiducials that are detectable by both imaging modalities. The method was tested using a prostate mimicking phantom. The results demonstrate that the method is sufficiently accurate and practical for clinical use.