Review of intraoperative imaging and planning techniques in permanent seed prostate brachytherapy

Techniques for permanent low dose rate seed brachytherapy for prostate cancer have evolved in the recent years with increasing use of interactive planning in the operating room (OR) during seed placement. This overcomes one of the main sources of error in the original two-stage technique in which a planning study performed at a time distant from the implant is used to define seed positions and then an attempt to reproduce this at the time of implant is required. This review addresses the various ways in which real-time dosimetry may be used. Three basic approaches are described; intraoperative planning when a plan is produced as a separate stage prior to the implant during a single OR procedure, interactive planning which incorporates stepwise modification of the treatment plan based on feedback from real-time tracking of the actual needle positions and dynamic dose calculation in which there is a continuous updating of the dosimetry using continuous feedback of the seed positions as they are implanted. The impact of these changes on dosimetric and biochemical outcome endpoints is considered demonstrating the superior results which can be obtained by closer integration of the planning processes with actual implantation and seed deposition.