Determining an effective planning volume for permanent prostate implants

Treatment planning for prostate brachytherapy is guided largely by the desire to determine a seed configuration that yields a prescription isodose surface that conforms with the prostate boundary. Currently, planning is based on the state of the prostate at a particular instant in time; typically, when the prostate is swollen. Unfortunately, a plan that conforms to the swollen prostate will not match the gland when shrinkage and seed displacement occur. Furthermore, these factors may directly affect the dose received by urethra and rectum over an extended period of time. The authors examine the possibility of defining an "effective planning volume" (EPV) that compensates for information that is unavailable during initial planning (e.g. changes in prostate volume, seed displacement).