EFFECT OF EDEMA ON THE POSTIMPLANT DOSIMETRY OF AN I-125 PROSTATE IMPLANT - A CASE-STUDY

Purpose: To investigate the effect of post-implant edema on the CT-bas ed calculation of the total dose delivered by an I-125 prostate implan t. Materials and Methods: CT scans of a transperineal I-125 prostate i mplant were obtained 1 and 39-days postimplant, Changes in the prostat e dimensions were determined from changes in the spatial distribution of the I-125 seeds. The total dose delivered to the target volume was computed from each CT scan, and the results compared. Results: The vol ume of the prostate decreased by approximately 17% during the 38-day i nterval between the first and second CT scans, As a result, the radiat ion dose computed from the second CT scan was 13% higher. Conclusion: Post-implant edema can cause a significant underestimation of the radi ation dose delivered by an I-125 prostate implant, Similar analysis sh ould be carried out among a larger cohort of patients to confirm or re fute these observations. (C) 1997 Elsevier Science Inc.