Permanent prostate seed implant brachytherapy: Report of the American Association of Physicists in Medicine Task Group No. 64

Abstract

There is now considerable evidence to suggest that technical innovations, 3D image-based planning, template guidance, computerized dosimetry analysis and improved quality assurance practice have converged in synergy in modern prostate brachytherapy, which promise to lead to increased tumor control and decreased toxicity. A substantial part of the medical physicist's contribution to this multi-disciplinary modality has a direct impact on the factors that may singly or jointly determine the treatment outcome. It is therefore of paramount importance for the medical physics community to establish a uniform standard of practice for prostate brachytherapy physics, so that the therapeutic potential of the modality can be maximally and consistently realized in the wider healthcare community. A recent survey in the U.S. for prostate brachytherapy revealed alarming variance in the pattern of practice in physics and dosimetry, particularly in regard to dose calculation, seed assay and time/method of postimplant imaging. Because of the large number of start-up programs at this time, it is essential that the roles and responsibilities of the medical physicist be clearly defined, consistent with the pivotal nature of the clinical physics component in assuring the ultimate success of prostate brachytherapy. It was against this background that the Radiation Therapy Committee of the American Association of Physicists in Medicine formed Task Group No. 64, which was charged ͑1͒ to review the current techniques in prostate seed implant brachytherapy, ͑2͒ to summarize the present knowledge in treatment planning, dose specification and reporting, ͑3͒ to recommend practical guidelines for the clinical medical physicist, and ͑4͒ to identify issues for future investigation.

A seed specific dose kernel method for low‐energy brachytherapy dosimetry

“…The task group recommends “ The medical physicist shall verify that the treatment planning system performs the correct dose summation at one or more locations in a simple configuration of multiple seeds ,” and “ Prior to implantation, the dosimetric plan should be checked using an independent procedure or by a second member of the physics staff ….” 2 While the two‐dimensional isodose comparisons illustrated in this study are not practical for routine quality assurance, the method described could easily calculate the dose at select points within a pre‐ or post‐implant seed distribution. Implementing this method would require easy access to the seed specific dose kernels and the summation program; details currently under consideration as part of a web‐based distribution.…”

“…A commercial treatment planning system will typically implement the TG‐43 protocol using one of three methods: point source approximation, line source approximation, or a two‐dimensional along‐away table. With respect to quality assurance of a commercial brachytherapy treatment planning algorithm, the recommendations of TG‐40 and TG‐64 emphasize the need for an independent calculation prior to implantation that will verify the TG‐43 calculation for at least one location based upon the implant seed distribution 2 , 3 . This paper provides an alternative calculation method for quality assurance purposes using a Monte Carlo based, brachytherapy seed‐specific dose kernel.…”

Reducing seed waste and increasing value of dynamic intraoperative implantation of Pd‐103 seeds in prostate brachytherapy

“…Transperineal interstitial permanent prostate brachytherapy (TIPPB) for early stage prostate cancer is an outpatient procedure involving insertion of radioactive seeds into the prostate under transrectal ultrasound guidance 1. Current radioisotopes used in TIPPB include 125 I, 103 Pd, and 131 Cs 1, 2, 3, 4. At our institution, 103 Pd seeds are implanted using a dynamic intraoperative technique1, 2, 3 and the workflow for seed ordering, implantation, and postimplant dosimetry is similar to that described in AAPM TG‐64 2.…”

“…Current radioisotopes used in TIPPB include 125 I, 103 Pd, and 131 Cs 1, 2, 3, 4. At our institution, 103 Pd seeds are implanted using a dynamic intraoperative technique1, 2, 3 and the workflow for seed ordering, implantation, and postimplant dosimetry is similar to that described in AAPM TG‐64 2. The workflow is as follows: (a) 103 Pd seeds are ordered using a nomogram based on preoperative prostate volume, (b) the 103 Pd seeds are independently assayed, (c) the 103 Pd seeds are implanted into the prostate under transrectal ultrasound guidance, (d) postoperative excess 103 Pd seeds (if applicable) are counted and disposed of by the medical physicist, and (e) postoperative dosimetry is performed approximately 4 weeks later.…”

A method for confirming a third‐party assay of I‐125 seeds used for prostate implants

“…There have been many recommendations by American Association of Physicists in Medicine (AAPM) task groups on the accuracy of seed calibration. The AAPM TG‐40,2 TG‐56,3 and TG‐644 all recommend that at least 10% of the I‐125 seeds have their activity verified against the manufacturers measurements, and if there is a discrepancy above 5% then it needs to be reported to the manufacturer. The task groups do not explicitly specify who should perform the assay of 10% of the seeds.…”