Room: Exhibit Hall | Forum 4
Purpose: Permanent seed implantation with Cs-131 is becoming popular for treating recurrent Head and Neck (H&N) cancers. However, there is a lack of literature on post-implant radiation exposure and associated patient release information. This study is to report the exposure rate after the Cs-131 mesh implant for H&N cancers.
Methods: Twelve patients were treated between January 2017 and October 2018 with Cs-131 mesh implants (Isoray Inc.) for recurrent H&N cancers as per IRB approved protocol. Patients were prescribed with 60-70Gy (median: 65Gy) to 5mm depth from the surgical bed. Seed strength and total activity were determined using pre-operative plan generated in MIM (MIM Software Inc.). Median activity was 2.8mCi (range: 2.5-3.5mCi). Total implanted seeds and activity ranged 11-68 (median:35) and 38.8-182.2mCi (median:101.2mCi), respectively. Radiation exposure rate was measured with Victoreen451B survey meter 1m from the implant site at the completion of the procedure, 1 day, and 5-8 days after. The exposure rate limit for authorizing patient release was calculated based on NRC regulation.
Results: Calculated exposure rate limit for patient release for Cs-131 was 6mR/hr. The average background reading was 0.04mR/hr. Total 42 measurements were performed for 12 patients. The exposure rate at the completion of the procedure, 1 day, and 5-8 days after ranged from 2.0-6.6mR/hr, 1.1-4.7mR/hr, and 0.7-2.7mR/hr, respectively. Exposure rate after 1 day of implantation procedure completion was below the limit for patient release (<6mR/hr). Exposure rate at the time of any patient release was less than 3mR/hr.
Conclusion: It appears that Cs-131 implant patients may be released even after one day of hospital stay, so far as the radiation exposure is concerned. In our institution, patients who received Cs-131 seed mesh implantation for H&N reirradiation were released 5-8 days after the procedure, which was safe for the public.