Research on radiation dose to prostate cancer patients from PET-CT examinations

Abstract

Objective To estimate effective and organ doses to prostate cancer patients result ing from the whole-body 18F-Choline, 11C-Choline and 68Ga-PSMA PET-CT examinations. Methods A total of 150 prostate cancer patients who underwent PET-CT scanning from May 2017 to June 2018 were retrospectively analyzed. They were divided into three groups, each with 50 patients, according to the type of positron radiopharmaceuticals injected. All patients used the same PET-CT scan protocol. PET component dose was calculated by using OLINDA/EXM (version 1.1) software which was based on the MIRD method. The CTDI values were measured by the standard CT phantoms and computed by ImPACT (version 1.0.4) CT, and ImPACT was used for dose calculation from CT. The tissue weighting factors according to ICRP Report 103 were used for effective dose calculation. Results The effective dose and organ equivalent dose from 18F/11C-Choline and 68Ga-PSMA PET/CT examinations were estimated. The voltage and current of Topogram scan were 120 kV and 35 mA, respectively, as well as 120 kV and (135.6±9.4) mA for low-dose CT scan. The injected activity of 18 F-Choline, 11C-Choline and68Ga-PSMA was (279.2±13.2), (350.2±39.9) and (186.8±19.4) MBq, respectively. The effective dose was (5.0±0.2), (1.6±0.2) and (3.0±0.3) mSv, respectively (F=837.0, P<0.001). The CT effective dose was (11.4±0.2) mSv. The total effective dose for three groups were (16.4±0.3), (13.0±0.3) and (14.4±0.4) mSv, respectively. The mean organ equivalent doses were statistically significantly different among groups (F=381.2-1 637.7, P<0.001). The highest organ equivalent dose was to kidney for18F-Choline and68Ga-PSMA PET/CT scans and thyroid for11C-Choline PET/CT scan. Conclusions The effective dose to the prostate cancer patients who underwent PET-CT scanning was from 13.0 to 16.4 mSv, with vast majority of these doses coming from CT scans. The lowest radiation dose to the patients was caused by 11C-Choline PET-CT examination, suggesting that it would be a potential prostate cancer PET radiotracer. Key words: PET-CT; Prostate cancer; Effective dose; Organ dose