Digital PET/CT in Relation to Reduction of Staff Occupational Exposure

Introduction: PET/CT technologists get high radiation dose exposures due to the high exposure rate constant of PET radiopharmaceuticals. In PET/CT facilities there are multiple factors that associate with the radiation dose exposure to the technologists. The type of PET/CT scanner used and the patient dose are important factors in relation to total staff exposure. The purpose of this study is to compare the radiation dose exposure of nuclear medicine technologists before and after the use of a digital PET/CT scanner.

Methods: A table was created to compare 8 technologists' body DDE radiation dosimeter readings in the 7 months period of an analog scanner vs. 8 technologists in the 7 months period of a digital PET/CT scanner. Period 1: July 2017 to January 2018: Analog PET/CT scanner. Weight-based doses range from 10 mCi to 18 mCi F-18 FDG. Total patients: 623 patients, an average of 89 patients/month. Average scan time: 25 minutes per patient after 1 hour uptake period. Period 2: July 2018 to January 2019: Digital PET/CT scanner Philips Vereos. A standardized dose of 12 mCi F-18 FDG was injected for every patient. Total patients: 718 patients, an average of 102 patients/month. Average scan time: 12 minutes per patient after 1 hour uptake period. The technologists in each period were further grouped together based on the number of days working in PET/CT. Group 1 with average working days in PET/CT for less than 15 days and group 2 with average working days in PET/CT for more than 15 days. Average monthly body DDE readings in mrem were calculated for each group of technologists.

Results: 4 technologists in period 1 group 1 with the average working days of 12.2 days have the average body exposure of 20.21± 7.8 mrem. 4 technologists in period 2 group 1 with the average working days of 11.75 days have the average body exposure of 13.93±3.69 mrem. A 31% reduction in staff dose exposure was seen in group 1. 4 technologists in period 1 group 2 with the average working days of 22.25 days have the average body exposure of 28.03±12.7 mrem. 4 technologists in period 2 group 2 with the average working days of 23 days have the average body exposure of 22.91±4.25 mrem. An 18% reduction in staff dose exposure was seen in group 2. The average dose exposure of all 8 technologists in period 1 for both groups was 24.12±10.6 mrem compared to 18.42±6.05 mrem in period 2.

Conclusions: There was an average of 24% reduction in radiation dose exposure across all staff members between the two evaluated periods (digital: 24.12 mrem vs. analog: 18.42 mrem). Digital PET/CT scanner significantly reduced the radiation exposure of technologists compared to an analog scanner. Due to a detector and system design, digital PET/CT permits improved small lesion detectability with less administered activity, which allows less dose exposure to the patient (weight-based vs. standardized dose of 12mCi F-18 FDG) and less radiation exposure to staff. All efforts were made to limit the exposure to the patient and the technologists according to the ALARA concept at the PET/CT facility without compromising exam quality and patient care.