Reduction of radiation dose in PET-CT: Low dose protocols and image quality

Objectives Attentions of radiation exposure dose increase recently and it become a crucial issue in PET-CT. In order to reduce the exposure dose of a patient in PET-CT, administrated dose of 18F-FDG and current (mA) factor related CT dose were controlled with the similar image quality in this study.

Methods Most of data were acquired in Discovery PET-CT 600. Radiation dose of CT was measured by using CTDI phantom in a center and periphery. Effective radiation dose of a patient was calculated by using simulation tool when the administrated dose of 18F-FDG was 0.2mCi/kg, 0.1mCi/kg, and 0.06mCi/kg. Voltages were 120kVp and 140kVp and range of current was between 50mA and 100mA. Scan duration in PET was 3min/bed. 2.5min/bed data and 2min/bed data were replayed from 3min/bed list-mode data. Patient’s images were reconstructed by adaptive statistical iterative reconstruction for CT data and full 3D iterative reconstruction with new point spread function method for PET data. Obtained clinic images were investigated by two nuclear medicine clinicians. SUV between 0.1mCi/kg image and 0.06mCi/kg image were also reviewed.

Results Equivalent dose of CT obtained by CTDI phantom was from 0.2mSv to 7.6mSv at center and from 0.6mSv to 17.2mSv at periphery. When 18F-FDG was injected 0.06mCi/kg to patient of weight between 60kg to 90kg, effective dose was about between 2.53mSv and 4.92mSv. Radiation exposure of PET and CT were decreased over 50% than previous PET-CT. When SUV of lower dose PET data was compared with that of higher dose PET data, their values showed low variance.

Conclusions Minimized radiation exposure imaging protocols for PET-CT were evaluated in this study. High sensitivity and new reconstruction methods were contributed for radiation dose reduction of patients.

Research Support The research was supported by a grant from the Institute of Medical System Engineering (iMSE) in the GIST, Korea