Evaluation of the risk of radiation exposure from new 18FDG PET/CT plans versus conventional X-ray plans in patients with pediatric cancers.

Objective: Unnecessary radiological examination should be avoided, particularly for children, who are more vulnerable to radiation than adults. Replacement of X-ray examination with 18F-fluoro-2-deoxy-D-glucose (18FDG) positron emission tomography/computed tomography (PET/CT) is a potential option for reduction of radiation exposure, and thus improvement in the quality of life (QOL) of patients. Therefore, this study aimed to evaluate new plans integrating 18FDG PET/CT versus current conventional imaging (CI) plans for patients with pediatric cancers. The effects of radiation exposure from the two kinds of plans were compared using shortening of the average life expectancy as an index, and the related findings and effects of radiation exposure are discussed.

Methods: Effective radiation doses from CT scanning were calculated using the ImPACT CT Patient Dosimetry Calculator software. Radiation doses in different organs and tissues from radiopharmaceuticals were obtained from the International Commission on Radiological Protection (ICRP) publication 80. Shortening of average life expectancy was calculated using software in which the linear non-threshold model (LNT) by the ICRP was adopted.

Results: In current CI plans, the mean effective dose was 168.8 mSv (range 50.5-513.4 mSv) for males and 127 mSv (range 54-239.7 mSv) for females. The mean shortening of average life expectancy was 177 days (range 53.3-542 days) for males and 185 days (range 80.4-371 days) for females. In new plans, the mean effective dose was 64.1 mSv (range 54.1-84.5 mSv) for males and 68.2 mSv (range 58.1-88.0 mSv) for females. The mean shortening of life expectancy was 67.6 days (range 57.1-89.2 days) for males and 102.5 days (range 86.8-132.6 days) for females.

Conclusions: New 18FDG PET/CT plans may relieve the patient's physical burden and contribute to improvement of the patient's QOL. These plans may also reduce medical costs because the number of examinations to be performed is reduced. Although deterministic effects are not observed in the CI plan, careful attention should be paid to other potential effects. Because the effective dose resulting from this plan is over 100 mSv, at which stochastic effects are known to occur, radiation-induced cancers may be expected.