Preliminary study on effective dose of patients in SPECT/CT fusion imaging

Objective: To assess the patient effective dose during SPECT/CT imaging. Methods: A total of 157 patients (85 males, 72 females; mean age: (60.46 ± 13.44) years, range: 24-88 years) who underwent SPECT/CT from April 2013 to September 2014 were retrospectively analyzed. They were divided into 3 groups: ⁹⁹Tc^m-MDP bone scan group (n = 113), ⁹⁹Tc^m-MIBI parathyroid imaging group (n = 23) and ⁹⁹Tc^m-MAA pulmonary perfusion imaging group (n = 21). The injection dose (MBq) was recorded and the effective dose (mSv) was estimated according to the International Commission on Radiological Protection (ICRP) guideline. The volume-weighted computed tomography dose index (CTDIvol) and dose length product (DLP) of CT were also recorded and the effective dose (mSv) due to CT was calculated. The effective doses among different groups were statistically compared by Kruskal-Wallis rank sum test and Wilcoxon rank sum test. Results: The effective dose from radiopharmaceuticals were (4.02 ± 0.35) mSv for ⁹⁹Tc^m-MDP bone scan, (6.13 ± 0.53) mSv for ⁹⁹Tc^m-MIBI parathyroici imaging and (1.66 ± 0.13) mSv for ⁹⁹Tc^m-MAA pulmonary perfusion imaging (χ² = 96.853; Z =1.533, 7.262 and 5.676; all P < 0.05). The effective dose due to CT were (3.84 ± 1.98), (1.04 ± 0.19), (4.05 ± 0.47) mSv respectively (χ² = 41.225, P < 0.05), and there were significant differences between ⁹⁹Tc^m-MIBI parathyroid imaging group and ⁹⁹Tc^m-MDP bone scan group, ⁹⁹Tc^m-MAA pulmonary perfusion imaging group(Z = 6.046 and 5.672, both P < 0.05), The total effective dose during SPECT/CT imaging were (7.86 ± 1.98), (7.21 ± 0.81) and (5.71 ± 0.45) mSv (χ² = 28.988, P < 0.05). There were significant differences between ⁹⁹Tc^m-MAA pulmonary perfusion imaging group and ⁹⁹Tc^m-MDP bone scan group, ⁹⁹Tc^m-MIBI parathyroid imaging group(Z = 4.967 and 4.994, both P < 0.05). Conclusions: The increase in effective dose due to spiral CT during SPECT/CT examination should be concerned. Appropriate utilization and optimization of SPECT/CT is needed. (authors)