Is sub-mSv CT for evaluation of non-specific findings in bone scintigraphy of oncological patients feasible?

Background Hybrid SPECT/CT systems allow the shortening of lead time for investigation of cancer patients, since a complementary CT for radiological characterization of focally increased isotope uptake of unclear origin in bone scintigraphy can be performed simultaneously. The use of low-dose CT (sub-mSv CT) reduces radiation dose compared to standard-dose CT and facilitates the application of complementary CT. Purpose To test the feasibility of sub-mSv CT for the characterization of non-specific findings in the bone scintigraphy of oncological patients. Material and Methods Nineteen oncological patients with a total of 50 findings of unclear origin on bone scintigraphy which required further correlation with morphologic data were included in the study. Each patient underwent two CT scan series consecutively: one low-dose CT and one standard-dose CT. The CT studies were randomized and each finding was rated by four blinded experienced radiologists. A shift in ratings between standard-dose and low-dose images were assessed using the Stuart-Maxwell chi-squared test. Inter-observer agreement and intra-observer agreement was assessed using Light's kappa and Cohen's kappa, respectively. Results The mean effective dose of low-dose CT scans was 0.8 mSv compared to 4.2 mSv for the standard-dose CT scans. No statistically significant shift in ratings was observed (P = 0.62). There was no statistically significant difference in the inter-observer agreements: the values for the standard-dose and low-dose groups were 0.68 (95% confidence interval [CI] 0.57-0.79) and 0.60 (95% CI 0.47-0.72), respectively. Conclusion These results indicate that sub-mSv CT for characterization of non-specific findings in bone scintigraphy of oncological patients is feasible.