Accurate sub-MSV CT coronary calcium score is a reality!

BACKGROUND: To evaluate the feasibility of sub-mSv CT Coronary Calcium Scoring (CCS). METHODS: A prospective study enrolling 55 clinical patients, 54 ± 6y, BMI 29 ± 4 who had CCS using volumetric CT 240-320 x 0.5mm. An initial clinical CCS scan was performed using aweight based protocol (S1, 120kV, 87.5-140mAs), followed by one of two research CCS scans performed using tube current stratification by Average Thoracic Diameter (ATD) (S2a, 120kV, 28-105mAs), or Scout Attenuation Coefficient (SAC) (S2b, 120kV, 17.5-140mAs). The final cohort included 30 patients with ATD and 25 patients with SAC stratified protocols. All CCS images were anonymized, randomized, and post-processed by 2 readers (R1, R2) to evaluate the Agatston Score (AS). The mean value of R1 + R2 readings for AS was used for each technique. Spearman's rank correlation coefficient was computed for the clinical and research CCS protocols. RESULTS: All images were of diagnostic quality, mean AS was 141.3 (range 0-1414) for S1 CCS protocols and 150.6 (range 0-1606) for S2 (a and b) CCS protocols. AS were increased up to 6% using research protocols. Spearman's rank correlation coefficient showed AS between both scans was highly correlated r = 0.93 (p<0.001). Mean dose length product (DLP) was 152.6±27.3,83.5±33.9, and62.8±39.5mGy∗cmforS1, S2a, and S2b; respectively. The average radiation dose was 2.14, 1.17, and 0.88mSv for weight, ATD, and SAC based stratified protocols, respectively. CONCLUSION: Accurate sub-mSv CCS is possible using patient stratification by the Scout Attenuation Coefficient which is easily obtained from the scout CT projections.