Subtraction improves the accuracy of coronary CT angiography for detecting obstructive disease in severely calcified segments

Objective To investigate the accuracy, diagnostic confidence, and interobserver agreement of subtraction coronary CT angiography (CCTA) versus invasive coronary angiography on 320-row CT in coronary segments with severe or non-severe calcification. Materials/methods Sixty-four patients (33 men, 66.6 +/- 8.2 years) with suspected coronary artery disease (CAD) were prospectively enrolled from October 2019 to June 2020. The cross-sectional circumferential extent of calcification was used to classify calcified segments as non-severely ( < 180 degrees) or severely calcified ( >= 180 degrees). Three independent, blinded radiologists evaluated the severity of coronary stenosis. Interobserver agreement was evaluated using Fleiss' kappa (kappa). A multiple-reader multiple-case receiver operating characteristic (ROC) method was conducted, and diagnostic accuracy was measured using the mean areas under the ROC curves (AUCs), with >= 50% stenosis as a cut-off. Diagnostic confidence, diagnostic accuracy, and interobserver agreement were compared between CCTA with or without subtraction information in severely and non-severely calcified segments. Results In cases with severe calcification (51 patients, 146 segments), CCTA with subtraction information achieved better diagnostic accuracy (per-patient AUC: 0.73 vs 0.57, p = 0.03; per-segment AUC: 0.85 vs 0.62, p = 0.01), diagnostic confidence (3.7 vs 2.6, p < 0.001), and interobserver agreement (kappa: 0.59 vs 0.30). Diagnostic accuracy (per-patient AUC: 0.81 vs 0.93, p = 0.30; per-patient AUC: 0.79 vs 0.82, p = 0.54) was not increased in cases with non-severe calcification (13 patients, 190 segments). Conclusions CCTA with subtraction information achieved better diagnostic accuracy in cases of severe calcification (circumferential extent >= 180 degrees). However, for non-severe calcification (circumferential extent < 180 degrees), the effect of calcium subtraction was unclear, as it did not improve diagnostic accuracy.

Automated summary

This study investigated the diagnostic accuracy, confidence, and interobserver agreement of subtraction coronary CT angiography (CCTA) compared to invasive coronary angiography on 320-row CT. Results showed that CCTA with subtraction information achieved better diagnostic accuracy and interobserver agreement in cases with severe calcification, but the effect was unclear in cases with non-severe calcification.