Clinical significance of transluminal attenuation gradient in 320-row area detector coronary CT angiography

The clinical significance of the transluminal attenuation gradient (TAG) has not been established. We evaluated the incremental diagnostic value of TAG by 320-row area detector computed tomography (320-ADCT). Subjects were 65 patients who underwent one-rotation scanning by 320-ADCT and invasive coronary angiography (ICA) within 3 months. TAG values were obtained for the major epicardial vessels 2 mm or more each in RCA, LAD and LCX using automatic analysis software. Moreover, TAG values that excluded calcified lesions in calculation of the regression line were also evaluated (excluded-TAG). In LAD, 21 intermediate lesions underwent functional flow reserve (FFR), and the incremental diagnostic value for functional stenosis was evaluated. The TAG values in the normal vessels were − 8.3 ± 5.0 (HU/cm) for the RCA (n = 32), − 23.3 ± 4.3 for the LAD (n = 9) and − 20.6 ± 10.0 for the LCX (n = 32). The RCA value was significantly higher (p