Improved diagnostic performance of transluminal attenuation gradient in combination with morphological evaluation of coronary artery stenosis using 320-row computed tomography

The transluminal attenuation gradient does not add diagnostic accuracy to coronary computed tomography

BACKGROUND

A method for improving the accuracy of coronary computed tomography angiography (CCTA) is highly sought after as it would help to avoid unnecessary invasive coronary angiographies. Measurement of the transluminal attenuation gradient (TAG) has been proposed as an alternative to other existing methods, i.e. CT perfusion and CT fractional flow reserve (FFR).

PURPOSE

To evaluate the incremental value of three types of TAG in high-pitch spiral CCTA with invasive FFR measurements as reference.

MATERIAL AND METHODS

TAG was measured using two semi-automatic methods and one manual method. A receiver operating characteristic (ROC) analysis was made to determine the usefulness of TAG alone as well as TAG combined with CCTA for detection of significant coronary artery stenoses defined by an invasive FFR value ≤0.80.

RESULTS

A total of 51 coronary vessels in 37 patients were included in this retrospective study. Hemodynamically significant stenoses were found in 13 vessels according to FFR. The ROC analysis TAG alone resulted in areas under the curve (AUCs) of 0.530 and 0.520 for the semi-automatic TAG and 0.557 for the manual TAG. TAG and CCTA combined resulted in AUCs of 0.567, 0.562 for semi-automatic TAG, and 0.569 for the manual TAG.

CONCLUSION

The results from our study showed no incremental value of TAG measured in single heartbeat CCTA in determining the severity of coronary artery stenosis degrees.

Prediction of degree of carotid stenosis with the transluminal attenuation difference ratio

PURPOSE

We aimed to assess the diagnostic performance of transluminal attenuation difference (TAD) in predicting the severity of internal carotid artery (ICA) stenosis.

METHODS

The study cohort consisted of 48 patients with <50% stenosis, 50%-69% stenosis, 70%-99% stenosis, and 51 controls without plaque development in ICA. A total of 143 measurements were performed through right and left internal and common carotid arteries. The TAD ratio was calculated as the difference between the mean attenuation values of the common carotid artery (CCA) and ICA, divided by the MAV of the CCA, multiplied by 100.

RESULTS

TAD ratio was significantly higher in severe (>70%) stenosis compared with control arteries and low-moderate stenosis. A TAD ratio cutoff of 4.5 predicted 70%-99% stenosis with a sensitivity of 100% and specificity of 93%. The inter- and intraobserver agreements in TAD measurements were almost perfect (ICC, 0.89-0.86).

CONCLUSION

Assessment of TAD ratio predicts the degree of stenosis in concordance with NASCET system.

New transluminal attenuation gradient derived from dynamic coronary CT angiography: diagnostic ability of ischemia detected by 13N-ammonia PET

Coronary computed tomography angiography (CCTA) has low specificity for detecting significant functional coronary stenosis. We developed a new transluminal attenuation gradient (TAG)-derived dynamic CCTA with dose modulation, and we investigated its diagnostic performance for myocardial ischemia depicted by ¹³N-ammonia positron emission tomography (PET). Data from 48 consecutive patients who had undergone both dynamic CCTA and ¹³N-ammonia PET were retrospectively analyzed. Dynamic CCTA was continuously performed in mid-diastole for five cardiac cycles with prospective electrocardiography gating after a 10-s contrast medium injection. One scan of the dynamic CCTA was performed as a boost scan for conventional CCTA at the peak phase of the ascending aorta. Absolute TAG values at five phases around the boost scan were calculated. The dynamic TAG index (DTI) was defined as the ratio of the maximum absolute TAG to the standard deviation of five TAG values. We categorized the coronary territories as non-ischemia or ischemia based on the ¹³N-ammonia PET results. A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff of the DTI for identifying ischemia. The DTI was significantly higher for ischemia compared to non-ischemia (8.8 ± 3.9 vs. 4.6 ± 2.0, p < 0.01). The ROC analysis revealed 5.60 as the optimal DTI cutoff to detect ischemia, with an area under the curve of 0.87, 85.7% sensitivity, and 76.2% specificity. TAG provided no additional diagnostic value for the detection of ischemia. We propose the DTI derived from dynamic CCTA as a novel coronary flow index. The DTI is a valid technique for detecting functional coronary stenosis.