Coronary flow quantification estimated by dynamic 320-detector CT angiography: validation by ¹³N ammonia PET myocardial flow reserve

Abstract

Objectives: Resting coronary flow index (rCFI) estimated by 320-detector low-dose dynamic coronary CT angiography (CCTA) is a direct flow quantification using intracoronary attenuation. We propose modified-rCFI from new protocol combining dynamic scan and standard CCTA using dose-modulation, and validate its consistency with quantitative values and ischemia depicted by 13N-ammonia PET (NH3-PET). Methods: 46 patients who underwent dynamic CCTA and NH3-PET for coronary artery disease were evaluated using original rCFI in 21 patients and modified-rCFI in 25 patients. Two types of rCFI were calculated for three major coronary arteries. Myocardial blood flow (MBF) at rest and stress, myocardial flow reserve (MFR), and the presence or absence of ischemia for three major territories were depicted by NH3-PET. Coronary territories were categorized as territories with MFR <2.0, ≥2.0, or with and without ischemia. Receiver operating characteristic analysis was performed to determine the optimal cut-off of rCFI to distinguish territories with MFR <2.0 or the presence of ischemia. Results: rCFI and modified-rCFI had significant positive correlations with stress MBF and MFR. The optical cut-offs of rCFI and modified-rCFI of 0.39 and 0.61 could detect territories with MFR <2.0, with AUCs of 0.75 and 0.73, sensitivities of 48 and 34%, and specificities of 97 and 98%. Optimal cut-offs of rCFI and modified-rCFI distinguished ischemic segments from non-ischemic segments, with AUCs of 0.75 and 0.91, sensitivities of 53 and 50%, and specificities of 93 and 95%. Conclusion: Two types of rCFI correlated with quantitative values from NH3-PET, and were consistent with a high specificity in detecting functional ischemia. Advances in knowledge: rCFI can contribute as additional functional test over standard CCTA in clinical work-up.

Dynamic coronary CT Angiography-Estimated coronary flow in Non-Obstructive, Plaque-free coronary Arteries: Association with dyslipidemia and diabetes

“…Using the previously reported maximum slope method [1] , [24] , we analyzed the time-attenuation curve of the evaluated coronary arteries based on the same dynamic CCTA data and presented the results of the coronary flow index calculation. The coronary flow indices for RCA#3, LAD#8, and LCX#13 were 0.90 ± 0.26, 0.82 ± 0.22, and 0.82 ± 0.20, respectively.…”

“…It has recently been reported that dynamic CCTA scanning can estimate functional myocardial ischemia [35] and can also estimate myocardial blood flow via ammonia PET [1] . The scan protocol used in this study, which combines standard CCTA with low-dose dynamic imaging using a 320-row scanner, does not increase radiation exposure as compared to conventional CCTA [23] .…”

“…Dynamic CCTA was performed on all patients using a protocol utilizing dose-modulation and consisting of one series of standard CCTA (boost scan and low-dose dynamic imaging); more specifically, CCTA was conducted with a 320-row CT scanner (Aquilion One; Cannon Medical Systems Co., Tochigi, Japan) [1] . In preparation, intravenous or oral metoprolol was administered to patients with a heart rate of ≥ 65 beats/min.…”

“…In addition, we analyzed time-attenuation curves for the evaluated coronary arteries based on the same dynamic CCTA data using the previously described maximum slope method ( Fig. 4 D) [1] , [24] .

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“…Recently, it has been reported that quantification of coronary flow using 320-row dynamic CCTA is useful for detecting myocardial ischemia and is likewise correlated with myocardial blood flow as estimated by ammonia positron emission tomography (PET) [1] . This is a unique technique that dynamically captures the contrast enhancement of coronary arteries in vivo and is expected to contribute information regarding coronary circulatory function (to a greater extent than to information regarding coronary artery morphology).…”