Stress myocardial perfusion imaging with photon-counting CT: Initial validation against reference modalities

The purpose of this study was to evaluate the feasibility and diagnostic performance of stress myocardial perfusion imaging (MPI) using a first-generation dual-source photon-counting CT (PCCT) scanner by comparison with reference standards.

Consecutive patients referred for coronary CT angiography (CCTA) with concomitant stress MPI using PCCT scanner and at least one functional reference test within one month were included. Static PCCT-MPI with regadenoson (Rapiscan, GE Healthcare) was acquired 12 s after the intravenous administration of 40 mL of iodinated contrast material and paired with myocardial delayed enhancement imaging. Reference tests for ischemia included stress cardiac magnetic resonance imaging, stress echocardiography, single-photon emission computed tomography, or invasive coronary angiography. Diagnostic performance was evaluated using sensitivity, specificity, accuracy, areas under receiver operating characteristic curve analysis (AUC) as well as Youden index-derived thresholds.

Forty-one patients were included. There were 28 men and 13 women with a median age of 62 years (Q1, 57; Q3, 70; range: 18-85 years). Of these, 35 patients (85 %) had obstructive coronary artery disease (CAD) on CCTA. PCCT-MPI identified myocardial hypoperfusion in 18 patients (44 %) with a median dose-length product of 97 mGy.cm (Q1, 76.8; Q3, 155.8). Visual assessment yielded 100 % sensitivity (95 % confidence interval [CI]: 81-100 %) and 96 % specificity (95 % CI: 78-100 %), with an AUC of 0.98 (95 % CI: 0.93-1.00) for the diagnosis of ischemic and infarcted myocardium. An optimal defect-to-remote iodine ratio cutoff of 0.79 showed 98 % accuracy (95 % CI: 87-100 %) and an AUC of 0.99 (95 % CI: 0.98-1.00 %). Integration of PCCT-MPI with CCTA could have obviated additional functional testing or invasive angiography in up to 50 % of patients with obstructive CAD.

Stress static PCCT-MPI is feasible and demonstrates excellent diagnostic accuracy for detecting myocardial ischemia. Defect-to-remote iodine ratio from spectral imaging further enhances performance, establishing PCCT as a comprehensive imaging modality that unifies anatomic and functional coronary assessment at a reasonable radiation dose, within a single examination.