High-Definition Computed Tomography for Coronary Artery Stent Imaging: a Phantom Study

Objective: To assess the performance of a high-definition CT (HDCT) for imaging small caliber coronary stents (${\leq}$ 3 mm) by comparing different scan modes of a conventional 64-row standard-definition CT (SDCT). Materials and Methods: A cardiac phantom with twelve stents (2.5 mm and 3.0 mm in diameter) was scanned by HDCT and SDCT. The scan modes were retrospective electrocardiography (ECG)-gated helical and prospective ECG-triggered axial with tube voltages of 120 kVp and 100 kVp, respectively. The inner stent diameters (ISD) and the in-stent attenuation value ($AV_{in-stent}$) and the in-vessel extra-stent attenuation value ($AV_{in-stent}$) were measured by two observers. The artificial lumen narrowing (ALN = [ISD - $ISD_{measured}$]/ISD) and artificial attenuation increase between in-stent and in-vessel (AAI = $AV_{in-stent}$ - $AV_{in-vessel}$) were calculated. All data was analyzed by intraclass correlation and ANOVA-test. Results: The correlation coefficient of ISD, $AV_{in-vessel}$ and $AV_{in-stent}$ between the two observers was good. The ALNs of HDCT were statistically lower than that of SDCT (30 ${\pm}$ 5.7% versus 35 ${\pm}$ 5.4%, p < 0.05). HDCT had statistically lower AAI values than SDCT (15.7 ${\pm}$ 81.4 HU versus 71.4 ${\pm}$ 90.5 HU, p < 0.05). The prospective axial dataset demonstrated smaller ALN than the retrospective helical dataset on both HDCT and SDCT (p < 0.05). Additionally, there were no differences in ALN between the 120 kVp and 100 kVp tube voltages on HDCT (p = 0.05). Conclusion: High-definition CT helps improve measurement accuracy for imaging coronary stents compared to SDCT. HDCT with 100 kVp and the prospective ECG-triggered axial technique, with a lower radiation dose than 120 kVp application, may be advantageous in evaluating coronary stents with smaller calibers (${\leq}$ 3 mm).