Comparison of image quality between photon-counting detector CT and energy-integrating detector coronary CT angiography in heart transplant patients

This study aims to compare the image quality between photon-counting detector computed tomography (PCD-CT) and energy-integrating CT (EID-CT) for coronary artery visualization post-heart transplant (HTx) patients, using a paired comparison within one patient. Consecutive HTx patients who underwent both 3rd generation dual source EID-CT and ultra-high-resolution PCD-CT scans as part of routine clinical care, with a maximum interval of two years between scans were included. Image quality was assessed subjectively using a 5-point Likert scale and quantitatively with the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Coronary segments were scored for presence, stenosis degree, presence of artifacts, and plaque composition. Thirty patients were included (mean age 50 ± 17 years; 21 (70%) men). The median interval between scans was 17[12-24] months. The median calcium score was 9[0-51] on the EID-CT scan and 25[0-92] on the PCD-CT. On the PCD-CT, 90% of coronary segments were rated very good or excellent compared to 71% on EID-CT (p < 0.001). Fewer segments were absent or non-evaluable due to size with PCD-CT compared to EID-CT (30% vs. 34%; p < 0.001). PCD-CT identified more mixed plaques (11% vs. 3%, p < 0.001). SNR and CNR were significantly higher on PCD-CT (22.1 ± 6.1 and 27.8 ± 6.8, p < 0.001) than on EID-CT (14.3 ± 3.4 and 16.9 ± 3.6, p < 0.001). The CT dose index volume was 6 [5-10] mGy on EID-CT and 19 [14-21] mGy on PCD-CT (p < 0.001). Ultra-high-resolution PCD-CT improves image quality compared to EID-CT in HTx patients. With superior SNR and CNR, and fewer non-evaluable segments, PCD-CT offers enhanced coronary artery visualization, though at the cost of an increased radiation dose.