High-pitch photon-counting detector computed tomography angiography of the coronary arteries: Qualitative and quantitative evaluation of monoenergetic image reconstructions

Dual-source photon-counting detector computed tomography (PCDCT) offers the opportunity to perform cardiac examinations within one beat and simultaneously the acquisition of spectral information. This study, evaluated subjective and objective image quality of virtual monoenergetic image (VMI) reconstructions using data from a first-generation, dual-source PCDCT scanner, operated in high-pitch scanning mode.

We retrospectively included 30 patients who underwent a clinically indicated CTA of the coronary arteries. VMI were reconstructed at five different energy levels. Subjective image quality was assessed by three radiologists according to a four-point Likert scale for four different quality features. To evaluate objective image quality, SNR and CNR were calculated via ROIs placed in the aorta, coronary arteries, myocardium, pectoral muscle, and epicardial fat.

VMI at 40, 50, 60, and 70 keV showed equal mean scores (4/4) for subjective vascular contrast, followed by 80 keV reconstructions with a mean score of 3/4. The 40 keV reconstruction yielded the lowest range (3-4) in Likert scores and highest percentage of reader agreement (80 %). Minor differences in subjective image noise, sharpness, and plaque visualization were observed with positive trends toward higher keV levels. SNR and CNR were superior for 40 keV, with a mean of 34.8 ± 1.7HU and 45.4 ± 2.7HU, respectively. Mean applied contrast volume was 65 ml, resulting in a mean CT value of 1150HU for 40 keV VMI.

First-generation PCDCT-derived VMI at 40 and 50 keV offer satisfying subjective and objective image quality, even when acquired in high-pitch scanning mode.