New research suggests that coronary computed tomography angiography (CCTA) with photon-counting detector CT (PCD CT) offers approximately 90 percent or higher sensitivity, specificity and accuracy for the detection of coronary artery stenosis.
For a new prospective study, recently reported in the American Journal of Roentgenology, researchers compared the use of standard resolution (SR) in 61 inpatients (total of 788 analyzed segments) and ultra-high resolution (UHR) in 61 inpatients (total of 825 analyzed segments), all of whom had CCTA by PCD CT.
The study authors noted that image reconstructions for SR exams were divided into SRnormal and SRvirtual non-calcium (SRVNCa) images, and the UHR exam reconstructions were divided into UHRnormal and UHRthin images. All image reconstructions were obtained at an 0.6 mm slice thickness and Bv40 kernel with the exception of UHRthin images obtained at an 0.2 mm slice thickness and a Bv64 kernel, according to the study.
For SRnormal images, the study authors noted average segment-level sensitivity, specificity and accuracy of 92.9 percent, 89.4 percent and 90 percent, respectively, for two reviewing radiologists. The SRVNCa image reconstructions offered respective average sensitivity, specificity and accuracy of 93.2 percent, 92 percent and 92.2 percent at the segment level, according to the researchers. The researchers also emphasized that vessel-level specificity with SRVNCa was 20 percent higher for both reviewing radiologists when assessing patients with Agatston scores > 100.
“By removing calcium within the coronary lumen, these virtual non-calcium (VNCa) images can also reduce blooming artifacts and aid assessment of stenoses in areas of calcified plaque,” wrote lead study author Mengzhen Wang, M.D., who is affiliated with the Department of Radiology at Ruijin Hospital and the Shanghai Jiao Tong University School of Medicine in Shanghai, China, and colleagues.
The researchers also found an average 96 percent sensitivity at the segment level with UHRnormal images along with 92 percent specificity and 92.6 percent accuracy. For UHRthin reconstructions, the study authors found average segment-level sensitivity, specificity and accuracy of 100 percent, 98.8 percent and 98.9 percent respectively.
While there was higher mean radiation dosing with UHR (9.3 mSv in comparison to 7.4 mSv with SR), the study authors found a higher correlation between invasive coronary angiography (ICA) and the SR group with respect to significant stenosis detection at segment and vessel levels in comparison to the UHR group.
For the SR cohort, the researchers noted a 6.5 percent higher correlation with ICA on the presence of > 50 percent stenosis in patients, a 13.7 percent higher vessel-level detection and a 4.8 percent higher segment-level detection in contrast to the UHR group.
“The SR group showed a significantly greater frequency of significant stenosis at the vessel and segment levels,” pointed out Wang and colleagues.
Three Key Takeaways
- High diagnostic accuracy with PCD CT. PCD CT demonstrated segment-level sensitivity, specificity, and accuracy of ≥90% across standard (SR) and ultra-high resolution (UHR) reconstructions, with UHRthin images achieving 100 percent sensitivity, 98.8 percent specificity and 98.9 percent accuracy.
- Improved assessment with virtual non-calcium image reconstructions.
SRVNCa reconstructions (which subtract calcium) significantly improved vessel-level specificity (20 percent higher in patients with Agatston scores > 100), reducing blooming artifacts and improving stenosis visualization in calcified vessels. - Clinical implications for imaging strategy. While SR showed slightly better correlation with invasive coronary angiography (ICA) for detecting significant stenosis, UHRthin imaging is optimal for patients with heavy coronary calcification or strong suspicion of severe CAD, suggesting a tailored imaging approach based on patient risk profile.
However, for the detection of significant coronary stenosis at the vessel level, UHRthin image reconstructions offered the best combination of sensitivity (100 percent) and specificity (89.7 percent) in patients with Agatston scores > 100.
“ … Radiology practices could consider prioritization of UHR mode for patients with known extensive coronary calcification or with strong clinical suspicion for severe CAD,” posited Wang and colleagues.
(Editor’s note: For related content, see “Photon-Counting Computed Tomography: Eleven Takeaways from a New Literature Review,” “Study Examines Potential of Ultra-High Spatial Resolution Photon-Counting CT for Coronary Plaque Quantification” and “Photon-Counting CTA for Patients with PAD: What the Research Reveals About Assessment for Stenotic Lesions.”)
Beyond the inherent limitations of a single-center study, the authors acknowledged that other differences beyond demographic characteristics or cardiovascular risk factors may have affected the comparison between SR and UHR modes. The researchers also noted that clinical outcomes were not evaluated in the comparison of SR and UHR groups.
