High-Resolution Head CTA: A Prospective Patient Study Comparing Image Quality of Photon-Counting Detector CT and Energy-Integrating Detector CT

Reader evaluation, PCD-CT versus EID-CT. Horizontal percentage stacked bar chart plots demonstrate reader 1 and 2 (R1, R2) scores for PCD-SR versus EID-SR (A) and PCD-UHR-CNN versus EID-SR (B). Bars are split into segments and the length of each bar is 100%. Segments from left to right: significantly superior (+2), somewhat superior (+1), equal quality (0), somewhat inferior (−1), significantly inferior (−2).

Data plot of diagnostic confidence of arterial findings. Grouped boxplot figure highlighting PCD-SR versus EID-SR and PCD-UHR-CNN versus EID-SR for diagnostic confidence scores of each reader. The bottom, top, and middle lines of each box indicate the 25th percentiles, 75th percentiles, and sample median of the data. Samples whose notches do not overlap are statistically significantly different at the 5% significance level. (Matlab 2021).

Iodine contrast, noise, and CNR quantitative evaluation. Grouped boxplots for (A) iodine contrast, (B) noise, and (C) iodine CNR results measured in the bilateral distal ICA and midcervical ICA for EID-SR, PCD-SR, and PCD-UHR-CNN. The bottom, top, and middle lines of each box indicate the 25th percentiles, 75th percentiles, and sample median of the data. Samples whose notches do not overlap are significantly different at the 5% significance level. (Matlab 2021).

Improved visualization of distal intracranial arterial branches on PCD-CT head CTA compared with EID-CT. Thin section oblique axial head CTA images highlighting the right M3 segment (arrows), by using EID-SR with 0.6-mm section thickness (A) and PCD-UHR-CNN CT with 0.2-mm section thickness (B) techniques. This distal intracranial arterial segment is best visualized by using PCD-CT rather than EID-CT, particularly with PCD-UHR-CNN–but also PCD-SR CT (the latter not shown). The right M3 segment is indeed difficult to visualize on EID-CT compared with PCD-CT. The insets demonstrate the improved visualization of the M3 segment (arrows) in the oblique sagittal plane.

Improved confidence for diagnosing infundibula on PCD-CT head CTA compared with EID-CT. Thin section oblique axial head CTA images, by using EID-SR with 0.6-mm section thickness (A) and PCD-UHR-CNN CT with 0.2-mm section thickness (B) techniques. The diagnostic confidence for diagnosing this infundibulum rather than possible aneurysm improves with PCD-SR matched to EID technique (not shown) and even more so with PCD-UHR-CNN CT at the thinnest section thickness. An ∼2-mm left supraclinoid ICA outpouching (infundibulum or aneurysm) is seen in an oblique axial plane on EID-CT (solid arrow in A), but better delineated on PCD-CT (arrow in B). The anterior choroidal artery arising from the apex of the outpouching is much better visualized on PCD-CT (arrowhead in B) than EID-CT (dashed arrow in A), thereby confidently diagnosing an infundibulum rather than an aneurysm. The insets demonstrate the improved visualization of the anterior choroidal artery arising from the apex of the outpouching in the oblique sagittal plane.