High-Pitch Multienergy Coronary CT Angiography in Dual-Source Photon-Counting Detector CT Scanner at Low Iodinated Contrast Dose

Abstract

ObjectivesThe aim of this study was to evaluate the high-helical pitch, multienergy (ME) scanning mode of a clinical dual-source photon-counting detector (PCD) computed tomography (CT) and the benefit of virtual monoenergetic images (VMIs) for low-contrast-dose coronary CT angiography (CTA).Materials and MethodsHigh-pitch (3.2) ME coronary CTA was performed in PCD-CT in 27 patients using low contrast dose (30 mL of iohexol 350 mg/mL) and in 26 patients at routine contrast dose (60 mL). Low-energy-threshold 120 kV images (also known as T3D images) and 50 kiloelectron volts (50 keV) and 100 kiloelectron volts (100 keV) VMIs were reconstructed using a 1024 × 1024 matrix and 0.6-mm slices. The CT numbers, noise, and contrast-to-noise ratio (CNR) were measured in the ascending aorta (AA), left main coronary artery (LMCA), and distal left anterior descending (LAD) artery. Confidence in grading luminal stenosis with calcific plaque, noncalcific plaque, and stent was evaluated by 2 independent readers on a 0–100 scale (0 the lowest), and a CAD-RADS score was assigned. Image contrast enhancement, sharpness, noise, artifacts, and overall image quality were rated using a 5-point ordinal scale (1 the lowest).ResultsThe radiation doses (CTDI) in low- and routine-contrast cohorts were 2.5 ± 0.6 mGy and 3.1 ± 1.7 mGy, respectively (P = 0.12). At all measured locations, the mean CT number was >300 HU in 120 kV (LMCA 382.9 ± 76.2, distal LAD 341.0 ± 53.9, AA 399.5 ± 76.1) and 50 keV images (LMCA 667.5 ± 139.9, distal LAD 578.1 ± 121.5, AA 700.8 ± 142.5) in the low-contrast cohort, with a 96% increase in CT numbers for 50 keV over 120 kV. The CT numbers were significantly higher (P < 0.0001) in 50 keV than 120 kV and 100 keV VMI. The CNR was also significantly (P < 0.0001) higher in 50 keV than 120 kV and 100 keV images in all vessels. Confidence in the assessment of luminal stenosis in the presence of calcific plaque was significantly higher (P = 0.001) with the addition of 100 keV VMI (median score, 100) than using 50 keV alone (median score, 70) and 120 kV (median score, 70) for reader 1, but no significant differences were seen for reader 2 who had same median scores of 100 for all image types. The confidence in the assessment of luminal stenosis within a stent improved with the use of 100 keV images for both readers (reader 1: median scores for 50 + 100 keV = 100, 50 keV = 82.5, 120 kV = 82.5; reader 2: 50 + 100 keV = 100, 50 keV = 90, 120 kV = 90). There were no significant differences in confidence scores for assessment of luminal stenosis from noncalcific plaques for both readers. The reader-averaged qualitative scores for vascular enhancement and overall image quality were significantly higher for 50 keV VMI than for 120 kV images in both low- and routine-contrast dose cohorts. The image sharpness was nonsignificantly higher at 50 keV VMI than 120 kV images, and the artifact score was comparable for 50 keV VMI and 120 kV images. The noise was higher in 50 keV VMI than in 120 kV images.ConclusionsHigh-pitch ME PCD-CT mode p...

Technical Basics and Clinical Benefits of Photon-Counting CT

“…Instead, they must be shown to have a positive impact on diagnostic accuracy and diagnostic confidence, and ideally to change the clinical management of patients. Initial studies already show an impact on diagnostic performance and diagnostic accuracy in various clinical fields, 46 , 68 , 77 , 86 , 87 and larger, more comprehensive clinical studies are sure to follow.…”

“…The addition of 100 keV VMIs improved the diagnostic confidence in the evaluation of luminal stenosis associated with calcific plaques and stents and downgraded CAD-RADS scores in 9 patients by reducing blooming artifacts. 68 Virtual monoenergetic images are also used in CT scans without contrast agent, in which case special attention must be paid to the choice of keV level for quantitative applications such as Ca scoring. By choosing an appropriate combination of keV and strength of iterative reconstruction (Quantum Iterative Reconstruction QIR, Siemens Healthcare), Ca scoring results of EID-CT can be reproduced on PCD-CT.…”

“…When using VMIs at 50 keV for coronary CTA with a PCD-DSCT at high pitch, a low contrast dose protocol (30 mL of a 350 mg I/mL contrast agent instead of the routine 60 mL) produced diagnostic image quality in a group of 27 patients. The addition of 100 keV VMIs improved the diagnostic confidence in the evaluation of luminal stenosis associated with calcific plaques and stents and downgraded CAD-RADS scores in 9 patients by reducing blooming artifacts 68 …”

“…The addition of 100 keV VMIs improved the diagnostic confidence in the evaluation of luminal stenosis associated with calcific plaques and stents and downgraded CAD-RADS scores in 9 patients by reducing blooming artifacts. 68 …”

Improving stenosis assessment in energy integrating detector CT via learned monoenergetic imaging capability

“…A recent advancement involves generating virtual monoenergetic images (VMIs) at higher keV levels (e.g., 100 keV) using photon counting detector (PCD) CT, which holds promise in reducing blooming artifacts and improving lumen visibility within cCTA images through its simultaneous high-resolution multi-energy imaging capability [2][3][4][5] . However, compared to PCD-CT, most EID-CT systems are limited to acquiring only single-energy CT (SECT) scans.…”