Prospective-triggered sequential dual-source end-systolic coronary CT angiography for patients with atrial fibrillation: a feasibility study.

BACKGROUND: Obtaining diagnostic coronary CT angiography with low radiation exposure in patients with irregular heart rhythms such as atrial fibrillation (AF) remains challenging. OBJECTIVE: We evaluated image quality and inter-reader variability with the use of prospective electrocardiographic (ECG)-triggered sequential dual-source acquisition at end systole for coronary artery disease (CAD) evaluation in patients with AF. METHODS: Thirty consecutive patients with AF who underwent prospective ECG-triggered sequential dual-source acquisition were evaluated. Images were reconstructed every 50 milliseconds from 250 to 400 milliseconds after the R wave. Two independent, blinded readers evaluated the coronaries for image quality on a 5-point scale (worst to best) and stenosis on 5-point semiquantitative (none to severe) and binary scales (>50% or <50%). Diagnostic image quality was graded for each reconstruction. RESULTS: Eleven patients (37%) had significant (≥50% stenosis) CAD. Average heart rate was 82 ± 20 beats/min and variability range was 71 ± 22 beats/min. Mean effective radiation dose was 6.5 ± 2.4 mSv. Diagnostic image quality was noted in 97.9% of 304 coronary segments with median image quality of 3.0. The 300-millisecond reconstruction phase provided the highest image quality; 70% of patients showed diagnostic image quality. Combination of all phases (250-400 milliseconds) performed significantly better than single or other phase combinations (P < 0.0005 for all comparisons). Inter-reader variability for stenosis detection was excellent, with 98.4% concordance by using a binary scale (50% stenosis cutoff). CONCLUSIONS: Prospective ECG-triggered sequential dual-source CT acquisition with the use of end-systolic acquisition provides diagnostic image quality with potentially low radiation doses for evaluation of CAD in patients with AF. Use of multiple end-systolic phases over a 150-millisecond window improves diagnostic image quality.

Cardiac computed tomography angiography with automatic tube potential selection: effects on radiation dose and image quality.

PURPOSE: Automatic exposure control (AEC) algorithms are widely available in coronary computed tomography angiography (CTA) and have been shown to reduce radiation doses by adjusting tube current to patient size. However, the effects of anthropometry-based automatic potential selection (APS) on image quality and radiation dose are unknown. We sought to investigate the effect of an APS algorithm on coronary CTA radiation dose and image quality. MATERIALS AND METHODS: For this retrospective case-control study we selected 38 patients who had undergone coronary CTA for coronary artery assessment in whom tube potential and tube current were selected automatically by a combined automatic tube potential and tube current selection algorithm (APS-AEC) and compared them with 38 controls for whom tube voltage was selected according to standard body mass index (BMI) cutoffs and tube current was selected using automatic exposure control (BMI-AEC). Controls were matched for BMI, heart rate, heart rhythm, sex, acquisition mode, and indication for cardiac CTA. Image quality was assessed as contrast-to-noise ratio and signal-to-noise ratio in the proximal coronary arteries. Subjective reader assessment was also made. Total radiation dose (volume-weighted computed tomography dose index) was measured and compared between the 2 groups. In the study group, comparison was made with conventional BMI-guided prior protocols (site protocols and Society of Cardiovascular Computed Tomography recommendations) through disagreement analysis. RESULTS: The APS-AEC cases received 29.8% lower overall radiation dose compared with controls (P=not significant). APS-AEC resulted in a significantly higher signal-to-noise ratio of the proximal coronary arteries (P<0.01) and contrast-to-noise ratio of the left main (P=0.01). In the study cases, the APS resulted in a change in tube potential versus site protocols and Society of Cardiovascular Computed Tomography recommendations in 45% (n=17) and 50% (n=19) of patients, respectively. CONCLUSION: Automated tube potential selection software resulted in significantly improved objective image quality versus standard BMI-based methods of tube potential selection, without increased radiation doses.

Potential of dual-energy computed tomography to characterize atherosclerotic plaque: ex vivo assessment of human coronary arteries in comparison to histology.

BACKGROUND: Noninvasive characterization of coronary atherosclerotic plaque is limited with current computed tomography (CT) techniques. Dual-energy CT (DECT) has the potential to provide additional attenuation data for better differentiation of plaque components. OBJECTIVE: We attempted to characterize coronary atherosclerotic plaque with DECT. METHODS: Seven human coronary arteries acquired at autopsy were scanned consecutively at 80 and 140 kVp with CT. Vessels were perfused with saline, and data were acquired before and after contrast agent injection. Lesions were identified, and attenuation measurements were made from CT image quadrants. CT quadrants were classified as densely calcified, fibrocalcific, fibrous, lipid-rich, or normal vessel wall, corresponding to matched histology images. Attenuation values at each peak tube voltage were compared within plaque types for both noncontrast and contrast scans. Further, dual-energy index (DEI) values computed from attenuation were analyzed for classification of plaque. RESULTS: In 14 lesions, a total of 56 quadrants were identified. Histology results classified 8 (14%) as densely calcified, 8 (14%) as fibrocalcific, 9 (16%) as fibrous, 5 (9%) as lipid-rich, and 25 (45%) as normal vessel wall. Calcified lesions attenuated significantly more at 80 kVp in both contrast and noncontrast scans, whereas fibrous plaque attenuated more at 80 kVp only for contrast-enhanced scans. No differences were found for lipid-rich plaques. Using DEI values, only densely calcified plaques could be distinguished from other plaque types except fibrocalcific plaques in contrast images. CONCLUSIONS: Only densely calcified and fibrocalcific plaques showed a true change in attenuation at 80 versus 140 kVp. Therefore, calcified plaques could be distinguished from noncalcified plaques with DECT, but further classification of plaque types was not possible.