Computed high concentrations of low-density lipoprotein correlate with plaque locations in human coronary arteries.

Subendothelial accumulation of low-density lipoprotein (LDL) in arterial walls is an initiator of atherosclerotic plaque formation. We report here on the correlation between healthy state subendothelial LDL concentration distribution and sites of subsequent plaque formation in coronary arteries of patients with coronary artery disease (CAD). We acquired left (LCA) and right coronary artery (RCA) and atherosclerotic plaque geometries of 60 patients with CAD using dual-source computed tomography angiography. After virtually removing all plaques to obtain an approximation of the arteries' healthy state, we calculated LDL concentration in the artery walls as a function of local lumen-side shear stress. We found that maximum subendothelial LDL concentrations at plaque locations were, on average, 45% (RCA) and 187% (LCA) higher than the respective average subendothelial concentration. Our results demonstrate that locally elevated subendothelial LDL concentration correlates with subsequent plaque formation at the same location.

Optimal image reconstruction intervals for non-invasive coronary angiography with 64-slice CT.

The reconstruction intervals providing best image quality for non-invasive coronary angiography with 64-slice computed tomography (CT) were evaluated. Contrast-enhanced, retrospectively electrocardiography (ECG)-gated 64-slice CT coronary angiography was performed in 80 patients (47 male, 33 female; mean age 62.1+/-10.6 years). Thirteen data sets were reconstructed in 5% increments from 20 to 80% of the R-R interval. Depending on the average heart rate during scanning, patients were grouped as < 65 bpm (n = 49) and > or = 65 bpm (n = 31). Two blinded and independent readers assessed the image quality of each coronary segment with a diameter > or = 1.5 mm using the following scores: 1, no motion artifacts; 2, minor artifacts; 3, moderate artifacts; 4, severe artifacts; and 5, not evaluative. The average heart rate was 63.3 +/- 13.1 bpm (range 38-102). Acceptable image quality (scores 1-3) was achieved in 99.1% of all coronary segments (1,162/1,172; mean image quality score 1.55 +/- 0.77) in the best reconstruction interval. Best image quality was found at 60% and 65% of the R-R interval for all patients and for each heart rate subgroup, whereas motion artifacts occurred significantly more often (P < 0.01) at other reconstruction intervals. At heart rates < 65 bpm, acceptable image quality was found in all coronary segments at 60%. At heart rates > or = 65 bpm, the whole coronary artery tree could be visualized with acceptable image quality in 87% (27/31) of the patients at 60%, while ten segments in four patients were rated as non-diagnostic (scores 4-5) at any reconstruction interval. In conclusion, 64-slice CT coronary angiography provides best overall image quality in mid-diastole. At heart rates < 65 bpm, diagnostic image quality of all coronary segments can be obtained at a single reconstruction interval of 60%.

Aortic stenosis: comparative evaluation of 16-detector row CT and echocardiography.

PURPOSE: To prospectively evaluate whether planimetric measurements of aortic valve area (AVA) with 16-detector row computed tomography (CT) allow classification of aortic stenosis (AS). MATERIALS AND METHODS: The study had institutional review board approval; patients gave informed consent. Twenty patients (11 men, nine women; mean age, 63 years) with AS and 20 patients (10 men, 10 women; mean age, 65 years) without underwent transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and retrospectively electrocardiographically gated 16-detector row CT. Twenty CT data sets were reconstructed in 5% steps of R-R interval; data analysis was performed with four-dimensional software. Maximum AVA in systole planimetrically measured with CT (AVA(CT)) was compared with AVA planimetrically measured with TEE (AVA(TEE)), AVA calculated with the continuity equation and TTE (AVA(TTE)), and transvalvular pressure gradients determined with the Bernoulli equation and TTE. Correlations among AVA(CT), AVA(TTE), AVA(TEE), and transvalvular pressure gradients were tested with bivariate regression analysis; agreement between methods was assessed with the Bland-Altman method. RESULTS: In patients without AS, mean AVA(CT) was 3.56 cm2 +/- 0.66 and mean AVA(TEE) was 3.43 cm2 +/- 0.69. In patients with AS, mean AVA(CT) was 0.89 cm2 +/- 0.35; mean AVA(TEE), 0.86 cm2 +/- 0.35; and mean AVA(TTE), 0.83 cm2 +/- 0.33. Mean transvalvular pressure gradient was 51 mm Hg +/- 22. Significant correlations were present between AVA(CT) and AVA(TEE) (r = 0.99, P < .001), AVA(CT) and AVA(TTE) (r = 0.95, P < .001), and AVA(CT) and transvalvular pressure gradients (r = -0.74, P < .01). Mean differences were -0.08 cm2 (limits of agreement: -0.32, 0.16) for AVA(CT) versus AVA(TEE) and 0.06 cm2 (limits of agreement: -0.15, 0.26) for AVA(CT) versus AVA(TTE). CONCLUSION: Planimetric measurements of AVA with retrospectively electrocardiographically gated 16-detector row CT allow classification of AS that is similar to that achieved with measurements by using echocardiographic methods.

Mitral regurgitation: quantification with 16-detector row CT--initial experience.

PURPOSE: To prospectively determine if retrospectively electrocardiographic (ECG)-gated multi-detector row computed tomography (CT) with a 16-detector row CT scanner can depict mitral regurgitation and enable quantification of the severity of the disease. MATERIALS AND METHODS: The study had institutional review board approval, and patients gave informed consent. Nineteen patients with mitral regurgitation (10 men, nine women; mean age, 66 years +/- 9 [standard deviation]; range, 41-83 years) and 25 patients without mitral regurgitation (14 men, 11 women; mean age, 68 years +/- 9; range, 43-83 years) as determined with transesophageal color Doppler echocardiography and ventriculography underwent retrospectively ECG-gated 16-detector row CT. Twenty CT data sets covering the entire mitral valve apparatus were reconstructed in 5% steps of the R-R interval for each patient, and data analysis was performed with four-dimensional software. Using planimetry, two readers measured in consensus the area of the regurgitant orifice during systole. These measurements were compared with semiquantitative data from transesophageal echocardiography and ventriculography by using Spearman rank order correlation coefficients. RESULTS: In the 25 patients without mitral regurgitation, no regurgitant orifice during systole could be detected with multi-detector row CT. In the 19 patients with mitral regurgitation, a regurgitant orifice could be visualized in all cases. The mean regurgitant orifice area at CT-45 mm(2) +/- 34 (range, 10-148 mm(2))-correlated significantly with the results at transesophageal echocardiography (r = 0.807, P < .001) and ventriculography (r = 0.922, P < .001). CONCLUSION: Planimetric measurements of the regurgitant orifice area at retrospectively ECG-gated 16-detector row CT enable quantification of mitral regurgitation.

Evaluation of peripheral arterial bypass grafts with multi-detector row CT angiography: comparison with duplex US and digital subtraction angiography.

PURPOSE: To assess the technical feasibility of multi-detector row computed tomographic (CT) angiography in the assessment of peripheral arterial bypass grafts and to evaluate its accuracy and reliability in the detection of graft-related complications, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. MATERIALS AND METHODS: Four-channel multi-detector row CT angiography was performed in 65 consecutive patients with 85 peripheral arterial bypass grafts. Each bypass graft was divided into three segments (proximal anastomosis, course of the graft body, and distal anastomosis), resulting in 255 segments. Two readers evaluated all CT angiograms with regard to image quality and the presence of bypass graft-related abnormalities, including graft stenosis, aneurysmal changes, and arteriovenous fistulas. The results were compared with McNemar test with Bonferroni correction. CT attenuation values were recorded at five different locations from the inflow artery to the outflow artery of the bypass graft. These findings were compared with the findings at duplex ultrasonography (US) in 65 patients and the findings at conventional digital subtraction angiography (DSA) in 27. RESULTS: Image quality was rated as good or excellent in 250 (98%) and in 252 (99%) of 255 bypass segments, respectively. There was excellent agreement both between readers and between CT angiography and duplex US in the detection of graft stenosis, aneurysmal changes, and arteriovenous fistulas (kappa = 0.86-0.99). CT angiography and duplex US were compared with conventional DSA, and there was no statistically significant difference (P >.25) in sensitivity or specificity between CT angiography and duplex US for both readers for detection of hemodynamically significant bypass stenosis or occlusion, aneurysmal changes, or arteriovenous fistulas. Mean CT attenuation values ranged from 232 HU in the inflow artery to 281 HU in the outflow artery of the bypass graft. CONCLUSION: Multi-detector row CT angiography may be an accurate and reliable technique after duplex US in the assessment of peripheral arterial bypass grafts and detection of graft-related complications, including stenosis, aneurysmal changes, and arteriovenous fistulas.

Multidetector-row helical CT: analysis of time management and workflow.

The purpose of this study was to evaluate time management and workflow for multidetector-row helical CT (MDCT). Time for patient and data handling of at total of 580 patients were evaluated at two different time periods (December 1999, August 2000), each for the following baseline measurements: (a) change of clothes/instruction; (b) patient placement on the CT table/i.v. catheter; (c) CT planning and programming; (d) CT data acquisition; (e) CT data reconstruction; (f) CT data storage/printing. All imaging was performed on a Somatom Volume Zoom (Siemens, Erlangen, Germany). Time measurements summarized for different CT protocols revealed the following: (a) 5:01 min (+/- 2.06 min); (b) 4:36 min (+/- 2.43 min); (c) 4:11 min (+/- 2.55 min); (d) 0:43 min (+/- 0.15 min); (e) 6:59 min (+/- 2.39 min); (f) 09:51 min (+/- 3.51 min). Planning and programming was most time-consuming for CT angiography, whereas chest and abdominal CT needed only 3:26 and 3:30 min, respectively. Reconstruction time was highest for HRCT (9:22 min) and CTA (9:03 min). Data storage/printing was most time-consuming for HRCT (13:02 min), followed by combined neck-chest-abdomen examinations (12:19 min). Comparing the two time periods, during which a software update was performed, a mean time reduction of 4:31 min per patient (15%, p<0.001) was achieved. Whereas CT data acquisition time is no longer a problem with MDCT, patient management, data reconstruction, and data storage are the most time-consuming parts. Well-trained technicians, state-of-the-art workstations, and fast networking are the most important factors to improve workflow.