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Rationale and Objectives: The aims of this study were to investigate image noise (standard deviation of computed tomographic value) and to assess variability in repeated coronary artery calcium (CAC) scoring on prospective electrocardiographically triggered 64-detctor computed tomography., Materials and Methods: Patients (n = 428) suspected of having coronary artery disease were scanned twice using three protocols: with tube current modified by body mass index (BMI; group A), by BMI and body height (group B), and by attenuation at the maximal heart diameter (group C). Image noise was plotted against BMI. Interscan variability of CAC scores was determined. The effective dose was estimated by computed tomographic dose index., Results: The mean effective dose and image noise, respectively, were 0.9 +/- 0.2 mSv (range, 0.6-1.5 mSv) and 19 +/- 4 Hounsfield units (HU) (range, 10-32 HU) for group A; 0.8 +/- 0.2 mSv (range, 0.5-1.4 mSv) and 18 +/- 4 HU (range, 10-31 HU) for group B; and 0.8 +/- 0.4 mSv (range, 0.3-2.2 mSv) and 20 +/- 2 HU (range, 16-26 HU) for group C. Group C used a wide dose range and controlled noise within a small range. The positive slopes of image noise versus BMI, 0.81 HU/(kg/m(2)) in group A and 0.62 HU/(kg/m(2)) in group B, suggested insufficient control of the tube current. In contrast, the nearly flat slope in group C, 0.091 HU/(kg/m(2)), indicated optimal control. The interscan variability for Agatston score, volume, and mass in patients with CAC (n = 300) was 13% (median, 8%), 12% (median, 7%), and 11% (median, 6%), respectively., Conclusions: CAC scoring on prospective electrocardiographically triggered 64-detector computed tomography using attenuation-based tube current control has the potential to favorably control image noise with low dose and low interscan variability.

Rationale and Objectives: The purpose of this prospective study was to assess image noise and variability in repeated coronary artery calcium (CAC) scoring on low-dose prospective electrocardiographically-triggered 64-slice multidetector computed tomography., Materials and Methods: Patients (n = 115) suspected of having coronary artery disease were scanned twice, using a tube current of 10 x body mass index mA. The standard deviation (SD) of the computed tomographic value in the ascending aorta and (mean + 2 x SD) were obtained. Repeated CAC scores (Agatston, volume, and mass) were measured by two observers, and the interscan and interobserver variability were determined., Results: The mean tube current used was 246 +/- 36 mA. The mean tube current-time product and mean estimated effective dose were 57 +/- 8 mA and 0.9 +/- 0.2 mSv, respectively. The SD and (mean + 2 x SD) computed tomographic values in the ascending aorta were 16 +/- 3 and 75 +/- 10 Hounsfield units, respectively. Repeated CAC scores were correlated (r(2) = 0.995-0.998). The interscan variability for observer 1 and observer 2, respectively, were 13% and 13% for Agatston score, 12% and 11% for volume, and 11% and 11% for mass. The interobserver variability for scan 1 and scan 2, respectively, were 3% and 3% for Agatston score, 5% and 3% for volume, and 3% and 3% for mass., Conclusion: Low-dose prospective electrocardiographically-triggered 64-slice multidetector computed tomography shows low interscan and interobserver variability on CAC scoring while maintaining low image noise.

The impact of visceral adiposity on subclinical coronary atherosclerosis is unclear in Japanese patients. We investigated the sex-specific relationship between the amount of visceral fat and coronary artery calcium (CAC) using multislice computed tomography (MSCT). This is a cross-sectional study of 321 consecutive Japanese patients (213 men and 108 women) who underwent MSCT scanning for the examination of coronary heart disease. CAC score, visceral fat area (VFA), subcutaneous fat area (SFA), and waist circumference (WC) were determined by MSCT for all patients. The prevalence of detectable CAC was 73% and 57% in men and women, respectively. Using a multivariable logistic and ordinal regression analyses adjusting for traditional cardiovascular risk factors and adiposity measurements, VFA represented an independent predictor of the presence and extent of CAC (odds ratio (95% confidence interval) per one-unit-standard deviation increase in VFA: 2.48 (1.23-6.05) in logistic regression analysis; 2.05 (1.18-3.98) in ordinal regression analysis). Similar relationships were observed across the gender. We further assessed the sex-specific cut-off levels of VFA and WC to predict the presence of CAC. The results of receiver operator characteristic analysis indicated that the VFA cut-off level in men was 116cm(2); and in women, it was 82cm(2), corresponding to WC values of 87.7cm in men and 82.6cm in women. In conclusion, we found that visceral adiposity measured by MSCT is significantly associated with the presence and extent of CAC as a marker of subclinical atherosclerosis in Japanese patients.

Objective: The purpose of our study was to investigate the cardiac phase with the least interscan variability and motion artifacts on coronary artery calcium studies using a 64-MDCT scanner., Subjects and Methods: Ninety-one patients with suspected coronary artery disease were scanned twice on retrospective ECG-gated helical scans. Images with 2.5-mm thickness and 1.25-mm interval at nine cardiac phases (center of cardiac phase: 40-80% in 5% increments) were reconstructed. The interscan variability of coronary artery scores (Agatston, volume, and mass) per patient and motion artifact scores per branch, subjectively assigned by motion artifact grading (1, none; 2, minor; and 3, major), were compared between cardiac phases for all patients, low (< 65 beats per minute [bpm]) and high (>or= 65 bpm) heart rate patient groups., Results: For all patients, two-factor factorial analysis of variance revealed that the interscan variability was different between cardiac cycles (p < 0.01); however, this was not statistically significant between scoring algorithms (p = 0.46). The least variability was obtained at 70% on Agatston (8%) and volume (7%) and at 75% on mass (7%). Adjacent categories logit model analysis revealed that the motion artifact score was the least at 75% (left anterior descending coronary artery, 1.3; left circumflex coronary artery, 1.4; and right coronary artery, 1.9 in all patients) and that a smaller difference in calcium scores between the scans led to a smaller motion artifact score (p < 0.05)., Conclusion: Middiastole reconstruction (center of cardiac phase: 70-75%), with the least interscan variability and the least motion artifacts, is recommended on 64-MDCT.

High reproducibility on coronary artery calcium scoring is a key requirement in monitoring the progression of coronary atherosclerosis. The purpose of this prospective study is to assess the reproducibility of 1.25-mm- and 2.5-mm-thickness images on prospective electrocardiograph-triggered 64-slice CT with respect to 2.5-mm-thickness images on spiral overlapping reconstruction. One hundred patients suspected of coronary artery disease were scanned twice repeatedly, both on prospective electrocardiograph-triggered step-and-shoot and retrospective electrocardiograph-gated spiral scans. Using 1.25-mm-thickness collimation, 1.25-mm- and 2.5-mm-thickness image sets on prospective scans and 2.5-mm-thickness image sets with 1.25-mm increment (overlapping) on retrospective scans were obtained. Coronary artery calcium scores, interscan variability and interobserver variability were evaluated. The mean interscan variability in coronary artery calcium measurement on 1.25-mm prospective/2.5-mm prospective/2.5-mm overlapping retrospective scans were Agatston: 10%/18%/12%, volume: 10%/12%/10% and mass: 8%/13%/11% for observer 1 and Agatston: 8%/14%/10%, volume: 7%/9%/10% and mass: 7%/10%/9% for observer 2, respectively. The mean interobserver variability was 5% to 14%. In conclusion, prospective electrocardiograph-triggered 64-slice CT using the 1.25-mm prospective scan shows the lowest variability. The 2.5-mm prospective scan on volume or mass scoring shows variability of around 10%, comparable to 2.5-mm-thickness spiral overlapping reconstruction images.

Background: Multislice computed tomography has recently been shown to have the potential to characterize noncalcified coronary atherosclerotic lesions (NCALs). We evaluated the relationship among computed tomography (CT) density, arterial remodeling, and the adherent calcium morphology of NCALs detected using 64-slice CT., Methods: We studied 138 patients with proven or suspected coronary artery disease who underwent contrast-enhanced 64-slice CT examination. For each NCAL detected within the vessel wall, we determined the minimum CT density, remodeling index (RI = lesion/reference vessel area), and the presence or absence of coronary calcium in or adjacent to each NCAL and its morphology. Intravascular ultrasound (IVUS) was additionally performed in a subset of 21 patients., Results: A total of 202 NCALs were detected in 97 patients. The mean CT density of 98 lesions with positive remodeling (PR) (RI >1.05) was significantly lower than that of 104 lesions without PR (25 +/- 23 vs 56 +/- 28 Hounsfield units, P < .001); and spotty calcium was more frequently observed with the PR lesions than non-PR lesions (59% vs 22%, P < .001). The mean CT density of the PR lesions with spotty calcium (n = 58) was substantially lower than that of the non-PR lesions without adherent calcium (n = 45) (20 +/- 20 vs 67 +/- 24 Hounsfield units, P < .001). Evaluation of the components, RI, and adherent calcium morphology of 38 NCALs by 64-slice CT was in close agreement with the IVUS findings., Conclusions: Lower CT density, PR, and adherent spotty calcium, which may indicate plaque vulnerability, are intimately co-related in NCALs detected using 64-slice CT; these findings are consistent with those of IVUS.

The purpose of this study is, using a 16-section multidetector-row helical computed tomography (MDCT) scanner with retrospective reconstruction, to compare variability in repeated coronary calcium scoring and qualitative scores of the motion artifacts. One hundred forty-four patients underwent two subsequent scans using MDCT. According to Agatston and volume algorithms, the coronary calcium scores during mid-diastole (the center corresponding to 70% of the R-R cycle) were calculated and the inter-scan variability was obtained. Motion artifacts from coronary artery calcium were subjectively evaluated and classified using a 5-point scale: 1, excellent; no motion artifacts; 2, fine, minor motion artifacts; 3, moderate, mild motion artifacts; 4, bad, severe motion artifacts; 5, poor, doubling or discontinuity. Each reading was done by vessels (left main, left descending, left circumflex and right coronary arteries) and the motion artifact score (mean of the scales) was determined per patient. The variability in the low (1.2+/-0.2) and high (2.4+/-0.6) motion artifact score groups was 7+/-6 (median, 6)% and 19+/-15 (16)% on the Agatston score (P<0.01) and 7+/-7 (6)% and 16+/-13 (14)% on the volume score (P<0.01), respectively. In conclusion, motion has a significant impact on the reproducibility of coronary calcium scoring.

Objective: High reproducibility on coronary artery calcium (CAC) scoring is a key requirement in monitoring the progression of coronary atherosclerosis. Retrospective ECG-gated helical CT has been shown to be superior to prospective gating helical CT in the reproducibility of CAC measurements. However, it brings with it a high level of radiation exposure. The purpose of this study was to compare low- and standard-dose protocols in the variability of CAC scores and in image quality, thereby assessing the feasibility of low-dose retrospective ECG-gated helical CT in CAC measurements., Subjects and Methods: Eighty-six patients with CAC were scanned using a tube current setting of 100 mA once and then a tube current setting equivalent to the patient's body weight twice. CAC scores (Agatston and volume) and interscan variability were evaluated. The mean and SD of the CT attenuation values in regions of interest in the aorta were measured, and the value (mean + 2 x SD) was obtained., Results: A high correlation of log(10) (Agatston score + 1) was observed between sequential helical CT scans (r = 0.998). The variability in CAC measurements ranged from 11% to 12% for both the Agatston and volume scores. With the tube current equivalent to body weight, the value (mean + 2 x SD) did not exceed a CT attenuation value of 130 H., Conclusion: Low-dose retrospective ECG-gated helical CT-yielding low variability and achieving the level of image quality needed to measure CAC-can be used to monitor patients with coronary atherosclerosis.

The purpose of this study was to investigate how accurately CAC volume we can be measured using electron beam computed tomography (CT) and 16-slice spiral CT. CAC models with known volume attached to a cardiac phantom were scanned. The error of measurement, variability between measured and real volumes, and inter-scan measurement variability were obtained. For spiral CT, seven different parameters were included: (1) slice thickness (0.625 mm, 1.25 mm and 2.5 mm), (2) retrospective spiral electrocardiograph (ECG)-gated or prospective axial ECG-triggering, (3) overlapping or non-overlapping. The error of measurement was 15% on electron beam CT and 8-20% on spiral CT. CAC volumes were underestimated in 92% and overestimated in 8% of the electron beam CT scans. Volumes were underestimated in 79%, correct in 5% and overestimated in 16% of the spiral CT scans. The best measurement and the least variability was observed on 0.625-mm retrospective spiral ECG-gated CT (error of 8%), a significant result (t-test: P<0.01) when compared with electron beam CT. CAC volume measurement on CT scanners may be significantly different and often underestimates the real volume of CAC. For precise evaluation of CAC volume, thin-slice retrospective spiral ECG-gated scan using a spiral CT scanner is desirable.

Objective: High reproducibility of coronary artery calcium (CAC) scoring is a key requirement for monitoring the progression of coronary atherosclerosis. The purposes of this study were to compare electron beam CT and 16-MDCT scanners in the variability of repeated CAC measurements and to assess the factors influencing this variability., Materials and Methods: CAC models of different sizes attached to a cardiac phantom with a programmable variable heart rate were scanned three times, and interscan variability of the CAC measurement was calculated each time. For helical CT, different slice-thickness images of either retrospective ECG-gated or prospective ECG-triggering reconstruction were obtained. The detection of small amounts of calcium, variability of the Agatston score, and CAC measurement algorithms (Agatston, volume, and mass scores) were compared between CT scanners and protocols., Results: All 1-mm-sized calcium models were detected on 0.625- and 1.25-mm helical CT, whereas some were missed on electron beam CT and 2.5-mm helical CT. Retrospective ECG-gated thin-slice helical CT showed the lowest variability. Reduction of variability by volume and mass scoring algorithms was less effective on 0.625- and 1.25-mm-thickness CT., Conclusion: Retrospective ECG-gated thin-slice helical CT has the potential to be a useful tool for monitoring coronary atherosclerosis.

Objective: High reproducibility on coronary calcium scoring is an important factor in monitoring the progression of coronary atherosclerosis. The purposes of this study were, using a 16-MDCT scanner with retrospective reconstruction, to compare the effects of thin-slice images and overlapping image reconstruction on the reproducibility of coronary calcium scoring and to compare 16-MDCT with electron beam CT (EBCT)., Materials and Methods: Fifty patients underwent two sequential examinations using both EBCT and MDCT. For MDCT, images were reconstructed from the same raw data using the following thicknesses and increments (thickness/increment): 1.25 mm/1.25 mm, 2.5 mm/2.5 mm, and 2.5 mm/1.25 mm. The Agatston, volume, and mass scores were calculated on four pairs of image sets. Statistical analysis was performed to determine significant differences in interscan variability among image acquisition protocols and among measurement algorithms., Results: Overlapping reconstructed images (thickness/increment, 2.5 mm/1.25 mm) obtained on a 16-MDCT scanner showed the lowest variability (mean, 13%; median, 10%) when compared with the Agatston score., Conclusion: The use of 16-MDCT with overlapping reconstruction by retrospective reconstruction, yielding low variability of coronary artery calcium measurement on two sequential scans, has an advantage over EBCT in monitoring the progression of atherosclerosis.

Objective: Our aim was to compare detection, quantification, and cardiovascular risk stratification of coronary artery calcium (CAC) between electron beam CT and 16-MDCT with retrospective reconstruction. SUBJECTS AND METHODS. One hundred patients underwent both electron beam CT and 16-MDCT, and coronary artery calcium score, volume, and mass were obtained., Results: Correlation between the two CT scanners was high for both calcium score (r(2) = 0.955), volume (r(2) = 0.952), and mass (r(2) = 0.977). Although electron beam CT is viewed as the gold standard, the sensitivity and specificity in the detection of CAC using 16-MDCT with a threshold of 130 H were 98.7% and 100%, respectively. The variability of calcium scores between the two CT scanners (26.5%) was comparable with two electron beam CT scanners reported previously. The variability of calcium volume (20.7%) and mass (20.3%) was lower than that of the score (Student's t test, r = 0.05, 0.01). In clinical cardiovascular risk stratification based on two CT calcium scores, the Cohen's kappa value was 0.929. There was no significant difference between the two scanners using Wilcoxon's signed rank test (p = 0.157)., Conclusion: The 16-MDCT scanner with retrospective reconstruction, showing high agreement for detection and quantification of CAC with electron beam CT, holds promise in the detection of coronary artery atherosclerosis.

Rationale and Objectives: Slow heart rate and small changes in heart rate are factors for improving image quality on spiral cardiac computed tomography (CT). The purpose of this study is to investigate whether it is possible to improve nonenhanced cardiac CT quality by delaying the data-acquisition window after breath hold. Materials and Methods: Electrocardiograph files (n = 240) for 16-slice nonenhanced cardiac CT scans were analyzed. Mean heart rates and maximal changes in heart rates between adjacent cardiac cycles were compared between phase 1 (defined as cardiac cycles 1–5), phase 2 (cardiac cycles 2–6), … , and phase 6 (cardiac cycles 6–10). Results: Heart rates gradually increased by phases, but were limited to a range of 66.8–68.0 beats/min. Maximal changes in heart rates were 2.5 beats/min (phase 1) at the highest and 1.3 beats/min (phases 5 and 6) at the lowest (t-test; P < .01). Maximal changes in heart rates for more than five beats/min occurred in 24, eight, and eight patients on phases 1, 5, and 6, respectively (chi-square test; P < .01). Conclusion: The delayed scan (four or five cardiac cycles after breath hold) has the potential to improve the quality of nonenhanced cardiac CT. [Copyright &y& Elsevier]