Coronary artery calcium scoring using 16-MDCT and a retrospective ECG-gating reconstruction algorithm

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.     

Coronary artery calcium: accuracy and reproducibility of measurements with multi-detector row CT--assessment of effects of different thresholds and quantification methods

PURPOSE: To evaluate the effects of different thresholds and quantification methods on the accuracy and reproducibility of coronary calcium measurements with multi-detector row computed tomography (CT). MATERIALS AND METHODS: A cardiac CT phantom containing predetermined calcified cylinders was scanned. Calcium volume and mass were measured at various threshold values ranging from 80 to 230 HU. In 32 patients, two consecutive CT scans were obtained, and the coronary artery calcium score, volume, and mass were measured by one observer at 130- and 90-HU thresholds. Correlation analysis and analysis of variance were performed to evaluate the measurement errors in the phantom study and the interscan variability in the clinical study. RESULTS: In the phantom, mass measurement error varied with threshold and calcium density (P <.01). Mass error was strongly correlated with volume error (r = 0.91, P <.01) but with a much smaller range. In the clinical study, interscan variability of mass measurements was significantly lower than that with other measurement methods for both patients and individual vessels. For the patients, the mean interscan variability of calcium score, volume, and mass at the 130-HU threshold was 20.4%, 13.9%, and 9.3%, respectively. For all methods, interscan variability was not significantly different between the 130- and 90-HU thresholds (P >.05). CONCLUSION: The mass measurement is more accurate, less variable, and more reproducible in coronary calcium quantification than are measurements with other algorithms. Accurate quantification of calcium in each calcified plaque may require that the threshold be set individually, depending on the calcium density.     

Interscan variation in coronary artery calcium quantification in a large asymptomatic patient population

OBJECTIVE: We evaluated interscan variation in coronary artery calcium scores in a large screening population as determined by electron beam CT. MATERIALS AND METHODS: One thousand patients (average age, 53 years; age range, 18-85 years) who were asymptomatic for coronary artery disease underwent two consecutive scans of the heart on an electron beam CT scanner. Scans were performed with ECG gating, breath-hold, 3-mm collimation, and 100-msec exposure. Two contiguous pixels with density values greater than 130 H were used as the minimum criterion for a calcific lesion. The calcium score was determined on a vessel-by-vessel basis for both scans of each patient. Interscan variation in calcium and vessels involved with calcification was evaluated on the basis of age, sex, and average calcium score. RESULTS: The percentage of difference between calcium scores in scans was 28.4% and 43.0% for women and men, respectively. For the individual epicardial arteries (left main, left anterior descending, circumflex, and right coronary), the percentage of difference for calcium scores was 20.2-24.2% for women and 30.5-44.9% for men. A difference between the two scans in at least one vessel of the total coronary arteries identified with calcium was noted in 31% of patients. CONCLUSION: Interscan variability in calcium scores may be important in the determination of risk stratification. Subjects with a nonzero calcium score may benefit from undergoing two scans at the time of initial imaging.     

Coronary artery calcium: a multi-institutional, multimanufacturer international standard for quantification at cardiac CT

PURPOSE: To develop a consensus standard for quantification of coronary artery calcium (CAC). MATERIALS AND METHODS: A standard for CAC quantification was developed by a multi-institutional, multimanufacturer international consortium of cardiac radiologists, medical physicists, and industry representatives. This report specifically describes the standardization of scan acquisition and reconstruction parameters, the use of patient size-specific tube current values to achieve a prescribed image noise, and the use of the calcium mass score to eliminate scanner- and patient size-based variations. An anthropomorphic phantom containing calibration inserts and additional phantom rings were used to simulate small, medium-size, and large patients. The three phantoms were scanned by using the recommended protocols for various computed tomography (CT) systems to determine the calibration factors that relate measured CT numbers to calcium hydroxyapatite density and to determine the tube current values that yield comparable noise values. Calculation of the calcium mass score was standardized, and the variance in Agatston, volume, and mass scores was compared among CT systems. RESULTS: Use of the recommended scanning parameters resulted in similar noise for small, medium-size, and large phantoms with all multi-detector row CT scanners. Volume scores had greater interscanner variance than did Agatston and calcium mass scores. Use of a fixed calcium hydroxyapatite density threshold (100 mg/cm(3)), as compared with use of a fixed CT number threshold (130 HU), reduced interscanner variability in Agatston and calcium mass scores. With use of a density segmentation threshold, the calcium mass score had the smallest variance as a function of patient size. CONCLUSION: Standardized quantification of CAC yielded comparable image noise, spatial resolution, and mass scores among different patient sizes and different CT systems and facilitated reduced radiation dose for small and medium-size patients.     

Coronary calcium scoring using 16-row multislice computed tomography: nonenhanced versus contrast-enhanced studies in vitro and in vivo

OBJECTIVES: We sought to assess the agreement of coronary artery calcium score in nonenhanced and contrast-enhanced multislice-spiral computed tomography. MATERIALS AND METHODS: Vessel phantoms and 36 patients underwent nonenhanced and contrast-enhanced cardiac multislice-spiral computed tomography (Sensation 16; Siemens, Germany). Reconstruction-parameters: slice thickness 3 mm, increment 2 mm, kernels B35f and B30f. The Agatston score, calcium mass, and number of lesions were calculated. Images were scored using detection thresholds of 130 Hounsfield units (HU) and 350 HU. Based on the Agatston score, risk stratification was performed. RESULTS: In the phantom and patient study, altering the threshold from 130 to 350 HU led to a significant decrease in the mean Agatston score (phantom: 54.6%, patients: 66.7%) and calcium mass (33.0%, 47.0%) (B35f). Contrast-enhanced studies (threshold: 350 HU) showed an increase of the mean Agatston score (71.0%, 20.7%) and calcium mass (81.0%, 16.0%) when compared with nonenhanced scans (threshold: 350 HU). A total of 57% of all patients were assigned to different risk groups. CONCLUSIONS: Contrast material may simulate calcification; therefore, calculation of the coronary calcium score from contrast-enhanced images is not reliable.     

Helical and single-slice conventional CT versus electron beam CT for the quantification of coronary artery calcification

OBJECTIVE: We compared electron beam CT with conventional CT to determine the best method for the assessment of the coronary calcium score. We used conventional CT to examine symptomatic and asymptomatic patients suspected of having coronary artery disease. SUBJECTS AND METHODS: One hundred sixty male patients underwent electron beam CT and helical CT with a pitch of 1 (n = 30) and 2 (n = 30) and using a single-slice mode with (n = 50) and without (n = 50) prospective ECG triggering. In another 50 patients, we determined reproducibility for repeated scanning using electron beam CT. For all images, we derived the calcium score according to the Agatston method. We performed regression analysis and determined mean variability. Mean variability was calculated as the ratio of the absolute difference to the mean of the corresponding calcium scores. RESULTS: The correlation coefficients for electron beam CT and all conventional CT modes were very high (range, 0.93-0.98). The mean variability was highest in the helical mode with a pitch of 2 (61.4%) and lowest for the single-slice mode with prospective ECG triggering (25.4%). For repeated electron beam CT, the correlation coefficient and mean variability were 0.99 and 22.1%, respectively. CONCLUSION: ECG-triggered single-slice conventional CT had the best agreement with electron beam CT calcium scores.     

Spiral versus electron-beam CT for coronary artery calcium scoring

PURPOSE: To determine differences in coronary artery calcium detection, quantification, and reproducibility, as measured at electron-beam computed tomography (CT) and subsecond spiral CT with retrospective electrocardiogram gating in an asymptomatic adult population. MATERIALS AND METHODS: Seventy subjects asymptomatic for coronary heart disease underwent both electron-beam CT and subsecond spiral CT. In all subjects, two images each were obtained with both scanners. Two experienced readers using three different algorithms scored each of the four scans: one score for the electron-beam CT images and two scores for the spiral CT images. RESULTS: With a 130-HU threshold for the quantification of calcium, there were no significant differences in interscan and interobserver variation in calcium scores between the electron-beam CT and spiral CT images. There was greater interobserver (P <.001) and interscan (P <.03) variation in scores when a 90-HU threshold was used for spiral CT images. With a 130-HU threshold, when calcium scores were used for clinical risk stratification, there was a significant difference between the results obtained with electron-beam CT and those obtained with spiral CT (P <.05). CONCLUSION: Spiral CT has not yet proved to be a feasible alternative to electron-beam CT for coronary artery calcium quantification. There are systematic differences between calcium scores obtained with single-detector array subsecond spiral CT and those obtained with electron-beam CT.     

Evaluation of subsecond gated helical CT for quantification of coronary artery calcium and comparison with electron beam CT

OBJECTIVE: Since its introduction early in the 1990s, helical CT has become the predominant technology for obtaining CT images for medical applications. Recent improvements in the temporal resolution of helical CT (subsecond) and the addition of retrospective cardiac gating are combined in this report evaluating cardiac-gated helical CT for quantifying coronary artery calcium. We compare total calcium scores determined on subsecond gated helical CT with the current reference for coronary calcium evaluation, electron beam CT. MATERIALS AND METHODS: We compared total calcium scores obtained using a general purpose, unmodified helical CT scanner with scores obtained using electron beam CT in 36 individuals who were 68+/-11 years old (age range, 41-85 years). RESULTS: Correlation coefficients ranged from 0.97 to 0.98 (Pearson's product moment) and from 0.95 to 0.96 (Spearman's rank order), depending on the coronary calcium scoring method used. Agreement in the classification of participants as "healthy" or "diseased" at threshold total calcium scores of 10, 100, 160, 200, 400, and 680 was, respectively, 94%, 97%, 89%, 92%, 94%, and 100% using the conventional electron beam CT scoring method and an equivalent method with helical CT. CONCLUSION: A general purpose, current generation helical CT scanner equipped for retrospective cardiac gating can accurately quantify coronary calcium, and the results are highly correlated to scores obtained with electron beam CT. As an alternative method for measuring coronary calcium, gated subsecond cardiac helical CT offers greater availability and lower cost, thereby making population-based screening for coronary artery calcium more feasible.     

Sensitivity of two electron beam tomography protocols for the detection and quantification of coronary artery calcium

OBJECTIVE: The purpose of this study was to compare the sensitivity of two electron beam tomography protocols for detection and quantification of coronary artery calcium. SUBJECTS AND METHODS: We selected 101 patients (57% men, mean age 53 +/- 10 years) to undergo two consecutive electron beam tomography and acquired imaging with both a 6-mm and a 3-mm slicing protocol. Three pixels (area, 1.03 mm(2)) and a minimal density of 130 H were used for definition of calcified plaque. RESULTS: We found coronary artery calcifications in 46 patients when we used a 6-mm protocol and in 61 patients when we used a 3-mm protocol (p < 0.001). The average total calcium score was 77 (+/-140) with a 6-mm protocol and 251 (+/-395) with a 3-mm protocol (p < 0.005). The average number of calcified lesions per patient was 1.7 for a 6-mm protocol and 3.7 for a 3-mm protocol (p < 0.01). Of 179 individual lesions seen using a 3-mm protocol, 103 (58%) were missed using a 6-mm protocol, and only 27% of the lesions with a calcium score less than or equal to 40 seen with a 3-mm protocol were detected with 6-mm slicing (p < 0.001). The mean lesion attenuation with a 6-mm protocol was 160 (+/-42) H, compared with 218 (+/-44) H with a 3-mm protocol (p < 0.001), indicating a significantly greater partial volume averaging with the former protocol. CONCLUSION: A 6-mm slicing protocol is significantly less sensitive than a 3-mm protocol for the detection and quantification of coronary artery calcium. Since one third of coronary events occur in patients with low calcium scores, a 6-mm protocol might be unreliable for risk assessment because of substantial loss of information in this calcium score range.     

Electron beam CT versus 16-MDCT on the variability of repeated coronary artery calcium measurements in a variable heart rate phantom

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.     

Controversies about effects of low-kilovoltage MDCT acquisition on Agatston calcium scoring

Recent articles have advocated the possibility of obtaining Agatston coronary calcium scoring at 100 kVp by using a single adapted elevated calcium threshold. To evaluate the influence of kilovoltage potential protocols on the Agatston score, we acquired successive scans of a calcium scoring phantom at 4 levels of kilovoltage potential (80, 100, 120, and 140 kVp, 55 mAs) and measured semiautomatically the individual and the total Agatston score of 6 inserts (of 5-mm and 3-mm diameter) containing hydroxyapatite at different concentrations (800, 400, 200 mg/cm³). Our results showed that Agatston scores obtained at various low-kilovoltage potential protocols can be highly overestimated in some particular cases. At 80 kVp, for example, mean measured Agatston score was multiplied by a factor from 1.06 (5-mm highest density insert) to 2.67 (3-mm lowest density insert) compared with the Agatston scores performed at 120 kVp. Indeed in the one hand, reducing kilovoltage potential in multidetector CT acquisitions increase the CT density of coronary calcifications that can be measured on the reconstructed images. On the other hand, Agatston score is a multi-threshold measurement (with a step weighting function). Consequently low kilovoltage potential can lead to overweight some calcifications scores. For these reasons, Agatston score with low kilovoltage potential acquisition cannot be reliably adapted by a unique recalibration of the standard calcium attenuation threshold of 130 HU and requires a standardized CT acquisition protocol at 120 kVp. Alternatives to performing low-dose coronary artery calcium scans are either using coronary calcium scans with reduced tube current (low mAs) at 120 kVp with the iterative reconstructions or using mass/volume scoring (not influenced by kilovoltage potential variations). Finally, we emphasized that incorrect Agatston score evaluation may have important clinical, financial, and health care implications.     

Mean density of computed tomography for predicting rotational atherectomy during percutaneous coronary intervention

BackgroundMulti-slice computed tomography (CT) allows noninvasive evaluation of the severity of coronary calcification. However, there has yet to be a definitive parameter based on the cross-sectional CT image for predicting the need for rotational atherectomy (RA). Therefore, we aimed to investigate the mean density of cross-sectional CT images to predict the need for RA during percutaneous coronary intervention (PCI).MethodsA total of 154 lesions with moderate to severe calcification detected in coronary angiography were identified in 126 patients who underwent coronary CT prior to PCI for stable angina. PCI with RA was performed for 48 lesions, and the remaining 106 were treated without RA. Multi-slice CT was retrospectively evaluated for its ability to predict the use of RA. We chose the most severely calcified cross-sectional image for each lesion. The mean density within the outer vessel contour, calcium arc quadrant of the cross-sectional CT image, calcium length, calcification remodeling index, and per-lesion coronary artery calcium score was studied.ResultsReceiver-operator characteristic curve analysis revealed 637 Hounsfield units (HU) (area under the curve ​= ​0.98, 95% confidence interval: 0.97–1.00, p ​< ​0.001) as the best mean density cutoff value for predicting RA. Multivariate logistic regression analysis showed that a mean calcium level >637 HU was a strong independent predictor (odds ratio: 32.8, 95% confidence interval: 7.0–153, p ​< ​0.001) for using RA.ConclusionsThe mean density of the cross-sectional CT image, a simple quantitative parameter, was the strongest predictor of the need for RA during PCI.     

CT measurement of coronary calcium mass: impact on global cardiac risk assessment

Coronary calcium mass percentiles can be derived from electron beam CT as well as from multidetector-row CT of all manufacturers. Coronary calcium mass may serve as a more individualized substitute for age for cardiac risk stratification. The aim was to investigate the potential impact of CT coronary calcium mass quantification on cardiac risk stratification using an adjusted Framingham score. Standardized coronary calcium mass was determined by multidetector-row CT in a total of 1,473 patients (1,038 male, 435 female). The impact on risk stratification of replacing the traditional Framingham age point score by a point score based on calcium mass relative to age was tested. Any coronary calcium found in males in the age group of 20–34 years and females in the age group of 20–59 years results in an increase of the Framingham score by 9 and 4–7 points, respectively. Only in males 65 years of age and older, none or minimal amounts of coronary calcium decrease the Framingham score by three points. The coronary calcium mass and age-related scoring system may have impact on the reassignment of patients with an intermediate Framingham risk to a lower or higher risk group.     

Quantification of coronary artery calcium using multidetector CT and a retrospective ECG-gating reconstruction algorithm.

OBJECTIVE: The purpose of our study was to evaluate the quality of and motion artifacts on multidetector CT scans and to compare the results with those of and on electron beam CT scans for the assessment of coronary calcium scores. MATERIALS AND METHODS: First, 20 volunteers were scanned using multidetector CT. We compared the signal-to-noise ratio in the heart, motion artifacts at the heart border, and the highest CT values in the regions of the coronary arteries using single-sector and multisector reconstruction algorithms. Next, 60 patients with coronary calcified deposits underwent both multidetector CT and electron beam CT. We compared coronary calcium scores determined with multidetector CT using the two algorithms (thresholds of 90 and 130 H) with those determined using electron beam CT. RESULTS: The signal-to-noise ratio was higher and motion artifacts were reduced when we used the multisector algorithm. The highest CT value in the region of the coronary arteries exceeded 90 H in one of 55 arteries on the multisector algorithm images and 17 of 55 arteries on single-sector algorithm images (chi-square test, p < 0.01). In coronary calcium scoring, correlation coefficients ranged from 0.920 to 0.992 (Pearson's product moment) and from 0.932 to 0.969 (Spearman's rank correlation coefficient). CONCLUSION: Multidetector CT with a retrospective ECG-gating algorithm (multisector reconstruction) produced cardiac images with fewer motion artifacts and showed a high correlation with coronary calcium scores determined using electron beam CT. Therefore, multidetector CT is a potential tool for coronary calcium scoring.     

Influence of scoring parameter settings on Agatston and volume scores for coronary calcification

Current multi-detector CT and electron beam tomography (EBT) technology enables the evaluation of coronary calcification. Multiple software packages are available to quantify calcification using several scoring algorithms implementing user-definable scoring parameters. We investigated the effect of scoring parameters on the calcium score outcome. Three parameters (four-connected or eight-connected, lesion size threshold and interpolation) are evaluated. Their theoretical influence on the scoring outcome is shown using simplified examples. To evaluate the effect in real data, we performed calcium scoring on randomly chosen EBT scans from 50 participants in an epidemiological study. Both the Agatston and volume scores were calculated. Changing from eight-connected to four-connected connectivity decreased both Agatston and volume scores (mean variability Agatston 3.15% and volume score –3.52%). Decreasing the threshold from 4 to 2 pixels increased the calcium scores because smaller lesions were also selected as calcified plaques (mean variability Agatston 16.23% and volume score 18.66%). Finally, the use of interpolation had a large negative effect on the volume score (mean variability –29.67%) and almost no effect on the Agatston score. Parameter settings in software for quantification for coronary calcification affect the calcium score outcome. Therefore, parameter settings for calcium scoring should be standardized.     

电子束CT检测冠状动脉钙化的方法及初步结果报告

目的：报告电子束ＣＴ检测冠状动脉钙化（ＣＡＣ）的方法和初步研究结果。材料和方法：将经ＩｍａｔｒｏｎＣ－１５０电子束ＣＴ机检查冠状动脉的９０例分为三组：（１）非冠心组；（２）可疑组；（３）冠心组。对各例冠状动脉的走行进行观察；对比分析各组ＣＡＣ的发生率和钙化定量积分。结果：电子束ＣＴ能清晰地显示冠状动脉主干及主要分支。ＣＡＣ发生率冠心组为９５．０％（１９／２０例），可疑组为４８．６％（１７／３５例），非冠心组为２２．９％（８／３５例），差别具有显著性（ｐ＜０．００１）。发生ＣＡＣ的４４例中，冠心组的定量总分显著高于可疑组和非冠心组（Ｐ值分别＜０．０５和＜０．０１）。结论：电子束ＣＴ检测ＣＡＣ可为早期冠心病的诊断、预测和防治提供依据。     

Coronary artery calcium measurement with multi-detector row CT and low radiation dose: comparison between 55 and 165 mAs

PURPOSE: To prospectively compare the results of coronary artery calcium (CAC) measurements obtained with 55- and 165-mAs electrocardiographically gated multi-detector row computed tomography (CT). MATERIALS AND METHODS: Institutional clinical study review board approval and written informed consent were obtained. Fifty-one consecutive subjects (mean age, 59 years +/- 10) were scanned consecutively by using 165 and 55 mAs. For each examination, the number of lesions, total calcium score (TCS) calculated with Agatston algorithm (130-HU threshold), and calcium mass (in milligrams) were measured. Noise was measured by averaging 1 standard deviation of the CT attenuation values in five consecutive transverse sections of the ascending aorta. Paired t test and Pearson correlation were used to compare measurements between the examinations. RESULTS: By using 55 mAs, CAC was detected (TCS > 0) in all 33 subjects in whom CAC was initially detected with 165 mAs. The mean values of CAC measures with 165 and 55 mAs, respectively, were as follows: number of lesions, 6.2 +/- 9.6 and 6.1 +/- 9.4; TCS, 123 +/- 223 and 126 +/- 225; and calcium mass, 23.25 mg +/- 43 and 24.25 mg +/- 44 (P value was not significant for all parameters). Significant high correlation was found between the two methods for all measures (r > 0.90, P < .01). Similar results were obtained with analysis by coronary vessel. Image noise was 9.3 HU +/- 2.1 with 165 mAs and 14.7 HU +/- 3.9 with 55 mAs (P < .001), with a parallel decrease in the volume CT dose index from 12 to 4 mGy. CONCLUSION: Radiation dose can be reduced (eg, 55 mAs) for CAC detection and measurement at multi-detector row CT and provides results comparable to those obtained with 165 mAs.     

Serial electron beam CT measurements of coronary artery calcium: Has your patient's calcium score actually changed?

OBJECTIVE: The objective of our study was to develop a model for determining the smallest statistically significant change in the coronary artery calcium score (CAC) between serial measurements in a given subject. MATERIALS AND METHODS: We assembled a convenience sample of 2,217 pairs of repeated electron beam CT coronary calcium scans acquired in quick succession. Each scan consisted of forty 100-msec, 3-mm sections obtained at 60% of the ECG R-R interval. A single observer quantified calcium in each scan independent of knowledge of calcium quantity in the repeated scan. We then modeled a relationship between the variation of the differences between repeated measurements of calcium and the magnitude of the calcium score and formulated 95% repeatability coefficient equations for the Agatston and volumetric CAC score. The equations allow determining the smallest statistically significant interval change in the calcium score between two serial measurements in a given subject. RESULTS: In a subject with measurable CAC at baseline, the smallest statistically significant interval change is +/- (4.930 x square root of baseline Agatston CAC score) or +/- (3.445 x square root of baseline volumetric CAC score). In a subject with no measurable CAC at baseline, a follow-up CAC score exceeding 11.6 Agatston units or 9.5 mm3 qualifies for statistically significant progression. The results were similar in men and women. CONCLUSION: By examining repeatability of quantitative electron beam CT measurements of coronary calcium as a function of the magnitude of the calcium score, we developed a model to determine the smallest statistically significant change between serial measurements in a given subject.     

老年人多排螺旋CT冠状动脉钙化扫描临床应用初探

目的：评估不同扫描层厚对冠状动脉钙化积分和冠状动脉显示的影响。方法：98例70岁以上疑为冠心病的病人进行不同层厚的多排螺旋CT冠状动脉钙化积分扫描，36例扫描层厚为1mm，其中28例病人同次先后进行层厚为1mm和2mm的扫描，62例层厚为2mm；对每次扫描进行钙化分析。结果：在层厚为1mm的扫描，78％的病人不能一次闭气完成扫描，出现呼吸伪影。在同次先后进行层厚为1mm和2mm扫描的28例病人，扫描层厚为1mm的钙化积分明显高于扫描层厚为2mm的扫描的钙化积分。结论：对于4层多排螺旋CT而言，使用2mm的扫描层厚进行冠状动脉钙化扫描较为合适。     

Clinical usefulness of multidetector-row CT to evaluate coronary artery calcium score in type 2 diabetes

PURPOSE: According to recent studies, multidetector-row CT (MDCT) with a retrospective ECG-gating reconstruction algorithm shows a high correlation with coronary artery calcium score determined using electron-beam CT. Diabetes leads to many macrovascular complications, including coronary artery disease. The aim of this study was to evaluate risk factors for cardiac macroangiopathy in type 2 diabetes using MDCT. MATERIALS AND METHODS: An observational cross-sectional study was performed in 90 patients with diabetes mellitus. Coronary calcium data was acquired by MDCT (SOMATOM Volume Zoom, Siemens AG, Medical Solutions, Germany). Physical examinations, laboratory data, glycemic control, and control of other risk factors were analyzed. RESULTS: The coronary artery calcium score increased with age. Multivariant analysis revealed that the coronary calcium score was closely correlated with electrocardiogram evaluation and control of hypertension. CONCLUSIONS: Coronary artery calcium score as determined by MDCT can be used as a screening radiological examination for cardiac macroangiopathy in diabetes patients with electrocardiogram abnormality and hypertension.