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.     

Variability of repeated coronary artery calcium measurements by 16-MDCT with retrospective reconstruction

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.     

Low-kV coronary artery calcium scoring with tin filtration using a kV-independent reconstruction algorithm

PurposeTo investigate the accuracy of Agatston scoring and potential for radiation dose reduction of a coronary artery calcium scoring (CACS) CT protocol at 100 kV with tin filtration (Sn100kV) and kV-independent iterative reconstruction, compared to standard 120 kV acquisitions.Materials and methodsWith IRB approval and in HIPAA compliance, 114 patients (61.8 ± 9.6 years; 66 men) underwent CACS using a standard 120 kV protocol and an additional Sn100kV CACS scan. The two datasets were reconstructed using a medium sharp convolution algorithm and in addition the Sn100kV scans were reconstructed iteratively based on a kV-independent algorithm. Agatston scores and radiation dose values were compared between the Sn100kV and the standard 120 kV protocol.ResultsMedian Agatston scores derived from the Sn100kV protocol with the kV-independent algorithm and the standard 120 kV were 21.4 (IQR, 0–173.8) and 24.7 (IQR, 0–171.1) respectively, with no significant differences (p=0.18). Agatston scores derived from the two different protocols had an excellent correlation (r = 0.99). The dose-length-product was 11.5 ± 4.1 mGy × cm using Sn100kV and 50.4 ± 24.9 mGy × cm using the standard 120 kV protocol (p < 0.01), resulting in a significantly lower (77%) effective dose at Sn100kV (0.16 ± 0.06 mSv vs. 0.71 ± 0.35 mSv, p < 0.01). Additionally, 99% of the patients were classified into the same risk category (0, 1–10, 11–100, 101–400, or >400) using the Sn100kV protocol.ConclusionCACS at Sn100kV using the kV-independent iterative algorithm is feasible and provides high accuracy when compared to standard 120 kV scanning. Furthermore, radiation dose can be significantly reduced for this screening application in a priori healthy individuals.     

Coronary artery calcium scoring using multicardiac computed tomography

OBJECTIVES: To test the hypothesis that multicardiac-phase computed tomography (CT) improves the quantification of coronary artery calcium. METHODS: Calcium-phosphate on a cardiac phantom and 108 calcified plaques from 50 patients were scanned, and multicardiac-phase images were obtained. Motion artifacts and calcium scores of the calcified plaques were compared between cardiac phases and CT scanners. RESULTS: In the phantom images, motion artifacts differed between cardiac phases; thus, the calcium scores were either higher or lower than the score from the static state. In the patient study, motion artifacts of calcifications on the various coronary branches varied with the cardiac cycle, which profoundly influenced the calcium scores. CONCLUSION: Multicardiac-phase CT has the potential to improve the quantification of coronary artery calcium by determining the cardiac phase where motion artifacts are the least on individual calcified plaques.     

Coronary artery calcium score: influence of reconstruction interval at 16-detector row CT with retrospective electrocardiographic gating

In 30 patients, Agatston and volumetric scores were assessed by using retrospectively gated multi-detector row computed tomography (CT). For each patient, 10 data sets were created at different times and were evenly spaced throughout the cardiac cycle. For each reconstruction, patients were assigned a percentile that described the level of cardiovascular risk. Nineteen (63%) of 30 patients could be assigned to more than one risk group depending on the reconstruction interval used. Agatston and volumetric scores both proved highly dependent on the reconstruction interval used (coefficient of variation, < or =63.1%) even with the most advanced CT scanners. Accurate and reproducible quantification of coronary calcium seems to require analysis of multiple reconstructions.     

Coronary artery calcium: A technical argument for a new scoring method

Coronary artery calcium (CAC) is a strong predictor for future cardiovascular events. Traditionally CAC has been quantified using the Agatston score, which was developed in the late 1980s for electron beam tomography (EBT). While EBT has been completely replaced by modern multiple-detector row CT technology, the traditional CAC scoring method by Agatston remains in use, although the literature indicates suboptimal reproducibility and subjects being incorrectly classified. The traditional Agatston scoring method counteracts the technical advances of CT technology, and prevents the use of thinner sections, obtained at lower tube voltage and overall decreased radiation exposure that has become available to other CT applications. Moreover, recent studies have shown that not only the total amount of CAC, but also its density and distribution in the coronary arterial tree may be of prognostic value. Acquisition and reconstruction techniques thus need to be adapted for modern CT technology and optimized for CAC quantification. In this review we describe the technical limitations of the Agatston score followed by our suggestions for developing a new and more robust CAC quantification method.     

320排容积CT三种心电扫描模式在胸腹主动脉CTA中的应用

目的探讨320排容积CT胸腹主动脉成像（CT angiography,CTA）在三种心电扫描模式下的图像质量及辐射剂量,为患者提供个性化扫描方案。方法183例疑似主动脉疾病患者随机分为三组。采用前瞻Wide-Volume扫描（A组）;前瞻性心电门控螺旋扫描（B组）;VHP扫描（可变螺距螺旋扫描）（C组）。每组再根据心率分成两个亚组,亚组1心率〉70次／min,亚组2心率〈70次／min。获得的6组图像数据分别进行图像处理,由2名有经验的放射科医师评价图像质量并进行统计学分析。结果183例患者全部获得满意图像质量。三组中,前瞻性心电门控螺旋扫描获图像质量最佳（主动脉评分-x=1．04分;冠状动脉评分-x=1．18分）,辐射剂量最低（-x=13．62mSv）,在低心率组（〈70次／rain）扫描时间最短（-x=14．1s）;前瞻Wide-Volume扫描在高心率组（〉70次／min）扫描时间最短（-x=14．5s）;VHP扫描辐射剂量最高（-x=24．04mSv）。各组间对比剂用量差异无统计学意义（A组-x=78．1ml;B组-x=79．6ml;C组-x=80．2ml,P〉O．05）。结论前瞻性心电门控螺旋扫描适用较低心率患者（心率〈70次／min）,前瞻Wide-Volume扫描适用于较高心率患者（心率〉70次／min）,VHP扫描辐射剂量较高,对比前两种方法无明显优势。     

Coronary calcium quantification using various calibration phantoms and scoring thresholds

RATIONALE AND OBJECTIVES: To compare scoring threshold and calibration method-dependent accuracy and variability of coronary calcium measurements by multidetector computed tomography (MDCT). METHODS: Ninety-five subjects were scanned with MDCT. We calculated Agatston score and volume score. Mineral mass (MM) was calculated using patient-based and scanner-based calibration methods. Accuracy of calibration was validated using artificial calcium cylinders. RESULTS: Patient-based and scanner-based calibration permitted accurate quantification of artificial calcium cylinders (bias: 0 mg and -2 mg). In the subjects, the mean relative difference of MM measurements performed at 90 and 130 Hounsfield units threshold (59%) was lower than for Agatston score (94%) and volume score (109%; P < 0.05). Patient-based and scanner-based calibration yielded systematically different MM measurements (bias: 22%). CONCLUSIONS: MM lowers threshold-dependent variability of coronary calcium measurements. Patient-based and scanner-based calibration allows accurate calcium quantification ex vivo but reveal systematic differences in subjects. Patient-based calibration may better account for subject size and composition.     

Coronary artery calcium scoring: diagnostic accuracy of different software implementations

PURPOSE: To compare the diagnostic power of different software implementations for the quantification of coronary artery calcium. MATERIALS AND METHODS: Electron beam computed tomography was performed in 109 heart transplant recipients at the same time as catheter coronary angiography and intracoronary ultrasound. Electron beam computed tomography images were analyzed by 3 software packages marketed for the quantification of coronary calcifications using the same software settings, and the resultant calcium scores correlated with the invasive reference methods by Bland-Altman plots and analysis of the receiver operating characteristics. RESULTS: Although all scoring systems displayed close correlations upon regression analysis (r2=0.94-0.99), their ability to detect disease as per the invasive reference method varied significantly in some instances. The area under the ROC curve varied between Az=0.78 and 0.85 for the detection of coronary artery stenosis upon coronary angiography (P=0.05-0.13), and between Az=0.75 and 0.83 for the detection of accelerated intimal proliferation (P=0.03-0.18). CONCLUSIONS: Different software implementations for the quantification of coronary artery calcium load may display diagnostically relevant differences in spite of close direct correlation.     

CT coronary calcium scoring with tin filtration using iterative beam-hardening calcium correction reconstruction

ObjectivesTo investigate the diagnostic accuracy of CT coronary artery calcium scoring (CACS) with tin pre-filtration (Sn100 kVp) using iterative beam-hardening correction (IBHC) calcium material reconstruction compared to the standard 120 kVp acquisition.BackgroundThird generation dual-source CT (DSCT) CACS with Sn100 kVp acquisition allows significant dose reduction. However, the Sn100 kVp spectrum is harder with lower contrast compared to 120kVp, resulting in lower calcium score values. Sn100 kVp spectral correction using IBHC-based calcium material reconstruction may restore comparable calcium values.MethodsImage data of 62 patients (56% male, age 63.9 ± 9.2years) who underwent a clinically-indicated CACS acquisition using the standard 120 kVp protocol and an additional Sn100 kVp CACS scan as part of a research study were retrospectively analyzed. Datasets of the Sn100 kVp scans were reconstructed using a dedicated spectral IBHC CACS reconstruction to restore the spectral response of 120 kVp spectra. Agatston scores were derived from 120 kVp and IBHC reconstructed Sn100 kVp studies. Pearson’s correlation coefficient was assessed and Agatston score categories and percentile-based risk categorization were compared.ResultsMedian Agatston scores derived from IBHC Sn100 kVp scans and 120 kVp acquisition were 31.7 and 34.1, respectively (p = 0.057). Pearson‘s correlation coefficient showed excellent correlation between the acquisitions (r = 0.99, p < 0.0001). Agatston score categories and percentile-based cardiac risk categories showed excellent agreement (ĸ = 1.00 and ĸ = 0.99), resulting in a low cardiac risk reclassification of 1.6% with the use of IBHC CACS reconstruction. Image noise was 24.9 ± 3.6HU in IBHC Sn100 kVp and 17.1 ± 3.9HU in 120 kVp scans (p < 0.0001). The dose-length-product was 13.2 ± 3.4 mGy cm with IBHC Sn100 kVp and 59.1 ± 22.9 mGy cm with 120 kVp scans (p < 0.0001), resulting in a significantly lower effective radiation dose (0.19 ± 0.07 mSv vs. 0.83 ± 0.33 mSv, p < 0.0001) for IBHC Sn100 kVp scans.ConclusionLow voltage CACS with tin filtration using a dedicated IBHC CACS material reconstruction algorithm shows excellent correlation and agreement with the standard 120 kVp acquisition regarding Agatston score and cardiac risk categorization, while radiation dose is significantly reduced by 75% to the level of a chest x-ray.     

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.