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The Agatston Calcium Score is a predictor of major adverse cardiovascular events but it is unable to identify high-risk lesions. Recent research suggests that examining calcification phenotype could be more indicative of plaque stability.To examine the Agatston score's ability to determine atherosclerotic calcification phenotype.Micro-Computed Tomography was performed on 20 carotid and 20 peripheral lower limb lesions. ImageJ pixel histogram analysis quantified the non-calcified (≥30HU,130HU) and calcified (≥130HU) tissue volumes. ImageJ '3D Objects Counter' plugin determined the calcified particle count, volumes and maximum attenuation density of each particle. Image stacks were subsequently downsampled to a resolution of 0.7 × 0.7 × 3 mm and an approximation for the Extra-Coronary Calcium Scores (ECCS) were calculated. Spearman's correlation examined the relationships between ECCS approximations and calcification parameters.ECCS has a strong positive correlation with the Calcified Volume Fraction (CVF) (rThe density-weighted Agatston calcium scoring methodology needs to be reviewed. Calcium scoring which differentiates between critical calcification morphologies, rather than presenting a density-weighted score, is required to direct high-risk plaques towards tailored treatment.

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/cm(3)). 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.

Background Test phantoms with simulated micro-calcifications of true calcium hydroxyapatite (CaHA) density were not available to validate advanced calcium scoring methods or plaque density measurements. Objectives We evaluated a coronary calcium scoring (CCS) test phantom containing very small CaHA microspheres and validated a new scoring method for measurements of plaque densities. Methods The semianthropomorphic CCS phantom was constructed with CaHA microspheres (volumes, 0.05–3.1 mm 3 ) with the approximate density of biologic calcifications. QRM and CCS phantoms were scored with a new calibrated and automated calcium scoring method (N-vivo; Image Analysis). The densities of the microspheres and 609 individual patient plaques were measured. Results The range of measured densities of the CaHA microspheres was approximately equivalent to that measured in the patient coronary calcifications. The smallest microspheres scored with the calibrated/automated and the Agatston methods had volumes of 0.075 mm 3 and 0.27 mm 3 , respectively. The standard deviations of the mass scores of the microspheres ranged from 0.02 to 0.17 mg with regression slope of 0.962 and R 2 = 0.997. The relationship of measured density to measured mass of the patient plaques was similar to that of the microspheres, suggesting that vascular calcifications are CaHA density. Conclusions The CaHA microspheres of the CCS test phantom were found to be representative in density and size of coronary calcifications. The measurements show that CT calcium scoring underestimates plaque density and greatly overestimates volume. The heterogeneity of calcium concentration densities measured in the patient plaques was due largely to CT scanner measurement errors.