Current calcium scoring products provide a fixed plaque threshold based on uncalibrated HU values, typically 85 or 130 HU. The Agatston score is defined as 2 adjacent voxels above this threshold and was defined from 3 mm slice thicknesses. Small plaques are frequently observed in patient images which fail to satisfy this fixed threshold criteria. In noisy images, it is also clear that false plaques are more likely and are patient and scanner dependent. Although phantom calibration greatly improves on these problems, the variable noise level of images makes plaque identification and quantification in part a statistical challenge. This represents a classical signal-to-noise ratio problem.
Our N-VivoTM Calcium Scoring Application provides plaque thresholds, which are patient, scanner, and technique dependent i.e., the voxel mass calculations and plaque thresholds are calibrated and specific for each patient scan and CT scanner. After hybrid calibration of image voxels, plaques are identified and quantified based on the calibrated attenuation of the regions of the heart of the particular patient. Voxels, which may be included in the calculation of plaque mass, are therefore not only calibrated but are included in the final calcium score only after making statistical computations from the specific patient's images. (The uncalibrated Agatston and Volume scores, also provided by our software does not use these advanced techniques but are provided for backwards continuity and reference to other methods).
THE LEADER IN CALCIUM SCORING AND BMD
IMAGE ANALYSIS, INC.
1380 Burkesville Street
Columbia, Kentucky 42728
(270) 384 - 6400
