Coronary calcium test phantom containing true CaHA microspheres for evaluation of advanced CT calcium scoring methods.
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.


OBJECTIVE
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.
Arnold
Ben A
BA
Image Analysis, 1380 Burkesville Road, Columbia, KY 42728, USA. arnold@image-analysis.com
Budoff
Matthew J
MJ
Child
Janis
J
Xiang
Ping
P
Mao
Song S
SS
D057205:Automation, Laboratory; D002114:Calcinosis / Q000000981:diagnostic imaging*; D002138:Calibration; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D017886:Durapatite / Q000737:chemistry*; D004867:Equipment Design; D006801:Humans; D008863:Microspheres; D019047:Phantoms, Imaging; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed / Q000295:instrumentation* / Q000592:standards
D017886:Durapatite