ACCURACY OF QUANTIFYING CORONARY HYDROXYAPATITE WITH ELECTRON-BEAM TOMOGRAPHY

RATIONALE AND OBJECTIVES. The electron beam tomography coronary calciu m score continues to be used without experimental validation. To deter mine its accuracy, a series of experiments was performed. METHODS. A c hest phantom model was constructed with coronary arteries represented by cylindrical holes containing hydroxyapatite granules embedded in a gelatin matrix to simulate coronary arteries. Experiments were perform ed to determine the relationship between the mass of hydroxyapatite in each of these arteries, the coronary calcium score currently used in coronary screening, and an alternative method of estimating mass from the images. The model was scanned with equal amounts of hydroxyapatite in each artery: 1) when the cylindrical heart was rotated 36 degrees 10 times between scans, and 2) when the particle diameters varied from 0.1 mm to 4 mm. The scores were calculated, and a subtraction algorit hm was applied to estimate the exact mass of hydroxyapatite in each ar tery. RESULTS. The hydroxyapatite scores varied by 42% with position a nd by 1.54 X 10(6)% with particle diameter. The estimated masses from the subtraction algorithm were more stable with position and particle size, with maximum percent errors of 10% and 14% for position and part icle size, respectively. CONCLUSIONS. These results suggest that the c oronary calcium score is invalid, and that more precise and clinically relevant methods, such as the arterial summation method, should be ri gorously tested in clinical studies.