Haruhiko Machida MD, Presenter: Nothing to Disclose

Isao Tanaka, Abstract Co-Author: Nothing to Disclose

Rika Fukui, Abstract Co-Author: Nothing to Disclose

Takuya Ishikawa, Abstract Co-Author: Nothing to Disclose

Etsuko Tate, Abstract Co-Author: Nothing to Disclose

Eiko Ueno MD, Abstract Co-Author: Nothing to Disclose

Yun Shen PhD, Abstract Co-Author: Employee, General Electric Company Researcher, General Electric Company

Ex vivo studies have suggested hydroxyapatite (HA) as the major component of calcification in the coronary arteries (CAC). We retrospectively measured the effective atomic number (EAN) of CAC in coronary CT angiography (CCTA) images of non-dialysis patients obtained using ECG-gated single-source dual-energy CT with fast kVp switching (Gemstone Spectral Imaging [GSI] Cardiac) to identify the major component of CAC.

For 52 consecutive non-dialysis patients who underwent CCTA by GSI Cardiac, we reconstructed monochromatic CCTA images at 65 keV with 0.625-mm slice thickness and 5-cm field of view. We measured the median EAN for CAC in regions of interest (ROIs) placed within the CAC to avoid error from partial volume averaging and calculated the average of this EAN for all the ROIs. Similarly, we placed 9 ROIs within a high purity (≥ 98%) HA pellet on the surface of a cardiac phantom to measure the mean EAN for HA. We compared the in vivo EAN for CAC with the in vitro EAN for HA from this experiment and the in vivo EAN previously determined by GSI for calcium oxalate monohydrate (COM, 11.2-14.4), a possible CAC component.

We measured the EAN for CAC in 177 ROIs from 48 non-dialysis patients (29 men, 19 women; mean age, 69 ± 9 years), since no CAC was identified in the remaining 4 patients. The average of the median in vivo EAN for CAC was 13.8 ± 0.8 (95% confidence interval, 13.7-13.9), which is near the theoretical EAN for COM (13.8) and equivalent to the in vivo EAN for COM (11.2-14.4) in 144 ROIs (81.4%). This value was lower than 11.2 in one ROI (0.6%) and higher than 14.4 in 32 ROIs (18.1%). The mean in vitro EAN for HA was 16.5 ± 0.1 (range, 16.1-16.6), similar to the theoretical EAN for HA (16.1) and higher than the EAN for CAC in all 177 ROIs (100%).

The EAN for CAC in non-dialysis patients with CCTA obtained by GSI Cardiac is often equivalent to that for COM and lower than that for HA.

Using a pair of iodine and COM as the major CAC component, more frequently than HA, imaging of material decomposition may be useful for acquiring CAC-free CCTA by GSI Cardiac.

Machida, H, Tanaka, I, Fukui, R, Ishikawa, T, Tate, E, Ueno, E, Shen, Y, In Vivo Measurement of Effective Atomic Number for Coronary Arterial Calcification in Non-dialysis Patients with Coronary CT Angiography by ECG-gated Single-source Dual-energy CT with Fast kVp Switching.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045587.html