Masao Kiguchi RT, Presenter: Nothing to Disclose

Jun Horiguchi MD, PhD, Abstract Co-Author: Nothing to Disclose

Chikako Fujioka RT, Abstract Co-Author: Nothing to Disclose

Minoru Ishifuro, Abstract Co-Author: Nothing to Disclose

Katsuhide Ito MD, Abstract Co-Author: Nothing to Disclose

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

Takashi Furukawa RT, Abstract Co-Author: Nothing to Disclose

The purpose of this study was to compare prospective electrocardiograph (ECG)-triggered and retrospective ECG-gated coronary 64-slice CT angiography (CTA) as to radiation dose, image quality, accuracy of stenoses measurement and CT densitometry.

Coronary artery plaque models (diameter; 4mm) with different stenosis levels (area; 18%, 50% and 82%) and densities (soft:50 HU, intermediate:110 HU and calcified:1000 HU) on a pulsating cardiac phantom were scanned in variable heart rate sequences (n=14) with both prospective ECG-triggered and retrospective ECG-gated scans. On prospective ECG-triggered scan, the minimal X-ray exposure time (233mm) was used to keep the radiation exposure ‘as low as reasonably achievable’. Radiation dose, image quality graded by motion and stair-step artifacts (grade 1:excellent to 4:poor), accuracy of stenoses measurement and CT densitometry of plaques were compared between the two protocols.

Radiation dose of prospective ECG-triggered CTA (3.0 mSv) was lower than that of retrospective ECG-gated CTA (~12.0 mSv). Prospective ECG-triggered CTA images were assigned satisfactory quality rating (grade 1 or 2) in stable hearts rate up to 75 bpm. In this range, there were no significant differences in image quality (Mann-Whitney’s U test, p=0.32 to 0.84), stenoses measurement (Repeated measures ANOVA, p=0.17) and CT densitometry (54HU vs 55HU for soft plaque and 113HU vs 112HU for intermediate plaque, Repeated measures ANOVA, p=0.93) between the two protocols.

Prospective ECG-triggered 64-slice coronary CTA has the potential to significantly reduce radiation exposure. When using the minimal X-ray exposure time (minimal radiation dose), prospective ECG-triggered coronary CTA is comparable to retrospective ECG-gated coronary CTA on stable heart rate up to 75 bpm.

For ‘ALARA’ coronary CTA, we recommend 'SnapShot Pulse' Prospective ECG-triggered 64-slice coronary CTA (3.0 mSv) in stable hearts rate up to 75 bpm.

Kiguchi, M, Horiguchi, J, Fujioka, C, Ishifuro, M, Ito, K, Shen, Y, Furukawa, T, Radiation Dose, Image Quality, Measurement of Stenoses, and CT Densitometry Using Prospective Electrocardiograph-triggered Coronary 64-slice CT Angiography 'SnapShot Pulse: A Phantom Study.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5006041.html