Prospective cardiac gating of carotid three-dimensional ultrasound

Quantitative measurements of carotid atherosclerosis can be determined using three-dimensional ultrasound (3DUS). This pilot study involved the development of prospective cardiac gating of 3DUS carotid images to reduce cardiac cycle-derived arterial pulsatility. The method developed uses electrocardiograph signal detection of the cardiac cycle R wave with imaging acquisition delayed in time (deltat) after the R wave is detected. Pulsatility of the common carotid artery was measured by calculating the mean percentage change in arterial cross-sectional area (%deltaA) in moderate atherosclerosis (MA) patients (12% +/- 1%) and healthy volunteers (HVs) (16% +/- 3%) and found that %deltaA was significantly higher for HV than for MA (p = 0.016) when no cardiac gating was used. The cardiac gating method was tested with deltat = 250 ms and deltat = 400 ms in young healthy volunteers and rheumatoid arthritis (RA) patients. For all 3DUS measurements acquired without gating, there was a significant association between %deltaA and age (r2 = 0.20, p = 0.035), and mean %deltaA (in HV and RA) was 13% +/- 5% [95% confidence interval (CI) = 10%-17%]. For deltat = 250 ms mean %deltaA was significantly different and decreased to 7% +/- 3% (95% CI = 5%-10%) and for deltat = 400 ms it was significantly different and decreased to 6% +/- 1% (95% CI = 6%-7%) (p = 0.001 for both comparisons). There was no significant difference in mean %deltaA between gating conditions (p = 0.8); however, the 95% CI for %deltaA was decreased for deltat = 400 ms as compared to deltat = 250 ms. Both gating methods also significantly decreased %deltaA to below the reference standard of 12% +/- 1% for MA (p < 0.01 for both comparisons), suggesting that prospective cardiac gating of carotid 3DUS reduces pulsatility effects in HV and RA to levels lower than observed for much older MA patients.