Prospective cardiac gating of carotid three-dimensional ultrasound

Abstract

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 (Δt) 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 (%ΔA) in moderate atherosclerosis (MA) patients (12%±1%) and healthy volunteers (HVs) (16%±3%) and found that %ΔA was significantly higher for HV than for MA (p=0.016) when no cardiac gating was used. The cardiac gating method was tested with Δt=250 ms and Δt=400 ms in young healthy volunteers and rheumatoid arthritis (RA) patients. For all 3DUS measurements acquired without gating, there was a significant association between %ΔA and age (r2 =0.20, p=0.035), and mean %ΔA (in HV and RA) was 13%±5% [95% confidence interval (CI) =10%-17%]. For Δt=250 ms mean %ΔA was significantly different and decreased to 7%±3% (95% CI=5%-10%) and for Δt=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 %ΔA between gating conditions (p=0.8); however, the 95% CI for %ΔA was decreased for Δt=400 ms as compared to Δt=250 ms. Both gating methods also significantly decreased %ΔA 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. © 2009 American Association of Physicists in Medicine.