Pressure Difference Estimation in Carotid Bulbs using Vector Flow Imaging - A Phantom Study

Hypertension is a common health problem and may be caused by dysfunction of the stretch sensitive baroreceptors in the carotid bulb. Velocity changes and vortices are present in the carotid bulb, and a better evaluation of the local flow and pressures may be important to further understand hypertension. The intravascular pressure catheter is a common tool in the clinic and is currently considered to be the reference standard for intravascular pressure measurement, but the method is invasive, ionizing, and has been reported to be inaccurate. Vector flow imaging (VFI) is an angle independent, noninvasive, and nonionizing ultrasound method that can estimate pressure differences. In this study, pressure differences between the common carotid artery and the carotid bulb obtained with VFI were compared with catheter measurements in three carotid bifurcation phantoms. A fluid-structure interaction (FSI) simulation model was used as reference. Additionally, 10 repeated VFI and catheter measurements were performed in one phantom for a precision assessment. The mean absolute pressure difference between the catheter and FSI method in the three phantoms was 140.5 Pa, and 10 repeated catheter tests measured a mean pressure decrease with a large variation (mean: -133.3 Pa, SD: 786%). VFI estimated pressure increases in all phantoms with a mean standard deviation of 11.6%, and the mean absolute pressure difference compared with FSI was 16.7 Pa. Ten repeated VFI estimations found a mean pressure increase with low variation (mean: 40.1 Pa, SD: 10.9%). VFI precisely estimated small pressure differences in a carotid bifurcation phantom setup, whereas the fluid-filled pressure catheter measurements were imprecise.