Feasibility and Validation of 4-D Pulse Wave Imaging in Phantoms and In Vivo

Pulse wave imaging (PWI) is a noninvasive technique for tracking the propagation of the pulse wave along the arterial wall. The 3-D ultrasound imaging would aid in objectively estimating the pulse wave velocity (PWV) vector. This paper aims to introduce a novel PWV estimation method along the propagation direction, validate it in phantoms, and test its feasibility in vivo. A silicone vessel phantom consisting of a stiff and a soft segment along the longitudinal axis and a silicone vessel with a plaque were constructed. A 2-D array with a center frequency of 2.5 MHz was used. Propagation was successfully visualized in 3-D in each phantom and in vivo in six healthy subjects. In three of the healthy subjects, results were compared against conventional PWI using a linear array. PWVs were estimated in the stiff (3.42 +/- 0.23 m.s(-1)) and soft (2.41 +/- 0.07 m.s(-1)) phantom segments. Good agreement was found with the corresponding static testing values (stiff: 3.41 m.s(-1) and soft: 2.48 m.s(-1)). PWI-derived vessel compliance values were validated with dynamic testing. Comprehensive views of pulse propagation in the plaque phantom were generated and compared against conventional PWI acquisitions. Good agreement was found in vivo between the results of 4-D PWI (4.80 +/- 1.32 m.s(-1)) and conventional PWI (4.28 +/- 1.20 m.s(-1)) (n = 3). PWVs derived for all of the healthy subjects (n = 6) were within the physiological range. Thus, the 4-D PWI was successfully validated in phantoms and used to image the pulse wave propagation in normal human subjects in vivo.