Performance assessment of pulse wave imaging using conventional ultrasound in canine aortas ex vivo and normal human arteries in vivo

Abstract

The propagation behavior of the arterial pulse wave may provide valuable diagnostic information for cardiovascular pathology. Pulse Wave Imaging (PWI) is a noninvasive, ultrasound imaging-based technique capable of mapping multiple wall motion waveforms along a short arterial segment over a single cardiac cycle, allowing for the regional pulse wave velocity (PWV) and propagation uniformity to be evaluated. The purpose of this study was to improve the clinical utility of PWI using a conventional ultrasound system. The tradeoff between PWI spatial and temporal resolution was evaluated using an ex vivo canine aorta (n = 2) setup to assess the effects of varying image acquisition and signal processing parameters on the measurement of the PWV and the pulse wave propagation uniformity r2. PWI was also performed on the carotid arteries and abdominal aortas of 10 healthy volunteers (24.8 ± 3.3 y.o.) to determine the waveform tracking feature that would yield the most precise PWV measurements and highest r2 values in vivo. The ex vivo results indicated that the highest precision for measuring PWVs ~ 2.5 – 3.5 m/s was achieved using 24–48 scan lines within a 38 mm image plane width (i.e. 0.63 – 1.26 lines/mm). The in vivo results indicated that tracking the 50% upstroke of the waveform would consistently yield the most precise PWV measurements and minimize the error in the propagation uniformity measurement. Such findings may help establish the optimal image acquisition and signal processing parameters that may improve the reliability of PWI as a clinical measurement tool.

Pulse wave imaging using coherent compounding in a phantom andin vivo

“…The 50% upstroke was defined as the time-point, at which v PWI was closest in value to the average between the foot and the peak of the v PWI at each beam location. The choice of this tracking feature is justified because the early wavefront is less affected by the generated reflected waves [2] and also because previous studies have shown that it is the most robust compared to alternative tracking features (foot, 25% upstroke, 75% upstroke) [23]. In the case of the phantom, the initial pulse wave corresponds to a drop in pressure so the 50% downstroke was used as the tracking feature and was defined as the average between the foot and the negative peak of the v PWI .…”

“… Regional and piecewise PWV values : Comparison to static testing derived values in the case of the phantom and evaluation of repeatability and agreement between regional and mean piecewise PWVs in the case of the healthy volunteers. Coefficient of determination (r 2 ) : Comparison of r 2 values for different parameter configurations provides a quality metric contingent upon both varying image SNR as well as frame rate [23]. …”

“…Coefficient of determination (r 2 ) : Comparison of r 2 values for different parameter configurations provides a quality metric contingent upon both varying image SNR as well as frame rate [23]. …”

“…In order to address this issue, stroboscopic techniques based on ECG-gating that reconstruct image sequences by using images from different cardiac cycles have been previously reported [16], [22] as well as exploiting the tradeoff between scan line density and frame rate on conventional scanners. In particular, this tradeoff is a significant one and has been experimentally evaluated [23]. Plane wave imaging [24]–[26] has been proposed to achieve ultrafast frame rates (i.e.…”

An inverse approach to determining spatially varying arterial compliance using ultrasound imaging

“…The transducer was positioned so that the pulse wave propagated in the opposite direction to the beam sweeping, and the time delay of each line was compensated for during post processing (Li et al 2015). RF signals were collected in 1 s acquisitions and digitized at 20 MHz which covered 3–4 pulses of the peristaltic pump.…”