Interest in ultrasound perfusion imaging has grown with the development of more sensitive algorithms to detect slow blood flow. Unfortunately, there are not many phantoms that can be used to evaluate these techniques. Some have used small linear tubes, while others have adapted dialysis cartridges. Here we propose a technique using conventional gelatin cast around a sacrificial polymer network. Specifically, we form a gelatin phantom, doped with graphite scatterers to mimic the diffuse scattering in soft tissue, around a polymer resin. The resin structure can be dissolved leaving behind a network of small randomly oriented channels that are connected to a large channel which is connected to a pump to perfuse blood mimicking fluid through the phantom. The phantoms were qualitatively demonstrated to show perfusion through visual confirmation and the speckle SNR, and speed of sound were calculated.
Tissue clutter caused by patient and sonographer hand motion makes perfusion ultrasound imaging difficult. We previously introduced an adaptive frequency and amplitude demodulation scheme to address this challenge. Our initial implementation used a conventional high-pass infinite impulse response (IIR) filter to attenuate the tissue signal after applying adaptive demodulation. However, other groups have shown that singular value decomposition (SVD) filtering is superior to conventional frequency domain filters. Here we evaluate the SVD filter both in comparison and in conjunction with our proposed adaptive demodulation technique. Blood-to-background SNRs were compared using power Doppler images made from single small vessel simulations with realistic tissue clutter. Additionally, filtering methods were qualitatively assessed using power Doppler images of a cut-in-half perfusion-mimicking phantom. Furthermore, in vivo power Doppler images were compared before and after muscle contraction. SVD filtering with adaptive demodulation resulted in a 7dB increase in simulated blood-to-background SNR compared to a conventional IIR filter and a 54.6% increase in power after in vivo muscle contraction compared to a 1.74% increase using a conventional IIR filter.