Wall-less vascular poly(vinyl) alcohol gel ultrasound imaging phantoms using 3D printed vessels

Vascular phantoms are crucial tools for clinical training and for calibration and validation of medical imaging systems. With current methods, it can be challenging to replicate anatomically-realistic vasculature. Here, we present a novel method that enables the fabrication of complex vascular phantoms. Poly(vinyl alcohol) (PVA) in two forms was used to create wall-less vessels and the surrounding tissue mimicking material (TMM). For the latter, PVA cryogel (PVA-c) was used as the TMM, which was made from a solution of PVA (10% by weight), distilled water, and glass spheres for ultrasonic scattering (0.5% by weight). PVA-c is not water soluble, and after a freeze-thaw cycle it is mechanically robust. To form the wall-less vessels, vessel structures were 3D printed in water-soluble PVA and submerged in the aqueous solution of PVA-c. Once the PVA-c had solidified, the 3D printed PVA vessel structures were dissolved in water. Three phantoms were created, as initial demonstrations of the capabilities of this method: a straight vessel, a stenosed (narrowed), and a bifurcated (branched) vessel. Ultrasound images of the phantoms had realistic appearances. We conclude that this method is promising for creating wall-less, anatomically realistic, vascular phantoms.