An anthropomorphic prostatic urinary tract phantom for Doppler-based assessment of voiding dysfunction

Abstract

Direct assessment of urinary flow dynamics during voiding is challenging to perform in vivo. New Doppler ultrasound techniques are being developed for this purpose, but their performance needs to be systematically evaluated using phantoms. Here, we present a new design protocol to fabricate a urinary tract phantom with realistic anatomical, mechanical and urodynamic properties. In this protocol, computer-aided design of the urethra geometry was first drafted and it was physically built using 3-D printing. Subsequently, the flexible urinary tract tube was fabricated from polyvinyl alcohol cryogel (Young’s modulus: 26.6 kPa), while an agar–gelatin mixture (Young's modulus: 17.4 kPa) forms the surrounding tissue mimic. Finally, the urethra phantom was connected to a flow circuit that simulates voiding. Deformable phantoms were devised for a normal urethra and a diseased urethra with benign prostatic hyperplasia (BPH) obstruction. The phantoms’ morphologies were measured with ultrasound imaging and their flow profiles were assessed using Doppler ultrasound. During voiding, short-axis lumen diameter at the obstruction of the BPH-featured phantom was significantly smaller (0.91 vs 2.49 mm) while the maximum flow velocity was higher (59.3 vs 22.7 cm/s) compared to those of the normal urethra. These fabricated phantoms were effective in simulating urethra deformation resulting from urine passage and may promote the development of new Doppler-based urodynamic measurement techniques.