Devika Jain (MHSc): Design of a Reusable Polyurethane Replacement for Ultrasound Gel

September 27, 2017 @ 9:30 am – 10:00 am
Rosebrugh Building
Rosebrugh Bldg, Toronto, ON M5S 3G9

Room: RS 211


Ultrasound is a safe and decisive diagnostic imaging tool that, in low-access areas, is more accessible than magnetic resonance imaging or computed tomography machines, especially with recent improvements to the battery life, ease of use, durability, training, and affordability of portable scanners. However, access to requisite ultrasound gel in low-access areas remains a challenge due to heavy transport weight and relatively high cost. Common replacements (oil, shampoo, corn starch slurry) are expensive and/or unavailable in local markets, and locally-made plant slurries are difficult to store without bacterial growth. Polyurethane hydrogels are often biocompatible and tunable to strength, water-absorbance, and other necessary properties for a couplant replacement. Existing polymer ultrasound couplants are available but not cheaper than ultrasound gel.

A specific tunable and biocompatible polyurethane hydrogel, Degradable Polar Hydrophobic Ionic Polyurethane (D-PHI PU) has been shown to be biocompatible and specifically tunable to different properties. It will be modified to produce a cheap and reusable Polyurethane Transducing Pad (PtP) as a replacement for commercial ultrasound gel.

A PtP that can transmit ultrasound waves with comparable image quality to ultrasound gel requires high water content to make it acoustically similar to the human body. To achieve this, D-PHI PU’s porosity and chemistry will be altered to promote water uptake. Swelling of the D-PHI PU after immersion in water will be measured and overall image quality will be assessed using an analytic hierarchal process. To generate a reusable PtP, D-PHI PU chemistry will be further modified to enhance lubricity, durability, shelf-life stability, and lack of pathogen transmission.

Efficacy of the PtP will be validated, following ethics approval, through a controlled study where physicians and technicians will use the PtP on patients during a routine exam and assess its usability and the acquired images.

Preliminary Results
Preliminary modification of D-PHI PU microporosity increased PU swelling from 7.7% ± 2.6% (classical D-PHI PU formulation) to 22.4% ± 7.3% (preliminary modification) and created a better image of a kidney, when compared to no couplant. However, it is expected, based on previous patents and products, that 70% water content is required to produce adequate ultrasound images. Further modification of ionic, hydrophilic, and crosslinking properties has so far shown a maximum swelling in water of more than 250%, however PtPs with this much swelling also more readily break apart, are difficult to handle, and therefore do not necessarily facilitate the best ultrasound image. Comparable ultrasound images (to ultrasound gel) have been acquired through modifications to the crosslinker and crosslinking density and monomer lengths in the PtP. Further testing of the durability of these formulations, as well as incorporation of non-transmissivity of pathogens between uses, shelf-life ability, and lubricity, must still be performed.

This project will yield a practical, affordable, reusable, and attachable PtP with the aim of increasing affordability and prevalence of ultrasound diagnostic imaging, particularly in the Great Lakes Region of Africa.