Fabrication of Tuneable Tissue-Mimicking Phantom for Optical Methods.

Abstract

Background: Tissue mimicking optical phantoms are commonly used to calibrate or validate the performance of near-infrared spectroscopy or tomography. Human tissue is not only irregular in shape, but also exhibits dynamic behaviour, which can cause changes in optical properties. However, existing phantoms lack complex structures and/or continuously varying optical properties.

Aim: The project aimed to design, fabricate and characterise a novel phantom system for testing near-infrared imaging devices.

Material and methods: We designed a dynamic tissue-mimicking phantom platform which features arbitrary internal shapes and variable optical properties. The solid part of phantom was made of silicone material with absorbing and scattering properties similar to the brain. We printed a semi-ellipsoidal sphere (a major axis = 20 mm and a minor axis = the third axis = 12 mm) using a water-soluble material polyvinyl alcohol (PVA). The shape was placed at the depth of 5 mm in the silicone bulk. The desired internal hollow structure was formed after curing and submerging the phantom in water. The liquid part contained dyes and Intralipid. The optical properties within the internal shape were adjusted by injecting the liquid solutions of varying dye concentrations with a syringe pump at a constant rate. The phantom was measured by a frequency domain near-infrared spectroscopy (FD NIRS) and imaged by a time domain near-infrared optical tomography (TD NIROT).

Results and discussion: A dynamic phantom system with a complex internal structure and varying optical properties was created. Changes in light intensity were detected by the FD NIRS. The internal structure of this phantom was accurately recovered by NIROT image reconstruction.

Conclusion: We successfully developed a novel phantom system with an internal complex shape and continuously adjustable optical properties. This phantom was accurately imaged using NIROT, and the changing light intensity was detected by NIRS. It is a valuable tool for validating optical technologies.