Characterization of thin poly(dimethylsiloxane)-based tissue-simulating phantoms with tunable reduced scattering and absorption coefficients at visible and near-infrared wavelengths.

Gage J Greening,Darren Roblyer,Laura M Higgins,Raeef Istfan,Timothy J Muldoon,Mark C Pierce,Kartik Balachandran

doi:10.1117/1.jbo.19.11.115002

Abstract

Optical phantoms are used in the development of various imaging systems. For certain applications, the development of thin phantoms that simulate the physical size and optical properties of tissue is important. Here, we demonstrate a method for producing thin phantom layers with tunable optical properties using poly(dimethylsiloxane) (PDMS) as a substrate material. The thickness of each layer (between 115 and 880 μm) was controlled using a spin coater. The reduced scattering and absorption coefficients were controlled using titanium dioxide and alcohol-soluble nigrosin, respectively. These optical coefficients were quantified at six discrete wavelengths (591, 631, 659, 691, 731, and 851 nm) at varying concentrations of titanium dioxide and nigrosin using spatial frequency domain imaging. From the presented data, we provide lookup tables to determine the appropriate concentrations of scattering and absorbing agents to be used in the design of PDMS-based phantoms with specific optical coefficients. In addition, heterogeneous phantoms mimicking the layered features of certain tissue types may be fabricated from multiple stacked layers, each with custom optical properties. These thin, tunable PDMS optical phantoms can simulate many tissue types and have broad imaging calibration applications in endoscopy, diffuse optical spectroscopic imaging, and optical coherence tomography, etc.

Highlights

The translation of novel optical imaging techniques from a basic laboratory setting to a clinical setting requires substantial calibration and validation, which is often performed on tissuesimulating materials known as phantoms
The features of phantoms that are viewed as especially important include precise control of phantom geometry, the ability to modify and quantify scattering and absorption properties across commonly used wavelengths, stability over time, a comparable refractive index to human tissue, and the ability to introduce thin layers of different optical properties to simulate heterogeneities commonly seen in tissue.[1,3,4,8,9]
Coefficient of PDMS-Based Optical Phantoms Figure 3 shows the relationship between the TiO2 in the PDMS elastomer base (g/g) and the resulting μs[0] for six discrete wavelengths measured by spatial frequency domain imaging (SFDI) (591, 621, 659, 691, 731, and 851 nm)

Summary

Introduction

The translation of novel optical imaging techniques from a basic laboratory setting to a clinical setting requires substantial calibration and validation, which is often performed on tissuesimulating materials known as phantoms. The features of phantoms that are viewed as especially important include precise control of phantom geometry, the ability to modify and quantify scattering and absorption properties across commonly used wavelengths, stability over time, a comparable refractive index to human tissue, and the ability to introduce thin layers of different optical properties to simulate heterogeneities commonly seen in tissue.[1,3,4,8,9]

Methods

Results

Conclusion