Preparation of solid phantoms with defined scattering and absorption properties for optical tomography

Abstract

We have developed diffusely scattering solid phantoms with optical (scattering) properties amenable to theoretical calculations. Monodisperse quartz glass spheres were used as scatterers embedded in polyester resin. An infrared dye was added to simulate absorption by biological tissue. Solid phantoms were tested for their macroscopic homogeneity. Several phantoms were built with well-defined spatial variations in their transport scattering and absorption coefficients to be used for optical tomography. Scattering, transport scattering, and absorption coefficients of solid, homogeneous phantoms and of aqueous suspensions of monodisperse quartz glass spheres were derived from measurements of time-integrated collimated transmittance and time-resolved diffuse transmittance. For aqueous suspensions of monodisperse quartz glass spheres at known number density scattering and transport scattering coefficients calculated by Mie theory are in quantitative agreement with experimentally derived values. In addition, diffuse reflectance and diffuse transmittance of aqueous suspensions at various number densities were measured and found to be in excellent agreement with results of Monte Carlo calculations using theoretical values for the scattering coefficients and anisotropy parameters.

Deformable and durable phantoms with controlled density of scatterers

“…In addition, our technique offers other possibilities. With Mie theory, it would be possible to predict the absorption, scattering and anisotropy coefficients of the phantoms based on the refractive indices and the size of the microspheres with a good agreement (Sukowski et al 1996, Firbank et al 1995. To do so, a more precise evaluation of the refractive index of the microspheres is needed.…”

Performance assessment of photon migration instruments: the MEDPHOT protocol

“…The latter phantoms are based on resin with a scatterer added-typically titanium dioxide or calibrated microspheres-and a resinsoluble absorber. 11,12 These phantoms are solid, durable, and easy to machine and exchange; however, they are more cumbersome to prepare and, in some cases, to characterize. There has been much research on the design, testing, and characterization of phantoms, some of which have been circulated among different institutions.…”

How to Improve Quality Assurance in Fluorometry: Fluorescence-Inherent Sources of Error and Suited Fluorescence Standards

“…absorption, fluorescence, and scattering properties can be measured simultaneously or subsequently using the same geometry. A suited non-certified reference material developed by the PTB for this purpose consists of a cyanine dye and glass spheres as scattering centers embedded into a polymer matrix [155]. We used this reference material to derive the results shown in Fig.…”