Transillumination for Detection of Early Breast Cancer - Experimental and Computer Models

Abstract

Breast transillumination has received renewed interest as a noninvasive diagnostic method. However, it is still considered an experimental technique. Many aspects of the physics involved in transillumination have not yet been studied. In this project transillumination was simulated by experiments with a simple breast phantom of realistic dimensions. The light source used was a HeNe laser. From the experiments we found how the contrast of images of a spherical inhomogeneity (simulating a lesion e.g. tumor or cyst) depended on its size and position. The contrast was also measured as a function of the scattering and absorption coefficients of the inhomogeneity. The contrast of the image is shown to fit very well to the curve A(1-exp(-d(Σ^inh_eff – Σ_eff))), where a simple analytical model is developed, where A is identified to (1+B)^-1, B being a build-up factor depending on the surrounding medium and on the position of the inhomogeneity in the medium and d is identified as an effective optical diameter of the inhomogeneity. A three dimensional numerical diffusion program was developed to model the transillumination situation. It was found that diffusion theory gave accurate predictions of the contrast within the constraints of the mathematical model. The three dimensional diffusion approximation and its limitations are discussed in some detail.