IMAGING VERY-LOW-CONTRAST OBJECTS IN BREASTLIKE SCATTERING MEDIA WITHA TIME-RESOLVED METHOD

An investigation was performed of the effectiveness of a time-resolved method for imaging very-low-contrast features embedded in highly scat tering media. Experiments employed slabs of breastlike material into w hich were inserted small cylindrical objects having either a scatterin g or an absorption coefficient of 4, 2, 1.5, and 1.1 times greater tha n the surrounding medium. An attempt was made to quantify the degree o f contrast produced by each object. The results indicate that time-gat ing is far more effective at enhancing the contrast of the scattering inhomogeneities than of the absorbing inhomogeneities. This observatio n is shown to agree with a diffusion-based model, which also predicts that time-gating can decrease the contrast of absorbing inhomogeneitie s unless very short time-gates can be employed. (C) 1997 Optical Socie ty of America.