Reconstruction of optical scanned images of inhomogeneities in biological tissues by Monte Carlo simulation

• Simulation of multiport optical scanning system.
• Capable of differentiating the embedded inhomogeneities.
• Characterization of their optical properties.

The optical imaging of inhomogeneities located in phantoms of biological tissues, prepared from goat׳s isolated heart as control tissue and embedded with spleen and adipose tissues representing tumors, by Monte Carlo simulation, is carried out. The proposed scanning probe consists of nine units. Each unit is equipped with one photon injection port and three ports arranged in a straight line to collect backscattered photons emerging from various depths, and one port, placed coaxially to the source on the opposite side of the phantom, to collect the transmitted component. At each position of the grid, superposed on the tissue phantom, photons are introduced through source port into the phantoms and backscattered and transmitted photons are collected by respective ports. Based on the data collected from the entire grid surface the respective gray-level images are reconstructed. The inhomogeneity located at certain depth (2, 4, 6 mm) is visualized in three images formed by the backscattered data collected by three ports. Increase or decrease in normalized backscattered intensity (NBI) observed in their scans corresponds to that of high scattering (adipose) or absorbing (spleen) inhomogeneity compared to that of control tissue and also their location as determined by NBI variation as received at various ports. The images constructed from the transmitted data are associated with decrease in intensity. The scans of these images through their centers show that normalized transmitted intensity (NTI) attains its maximum value when the inhomogeneities are at depth 6 mm. These scans are of higher amplitude for spleen compared to that of adipose tissues. Thus the data received by backscattering and transmission complement each other in identifying the location and type of inhomogeneities.

Monte Carlo simulation is applied to imaging of photons backscattered and transmitted through a tissue phantom, made of heart tissues implanted with adipose or spleen tissues as inhomogeneities. The proposed optical scanning probe consists of nine units. Each unit has one photon injection port and three ports arranged in a straight line at 2, 4 and 6 mm to collect backscattered photons emerging from various depths, and one port to collect the transmitted component placed coaxially to the source on the opposite side of the phantom. The figure shows one unit of the optical scanning probe. The backscattered data are collected by first port located at 2 mm from the input port. The path-length of photons emerging out of first port is shorter compared to that of photons received by other ports. By collections of scanned signals on the tissue surface the tissues images located at various depths are constructed. By scanning of these images the normalized backscattered intensity (NBI) signals are obtained. By comparison of NBI signals the type of inhomogeneities and their locations are determined. Such data could be helpful in development of scanning devices for early detection of tumor in tissues.Figure optionsDownload high-quality image (148 K)Download as PowerPoint slide