Laser reflectance imaging of human chest for localization of internal organs

Simulation of laser backscattering system for imaging of inhomogeneity/tumor in biological tissues

BACKGROUND AND OBJECTIVES

The optical characteristics of biological tissues vary in health and diseases. By analysis of photons scattering process by Monte Carlo simulation (MCS) the inhomogeneities in tissues are to be identified and their images reconstructed.

METHODS

Digital phantoms with goat's heart as a control tissue embedded with inhomogeneities adipose (high scattering) and spleen (high absorption) are simulated. The phantoms considered are - (a) simulation of the developed stage of inhomogeneity by inclusion of adipose and spleen tissues in control and (b) its onset stage by increasing the optical parameters by 10% at fixed locations in control tissue. These phantoms are scanned by simulated system, consisting of nine ports for photon injection and backscattered photons from each port are received by three ports located at 2, 4 and 6mm from the injecting port, placed in the direction of x-axis. By the data collected from the entire surface, by processing, three grey-scale images are constructed. For localization of inhomogeneities these images are scanned in terms of normalized backscattered intensity (NBI).

RESULTS

The images obtained by MCS with 1 million photons, with error minimized, at respective ports, show the presence of inhomogeneities at various depths, which is further supported by the increase or decrease in the NBI compared to that of control for adipose or spleen, respectively. The increase or decrease is more at first port compared to others. The inhomogeneities located at 2mm below the surface are better identified by the receiving port located at 2mm on the surface. The same applies to inhomogeneities located at 4 and 6mm, respectively.

CONCLUSION

The present simulated system not only shows the presence of inhomogeneties at various depths in tissue phantom but also presents their characteristics.

Optical parameters of embedded abnormalities in tissues as determined by Monte Carlo simulation

Photon propagation through tissue phantoms, made of heart, adipose, and spleen tissues was simulated by Monte Carlo procedure. To detect the presence of deep-seated abnormalities, phantoms of heart with adipose and spleen tissues embedded into it were created and simulations were performed to scan the tissue surface with a source and four detector model. Profiles drawn showed variation in parameters such as backscattered intensity in regions where adipose and spleen tissues were embedded. This study shows that depending on the type of embedded tissue the backscattered fraction as measured at 2 mm from the input fiber is altered. This is enhanced for adipose and decreased for spleen tissue. This is not only shown in scanned profiles on the surface but also in constructed images.