Improving image quality in diffuse optical tomography

Abstract

Diffuse optical tomography (DOT) modality uses diffusion equation solution of low power laser distribution in the imaging tissue. DOT method has three main running mode and three geometric subbranches. Run modes are: Continuous Wave (CW), Time Resolved (TR) and Frequency Domain (FD) modes. These run modes might have transmission-through, back-reflected or ring geometry depend on the source and detector placements on tissue surface. In this work, we tested our novel imaging method on the frequency-domain back-reflected DOT simulation model. Our novelty is: selecting a great number of multi-frequency data in the wide frequency spectrum which was not tested before in the literature. Most of the literature works consist of narrow frequency band with the limited number of frequencies such as maximum 12 multi-frequency-data which cover from 100 up to 700 MHz. In our work, we tested and compared reconstructed inclusion images generated by our 500 wide spectrum multi-frequency data versus reconstructed inclusion images generated by 20 narrow band multi-frequency data which was generally used in FD DOT studies. We observed that our novel imaging method which used wide spectrum multi-frequency data is superior to the traditionally used narrow-band multi-frequency method based on the reconstructed inclusion image localization errors. Since most of the homogenous geometry consists of fat tissue, we selected background absorption coefficient µa = 0.2 cm−1 and tissue scattering coefficient $${\upmu }$$ s = 80 cm−1 for 800 nm laser source wavelength. Three-dimensional cubic imaging simulation media has 75-mm grid sizes in each direction. Two different imaging scenarios were tested. In the first scenario, one inclusion with absorption coefficient µa = 0.7 cm−1 was put inside the three-dimensional imaging geometry at 27 mm depth. In the second scenario one inclusion with absorption coefficient µa = 0.7 cm−1 was embedded in 48 mm depth location. Inclusions are cubic and they have 6 mm xyz length at each direction.