Abstract
Optical imaging methods such as near-infrared spectroscopy and diffuse optical tomography rely on models to solve the inverse problem. Imaging an adult human head also requires a head model. Using a model, which makes describing the structure of the head better, leads to acquiring a more accurate absorption map. Here, by combining the key features of layered slab models and head atlases, we introduce a new two-layered head model that is based on the surface geometry of the subject's head with variable thickness of the superficial layer. Using the Monte Carlo approach, we assess the performance of our model for fitting the optical properties from simulated time-resolved data of the adult head in a null distance source-detector configuration. Using our model, we observed improved results at 70 percent of the locations on the head and an overall 20 percent reduction in relative error compared to layered slab model.
Highlights
Near-infrared spectroscopy (NIRS) offers the ability to determine absolute absorption and scattering coefficients of biological tissues at multiple wavelengths
The result is the histogram of time-of-flights of photons reaching the detector, known as photon distribution of time-of-flight (DTOF) or temporal point spread function (TPSF)
The goals of the present study are: (1) to propose a new subject specific layered-head model to overcome the shortcomings of previous models and (2) to assess its performance on realistic TD-NIRS data obtained from a realistic head model and compare it with two-layered slab model with variable thickness presented by Selb et al [26]
Summary
Near-infrared spectroscopy (NIRS) offers the ability to determine absolute absorption and scattering coefficients of biological tissues at multiple wavelengths. The retrieved absorptions allows quantification of different chromophores’ concentrations within the tissue, mainly oxy-hemoglobin (HbO2) and deoxy-hemoglobin (Hb). Different approaches of NIRS are continues-wave (CW) [6,7,8], frequency-domain (FD) [9,10,11,12] and time-resolved (TR) or time-domain (TD) [13,14,15,16,17]. Continuous-wave methods only measure the amplitude of light intensity. They need spatially or spectrally resolved information in order to disentangle the absorption and scattering contributions. Frequencydomain approach measures both amplitude and phase change of the input light. The result is the histogram of time-of-flights of photons reaching the detector, known as photon distribution of time-of-flight (DTOF) or temporal point spread function (TPSF)
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