## 6 Conclusions  
In the early stages of epithelial cancer, changes occur in the structure and biochemistry of 200-500 \(\upmu\)m thick epithelium layer. In this paper, we carry out a detailed numerical evaluation of various probe geometries for early diagnosis of epithelial pre-cancer based on spatially resolved reflectance. It was concluded that a parallel-oblique fiber-optic probe, beveled at \(\beta=45^{\circ}\), and with minimal source detector distance is an appropriate choice. The fiber-optic probe was accordingly fabricated. The experimental SRR and epithelial sensitivity measurements for test phantoms were performed and were found in good agreement with computational data. Synthetic SRR data was generated by MC code for two-layered epithelial tissue phantoms, and contaminated with 5% Gaussian noise. Optical parameters of the top layer were accurately recovered using a MC-look up table based inversion scheme. To further check the efficacy of the algorithm, the top layer optical parameters were extracted from the SRR data, using the MC-LUT, when there was \(\sim\)10% error in the recovered optical parameters of the bottom layer. The top layer absorption coefficient thus recovered was found to be off by \(\sim\)20% of its true value, while the scattering coefficient was recovered quite accurately with a \(<\)6% error (Table 4). After the scheme of simultaneous recovery of absorption and scattering coefficients of top layer was numerically validated, it was further employed on experimental SRR measurements obtained using the fabricated probe from epithelial tissue-mimicking two-layered \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Phantom**} & \multirow{3}{*}{\begin{tabular}{c} **True Value** \\ **(Top Layer)** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } & \multirow{3}{*}{\
\begin{tabular}{c} **True Value** \\ **(Bottom Layer)** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } & \multicolumn{3}{c}{**Extracted Value**} & \multirow{3}{*}{
\begin{tabular}{c} **Std. Deviation** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } \\ \cline{2-2} \cline{5-8}  & \(\mu_{a}\) & \(\mu_{s}\) & \(\mu_{a}\) & \(\mu_{s}\) & \(\mu_{a}\) & \(\mu_{s}\) & \(\delta\mu_{a}\) & \(\delta\mu_{s}\) \\ \hline \(1\) & 5.2 & 72 & 3.8 & 225 & 6.0 & 73 & 0.3 & 2 \\ \(2\) & 5.2 & 72 & 3.8 & 275 & 6.2 & 74 & 0.2 & 2 \\ \(3\) & 5.2 & 72 & 4.8 & 225 & 6.1 & 74 & 0.3 & 2 \\ \(4\) & 5.2 & 72 & 4.8 & 275 & 5.9 & 73 & 0.3 & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Simultaneous recovery of absorption and scattering coefficients of the top layer from simulated data, when the bottom layer optical parameters are known with \(\sim\)10% error. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Phantom**} & \multirow{3}{*}{\begin{tabular}{c} **True Value** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Extracted Value** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } & \multirow{3}{*}{\
\begin{tabular}{c} **Std. Deviation** \\ **(cm\({}^{-1}\))** \\ \end{tabular} } & \multirow{3}{*}{
\begin{tabular}{c} **Error** \\ **(\%)** \\ \end{tabular} } \\ \cline{2-2} \cline{5-8}  & \(\mu_{a}\) & \(\mu_{s}\) & \(\mu_{a}\) & \(\mu_{s}\) & \(\delta\mu_{a}\) & \(\delta\mu_{s}\) & \(\epsilon\mu_{a}\) & \(\epsilon\mu_{s}\) \\ \hline \(1\) & 3.0 & 60 & 3.2 & 58 & 0.2 & 2 & 6.7 & 3.3 \\ \(2\) & 2.5 & 80 & 2.4 & 82 & 0.3 & 3 & 4 & 2.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Simultaneous reconstruction of absorption and scattering coefficients of the top layer from experimental SRR data with prior knowledge of both the optical properties of bottom layer. phantoms. The top layer optical parameters were accurately recovered with absorption and scattering coefficients extracted within 6.7% and 3.3% of their respective true values. The top layer optical properties were reconstructed by measuring only spatially resolved reflectance measurements at a single wavelength (450 nm).