Quantitative near-infrared spectroscopy of cervical dysplasia in vivo

The aims of this study were: (i) to quantify near-infrared optical properti es of normal cervical tissues and high-grade squamous intra-epithelial lesi ons (H-SIL); (ii) to assess the feasibility of differentiating normal cervi cal tissues from H-SIL on the basis of these properties; and (iii) to deter mine how cervical tissue optical properties change following photodynamic t herapy (PDT) of H-SIL in vivo. Using the frequency domain photon migration technique, non-invasive measurements of normal and dysplastic ecto-cervical tissue optical properties, i.e. absorption (mu(a)) and effective scatterin g coefficients, and physiological parameters, i.e. tissue water and haemogl obin concentration, percentage oxygen saturation (%SO2), were performed on 10 patients scheduled for PDT of histologically-proven H-SIL. Cervix absorp tion and effective scattering parameters were up to 15% lower in H-SIL site s compared with normal cervical tissue for all wavelengths studied (674, 81 1, 849, 956 nm). Following PDT, all CL, values increased significantly, due to elevated tissue blood and water content associated with PDT-induced hyp eraemia and oedema. Tissue total haemoglobin concentration ([TotHb]) and ar terio-venous oxygen saturation measured in H-SIL sites were lower than norm al sites ([TotHb]: 88.6 +/- 35.8 mu mol/l versus 124.7 +/- 22.6 mu mol/l; % SO2: 76.5 +/- 14.7% versus 84.9 +/- 3.4%).