Optical methods based on diffuse reflectance spectroscopy (DRS) have shown significant promise in predicting response to NAT in breast cancer, but the anatomy of the distal colon requires the use of endoscopically-deployable methods. We have developed a small-diameter (0.78 mm) multimodal optical imaging and diffuse reflectance spectroscopy (DRS) probe which can be deployed via the biopsy port of a commercial veterinary colonoscope (Karl Storz COLOView) to be used in a chemically-induced (azoxymethane (AOM)) orthotopic model.
Total diffuse reflectance measured by the probe was correlated with the reduced scattering (μ’s(λ)) and absorption coefficients (μa(λ)) for λ = 450 – 800nm via a look-up table (LUT). Liquid phantoms were used to create the LUT and validate the measured μ’s and μa values. The LUT has a maximum total reflectance of 0.14 and ranges for μa and μ’s are 0-10 cm-1and 3-18 cm-1, respectively. Error for μ’s and μa has been 10.7±8.8% and 7.9±5.3%, respectively. For the imaging component, circular active area diameter is 325 μm and center-to-center fiber spacing of 3.3 μm.
Building on previous work this DRS approach enables quantification of total hemoglobin (Hb) content, oxygen saturation (SaO2), estimates mean vessel diameter and scattering component, and allows for co-registered highresolution image data of superficial mucosa in vivo of tumor perfusion and microstructure, which can translate to the clinic to help physicians determine the response of tumors to therapy.
