METHOD FOR IDENTIFYING MALIGNANCIES IN BARRETT'S ESOPHAGUS USING WHITE LIGHT ENDOSCOPY
A method is described for computing a statistically significant difference between dysplasia and Barrett's esophagus (both with and without inflammatory component) using a discriminate function with diffuse reflectance measurements performed at a minimum of four different wavelengths of 485, 513, 598, and 629 nm. The discriminate function found depends both on local blood fraction volume T HB and oxygenation SO 2 . A pull-back approach of spectral data acquisition is disclosed which takes into account tissue motility in esophagus and measurement geometry peculiarities. The pull-back approach provides a significant improvement of measurement reproducibility and reduction of data deviation by 75-100%, resulting in a better discrimination between different histological groups.
1 . A method for assessing cancer risk by diffuse reflectance spectroscopy, comprising the steps of:
illuminating tissue with light in a wavelength range that includes at least a portion of the visible spectrum,
selecting at least four distinct narrow wavelength bands in the wavelength range of the illumination light,
measuring intensity of diffusely reflected light in the at least four distinct narrow wavelength bands at different tissue sampling sites,
computing a parameter value with a predetermined linear discriminate function, and
assessing malignancy of the tissue based on the computed parameter values from the different tissue sampling sites.
2 . The method of claim 1 , wherein the at least four distinct narrow wavelength bands include the wavelength 485±5, 513±5, 598±2, 629±5 nm.
3 . The method of claim 2 , wherein the discriminate function is
B 4=−14.32+626.88* Rd 485 −721.31* Rd 513 +253.76* Rd 598 +75.16* Rd 629
and the computed parameter value is represented by B4.
4 . The method of claim 3 , wherein the diffuse reflectance measured at 485±5, 513±5, 598±2, 629±5 nm is normalized with respect to reflectance in the infrared wavelength range (650-750 nm) where absorption of blood is negligible.
5 . The method of claim 1 , further comprising the steps of lifting a measurement probe (pull-back) from close proximity to the tissue surface to a distance where the measurement probe no longer shadows the tissue.
6 . The method of claim 6 , wherein the lifting is repeated at least once for a tissue spot.