Comprehensive approach to breast cancer detection using light: photon localization by ultrasound modulation and tissue characterization by spectral discrimination

摘要

Abstract: A new technique called Ultrasound Tagging of Light(UTL) for imaging breast tissue is described. In thisapproach, photon localization in turbid tissue isachieved by cross- modulating a laser beam withfocussed, pulsed ultrasound. Light which passes throughthe ultrasound focal spot is `tagged' with thefrequency of the ultrasound pulse. The experimentalsystem uses an Argon-Ion laser, a single PINphotodetector, and a 1 MHz fixed-focus pulsedultrasound transducer. The utility of UTL as a photonlocalization technique in scattering media is examinedusing tissue phantoms consisting of gelatin andintralipid. In a separate study, in vivo opticalreflectance spectrophotometry was performed on humanbreast tumors implanted intramuscularly andsubcutaneously in nineteen nude mice. The validity ofapplying a quadruple wavelength breast cancerdiscrimination metric (developed using breast biopsyspecimens) to the in vivo condition was tested. Ascatter diagram for the in vivo model tumors based onthis metric is presented using as the `normal' controlsthe hands and fingers of volunteers. Tumors atdifferent growth stages were studied; these tumorsranged in size from a few millimeters to twocentimeters. It is expected that when coupled with asuitable photon localization technique like UTL,spectral discrimination methods like this one willprove useful in the detection of breast cancer bynon-ionizing means. !11