Near-infrared Raman spectroscopy for in vivo detection of cervical precancers

This study evaluates the potential of near-infrared Raman spectroscopy for in vivo detection of squamous dysplasia, a precursor to cervical cancer. A pilot clinical trial was carried out at three clinical sites. Raman spectra were measured from one colposcopically normal and one abnormal area of the cervix. These sites were then biopsied and submitted for routine histologic analysis. Twenty-four evaluable measurements were made in vivo in 13 patients. Cervical tissue Raman spectra contain peaks in the vicinity of 1070, 1180, 1195, 1210, 1245, 1330, 1400, 1454, 1505, 1555, 1656, and 1760 cm^-1. The ratio of intensities at 1454 to 1656 cm^-1 is greater for squamous dysplasia than all other tissue types, while the ratio of intensities at 1330 to 1454 cm^-1 is lower for samples with squamous dysplasia than all other tissue types. A simple algorithm based on these two intensity ratios separates high-grade squamous dysplasia from all others, misclassifying only one sample. Spectra measured in vivo resemble those measured in vitro. Cervical epithelial cells may contribute to tissue spectra at 1330 cm^-1, a region associated with DNA. In contrast, epithelial cells probably do not contribute to tissue spectra at 1454 cm^-1, a region associated with collagen and phospholipids.