Determination of the Cervical Scattering Spectroscopy Transformation Zone Using Elastic-

Optical measurements of the cervical transformation zone (sometimes referred t o as the transition zone) using elastic-scattering spectroscopy, demonstrate sensitivity t o the epithelial cell-type differences. keywords: optical biopsy, tissue spectroscopy, elastic scattering, noninvasive diagnostics INTRODUCTION AND BACKGROUND The transformation zone of the cervix, near the external os, designates the boundary area where the cervical epithelium changes from predominantly columnar cells of the interior of the uterus to predominantly squamous cells that are exposed t o the vaginal cavity. The transformation zone is well studied because it is the site where most cervical cancer originates. Under culposcopy the transformation zone can be seen in about two-thirds of women examined, but its location is not clearly discernible in the remaining one-third. Changes in the location and extent of the transformation zone are known to precede the onset of labor and to appear earlier than other indications, such as dilation or contractions. Cervical "ripening" prior to labor generally involves an increased water content of the tissue and increased microvascularization, but is generally tracked simply by. palpation. A noninvasive, objective method to measure and track the changes in the condition of the tissue of the transformation zone would be of significant value in gynecological research. We have clinically investigated the use of elastic-scattering spectroscopy, with a fiber-optic probe from a portable instrument, for locating and characterizing tissue near the transformation zone. Tissue differences are detected/diagnosed using spectral measurements of elastically scattered light in an optical geometry that results in sensitivity to'both the absorption and scattering properties of the tissue, over a wide range of wavelengths (300 750 nm). The intent'of these preliminary studies is to determine the ability to distinguish the squamous-cell and columnar-cell epithelia in the region of the cervical transformation zone. Laser-induced-fluorescence (LIF) has been used to detect malignant and pre-malignant conditions in the cervix.[1,2] The LIF' spectral signatures are expected to reflect biochemical changes in the tissue corresponding to malignant states. Our initial interest here is to distinguish different types and conditions of normal tissue, which relate to differences in cellular structure, and which may or may not be accompanied by any biochemical differences. Measurements made on 11 patients indicate that reliable spectroscopic distinction is possible, and that the transformation in the composition of cellular structure across the zone is reflected in a transformation from the spectrum that is characteristic of columnar cells to the one that is characteristic of squamous cells. Figures 1 and 2 illustrate the epithelial structures that result in different histological appearances of squamous-cell and columnarcell epithelia, respectively.