Su2014 A Multichannel Wireless Mapping System for Monitoring Gastric Slow Wave Propagation

Abstract

Aim To investigate the relative importance of both linear and circular polarization parameters, derived from 4x4 Mueller matrix measurements, in discriminating gastric cancer from normal gastric tissues over the visible spectral region from 470 nm to 632 nm. Methods A total of 46 tissue samples, obtained from 40 patients, were examined in this study, in which 26 normal gastric samples were obtained as endoscopic biopsies while 20 gastric cancer samples were obtained from gastrectomy. Informed consent was obtained before tissue samples were used in this study. For multiple normal samples from one single patient, the values of polarization parameters were averaged to represent only one sample in each classification. This yielded a total of 20 sets of data for normal samples and 20 sets of data for cancer samples, one set for each patient. Each sample was fixed using 10%-formalin solution before it was embedded in paraffin. Then two 4-μm vertical sections immediately next to each other were made in the sample. One tissue section was routinely stained with Hematoxylin and Eosin (H&E) to generate a pathological report. The other tissue section was not stained, which was placed on a microscope slide without a cover slip for polarimetry measurements. Results The studied polarization parameters were retardance, diattenuation and depolarization of normal and cancerous gastric samples at nine wavelengths from 470 nm to 632 nm. The average retardance of normal samples was smaller than that of cancer samples. There was no overlap in the error bars between normal samples and cancerous samples at all nine wavelengths, suggesting that retardance could be used to effectively differentiate normal and cancer samples. In contrast, there were significant overlaps in the error bars of diattenuation and depolarization between normal and cancer samples at all wavelengths. It was found that the combination of linear depolarization and linear retardance showed the highest overall accuracy (95.00%) among all the possible combinations of two parameters. This combination also demonstrated considerable improvement in overall accuracy compared to that for either linear retardance (82.50%) or linear depolarization (77.50%) alone. Conclusion There were significant differences in most polarization parameters between normal and cancer tissue samples. The combination of linear depolarization and linear retardance yielded the highest accuracy in sample classification.