Evaluation of the Diagnostic Ability of Optical Enhancement System in Early Gastric Cancer Demarcation

Misato Nagao, Jun Nishikawa, Ryo Ogawa, Sho Sasaki, Munetaka Nakamura, Junichi Nishimura, Atsushi Goto, Shinichi Hashimoto, Takeshi Okamoto, Masato Suenaga, Yoshihiko Hamamoto, Isao Sakaida, Misato Nagao, Jun Nishikawa, Ryo Ogawa, Sho Sasaki, Munetaka Nakamura, Junichi Nishimura, Atsushi Goto, Shinichi Hashimoto, Takeshi Okamoto, Masato Suenaga, Yoshihiko Hamamoto, Isao Sakaida

Abstract

This study aimed to evaluate the utility of optical enhancement (OE) in early gastric cancer demarcation. Twenty lesions of early gastric cancer were examined by PENTAX endoscopy system with OE-1 and OE-2 functions. The areas of tumor demarcation identified by 12 evaluators (6 novice and 6 experienced) were compared to the corresponding correct areas determined by postoperative histopathology findings. The misdiagnosed scores that were the sums of false-positive and false-negative areas were compared. Color of one hundred pixels from the inside of the cancerous area and the outside of the cancerous area was expressed as three-dimensional RGB component vectors. The mean vectors and covariance matrixes were calculated and the Mahalanobis distance, indicative of color differences between two areas, was tested. Comparisons of the misdiagnosed score revealed that OE-1 was preferred over WL-1 for gastric cancer demarcation for all 12 evaluators (p = 0.008) and in novice evaluators (p = 0.026). OE-2 was not significantly different from WL-2 in all cases. OE-1 images gave significantly larger Mahalanobis distances, indicative of color differences, than WL-1 images (p = 0.002). It was demonstrated that the OE Mode 1 has a significant advantage over the white light mode in demarcation of early gastric cancer.

Figures

Figure 1
Figure 1
Comparative analysis of misdiagnosed score on WL-1 and OE-1 images. Compared with WL-1 images, misdiagnosis score on OE-1 images was smaller for the 6 novice evaluators and for all 12 evaluators. No significant difference was observed among the 6 experienced evaluators.
Figure 2
Figure 2
Comparative analysis of misdiagnosed score on WL-2 and OE-2 images. No significant difference was observed between the WL-2 and OE-2 images of different lesions.
Figure 3
Figure 3
Evaluation using the RGB color system. Compared with WL-1, Mahalanobis distance was significantly larger on OE-1 images. No significant difference was observed between OE-2 and WL-2 findings.
Figure 4
Figure 4
Histogram display of the misdiagnosed area. Early gastric cancer 0-I + IIa at the angle of the lesser curvature. (a) WL-1 images; (b) OE-1 images; (c) WL-1 image histograms; and (d) OE-1 image histograms. Blue color depicts the false-negative area, and green color depicts the false-positive area. The areas with darker colors indicate a higher incidence of misdiagnosis. In this study, areas of misdiagnosis were smaller and the color was lighter on OE-1 images than on WL-1 images.

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