Diagnostic Ability of High-definition Imaging Using Ultraslim Endoscopes in Early Gastric Cancer

Abstract

Purpose: It is unclear whether high-definition (HD) imaging improves visibility and diagnostic ability in early gastric cancer (EGC) compared with standard-definition (SD) imaging. We aimed to compare the diagnostic performance and visibility scores of HD and SD ultraslim endoscopes in EGC.

Materials and methods: We used HD and SD ultraslim endoscopes to obtain 60 images with similar compositions of gastric environments. Of the 60 images, 30 showed EGC (15 images for each modality) and 30 showed no EGC (15 images for each modality). Seventeen endoscopists evaluated the presence and location of the lesions in each image. Diagnostic ability was compared between modalities. The color difference between a lesion and the surrounding mucosa (ΔE) was measured and compared between the modalities.

Results: The ability of HD to detect EGC was significantly higher than that of SD (accuracy: 80.8% vs. 71.6%, P=0.017; sensitivity: 94.9% vs. 76.5%, P<0.001; positive predictive value, 76.2% vs. 55.3%, P<0.001; and negative predictive value (NPV), 94.1% vs. 73.5%, P<0.001). The ability of HD to determine the horizontal extent of EGC was significantly higher than that of SD (accuracy: 71.0% vs. 57.8%, P=0.004; sensitivity: 75.3% vs. 49.0%, P<0.001; NPV, 72.9% vs. 55.9%, P<0.001; and area under the curve: 0.891 vs. 0.631, P=0.038). The mean ΔE was significantly higher for HD than for SD (10.3 vs. 5.9, P=0.011).

Conclusions: The HD ultraslim endoscope showed a higher diagnostic performance in EGC than the SD endoscope because it provided good color contrast.

Keywords: Diagnosis; Diagnostic imaging; Endoscopy; Gastric cancer; Screening.

Fig. 1. Definition of detection of gastric cancer and determination of the horizontal extent of gastric cancer. (A) Type 0-IIc early gastric cancer is shown on the bottom left of the endoscopic image (yellow arrows). (B) Endoscopic images were divided into 9 sections using lines that divided the length and width into 3 equal parts. The lesion is present in sections 4 and 7. Detection of gastric cancer was defined as correct when any of the sections that included gastric cancer (either section 4 or 7 in this image) were identified. Determination of the horizontal extent of gastric cancer was defined as correct when all the sections that included gastric cancer (both sections 4 and 7 in this image) were identified. (C) When endoscopists selected section 4, the detection of gastric cancer was correct, but the determination of the horizontal extent of gastric cancer was incorrect. (D) When endoscopists selected both sections 4 and 7, both detection of gastric cancer and determination of the horizontal extent of gastric cancer were correct.

Fig. 2. Process of measuring the color value of the lesion and the surrounding mucosa. (A) A border line between the lesion and the surrounding mucosa (black) was drawn. (B) An outer line (blue) was drawn parallel to the border line, enclosing an area twice as large as the area enclosed by the border line. An inner line (green) was drawn inside and parallel to the border line, and the width between the border line and the inner line was equal to the width between the border line and the outer line. A rectangle (white line) was drawn in the center of the lesion with a width of one-third of the width of the lesion. (C) The sections separated by this rectangle and the 3 lines were the ROI of the lesion (red shaded area) and the surrounding mucosa (blue shaded area). The color value of the lesion and the surrounding mucosa was defined as the average of the color value in each ROI.

ROI = region of interest.

Fig. 3. The receiver-operating characteristic curve and the AUC values of HD and SD images in the detection of gastric cancer (A) and determination of the horizontal extent of gastric cancer (B). (A) The AUC value for the detection of gastric cancer in HD images was higher than that in SD images; however, it did not reach statistical significance (1.000 vs. 0.876, P=0.056). (B) The AUC value for the determination of the horizontal extent of gastric cancer in HD images was significantly higher than that in SD images (0.891 vs. 0.631, P=0.038).

AUC = area under the curve; HD = high-definition; SD = standard-definition.

Fig. 4. Comparison of ΔE, ΔL*, Δa*, and Δb* between HD and SD images. (A) ΔE (mean±standard deviation) was 10.3±4.9 in HD images and 5.9±3.1 in SD images. The difference was statistically significant (P=0.011). (B) ΔL* was significantly higher in HD images than in SD images (5.9±3.6 vs. 3.3±2.2, P=0.025). There was no significant difference between Δa* (5.9±3.5 vs. 4.1±2.0, P=0.135) and Δb* (4.1±2.4 vs. 2.3±1.4, P=0.051).

HD = high-definition; SD = standard-definition.