Effectiveness of computer-aided diagnosis of colorectal lesions using novel software for magnifying narrow-band imaging: a pilot study

Abstract

Background and study aims: Magnifying narrow-band imaging (M-NBI) enables detailed observation of microvascular architecture and can be used in endoscopic diagnosis of colorectal lesion. However, in clinical practice, differential diagnosis and estimation of invasion depth of colorectal lesions based on M-NBI findings require experience. Therefore, developing computer-aided diagnosis (CAD) for M-NBI would be beneficial for clinical practice. The aim of this study was to evaluate the effectiveness of software for CAD of colorectal lesions.

Materials and methods: In collaboration with Yamaguchi University, we developed novel software that enables CAD of colorectal lesions using M-NBI images. This software for CAD further specifically divides original Sano's colorectal M-NBI classification into 3 groups (group A, capillary pattern [CP] type I; group B, CP type II + CP type IIIA; group C, CP type IIIB), which describe hyperplastic polyps (HPs), adenoma/adenocarcinoma (intramucosal [IM] to submucosal [SM]-superficial) lesions, and SM-deep lesions, respectively. We retrospectively reviewed 121 lesions evaluated using M-NBI.

Results: The 121 reviewed lesions included 21 HP, 80 adenoma/adenocarcinoma (IM to SM-superficial), and 20 SM-deep lesions. The concordance rate between the CAD and the diagnosis of the experienced endoscopists was 90.9 %. The sensitivity, specificity, positive and negative predictive values, and accuracy of the CAD for neoplastic lesions were 83.9 %, 82.6 %, 53.1 %, 95.6 %, and 82.8 %, respectively. The values for SM-deep lesions were 83.9 %, 82.6 %, 53.1 %, 95.6 %, and 82.8 %, respectively.

Conclusion: Relatively high diagnostic values were obtained using CAD. This software for CAD could possibly lead to a wider use of M-NBI in the endoscopic diagnosis of colorectal lesions.

Fig. 1

Sano’s classification (modified for this study). In this study, Sano’s classification was further divided broadly into three groups: group A, capillary pattern (CP) type I; group B, CP type II + CP type IIIA; group C, CP type IIIB.

Fig. 2

The user interface of software for computer-aided diagnosis (CAD). The first step when using this software for CAD is to choose the region of interest using the cursor that appears on the attached narrow-band image (right-side window). Then, by clicking “Calculate” and “Classify,” the image is automatically classified into 1 of the 3 groups.

Fig. 3

Lesions diagnosed differently between the endoscopists and the software for computer-aided diagnosis. a Lesion diagnosed as group B by the endoscopists, and diagnosed as group C by the software for computer-aided diagnosis Macroscopic Type: Is, Pathological diagnosis: Intramucosal adenocarcinoma in tubular adenoma. b Lesion diagnosed as group B by the endoscopists, and diagnosed as group C by the software for computer-aided diagnosis Macroscopic Type: Is + IIa, Depth of invasion: Intramucosal adenocarcinoma in tubulovillous adenoma. c Lesion diagnosed as group C by the endoscopists, and diagnosed as group B by the software for computer-aided diagnosis Macroscopic Type: Ip + IIc, Pathological diagnosis: Intramucosal adenocarcinoma with adenoma component. Depth of invasion: Submucosal Deep (3600 um). d Lesion diagnosed as group C by the endoscopists, and diagnosed as group B by the software for computer-aided diagnosis Macroscopic Type: Is, Depth of invasion: Intramucosal adenocarcinoma in tubular adenoma.