Photoacoustic imaging for the differential diagnosis of cholesterol polyps from neoplastic polyps in the gallbladder

Abstract

Introduction: The differential diagnosis between cholesterol polyps and neoplastic polyps of gallbladder (GB) is important due to the malignant transformation potential of adenomas. Photoacoustic (PA) imaging is a new imaging technique with clinical potential in the real-time functional and molecular imaging. The purpose of our study was to assess the feasibility of ex vivo multispectral PA imaging in differentiating benign cholesterol polyps from adenomas and adenocarcinomas. Methods: Surgically confirmed 24 polyps (17 cholesterol polyps, 4 adenomas, 3 adenocarcinomas) of 24 patients were prospectively included in this study between April 2014 and October 2014, with written informed consents. The surgical specimens were set on a scatter-free gel pad, which was immersed in a 0.9% saline-filled container. Then the PA intensities of polyps were measured for two separate wavelength intervals (421-647 nm, 692-917 nm). Mann-Whitney U test was performed for the comparison of normalized PA intensities between cholesterol and neoplastic polyps and between benign and malignant polyps. Then Kruskal-Wallis test was conducted for the comparison of normalized PA intensities among cholesterol polyps, adenomas, and adenocarcinomas. Results: There were significant differences in the patients age (P = .004) and size of the polyp (P = .015) among three groups. There was no significant difference in the normalized PA intensities between cholesterol polyps and neoplastic polyps. But there were significant differences of the normalized PA intensities between benign and malignant polyps at 555 nm, 575 nm, 592 nm, 692 nm, 709 nm, 765 nm, 787 nm, 807 nm, 826 nm, and 853 nm (P < 0.05). The comparison of the normalized PA intensities among cholesterol polyps, adenomas, and adenocarcinomas demonstrated significant differences at 692 nm, 709 nm, 765 nm, 787 nm, and 853 nm (P < 0.05). Conclusions: This preliminary result indicates that GB polyps might have different spectral pattern between benign and malignant polyps on multispectral PA imaging.