Hyperspectral imaging as a diagnostic tool to differentiate between amalgam tattoos and other dark pigmented intraoral lesions

Abstract

The goal of this project is to identify any in‐depth benefits and drawbacks in the diagnosis of amalgam tattoos and other pigmented intraoral lesions using hyperspectral imagery collected from amalgam tattoos, benign, and malignant melanocytic neoplasms. Software solutions capable of classifying pigmented lesions of the skin already exist, but conventional red, green and blue images may be reaching an upper limit in their performance. Emerging technologies, such as hyperspectral imaging (HSI) utilize more than a hundred, continuous data channels, while also collecting data in the infrared. A total of 18 paraffin‐embedded human tissue specimens of dark pigmented intraoral lesions (including the lip) were analyzed using visible and near‐infrared (VIS–NIR) hyperspectral imagery obtained from HE‐stained histopathological slides. Transmittance data were collected between 450 and 900 nm using a snapshot camera mounted to a microscope with a halogen light source. VIS–NIR spectra collected from different specimens, such as melanocytic cells and other tissues (eg, epithelium), produced distinct and diagnostic spectra that were used to identify these materials in several regions of interest, making it possible to distinguish between intraoral amalgam tattoos (intramucosal metallic foreign bodies) and melanocytic lesions of the intraoral mucosa and the lip (each with P < .01 using the independent t test). HSI is presented as a diagnostic tool for the rapidly growing field of digital pathology. In this preliminary study, amalgam tattoos were reliably differentiated from melanocytic lesions of the oral cavity and the lip.

New perspectives of hyperspectral imaging for clinical research

“…92–94 So far, HSI provides diagnostic information for anemia, hypoxia, cancer detection, skin lesions and ulcer identification, and urinary stone analysis. 12–14,95–106 Additional applications range from in vivo to ex vivo measurements including image-guided surgery, 12,106–108 endoscopy, 78,109 dermatology, 110 macroscopic investigations of ex-vivo tissue specimens 111–113 and histology. 13,14,114…”

“…Ex vivo, digital pathology as an emerging technology promises quantitative diagnosis of pathological samples, relying on RGB digitized histology images. 13,14,114,120–123 In Figure 3 an exemplary workflow for HSI as a diagnostic tool to differentiate amalgam tattoos from melanocytic lesions is presented.…”

“…Workflow proposal for HSI as a diagnostic tool to differentiate amalgam tattoos from melanocytic lesions. 14 The current workflow for tissue diagnosis involves sample preparation, assessment of tissue morphology by a pathologist, measurements of several tissue sections, analysis of the obtained data, and direct comparisons of the HSI results with the pathological examination.…”

“…First applications investigated the earth’s surface and atmosphere using air- or satellite-supported cameras for mineral exploration, 9 vegetation monitoring, 10 and marine analysis. 11 The subsequent technical development of HSI cameras and the associated decreasing costs made it possible to use them in laboratories, such as medical diagnostics 12–14 or food safety issues. 15–17 In parallel to hardware evolution, information extraction methods have been developed.…”

“…15–17 In parallel to hardware evolution, information extraction methods have been developed. 13,14,18,19 Today, HSI is a promising non-invasive and non-ionizing technique that supports the rapid acquisition and analysis of diagnostic information in several fields. This technology is nowadays used for remote sensing, 20,21 archeology, 22,23 drug identification, 24–27 forensics, 28–30 defense and security, 31,32 agriculture, 33,34 food safety inspection and control.…”