Computer-assisted visualization and quantitation of experimental gastric lesions in rats

Abstract

Introduction: Photography is commonly used to evaluate macroscopic morphology of experimental gastric lesions. The conventional methods for quantitation of these lesions tend to be highly subjective, error-prone, and tedious. This study reports a simple and novel method for visualization of experimental gastric lesions by direct scanning of stomach samples and their quantitation by using computer-assisted image analysis. Methods: Gastric mucosal lesions were produced by indomethacin or ethanol in male Wistar rats. The stomachs were removed, opened along the greater curvature, and washed. The flattened stomach samples were sandwiched within a transparent plastic folder and scanned. The captured image was saved and subjected to lesion quantitation using a freely accessible image analysis program, Scion Image. A macro subroutine was optimized for automation of the entire procedure for ease in frequent applications. Results: The images obtained by direct scanning of stomach samples showed excellent morphologic visualization of gastric lesions. The standard spots having variable areas of same density, or same areas of variable densities, showed a direct relation with signal intensity (pixels). A linear correlation was observed between measured and actual values of the known standard areas. The representative samples of indomethacin- and ethanol-induced gastric ulcers showed the total lesion areas of 4.62±0.74 and 169.26±13.23 mm², respectively. Discussion: Direct scanning of stomach samples is a simple, cost-effective, rapid, and efficient procedure for morphologic evaluation of experimental gastric lesions. The output images of scanned stomach samples are superior to scanned photographs, and can be instantly used for quantitative assessment of mucosal injury using the image analysis program.

Introduction

The quantitative assessment of experimentally induced gastric lesions is a problematic and error-prone task due to their predominantly multiple and irregularly shaped occurrence Parmar & Desai, 1993, Szabo et al., 1985. The simplest type of lesion index for quantification of stress- or chemically induced ulcers has been described as the cumulative length (mm) of all hemorrhagic erosions Liu et al., 1998, Santucci et al., 1995, Trapkov et al., 1997. For comparatively better approximation of total ulceration, the width of lesion has also been taken into account (ulcer index=length×width) (Watanabe et al., 2000). Several investigators have measured the area (mm²) of gastric lesions with the help of squared grid under dissecting microscope, summed per stomach and used as lesion score Naito et al., 1998, Suzuki et al., 2000, Takeuchi et al., 1993. Tracing of the outermost lining of acetic acid- or ethanol-induced ulcerated tissue on a transparency or glass plate and its copying on squared grid or graph paper has also been used to calculate the ulcer area Shen et al., 2001, Shin et al., 2002. Photographs of lesioned stomachs have helped in the usage of digital calipers (Santucci et al., 1995) and their enlargements for better visibility of indomethacin-induced tiny lesions (Joseph, Varela, Kanji, Subramony, & Mihas, 1999). A technical advancement based on microprocessor-linked planimetry with a stereomicroscope was introduced about two decades ago (Szabo et al., 1985) and was successfully applied for sensitive and accurate quantification of gastric lesions Sun et al., 2000, Tepperman et al., 1993, Wallace et al., 1990. However, this technique remained beyond the reach of small laboratories due to its high cost and instrumental sophistication, while many investigators still rely on conservative grading system for the quantitation of gastric lesions Al Moutaery & Tariq, 1997, Joseph et al., 1999, Lee et al., 1992, Schiantarelli et al., 1984, Valcavi et al., 1982.

In this investigation, an attempt was made to develop a simple, inexpensive, and rapid method for visualization and quantitation of experimental gastric lesions in rats. The approach is primarily based on direct scanning of stomach samples instead of conventional photography, whereas a freely available image analysis program was used for lesion quantification.