New Dimensions in Medical Imaging: Bioendoscopy

Introduction

Despite the many technological advances that have occurred in the field of diagnostic endoscopy over the past few decades, remarkably the histological identification of dysplastic changes occurring within the gastrointestinal mucosa remains at present the best ”risk marker” for advancement to adenocarcinoma. On going research continues at the basic and clinical levels to evaluate putative molecular markers (i. e. fecal, serological, or urinary) which may facilitate the detection of early neoplastic disease, but unfortunately no such markers have been reported with reliable diagnostic value. Ideally, such tests would offer a means to better select asymptomatic patients for endoscopic examination, and the ability to identify subtle mucosal lesions allowing curative intervention either by ablation or minimally invasive surgery.

Conventional endoscopic screening detects lesions in patients presenting with symptoms of obstruction, pain or bleeding due to cancer caused by lesions that are usually large and obvious with endoscopy or radiology, and at such an advanced stage are generally incurable. Unfortunately, conventional white light endoscopy is suboptimal at detecting dysplasia and is associated with a disproportionate miss rate for subtle lesions, e. g. flat adenomas. A further complication is the difficulty of detecting dysplasia within fields of transformed mucosa, such as Barrett’s esophagus and long standing chronic ulcerative colitis. These limitations present a significant clinical challenge and provide the incentive for development of new endoscopy systems to complement white light endoscopy.

Novel photodiagnostic modalities are being developed and evaluated clinically for adjunctive use with standard endoscopy. These emerging technologies are based on the relative differences in the way light interacts with normal tissues and abnormal tissues which, during disease transformation, acquire altered optical properties. While conventional endoscopy is limited to detect lesions based on gross morphological changes, these new optically-based methods collectively offer a new strategy for endoscopic detection, ”bioendoscopy”, with the potential of detecting the very earliest mucosal changes at the microstructural, biochemical and molecular levels in realtime.

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