Reply to Heatley and Bell

Abstract

Endoscopy several months ago [1]. On the basis of studies that were published between 1993 and 1998, they argue that it is inappropriate in feasibility studies of tele-endoscopy to focus exclusively on the picture quality. They state that it is ªimportant to take in wider considerations, such as cost, flexibility, availability, medical practices, audio requirements, etc.º. In our view, however, a new technology should initially be evaluated in high-quality feasibility studies that examine the focal point, and secondly in comparative studies to demonstrate its equality or superiority to existing techniques. In addition, it is important to take into account appropriate clinical applications and the demand for a new technique.The major issue in video endoscopy is picture quality. In recent years, all endoscope manufacturers have significantly increased the resolution of the video endoscopes that are available. In the near future, it will become possible to visualize the blood flow in mucosal capillaries, using endoscopes with 1 million pixels and 200-fold magnification. High-resolution video endoscopy and chromoendoscopy are already allowing today's endoscopists to identify flat adenomas, intraepithelial neoplasia, and early carcinoma which were too often overlooked in the past due to inadequate image resolution and also probably because of low attention to such conditions or inexperience on the part of endoscopists [2]. Since these lesions are curable by local endoscopic therapy [3], requirements in video endoscopy examinations have rapidly changed in recent years. We therefore consider that it is not only appropriate but also necessary to focus on picture quality when analyzing tele-endoscopy.We therefore carried out a prospective study using a highly sophisticated and technically well-defined system for digital video transmission [4]. The participating endoscopists were asked to give a rating for whether they would be able to identify all mucosal lesions on basis of the picture quality displayed which was also quantified in the study. We concluded from the results that endoscopic video material transmitted at 40 megabit/s in Moving Pictures Experts Group 2 (MPEG2) [4 : 2:2] format has unlimited diagnostic validity and can therefore be used for real-time telemedical applications without restriction. The technical equipment was then used to modify a variety of parameters in a randomized fashion within a wide range: compression algorithms, network bandwidths, and impairments due to network overload situations. The evaluation of the video material by experienced endoscopists turned out to be surprisingly uniform, and the test subjects were evidently capable of recognizing and rating technically objective changes in the quality of the video picture. Finally, all tested technical parameters had a significant impact on the quality of the video picture, and the resulting picture quality subsequently influenced the usability of the images for diagnostic purposes. In summary, real-time digital video transmissions using MPE...