Analyzing web log files of the health on the net HONmedia search engine to define typical image search tasks for image retrieval evaluation.

Medical institutions produce ever-increasing amount of diverse information. The digital form makes these data available for the use on more than a single patient. Images are no exception to this. However, less is known about how medical professionals search for visual medical information and how they want to use it outside of the context of a single patient. This article analyzes ten months of usage log files of the Health on the Net (HON) medical media search engine. Key words were extracted from all queries and the most frequent terms and subjects were identified. The dataset required much pre-treatment. Problems included national character sets, spelling errors and the use of terms in several languages. The results show that media search, particularly for images, was frequently used. The most common queries were for general concepts (e.g., heart, lung). To define realistic information needs for the ImageCLEFmed challenge evaluation (Cross Language Evaluation Forum medical image retrieval), we used frequent queries that were still specific enough to at least cover two of the three axes on modality, anatomic region, and pathology. Several research groups evaluated their image retrieval algorithms based on these defined topics.