On Archiving and Retrieval of Sequential Images From Tomographic Databases in PACS

In the picture archiving and communication systems (PACS) used in modern hospitals, the current practice is to retrieve images based on keyword search, which returns a complete set of images from the same scan. Both diagnostically useful and negligible images in the image databases are retrieved and browsed by the physicians. In addition to the text-based search query method, queries based on image contents and image examples have been developed and integrated into existing PACS systems. Most of the content-based image retrieval (CBIR) systems for medical image databases are designed to retrieve images individually. However, in a database of tomographic images, it is often diagnostically more useful to simultaneously retrieve multiple images that are closely related for various reasons, such as physiological continguousness, etc. For example, high resolution computed tomography (HRCT) images are taken in a series of cross-sectional slices of human body. Typically, several slices are relevant for making a diagnosis, requiring a PACS system that can retrieve a contiguous sequence of slices. In this paper, we present an extension to our physician-in-the-loop CBIR system, which allows our algorithms to automatically determine the number of adjoining images to retain after certain key images are identified by the physician. Only the key images, so identified by the physician, and the other adjoining images that cohere with the key images are kept on-line for fast retrieval; the rest of the images can be discarded if so desired. This results in large reduction in the amount of storage needed for fast retrieval.