A preprocessing algorithm for error-free image compression

Depending on the purpose for which a radiological image is taken, some areas of it contain more clinical information than others. These areas are usually considered as region of interest (ROI). The areas outside the ROI are either the background or contain some clinical information with relative importance. The original images are changed by the proposed preprocessing algorithm and their altered version is passed to an error-free compression routine. The area inside the ROI is reconstructed identically, but those outside it are either reconstructed irreversibly or replaced by an optional background gray level. (author)