Yottalook is a free radiology-centric search engine based on Google’s indexing technology with proprietary relevance algorithm by iVirtuoso. Currently, Yottalook Images and Yottalook References search engines are available for use. Yottalook Image has specially been designed to search radiology images from various peer-reviewed online sources and currently has access to over 100,000 images. Yottalook References has been designed to search online radiology sources only. Try various refinement options to narrow your search requests even further.
Appears to be a great application of the Custom Search Engine tools from Google Co-Op.
Please note: I can’t get it to work with Firefox, but it works fine in IE7. YMMV.