All the images in the database are divided into a number of image groups based on {HEAD ~ the image characteristic index} of each image in {TAIL ~ the database} and the CAD scheme is optimized for each image group 
in
All the images in the database are divided into a number of image groups based on { HEAD ~ the image characteristic index } of each image in { TAIL ~ the database } and the CAD scheme is optimized for each image group
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH