Combined-Coding Techniques For Radiographic Image Data Compression

A new coding scheme, namely combined coding (CC) is proposed in this paper. The main point behind CC is to divide the image into two image sets with different statistical properties, then exploit those properties to code the sets more efficiently. Three variations are distinguished and discussed. Two particular CC schemes are identified as CC scheme 1 and CC scheme 2. For the CC 1, i.e. Run-length mapping then entropy coding for the upper image set (UIS) and Peano-differential mapping then Ziv-Lempel coding for the lower image set (LIS), the experimental results are tabulated and compared with other methods. For CC scheme 2, i.e. same coding method for the UIS and transform coding the LIS, both the rate-distortion performance and actual coding results are given. It is noted that the CC significantly reduces the "blocking effect" and this property is very useful for clinical decisions. This scheme seems to provide a good tradeoff and an efficient solution to practical image transmission and archival applications.