CHOICE OF WORD-LENGTH IN THE DESIGN OF A SPECIALIZED HARDWARE FOR LOSSLESS WAVELET COMPRESSION OF MEDICAL IMAGES

Image compression plays an important role in the archiving and transmi ssion of medical images, Discrete cosine transform (DCT)based compress ion methods are not suitable for medical images because of block-like image artifacts that could mask or be mistaken for pathology. Wavelet transforms (WTs) are used to overcome this problem. When implementing WTs in hardware, finite precision arithmetic introduces quantization e rrors, However, lossless compression is usually required in the medica l image field, Thus, the hardware designer must look for the optimum r egister length that, while ensuring the lossless accuracy criteria, wi ll also lead to a high-speed implementation with small chip area. In a ddition, wavelet choice is a critical issue that affects image quality as well as system design, We analyze the filters best suited to image compression that appear in the literature. For them, we obtain the ma ximum quantization errors produced in the calculation of the WT compon ents. Thus, we deduce the minimum word length required for the reconst ructed image to be numerically identical to the original image. The th eoretical results are compared with experimental results obtained from algorithm simulations on random test images. These results enable us to compare the hardware implementation cost of the different filter ba nks. Moreover, to reduce the word length, we have analyzed the case of increasing the integer part of the numbers while maintaining constant the word length when the scale increases. (C) 1997 Society of Photo-O ptical Instrumentation Engineers.