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The full -frame bit allocation algorithm for radiological image compression developed in our laboratory can achieve compression ratios as high as 30:1. The software development and clinical evaluation of this algorithm has been completed. It involves two stages of operations: a two -dimensional discrete cosine transform and pixel quantization in the transform space with pixel depth kept accountable by a bit allocation table.The greatest engineering challenge in implementing a hardware version of the compression system lies in the fast cosine transform of 1Kx1K images.Our design took an expandable modular approach based on the VME bus system which has a maximum data transfer rate of 48 Mbytes per second and a Motorola 68020 microprocessor as the master controller.The transform modules are based on advanced digital signal processor (DSP) chips microprogrammed to perform fast cosine transforms.Four DSP's built into a single -board transform module can process an 1K x 1K image in 1.7 seconds. Additional transform modules working in parallel can be added if even greater speeds are desired.The flexibility inherent in the microcode extends the capabilities of the system to incorporate images of variable sizes. Our design allows for a maximum image size of 2K x 2K.

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