Diagnostic Quality Evaluation of Compressed Medical Images for Telemedicine Applications

Many techniques for achieving data compression have been introduced. The fundamental goal of image data compression is to reduce the bit rate for transmission or storage while maintaining an acceptable reproduction quality, but it is natural to raise the question of how much an image can be compressed and still preserve sufficient information for a given telemedicine application. Evaluation of the quality of compressed medical image for telemedicine applications still remains an important issue. In this paper, the evaluation of diagnostic quality of compressed medical images using objective and subjective testing will be presented. Three different medical image modalities which are CT, MRI, and X-ray have been compressed and decompressed using DWT for different compression ratios. The quality of the reconstructed images has been measured objectively using objective measures such as MSE, MAE, SNR, and PSNR. Ten non specialist observers have been involved to carry out the subjective evaluation. Based on the quality of the reconstructed images, the PSNR obtained has been between 35.3dB to 58.0dB for CT scan images, 38.6dB to 55.0dB for MRI and 34.5dB to 51.0dB for x-ray images. For clinical applications such as telemedicine or teleradiology, the compression ratio of 30:1 is acceptable for CT images, and a compression ratio of 40:1 is acceptable for MRI, and compression ratio of 20:1 is acceptable for x-ray images.