Diagnostic Quality of Compressed Medical Images: Objective and Subjective Evaluation

Abstract

Without image compression, images data would become much larger and consequently retrieval of images will be slow, thus telemedicine would in many situations be impractical. But it is natural to raise the question of how much an image can be compressed and still preserve sufficient information for a given clinical application. Evaluation of the diagnostic quality of compressed medical image still remains an important issue. In this paper, three different medical image modalities have been compressed and decompressed using DWT for different compression ratios and evaluated using objective and subjective testing. The quality of the reconstructed images has been measured using objective measures such as MSE, MAE, SNR, and PSNR. Ten observers have been involved to carry out the subjective evaluation. Based on the quality of the reconstructed images, the PSNR obtained has been between 35.3 dB to 58.0 dB for CT scan images, 38.6 dB to 55.0 dB for MRI and 34.5 dB to 51 MB for X-ray images. For radiology applications, 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.