Effectiveness of radiological image data compression

This study was designed to evaluate effectiveness of radiological image data compression in terms of image quality and archiving material costs using DLT tapes, and to assess the relationship between loss of quality and cost savings. Six radiologists used Subjective Fidelity Criteria (SFC) in random fashion to evaluate the quality of 105 digitally acquired radiological images. In addition, 5 radiologists and 2 nonradiologists evaluated at random three phantom images exposed in conditions mimicking chest, bone, and colon examinations, displayed in five modes (a total of 15 images). Both patient images and phantom images were submitted to 3:1 (Ziv-Lempel method) and 10:1 compression (wavelet-based compression method). Cost information on material cost savings and the effect of compression on tape space requirements were compared. The results indicate that image quality was not degraded using either of the compression ratios. The interobserver proportion of agreement exceeded overwhelmingly the limit of a good proportion of agreement regarding each compression ratio and each image type. The divergence in the rest of the assessments was not consistent. The adoption of 10:1 compression would not bring a substantial decrease of archiving costs as compared to the total yearly operating costs, and especially as considering the consequences of possible image quality deterioration.