FOCAL HEPATIC-LESIONS - EFFECT OF 3-DIMENSIONAL WAVELET COMPRESSION ON DETECTION AT CT

PURPOSE: To evaluate the effect of three-dimensional, wavelet-based co mpression on the detection of focal hepatic lesions at computed tomogr aphy (CT). MATERIALS AND METHODS: CT images obtained in 69 patients wi th focal hepatic lesions were studied (35 consecutive cases and 34 cas es selected to be difficult on the basis of lesion size or contrast). Image data were compressed by means of a three-dimensional, wavelet-ba sed algorithm at ratios of 10:1, 15:1, and 20:1. Normal and abnormal s ections (on original and compressed images) were reviewed by using an interactive workstation. Four readers rated the presence or absence of a lesion with a five-point scale. RESULTS: At receiver operating char acteristic analysis, no statistically significant difference was detec ted for all cases considered together. Differences approached but did not reach statistical significance for the diagnostic performance of o ne reader with compressed images (15:1, P = .054; 20:1, P = .051). For the subset of difficult cases, a significant difference was observed with 20:1 compressed images for one reader (P = .026). Diagnostic perf ormance of readers was less certain in normal than in abnormal cases w ith both original and compressed images (difference was significant fo r 15:1 [P = .035] and 20:1 [P < .0001] compressed images). CONCLUSION: Three-dimensional wavelet compression is satisfactory at ratios of at least 10:1. Additional studies with a larger sample would help confir m findings with higher ratios.