A prior ultrasound study indicated that images with low to moderate levels of JPEG and wavelet compression were acceptable for diagnostic purposes. The purpose of this study is to validate this prior ®nding using the Joint Photographic Experts Group (JPEG) baseline compression algorithm, at a compression ratio of approximately 10:1, on a suf®ciently large number of grayscale and color ultrasound images to attain a statistically signi®cant result. The practical goal of this study is to determine if it is feasible for radiologists to use irreversibly compressed images as an integral part of the day to day ultrasound practice (ie, perform primary diagnosis with, and store irreversibly compressed images in the ultrasound PACS archive). In this study, 5 Radiologists were asked to review 300 grayscale and color static ultrasound images selected from 4 major anatomic groups. Each image was compressed and decompressed using the JPEG baseline compression algorithm at a ®xed quality factor resulting in an average compression ratio of approximately 9:1. The images were presented in pairs (original and compressed) in a blinded fashion on a PACS workstation in the ultrasound reading areas, and radiologists were asked to pick which image they preferred in terms of diagnostic utility and their degree of certainty (on a scale from 1 to 4). Of the 1,499 total readings, 50.17% (95% con®dence intervals at 47.6%, and 52.7%) indicated a preference for the original image in the pair, and 49.83% (95% con®dence intervals at 47.3%, and 52.0%) indicated a preference for the compressed image. These ®ndings led the authors to conclude that static color and gray-scale ultrasound images compressed with JPEG at approximately 9:1 are statistically indistinguishable from the originals for primary diagnostic purposes. Based on the authors laboratory experience with compression and the results of this and other prior studies JPEG compression is now being applied to all ultrasound images in the authors radiology practice before reading. No image quality±related issues have been encountered after 12 months of operation (approximately 48,000 examinations).KEY WORDS: Compression, Joint Photographic Experts Group, ultrasound, medical images, PACS, teleradiology, archive W ith the rapidly dropping cost of digital storage and conservative use of standards-based irreversible (lossy) compression techniques, it is becoming practical to maintain large volumes of clinical images online, and distribute them eciently over networks.A prior ultrasound compression study was performed by our group to evaluate the eects of irreversible wavelet compression on ultrasound images and to determine how much compression can be applied, and still have the images be``acceptable for diagnostic purposes.'' 1 That study focused speci®cally on grayscale ultrasound images and considered a variety of factors including wavelet compression at several compression levels, different acquisition techniques (frame-grabbed v directly digitally acquired) and the eects of text that is`b ur...