The effects of irreversible JPEG compression on an automated algorithm for measuring carotid artery intima-media thickness from ultrasound images.

Our ultrasound practice has begun to investigate automated measurements of carotid artery intima-media thickness (IMT) as an indicator of subtle atherosclerosis. Since our clinical ultrasound images are irreversibly compressed, we investigated the effects of this compression on our IMT measurements. We obtained 10 ultrasound images of normal carotid arteries. These were compressed using JPEG to ratios of 5:1, 10:1, 15:1, 20:1, and 30:1. IMT measurements made from all compressed and uncompressed images were compared. For compression ratios ?10:1, IMT deviations between compressed and uncompressed images were ?0.03 mm. Higher than 10:1, the overall IMT deviations were small (0.01 +/- 0.04 mm), although one 25% deviation was measured. Comparison of other parameters yielded similar results. This initial study indicates that compression at 10:1 using baseline JPEG should have little effect on IMT measurements made using the current algorithm, and that compression to 20:1 or 30:1 may be feasible.

Requirements for an enterprise digital image archive.

This report describes several image archival problems facing the authors' department and the results of their attempt to define the requirements for an enterprise digital image archive. The problems identified include the costs of supporting multiple distinct archives, the increased complexity of supporting multiple archive interfaces, the differences in data handling policies and resulting variations in data integrity, and variability in support for nonimage data. The authors also describe the data collected including image volumes and trends and imaging device trends. Finally, the resulting specification for an enterprise digital image archive, including storage and retrieval performance and interface requirements are presented.

An evaluation of JPEG and JPEG 2000 irreversible compression algorithms applied to neurologic computed tomography and magnetic resonance images. Joint Photographic Experts Group.

We performed visual comparison of 200 head magnetic resonance (MR) and 200 head computed tomography (CT) images compressed at two levels using standard Joint Photographic Experts Group (JPEG) irreversible compression and a preliminary version of the JPEG 2000 irreversible algorithm. Blinded evaluations by neuroradiologists compared original versus either JPEG or JPEG 2000. We found that this version of JPEG 2000 did not perform as well as the current JPEG for head CTs, but for MR images, JPEG 2000 performed as well or better. Around 7:1 compression ratio seemed to be a conservative point where there was no perceptible difference.

Ultrasound grayscale image compression with JPEG and wavelet techniques.

The purpose of the study was to evaluate the effects of lossy compression on grayscale ultrasound images to determine how much compression can be applied while still maintaining images that are acceptable for diagnostic purposes. The study considered how the acquisition technique (video frame-grabber versus directly acquired in digital form) influences how much compression can be applied. For directly acquired digital images, the study considered how text (that is burned into the image) affects the compressibility of the image. The lossy compression techniques that were considered include JPEG and a Wavelet algorithm using set partitioning in hierarchical trees (SPIHT).

Detection of subtle abnormalities on chest radiographs after irreversible compression.

PURPOSE: To assess the effect of wavelet-based compression of posteroanterior chest radiographs on detection of small uncalcified pulmonary nodules and fibrosis. MATERIALS AND METHODS: Computed tomography (CT) of the chest was used to identify 20 patients with normal posteroanterior chest radiographs, 20 with a solitary uncalcified pulmonary nodule 1-2 cm in diameter, and 20 with fibrotic disease. A double-blind protocol for readings of original images and images compressed at 40:1 and 80:1 was analyzed by using the nonparametric receiver operating characteristic to measure differences in diagnostic accuracy and their statistical significance. RESULTS: There was no substantial difference in the overall diagnostic accuracy (measured by the area under the curve index) for both nodules and fibrosis between images compressed at 40:1 and 80:1 and uncompressed images. Readers tended to perform better on images compressed at 40:1 compared with uncompressed images. The "high-sensitivity" portion of the 80:1 compression curve for nodules was below that for the uncompressed curve, although this was not statistically significant. CONCLUSION: Lossy compression of chest radiographs at 40:1 can be used without decreased diagnostic accuracy for detection of pulmonary nodules and fibrosis. There is no statistically significant difference in diagnostic accuracy at 80:1 compression, but detection ability is decreased.

Evaluation of irreversible compression of digitized posterior-anterior chest radiographs.

The purpose of this article is to assess lossy image compression of digitized chest radiographs using radiologist assessment of anatomic structures and numerical measurements of image accuracy. Forty posterior-anterior (PA) chest radiographs were digitized and compressed using an irreversible wavelet technique at 10, 20, 40, and 80:1. These were presented in a blinded fashion with an uncompressed image for A-B comparison of 11 anatomic structures as well as overall quality assessments. Mean error, root-mean square (RMS) error, maximum pixel error, and number of pixels within 1% of original value were also computed for compression ratios from ratios from 5:1 to 80:1. We found that at low compression (10:1) there was a slight preference for compressed images. There was no significant difference at 20:1 and 40:1. There was a slight preference on some structures for the original compared with 80:1 compressed images. Numerical measures showed high image faithfulness, both in terms of number of pixels that were within 1% of their original value, and by the average error for all pixels. Our findings suggest that lossy compression at 40:1 or more can be used without perceptible loss in the representation of anatomic structures. On this finding, we will do a receiver-operator characteristic (ROC) analysis of nodule detection in lossy compressed images using 40:1 compression.