A comparison of wavelet and Joint Photographic Experts Group lossy compression methods applied to medical images.

This presentation focuses on the quantitative comparison of three lossy compression methods applied to a variety of 12-bit medical images. One Joint Photographic Exports Group (JPEG) and two wavelet algorithms were used on a population of 60 images. The medical images were obtained in Digital Imaging and Communications in Medicine (DICOM) file format and ranged in matrix size from 256 x 256 (magnetic resonance [MR]) to 2,560 x 2,048 (computed radiography [CR], digital radiography [DR], etc). The algorithms were applied to each image at multiple levels of compression such that comparable compressed file sizes were obtained at each level. Each compressed image was then decompressed and quantitative analysis was performed to compare each compressed-then-decompressed image with its corresponding original image. The statistical measures computed were sum of absolute differences, sum of squared differences, and peak signal-to-noise ratio (PSNR). Our results verify other research studies which show that wavelet compression yields better compression quality at constant compressed file sizes compared with JPEG. The DICOM standard does not yet include wavelet as a recognized lossy compression standard. For implementers and users to adopt wavelet technology as part of their image management and communication installations, there has to be significant differences in quality and compressibility compared with JPEG to justify expensive software licenses and the introduction of proprietary elements in the standard. Our study shows that different wavelet implementations vary in their capacity to differentiate themselves from the old, established lossy JPEG.

"Robo-Rad": an inexpensive user-friendly multimedia report system for radiology.

BACKGROUND AND PURPOSE: The complex information obtained by CT, MR, and ultrasound examinations is often difficult to convey with a written report. Today's multimedia computer technology provides a medium within which the audio and the visual components of a radiologic consultation can be made available simultaneously, with the projected capability of remote access from any personal computer. A system was developed to run on low-end computer systems with image quality adequate for reporting purposes and prudent memory management (each report occupies < 4 MB). With this system-"Robo-Rad"-the image and radiologist are recorded simultaneously while he or she describes and points out (with a mouse) areas of interest. This dynamic report, along with patient data, can be retrieved and viewed by the consulting physician at his/her convenience using a low-end PC or Macintosh computer. MATERIALS AND METHODS: To assess the clinical utility of Robo-Rad, survey responses were solicited from clinical physicians at the Penn State University Hospital (41.5% faculty/fellows, 31.7% residents, 11.8% medical students, 2% clinical nursing; n = 101) during a hands-on demonstration using studies of 35 consecutive inpatients whose CT scans had been dictated into the system. RESULTS: In an average week, the surveyed professionals ordered 3.2 +/- 3.0 CT studies, reviewed 3.8 +/- 3.0 CTs, spent 1.5 +/- 2.0 hours locating Ct studies, and discussed 2.3 +/- 1.9 CT cases with a radiologist. The average time spent discussing a single CT case with a radiologist was reported as 9.4 +/- 5.9 minutes. On a five-point rating scale (1 = not at all to 5 = very much so), respondents indicated that the Robo-Rad report was helpful (4.3 +/- 0.7) and provided clinically important information that would be difficult to convey with current dictation systems (4.2 +/- 0.8). Desire to discuss the case with a radiologist in addition to viewing the Robo-Rad report scored 3.2 +/- 1.0. If such a system were readily available, 91.8% of the respondents indicated that they would use it in addition to the currently available written report and audio dictation system, and 96.6% would use it instead of the current system. Local area network and modems were the modalities of highest interest for remote access (69.3% and 44.6%, respectively). CONCLUSIONS: Judging by these data, the Robo-Rad system would be of benefit to clinicians. It provides a user-friendly, low-cost multimedia radiology report utilizing readily available technology to improve radiologist-clinician communication.