JPEG2000 stirs new interest in radiology

JPEG, the stodgy Web image coding standard of the last century, has finally received a facelift. JPEG2000 is a state-of-the-art compression standard incorporating wavelet compression technology, widely recognized as a superior method. Recently adopted by the DICOM standard, JPEG2000 is having a significant impact on radiology.

"Until early 2001, the new compression schemes that are part of JPEG2000, such as wavelet, could only be implemented in a proprietary manner, which didn't allow interoperability between vendors," said Herman Oosterwijk, president of OTech.

Prior to the ratification of the DICOM standard, major vendors were hesitant to implement wavelet compression, but now they can, he said. The DICOM image compression task force (Working Group 4) can also move ahead on methods for handling progressive image transmission, a feature supported by JPEG2000.

"This will allow transmitting images with a resolution and quality that gets better over time, which will be extremely useful in teleradiology and in some PACS network environments," said Dr. Alan Rowberg, chair of DICOM Working Group 4.

The JPEG2000 image compression method was included in the DICOM standard as a transfer syntax less than a year ago, but it has already become available in some commercial products. Sarnoff Corporation has developed JNDmetrix software, which the company exhibited at the RSNA meeting last year. This software compares an original image with a processed version of the same image and determines the extent to which a human observer can see a difference between the two. Along with clinical partners, Sarnoff is exploring how this can be used to measure changes in image quality after lossy compression and decompression.

"Sarnoff's technology might be used to evaluate JPEG2000 or other image compression techniques in a variety of clinical settings in an automatic manner. Only the final evaluation need be done with the more expensive observer studies," Rowberg said.

He expects techniques such as this to increase the speed of adoption of JPEG2000 for healthcare applications.

"We are starting to see a very strong interest in JPEG2000 in the medical imaging and radiology marketplace," said Rob Mungovan, vice president of advanced products at Aware. "Many systems already incorporate proprietary wavelet image compression technologies. JPEG2000 should facilitate the interoperability of these systems by providing a wavelet compression algorithm based on an ISO standard."

Though DICOM will support the use of JPEG2000 through referencing appropriate parts of the JPEG2000 standard, the DICOM Standards Committee does not endorse the use of non-bit-preserving compression. Whether lossy compression is appropriate is a decision left to professional organizations and practitioners.