SAN ANTONIO - The growth in size and complexity of multidetector-row CT (MDCT) and MR images represents one of the biggest challenges to the digital healthcare enterprise.
To help manage the problem, institutions can take advantage of tools such as enhanced DICOM CT and MR objects and image compression, along with improved network and storage infrastructure, according to Dr. Eliot Siegel, chief of imaging for the VA Maryland Healthcare System in Baltimore.
Siegel spoke during a talk at this week's PACS 2007 conference, sponsored by the University of Rochester School of Medicine & Dentistry in New York.
CT and MRI, along with many other imaging modalities, are growing in volume and complexity, Siegel said. While the matrix size of CT images has remained the same at 512 x 512, the number of images has increased precipitously.
"It wasn't that long ago that a typical CT was 40 to 60 images, but at our facility, the average size of a CT dataset is 900 images," he said. "And what we're doing is we're scanning at 0.75 mm and we're saving the original datasets on all of the studies that we do."
In addition, multiple series are being obtained. Reconstructions are also being performed, and they may be saved as well, he said. The number of CT angiography images is even larger.
For MR, the number of images typically ranges from 40 to 500, but can be much more, according to Siegel. The number of series continues to get larger and larger. "We have some studies where there are 15 to 20 or more series," he noted.
As for MR angiography and cardiac MR, images can range as high as 15,000, with a larger number of series, Siegel said.
"The workflow issues associated with multidetector CT and increasingly complex MR studies just related to the complexity and the volume are significant," he said.
In addition to dealing with surging utilization, institutions are also being faced with longer and longer CT image processing time, Siegel said. For CT, the bottleneck used to be tube cooling time. Now, the bottleneck is the time required for reconstruction of complex datasets or the time required to get the images out of the scanner, he explained.
Enhanced DICOM objects
While approaches such as server-side rendering and network and storage infrastructure enhancements help, use of enhanced CT or MR objects added to the DICOM standard in 2003 could have a real impact, according to Siegel.
But at this time, hardly anybody is taking advantage of the new objects, because PACS vendors have been really slow to support them and CT vendors have been slow to adopt them, he said.
DICOM 3.0 in 1993 contained many MR and CT attributes, but are now outdated, Siegel said. Important information was needed for advanced applications, and interoperability using the old standard was difficult to achieve with the more sophisticated CT and MR datasets.
The additions in 2003 included more attributes, but now they had a clinically oriented structure, Siegel said. The new attributes removed the need for many private attributes used by vendors, he said.
The new objects support advanced applications such as diffusion imaging, diffusion tensor imaging, MR perfusion imaging, MR spectroscopy, and functional MRI. They also facilitate improved networking performance, context information, and clinical information, Siegel said.
"The trick now is to get the acquisition modality vendors and the PACS vendors to actually adopt this," he said. "If you're going out to buy a new PACS system or a new MRI or CT scanner, you'll be doing yourself and everybody a favor by asking (vendors about their support)."
Compression
Compression offers another potential means of helping users deal with MDCT and MR data. It's challenging, however, to compress very thin section datasets, Siegel said.
"Very thin slices are significantly noisier than the thicker sections, so the more noise on the data the more difficult it is because there's less redundant information," he said.
In a positive development, 3D JPEG 2000 compression has shown promise in lossy compression of thin-section data, according to Siegel. Many people fail to take advantage of the compression capabilities of their PACS due to medicolegal concerns, however.
"Image compression may be useful and has been proven to be clinically effective, but medicolegal concerns have really significantly slowed their adoption," he said.
The legal requirements for storing images vary widely from state to state, and are typically based upon the age of the patient. For minors, the majority of jurisdictions require a retention period of seven years beyond the age of majority, Siegel said. Federal regulations also differ in how they are applied from state to state.
With these issues in mind, retention policies for storage and backup should be formed as far in advance as possible, he said.
By Erik L. Ridley
AuntMinnie.com staff writer
March 23, 2007
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