|Cardiac CTA volume reconstruction on the TeraRecon Aquarius workstation highlights the coronary vessels.|
Advanced visualization has shot from the realm of experimental, futuristic technology to almost routine practice in just a few short years. While the reliance by physicians on 3D varies, clinicians can often determine the presence and extent of heart disease without an invasive procedure. On the horizon, 3D users see further improvements that will reduce radiation exposure and speedier interpretation times.
"Over the past two to three years, 3D post-processing has gone from something we kind of played with to something that has been incorporated into the general management of patients with cardiovascular conditions,” says David Bush, MD, director of the cardiac catheterization lab at Johns Hopkins Bayview Medical Center in Baltimore, Md.
Bush has been using Vitrea workstations and VitalCardia software from Vital Images since 2003. The technology helps him provide a conclusive answer about the extent of coronary disease in patients. For patients who are younger or who otherwise fall outside the typical risk group for coronary disease, they are great candidates for cardiac CT. “The expectation is that they’re not going to have much disease and if you can confirm that, you’ve saved them an invasive test.”
“Cardiac CT is relatively new. Not that many cardiologists do it because you are required to have very sophisticated software to read coronary CT angiograms. It puts a lot of demand on software,” says John Lesser, MD, cardiologist at the Minneapolis Heart Institute/Abbott Northwestern Hospital in Minnesota. He has been using Vitrea workstations and VitalCardia software since venturing into cardiac CT in 2003.
VitalCardia lets Lesser read studies more quickly and accurately. He finds 3D cardiac imaging particularly helpful when treating peripheral vascular disease and complicated congenital heart disease.
Carter Newton, MD, a cardiologist at the University of Arizona in Tucson is another early adopter of 3D imaging. He uses TeraRecon’s Aquarius workstation and AquariusNET server for his monthly CT reading and reporting classes for radiologists and cardiologists.
Better than surgical dissection
3D imaging allows for both static and moving images. “The use of static images rendered without motion artifact is extremely useful for high resolution coronary artery analysis,” he says. “That’s really the thing that turns everybody on.”
This high resolution structural imagery allows for study of the various elements, including arteries, veins, valves and other various heart structures. “You can actually visualize the heart in a ‘virtual’ anatomic presentation than in an actual surgical dissection,” says Newton. Users also can control how brilliantly the tissues are rendered and emphasize cardiac structures that are the subject of inquiry: ventricular muscle and pulmonary vein connection, for example.
Dynamic images let clinicians watch phases of the heart cycle come together in repetitive action. Cine, or 4D, imaging lets clinicians add time and view via animation. “We can watch the beating heart from any angle and detect even subtle variations from the norm. Wall motion, valvular motion and other complex elements of the cardiac cycle are observed in detail. The ventricular performance parameters are easily measured,” he says. This information, in addition to coronary artery analysis, is key to an accurate diagnosis and treatment plan. 3D advanced visualization tools also let cardiologists isolate sections of the heart: particular chambers or particular arteries.
These segmentation tools, evoked with a simple click of a mouse button isolate a particular structure for analysis and as such are big time savers, Newton says. “You may only be looking at 5 percent of the total information in the scan, but it’s the information relevant to your inquiry,” says Newton. “It speeds and simplifies the analysis.” The volumetric detail of a heart scan also can be merged with information obtained from another modality, such as electrophysiologic details of electrical pathways in patients with heart rhythm disorders. The fused information can help plan and guide a surgical or transcatheter intervention.
Accuracy and speed
Lesser has learned the value of 3D software in helping with accuracy and speed in coronary CT. “When you’re a cardiologist, you don’t have much familiarity with software in this regard, so cardiologists may not understand the importance of the software and the problems it helps to solve. Without it, you’re in big trouble.”
With CT scanners that allow for gated imaging, clinicians can get 3D information from the whole chest in one breath hold, Lesser says. “That’s revolutionary for cardiology, that we can do all of this in one breath hold. We can see the arteries that feed the heart very accurately, reconstruct the data and make a diagnosis.”
These tools are “terrifically useful,” says Newton. Until CT angiography arrived, the precise anatomic information about the coronary arteries needed for an accurate diagnosis was only available with an invasive coronary angiogram. Now the ordeal of that procedure and its risks can be eliminated altogether. Both the patients and the insurance carriers note the appeal of a noninvasive alternative at a fraction of the cost. This will soon change our approach to diagnostic cardiology, simplify it and hopefully streamline care. This change will be huge and it is just around the corner, Newton says.
The value is very obvious, particularly to vendors, Newton says. “The four major scanner manufacturers wouldn’t be pouring money into this if the opportunity for explosive growth were not apparent. It’s very clear that improved noninvasive imagery is going to become more and more integral to medicine.” Advanced visualization is changing everything, he says. As a result, radiologists are being called on for imagery of things they never had to image before. “Many radiologists don’t know coronary artery anatomy or the pathobiology of coronary atherosclerosis because that knowledge has not been needed in their practices,” he says. “And, many cardiologists never thought they’d be looking at CT imagery of the heart or peripheral arteries.” Once images are post-processed, however, the renderings are straightforward and visually familiar. Thus, communicating the findings to an internist, general practitioner or even a patient becomes easier. As scanner technology advances and as workstation tools evolve, reading studies will get easier also. In fact, this is already happening. This ease will challenge the role or the radiologist or cardiologist. Simply put, years of training will not be needed for highly competent coronary analysis by coronary CT.
Until that happens, users offer advice on how to make advanced visualization work. Bush recommends joint cooperation between radiologists and cardiologists. “This is one of those places where cardiology and radiology intersect.” That intersection is adversarial in a lot of facilities, he says. Joint cooperation can result in greater acceptance of the technology. “It tends to grow better than when one or the other tries to do it to the exclusion of the other. We’ve had a fully cooperative interaction and the two groups have been able to teach each other.”
Another factor to consider is good image acquisition on the front end, says Bush. “It’s technically demanding to produce good studies.” Technologists, radiologists and cardiologists need to be aware of the importance of good patient preparation, including slowing the heart rate and breath hold instructions. “If one tries to push these scans through too fast, you wind up with studies that are much more difficult to interpret. You spend more time wrestling with something that could have been acquired better on the front end.”
Users also need to take the time to master the special functions of the 3D workstation required to perform post-processing.
Time for training
To help clinicians master 3D interpretation, John Rumberger, MD, professor of cardiology at Ohio State University and medical director for Healthwise Wellness Diagnostic Center in Cleveland, has conducted an intensive training program on post-processing tools for about two years. Having viewed the heart in three dimensions for 27 years, he has worked with TeraRecon to develop interfaces and uses their Aquarius workstations and software.
Rumberger’s course is frequently sold out and he has increased the frequency to accommodate demand. The three-and-a-half day course with two Level III instructors in the room at all times runs $6,500 to $7,000. Cardiologists primarily attend the course to learn how to do cardiac CT and read and interpret the studies. “They come into the training program suspecting that it will take them half an hour to read a single study. I tell them that they should be able to have it done in 10 minutes. They are surprised at how easy it is.”
Medicare is the only payor reimbursing for coronary CTA at a range of $800 to $1,100, depending on location and the addition of the information on heart function. Private payors are coming along, Rumberger says. “It’s important to have enough doctors that know how to read them for payors to pay attention.”
Sixty-four slice CT technology has allowed for a more universal scanning platform. “We can use the same scanner for the heart that we use to image the brain, legs and lungs. Plus, there have been hundreds of papers coming out every year showing how this can be used to do heart work. As people use this, they realize it probably eclipses just about anything else we use in cardiology for imaging.”
Ten years ago, electronic beam CT scanning was a fantastic way to do cardiac work, says Rumberger. “The problem was that the slices were too thick. You’d end up with difficulty doing 3D manipulations.” Clinicians now have the ability to have very, thin slices and very uniform picture elements to twist the images around without losing fidelity. That’s the result of a combination of improvements, says Rumberger. That comes with new considerations, however. “The electron beam images of 10 years ago might have been 60 to 70 images,” he says. “Now we’re talking about 3,000 to 5,000 images.”
Newton started the cardiac CT imaging program at the South Carolina Heart Center in 2003 and the team learned as they went along. “In the beginning, there were no experts so we learned by doing. We developed our protocols, our own patient selection criteria, our pricing structure, our relationship with the local radiologists, and a method to look at the economic impact of CT scanning in the practice. We had to learn about networks, storage systems, and over-reading for quality assurance. We marketed our CT service and had to meet the demand we created with quality reports delivered to the referring doctor quickly.” These large volumes of information stressed the network terrifically so they developed a means, now commonplace, for a scan to be done in South Carolina, over-read in Arizona, and reported the same day back in South Carolina. Today, most centers have broadband networks and quick commercial connectivity.
In the future…
Despite the rapid technological changes that have already occurred, more advances are in the works for 3D imaging.
Further advances in CT technology will continue to reduce the radiation dose and that will eliminate the safety arguments of cardiac CT, says Newton. The ability to take a snapshot of the heart with one momentary exposure with only 20 percent of the radiation exposure used now, takes “a very significant bite out of the risk element. That will probably arrive with the next generation of scanners.”
More information about cardiac function and coronary artery perfusion will follow that, Newton says. How well the heart contracts and other details will soon be extractable from CT. “I think it’s just getting started,” he says.
Rumberger anticipates increased ability to use advanced visualization software from any location, allowing for more convenient reading. Thin-client systems allow clinicians to log in on a standard computer from any location. “All of the heavy lifting is done by the server,” he explains. That breaks down the barriers of location, says Newton, and offers “the ability to move the images around to people who are wide awake or have particular expertise.”
It is common in cardiology to comment in reports on several elements, even when those elements are normal. So, better integration of the reporting and reading tools would be welcome, says Bush. “Measurements are thought to have some value,” so the ability to add to the report during interpretation rather than dictating all the details at the end would be helpful.
Aside from technological improvements, new applications may be on the horizon, says Lesser. “We’re going to try to see if 3D imaging can help not just with diagnosis but guide therapy.” Regardless of when the capability comes into practice, Lesser says the progress already made is “incredible.”