Cardiac CT & MR: Defining the Strengths

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Both cardiac CT and MR imaging are poised for continued growth. Efforts to improve MR’s simplicity and reduce the radiation exposure associated with CT will keep drawing both cardiologists and radiologists into the fold.

“Cardiac CT is experiencing enormous clinical growth,” says James Min, MD, assistant professor of medicine in radiology at Weill Medical College of Cornell University and director of cardiac CT at New York Presbyterian Hospital in New York City. “As more data accrue on CT, people are starting to gradually more and more see the great clinical impact the test can have on patient care. The test will become even more popular. Even now, the images are just exquisite.”


Show them the money



One drawback to cardiac CT is reimbursement or the lack thereof. The Centers for Medicare & Medicaid Services has said that it might consider the technical component of the exam to be the median average of local Medicare. That would come to $312.

“If reimbursement is not in that ballpark, nobody is going to buy a scanner,” says Min. Reimbursement has proven to be “a moving target,” he says. Medicare assigned experimental billing codes to drive data collection based on utilization patterns. Other payors then said that since Medicare considers the procedure experimental, they won’t pay. A “final” national coverage determination expected next March will probably just keep the issue in limbo, Min says.

Meanwhile, research has shown that the test is highly accurate and can rule out obstructive coronary disease. “We’ve seen a high amount of clinical acceptance,” Min says. In fact, the Society of Cardiovascular CT, formed in 2005, already has more than 4,000 members from a pool of 30,000 to 40,000 cardiologists in the United States. “Clearly, people like this test and think it’s going to be useful in managing patients with cardiac conditions.”

Min uses 64-slice GE Healthcare LightSpeed VCT and VCT XT with SnapShot Pulse and the GE Healthcare Advantage Workstation. The XT version offers prospective axial gating. By only exposing the patient at brief points in the heart’s cycle, radiation dose is reduced by 80 to 85 percent. He plans on purchasing another 64-slice scanner, solely for cardiac imaging, for an outpatient imaging center.

“We anticipate growth. We’re of the mind that it’s better to establish practice patterns early and worry about the money later.”

It can be tricky deciding when to jump into a new modality. Currently, cardiac CT is not a big moneymaker at most facilities, says Arthur Stillman, MD, professor of radiology and director of cardiothoracic imaging at Emory University School of Medicine in Atlanta, Ga. Stillman installed a Somatom Definition 64-slice scanner from Siemens Medical Systems in January. Depending on their situation, clinicians may want to wait until reimbursement improves. However, there is an advantage to being the leader in the local market. “Once established, it’s a powerful position to be in.”

Min favors getting into cardiac CT early. The private facilities that have made it work financially first and foremost provide a good service, he says. “The technology is there. If you wait four years and somebody else has set up shop—referral patterns are hard to break.”

Despite his satisfaction with the scanner, “until third-party payors are on board with this, we’re not going to see a lot of rapid growth,” Stillman says. More research on outcomes should help push payors along, he says. The technology is good for two large groups of patients: acute and chronic. “Most people don’t see this as a screening test for the worried well,” he says. “It probably isn’t worth the cost or even the radiation risk. But for someone with chest pain, it really changes the dynamics.”


Managing chest pain


Stillman says there is a lot of interest right now in acute chest pain. Patients with no changes seen in an electrocardiogram and unchanged enzymes make the cause of their chest pain unclear. “Oftentimes, these patients are admitted, they have multiple tests and are ultimately sent home because they don’t have a cardiac cause for chest pain. It’s very costly to do all of that.” Coronary CT angiography’s high negative predictive value makes it safe to send these patients home and several studies have demonstrated that.

Those with chronic chest pain are a much larger group. Up to 85 percent of patients at the typical cardiac cath lab don’t have acute chest pain. The COURAGE study, published earlier this year in The New England Journal of Medicine, found that the use of drug therapy is just as effective in preventing heart attacks or death when compared to a combination of drug therapy and stent implantation. “Those patients who had their angiography and stents could have been equally well treated medically at a substantial cost savings. You can argue that you can just document coronary disease, treat it medically and cath them later if necessary.”


MR knowledge needed


Cardiac MR also is growing, but the biggest obstacle is the small number of locations where clinicians can train, says Tony Fuisz, MD, cardiologist at Washington Hospital Center in Washington, D.C. Fuisz uses the MR suite from Philips Medical Systems as well as 1.5T and 3T scanners from Philips.

“A certain amount of technical background and knowledge is needed to perform these studies well but the number of places to learn is small,” he says. To address the problem, the American College of Radiology is ensuring a radiology presence in cardiac MR by including the modality on the exams given to graduating radiology residents. On the cardiology side, there is an effort underway to include cardiac MR in training programs. Despite these efforts, the modality “almost always requires someone to invest more time to learn.”

Cardiac MR has taken a lesson from CT, which offers one-button studies, says Fuisz. “Cardiac MR has gotten significantly simpler in the last 10 years.”

Once learned, the modality is good for a wide range of patients who are potential candidates. “In any given day, we might go from a patient with a complex congenital heart problem to a patient with chest pain and enzyme rise and might diagnosis a myocardial infarction.” The wide range of applications separates cardiac MR from cardiac CT. Fuisz says that the focus in cardiology is moving away from treating patients with catheters and other invasive procedures and toward earlier diagnosis of problems—at a point where they can be effectively treated with pharmaceuticals.


A novel technique


Timothy Albert, MD, director of cardiovascular imaging center at Ryan Ranch in Salinas Valley Hospital, Salinas, Calif., and assistant consulting professor of medicine at Duke University, looks at utilization of cardiac MR. “For cardiologists, it’s a very novel technique,” he says. He has worked to simplify it, define protocols and make the uses clear.

Albert has been working with Toshiba America Medical Systems for about a year and uses the company’s Aquilion 64-slice scanner and Vantage MR system powered by Atlas. He did an advanced fellowship at Duke University at their cardiovascular MR center and then started the cardiovascular imaging center in Salinas. He now works with both Toshiba and Duke in a joint research relationship.

“Even amongst physicians, there is deep confusion between CT and MR. I look at them as being synergistic tools,” he says. There is a lot of overlap but they also have unique strengths they bring to cardiovascular patients. MR is used extensively for cardiac valve assessment, heart structure assessment, scar from prior heart attacks, and diagnosis of a previous heart attack. “We are finding that more and more patients have silent myocardial infarctions (MIs),” Albert says. A recent study showed that about 20 percent of people over 70 have had a silent MI and the only way to definitively diagnosis that is with MR.

Albert also is working on setting up stress MR/perfusion testing. “MR is the newest tool for stress testing,” he says, because it allows for viewing of structure and function and higher resolution images of blood flow to the heart.

Physicians struggle with how MR fits into their practice, says Albert. “MR has so many different applications and affects so many different tests we already do. It’s hard to pin it to one category.” MR, however, has the benefit of having well-established and universally accepted billing codes. “MR is maybe a little harder to apply in practice but the billing isn’t as unknown.”


Coming soon


Both CT and MR are going to be dominant technologies in cardiovascular imaging, says Albert. While vendors are working on reducing the radiation exposure involved in CT, “I still think MR has the potential to do all of these things and do them more safely.” MR has to achieve higher resolution coronary imaging, he says, but “that’s something that’s being worked on aggressively. Once that hurdle is overcome, you’ve really got MR doing a lot, if not everything, CT was doing without the inherent risks of CT.”

Albert agrees that MR will be better than CT in the future. Since age is the most common predictor of coronary calcification, the Baby Boomers may not be the best population for CT. Plus, anyone with kidney problems will have a problem with the contrast required for CT.

Both technologies need further development, says Min. “64-slice is going to be the workhorse for the next 4 to 6 years. There are definitely going to be advances in spatial resolution, number of detectors, maybe even a complete rehaul of engineering design. But, the next true generation of scanners will come in 5 to 7 years, not 3 to 5.”

A bigger issue than technological improvements might be an increasing need to image patients. “The number of patients far exceeds the number of individuals trained to evaluate the images,” says Stillman. Fortunately, interest in education is growing.

 

Cardiac CT and MR: What’s in the Pipeline
The major vendors in CT and MR are working fast and furious to improve the technologies for the burgeoning cardiovascular imaging demand. From reducing dose in CT to factoring in data management, companies are addressing virtually every concern.

Before the advent of coronary CT, MRI was growing pretty rapidly within the cardiology segment, says Nancy Gillen, zone general manager for Siemens Medical Solutions’ northeast region. MR is coming back into prominence, she says, but CT is still the dominant modality. That may change because MR can do perfusion and certain other diagnostic tests better and with no radiation.


New apps, simplification

Within MR, there is a constant push to see whether there are new applications in cardiology and to improve ease of use, says Gillen. “MR is more complex so there needs to be a greater understanding of the technology.”

Adrian Knowles, MR clinical development leader for GE Healthcare, echoes Gillen on MR’s need to improve ease of use. “Ultimately, MR is a more complex procedure but we’re really trying to get close to the simplicity of CT.” Right now, he sees 1.5T MR as the mainstream technology, but 3T “will grow rapidly over the next few years,” he predicts.

MR beats CT in its multiplanar reformatting capabilities. It also can utilize multiparametric information acquired from different mechanisms which isn’t possible with CT, says Knowles. MR lets users study morphology, tissue characterization and viability, which has a big impact on cardiac applications, says Piero Ghedin, MR advanced applications specialist for GE Healthcare. Those are unique features of MR—the ability to quantify blood flow.”

Gillen points out that the IT aspect of cardiovascular imaging is critical in diagnosing and managing patients. “All of this information is great but we need to bring it together in one place to look at over time.” Knowles, too, looks to improvements in workflow for cardiac MR reporting and post-processing. “That’s where we see the bottleneck moving,” he says. “Away from acquisition and to review of images.”


CT in the crystal ball

On the cardiac CT front, Don Reed, product manager of cardiac CT for Philips Medical Systems, says that the market isn’t growing as fast as it was in 2005 and 2006, but he still anticipates growth—probably by early 2009.

Reimbursement issues played a role in that slowdown. “As a payor, the government is looking at CT as such a diverse and easy diagnostic tool, that it’s concerned there will be overuse,” says Reed. Hopefully, outcome studies due out soon will show that CT is cheaper and more accurate than other tools, thereby driving better reimbursement.

Philips is working on whole-organ coverage, lower radiation dose, low temporal resolution and high signal-to-noise ratio, says Reed. “You need to have something so simple to use that anybody, any technologist or physician, can access that information. That’s what Philips is driving toward.”

The drive for lower radiation led GE to bring its SnapShot Pulse technology to market earlier this year, says DeAnn Haas, global CT product marketing manager. Users can switch from helical to gated imaging, which reduces radiation by 70 percent. Less than four months after its release, more than 150 customers have installed SnapShot Pulse, she says.

“It’s very exciting in the world of CT because dose is a lot lower than it ever has been before,” says Haas. Looking forward, GE is focusing on developing ways to see more, know more and reduce dose. For example, today clinicians can determine whether a patient has greater or less than 50 percent stenosis or less than 50 percent. The goal is to get a more specific idea of the extent of stenosis.


256 is coming

There’s been lots of talk over the past couple of years about the 256-slice CT scanner in development by Toshiba America Medical Systems. After a successful beta trial at Johns Hopkins earlier this year, Robb Young, senior manager of the company’s CT business unit, says efforts are underway to have the system in production by next summer.

256-slice CT can capture the whole heart in a single heartbeat for a much lower dose of radiation. That could reduce the number of tests patients require for better control of costs. “If you can get your answer without going to nuclear medicine and MR and everything else, it’s better for the patient and for the hospital,” says Young. “Buyers also have to consider investing in capital equipment that can do a myriad of applications. As hospitals and businesses are looking at investing in technology, they’ve got invest in systems that give the widest range of applications to maximize their return on investment.”

New study results will give a better algorithm of which patients can benefit the most and should help with reimbursement, he says. The Core 64 study at nine centers blindly compared 64-slice coronary CTA to cath lab results; results are expected shortly.


Stay tuned

With this year’s annual RSNA meeting coming up soon, CT and MR vendors are sure to offer new features and enhancements for both technologies. To be sure to get the latest RSNA news, register for Health Imaging News at subs.HealthImaging.com.