The New Rhythm of Cardiology: Cardiac CT

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 Cardiac CT is hot. According to Health Imaging & IT’s most recent Top Trends Survey, CT is the top technology buying priority for facilities nationwide. What’s more, nearly three-quarters of sites budgeting for CT plan to invest in a 64-slice system.

The rationale is clear. Sixty-four slice scanners open the door to non-invasive CT angiography, providing hospitals, cardiology practices and imaging centers a new means of diagnosing coronary artery disease. Scans are more economical than invasive angiograms, and they can provide clearer results than stress tests. What’s more, they may allow cardiologists to diagnose and treat cardiac disease at earlier stages, potentially improving outcomes.

There are other benefits as well. Medicine is a business, and owning a state-of-the-art CT scanner can differentiate a practice or facility from its competitors. A well-managed cardiac CT program can boost business, better the bottom line and open the doors to other works such as peripheral vascular scanning.


Cardiac CT: Past and present

CT angiography is not exactly new, but 64-slice systems make it clinically viable and relevant for most patients and many practices. Take for example Grapevine Cardiology, a 70 cardiologist practice in Dallas. The practice has performed CTAs for about six years. “In the early days, resolution wasn’t great, and software was primitive. And the scan required a 60 to 70 second breath hold,” recalls John Osborne, MD, director of non-invasive angiography and preventative cardiology. Despite the drawbacks of early technology, the promise of CT angiography was apparent, says Osborne.

Fast forward a few years. Sixty-four slice scanners have made CT angiography nearly routine and are reinventing cardiovascular medicine. The new systems offer dramatic gains in resolution; it’s improved to an exquisite 0.4 mm isotropic spatial resolution. And breath hold is a manageable 12 to 25 seconds.

The advances translate into improved diagnosis and a golden era for some cardiology practices. “Cardiac CT is a paradigm-shifting technology,” says Tony DeFrance, MD, medical director of CVCTA Education Center in San Francisco, Calif. Grapevine Cardiology, for example, has seen its practice grow 30 percent since December 2005, when it deployed four Philips Medical Systems Brilliance 64-slice scanners. On the patient care end, fewer patients are referred for invasive angiograms.

On the flip side, the clinical advantages and practice gains are associated with some challenges. The primary considerations stem from the massive size of CT datasets. Sites need to develop an image storage and management plan before deploying cardiac CT.
 

CT = early diagnosis and intervention

DeFrance was an early convert to cardiac CT. DeFrance began using CT in 2001 to image the coronary arteries and detect cardiac disease at earlier stages. Last year, DeFrance’s practice invested in Toshiba America Medical Systems Aquilion 64-slice CT scanner. DeFrance also teaches radiologists and cardiologists how to perform and interpret cardiac CTA studies at CVCTA Education Center.

“The primary patient benefit of cardiac CT is that it allows physicians to look into the arteries and detect plaque decades earlier than other studies such as an invasive angiogram,” reports DeFrance. Earlier detection can correlate with more treatment options and improved outcomes.

On the practice side, 64-slice CT can generate new revenue and provide a competitive advantage. And because the images facilitate assessment of peripheral vascular disease, installing a scanner can drive a hefty peripheral vascular business.

Finally, cardiac CT is economical. An average invasive angiography costs $6,000 to $8,000 compared to $600 to $800 for a coronary CTA, says DeFrance. As practices learn about the financial and clinical benefits of 64-slice CT, more are turning to the technology; some are using it to re-create their practice.


Enabling point-of-care cardiology

In 2004, Grapevine Cardiology surveyed the cardiac CT landscape. “The 16-slice scanners were on the cusp of delivering viable every day CT angiography,” notes Osborne. But the practice opted to wait for 64-slice scanners. “We knew 64 slices would hit the sweet spot of high-resolution, reliable imaging of the coronary arteries,” says Osborne.

The other key consideration at Grapevine Cardiology was the practice model. The practice aimed to implement point-of-care testing for its patients, reconstructing and sharing images with patients at the time of the scan. The conventional cardiology patient paradigm is inefficient, says Osborne. The cardiac care model requires three ingredients — physician, patient and a test with results. In a conventional paradigm, gathering the three players is a time-consuming and expensive process.

That is, the patient is referred and evaluated for chest pain on the first visit to the cardiologist. One to two weeks later, the patient undergoes a stress test. Cardiologist and patient wait for results. Abnormal or equivocal results require another visit and invasive angiography and cardiac catheterization. “The cardiologist can’t talk to the patient immediately after the catheterization because he’s sedated, so another visit is scheduled,” says Osborne. After four to six visits, multiple tests and several weeks, the cardiologist should have the information necessary to determine appropriate treatment.

Cardiac CT allows sites to combine the essential ingredients to accelerate the process and also improve accuracy. The cardiologist can order a CT scan at the first visit to gather the necessary clinical data. This model eliminates multiple steps to accelerate and improve care. One hitch for efficient point-of-care CT scanning is reconstruction time, says Osborne. If reconstruction time stretches to 15 or 20 minutes, the model becomes inefficient; the cardiologist gets bogged down, and patients become impatient.

When Grapevine Cardiology performs a CT angiography, a tech immediately processes the images at Philips Brilliance Workspace, which delivers three to four minute reconstructions. The rapid reconstruction process provides cardiologists plenty of time to review images with patients at the display station. “The images provide a great teaching point. The patients see exactly what we’re looking at and what the problem is,” sums Osborne.

Cardiac CT has value beyond initial diagnosis, says Osborne. Cardiologists may use CT scans to follow plaque after time. “It’s possible to use CT to see plaque reversal in as little as six months,” states Osborne.

“The technology has phenomenally changed our practice,” sums Osborne. Cardiac CT has become the definitive cardiovascular test at Grapevine Cardiology. The practice no longer relies on stress tests or diagnostic angiograms, and the cath lab is reserved solely for interventional procedures. Since deploying Brilliance 64, the practice’s total cath volume has decreased by 60 percent while interventional volume has increased by one-third. In addition, the approach makes interventional cardiology more efficient because cardiac CT means fewer normal cases proceed to intervention. That’s because normal cases that might have proceeded to the cath lab after an equivocal or abnormal stress test are identified during the CT scan. Cardiac CT also can aid treatment of severe disease that requires intervention. Grapevine Cardiology is beginning to tap into CT-guided intervention, using cardiac CT scans to determine stent length and width.


Cardiac CT delivers flexibility

Last May, Cardiovascular Group in Atlanta, Ga., installed a GE Healthcare LightSpeed VCT and became the first private group in the state of Georgia to deploy 64-slice CT. Prior to the LightSpeed deployment, the 16-cardiologist practice relied on a 64-slice CT at the local hospital for cardiac CT scanning, but the arrangement was far from ideal, says Director of CT and MRI Imaging Salil Patel, MD.

Cardiologists could use the hospital scanner for cardiac scans only; peripheral angiography, carotid and aortic scans were off limits. In addition, patients were forced to trudge through the hospital admissions process. “The in-house scanner is more available, flexible and convenient,” sums Patel. The group uses the scanner for several applications: coronary artery imaging, prior to electrical ablation and to assess complex disease prior to an invasive angiogram. And the scanner has allowed the practice to grow its peripheral vascular business.

Despite the benefits and array of applications, Cardiovascular Group realized that the scanner represented a financial risk. “We purchased the scanner because this is where cardiovascular medicine is going. We expected to lose money in the first 12 to 18 months,” says Patel. Nevertheless, the group is slightly in the black in under a year of scanning up to 15 patients daily.


The dual source approach

Despite the advantages of 64-slice CT, it is not ideal for all patients. For example, patients with rapid heart rates often require beta blocking prior to a cardiac scan. Siemens Medical Solutions Somatom Definition dual source CT scanner provides another option for this population — since it doesn’t require beta blocking in most patients — and tweaks the cardiac CT model.

In May 2006, New York University Medical Center (NYU) of New York City deployed Siemens Somatom Definition CT scanner. The scanner changes the conventional approach to CT scanning that relies on a single x-ray source and one detector. Definition pairs two rotating x-ray sources and two detectors oriented at 90 degrees from each other. The end result of the new configuration is improved temporal resolution. “It takes half the time to acquire images, and there’s less blurring, so overall resolution is better,” confirms M. Barbara Srichai-Parsia, MD, cardiologist and associate professor of radiology and cardiology at NYU.

One of the primary benefits associated with Definition is the ability to scan patients without medication to slow the heart rate. Heart rate affects image quality, with faster rates translating into poorer scans. The conventional workaround is to administer beta blockers to slow the heart rate. But slowing the heart rate can slow workflow.

“Often, we didn’t know if the patient would require beta blockers until he arrived, so we required patients to arrive 90 minutes prior to the scheduled cardiac CT scan,” says Srichai-Parsia. The protocol allocated 20 to 30 minutes to paperwork and 60 to medication administration if necessary. If a patient required beta blocking, staff administered oral medication, asked the patient to wait 45 minutes and re-checked the rate prior to scanning.

The ability to eliminate beta blockers has improved workflow, says Srichai-Parsia.  Patients arrive 20 to 30 minutes prior to the scan to complete paperwork. “It’s very rare to give beta blockers because we can scan patients with heart rates up to 100 beats per minute with Definition,” confirms Srichai-Parsia.

Other patient populations benefit from the dual-source approach, too. For example, not all patients respond to beta blockers, and the medication is contra-indicated for patients with asthma or low blood pressure. In some cases, patients were referred for an invasive angiogram rather than a 64-slice cardiac CT scan. In others, the center proceeded with the scan but could not guarantee diagnostic quality images due to the rapid heart rate. Finally, sometimes physicians based decisions about catheterization or medical treatment on the initial stress test, which may not provide the diagnostic accuracy of other studies. 


Storage issues

Cardiac CT generates an enormous volume of data. Raw data alone can amount to 20 to 25 gigabytes (GB) of data, says DeFrance. And a single cardiac CT study can generate 3,000 to 4,000 separate DICOM images. The data onslaught forces sites to choose. How much data should be stored? Saving all raw data and processed images does provide the physician with the data necessary to complete reconstruction at a later date. On the downside, it requires a significant amount of storage. The decision of what to save and where varies by site.

As an academic medical center and research institution, NYU saves all cardiac CT studies on PACS. “Storage is a concern for regular practices,” admits Srichai-Parsia.

Like many practices, Grapevine Cardiology wrestled with the decision about how much CT data to store. “We decided to save every byte of data,” says Osborne. “The ability to reconstruct at a later date is safer. Plus, storage costs are falling.” The practice’s 3,000 cardiac CT scans require about 8 terabytes (TB) of storage.

The practice also invested in a web-based PACS in conjunction with its 64-slice CT scanners. The new system allows cardiologists to recall data from the office, cath lab or home and share images with primary-care physicians.

Cardiovascular Group is somewhat unique; the practice deployed 64-slice CT without PACS. “Our next step is an electronic medical record this summer. Then, we’ll look at PACS with an eye toward integration with the EMR,” explains Patel. As a result, the practice relies on a temporary solution, saving processed data with reconstructed phases on magneto optical disk (MOD). The group plans to transition into more economical CD or DVD storage prior to PACS. A 10 megabit internet connection provides the speed necessary to share studies with the private radiology group that overreads for the cardiologists.

DeFrance’s practice does not save raw data. After the scan, technologists use the raw data to create 15 to 20 reconstructions to send to the cardiologist for interpretation. The interpreting physician flags several images for archiving; raw data and other reconstructions are not saved. “The key is to get everything needed for diagnosis in the first few days after the scan,” states DeFrance.


Future directions

Despite all of the promise and tremendous market penetration, cardiac CT remains in its infancy. In the next few years, cardiac CT will continue to evolve and could demonstrate new application and benefits. For example:

Cardiologists could use different energies on dual-energy scanners to better define tissue composition and differentiate calcium, contrast and water. In addition, the ability to use dual energy to remove calcium could create high quality images as calcium can obscure/interfere with image quality, says Srichai-Parsia.

Currently, CT focuses on the most common site of cardiac disease—the coronary arteries. But the scans acquire additional information about valves, cardiac anatomy and function. CT scans could be applied to these areas particularly when other studies such as echocardiograms or MRI scans are inconclusive. CT also could measure vulnerable plaque and help determine which patients are at the highest risk for a cardiac event.

“Physicians are starting to figure out how to use CT to assess function and viability, but the real leap will come with increased detector rows,” predicts DeFrance. A 256-slice system will image the entire heart in the first rotation of the gantry and allow physicians to view perfusion with the next rotation. At least two are in development — stay tuned.


The 64-slice Decision
A 64-slice CT scanner represents a significant investment for any practice or hospital. Deciding whether or not to take the leap requires a careful analysis of the situation. Tony DeFrance, MD, medical director of CVCTA Education Center in San Francisco, Calif., identifies some of the essential criteria to consider.

Step 1: Create the business model. How will the scanning site operate and generate business? Will it partner with other physicians? A hospital? Is the group large enough to operate a CT scanner, or will the investment require additional staff? How do Stark laws affect the model?

Step 2: Run the numbers. Can the scanner generate a volume to support the investment? A 64-slice CT scanner requires a minimum of five to eight studies a day to break even, says DeFrance.

Step 3: Assess the physical space. Can the scanner be placed on site, or does it require a build out? Don’t forget to include these costs in the financial assessment.

Step 4: Evaluate IT readiness. The practice should be prepared to manage and store large datasets. PACS, redundant storage and IT support to manage data and handle integration are essential.

Step 5: Take it to market. Cardiac CT requires one or more physician champions. Referring docs have heard about 64-slice CT but don’t necessarily understand how to use or order studies. The build-it-and they-will-come model is not a base for success. The practice should plan to schedule multiple talks about the benefits of 64-slice CT.