Centennial's new open bore 1.5 Tesla MRI easily accommodates larger patients. While the new system still looks like conventional MRI equipment, with the patient inside the doughnut-shaped scanner, the diameter of the doughnut is larger.
Early this year, Centennial Medical Center added to its imaging arsenal open bore 1.5 Tesla magnetic resonance technology, and the result has been cardiac MRI capabilities that are unique in Middle Tennessee.
Centennial's Siemens system has a larger bore than traditional MRI systems. That's good news for larger and obese patients and for patients who suffer from claustrophobia or fear of confinement. "The actual patient size that the scanner will accommodate is much more like a CT scanner than a traditional MRI. We can actually fit patients up to 550 pounds into this scanner and take really high-quality pictures of their heart," said David Huneycutt, MD, who joined Centennial Heart in mid-2008. A specialist in cardiac MRI, Huneycutt received his medical degree from Emory University School of Medicine in Atlanta, where he was chief resident from 2004-2005. He also completed his cardiology fellowship at Emory.
"With an increasing number of obese Americans, oftentimes there is a pressing need for high-quality cardiovascular diagnostics on these patients. Many of them are at risk for heart disease and also might have symptoms that could be attributable to heart disease just by virtue of their obesity alone, including shortness of breath and exercise tolerance. So this scanner allows us to really take pictures of patients who otherwise we would have a lot of difficulty imaging," Huneycutt said. He added that current modalities, including echocardiography (which uses ultrasound) and nuclear cardiology, are "less than optimal and sometimes completely uninterpretable in this patient population." The same problem exists for CT scans, since the X-ray scatters and the picture quality suffers. That's just not the case with MRI. In fact, Huneycutt said the quality of MRI images of 450-pound patients is identical to those of 150-pound patients.
The secondary advantage of the open-bore design is the comfortable space – about 1 foot – between the patient and the scanner's edge. Even for patients who aren't large, many suffer from claustrophobia that's related to cardiovascular disease so the 1.5 Tesla Siemens system is an improved option. The design also allows for more flexibility — physicians may image patients feet first, head first or even lying on their stomach. The MRI can take a picture in any plane, offering doctors a variety of sequences and three-dimensional images of the beating heart in real time. It's the "best view possible," Huneycutt said, of the heart's chambers and the characteristics of the muscle.
"The Gold Standard"
For some but not all cardiac situations, there just isn't a substitute for an MRI. The imaging technique is not routinely available for all issues, however, because of the expense and expertise required.
"One of the strengths of MRI is that it remains the gold standard for both quantification of heart function as well as for assessment of scar within the heart muscle," Huneycutt explained. "This assessment of scar is very much linked to viability of the heart muscle, and this comes into play in folks who are contemplating stents or bypass surgeries." In short, physicians want to ensure that, before they restore blood flow, there's viable heart muscle capable of doing the job. "In many centers, this is the standard for evaluation of myocardial viability," he said.
MRI remains the most widely accepted modality for evaluation of congenital heart disease, as well as diseases and abnormalities of the pericardium. MRI also is useful to indicate coronary artery disease, cardiac masses and thrombi, aortic disease, cardiomyopathies and arrhythmia.
Two Centennial Heart surgeons, Christopher Jones, MD, and Gregory Bashian, MD, are using the new cardiac MRI capabilities pre-operatively to help create a high-resolution map of a patient's left atrium before an ablation procedure to treat atrial fibrillation. A catheter with a tip that creates a radio frequency is fed through a vein in the leg to the heart. Surgeons use the pictures to guide the catheters through the pulmonary veins, which vary widely from patient to patient.
"In selected patients, this ablation procedure can cure or dramatically reduce the frequency and severity of atrial fibrillation, the most common rhythm disturbance," Huneycutt said, adding that Centennial's use of cardiac MRI before ablation procedures "differentiates" the hospital. "That is not done in other centers, and we feel that this improves our effectiveness as well as safety and reduces the amount of radiation a patient is exposed to because, prior to the procedure, we know the number and location of the pulmonary veins."