The tug of war for cardiovascular imaging has not been kind to radiology. Although imaging of the heart and vessels originally resided in radiology, it soon became dominated by the echocardiogram and gamma camera and gradually migrated to cardiology. If cardiovascular imaging occurred in radiology at all, it was restricted to the nuclear medicine section.
As a result, hands-on exposure to CT and MR studies of cardiac anatomy and pathology fell by the wayside in radiology residencies. Except for those who have been actively involved in cardiac nuclear medicine, most radiologists have not dealt with cardiac anatomy and pathophysiology in any depth since medical school. Although radiologists review cross-sectional cardiac anatomy on CT and MR as part of the cardiothoracic section of radiology boards, a significant knowledge deficit remains in the general radiology community regarding the heart, coronary vasculature, and cardiovascular imaging.
"It's ironic because cardiac imaging is a huge area-half of the disease in the U.S. is cardiac. Yet radiologists have not been educated in cardiac disease to nearly the extent they have about abdominal or brain diseases. Unless they have been doing a lot of nuclear cardiology, they are lacking cardiac imaging experience in their practice," said Dr. E. Kent Yucel, director of cardiovascular imaging at Brigham and Women's Hospital.
But changes in technology, particularly the rise of multidetector CT scanning, are bringing cardiac imaging back to the radiology fold. And they are creating educational challenges for cardiologists as well.
Cardiologists are experienced in analyzing four-chamber views of the beating heart, but they may not immediately know what they're seeing on CT and MR images. Although cardiologists are well schooled in myocardial structure and function and clinical cardiac aberrations, they can't necessarily apply that knowledge to the interpretation of CT and MR scans. Many cardiologists just starting off with cardiac imaging don't fully understand the mechanics of MR or CT or how to run the right protocols for acquiring these images, said Dr. Norbert Wilke, director of cardiovascular MR and CT imaging at the University of Florida, Jacksonville.
Radiologists, on the other hand, know about the underlying MR and CT physics and the procedures for acquiring pictures, and they know how to view scans. But they are less familiar with cardiac disease and its manifestations. Although they can clearly spot an abnormality in the heart or the great vessels and coronary tree, radiologists don't necessarily come to an appropriate interpretation of it or understand how to put it in the context of the patient's clinical problem, Wilke said.
Nor do radiologists have much direct experience in the details of prepping cardiac patients-administering beta blockers to reduce the heart rate or using information from electrocardiograph leads to adjust scan time.
Some large academic medical centers are stepping in to close the cardiac imaging knowledge gap by offering cardiovascular MR and CT training to cardiology fellows and radiology residents and fellows. But smaller centers are not able to do that, and even some of the larger centers don't have the volume to support such education, said Dr. Pamela Woodard, an assistant professor in the chest radiology section at the Mallinckrodt Institute of Radiology, Washington University.
Also, the 16- and 64-slice multidetector CT scanners used for cardiovascular imaging are relatively new. Few imaging centers have broad experience with the machines.
"You have a fair number of people who have already been through radiology training and need to learn about cardiovascular imaging, along with people who come from imaging centers that don't do a lot of cardiovascular imaging. There is a learning curve, at least until radiology departments and cardiology fellowship training programs come up to speed," Woodard said.
FILLING THE EDUCATION GAP
The Manhattan Project is an initiative proposed by the Society of Chairmen of Academic Radiology Departments to address the education gap in cardiac imaging. Through the project, 12 academic medical sites across the country are offering week-long teaching workshops to give radiologists and cardiologists at least initial grounding in cardiac imaging through hands-on instruction, actually performing MR and CT scanning on patients with heart and coronary artery maladies.
Typical are the University of Florida's cardiovascular imaging courses. In addition to full-year, three-month, or monthly minifellowships, a three-day course focuses on advanced cardiac MR and CT imaging. This course includes perfusion and function protocols for rest-stress perfusion imaging and dobutamine cine studies for regional and global myocardial functional assessment. All the courses provide a complete array of postprocessing in a dedicated 3D lab with 12 workstations. Hands-on instruction is provided on how to process, display, and report cardiac imaging studies done by technologists and physicians.
Institutions such as the Cleveland Clinic and Stanford University provide full-year fellowships in cardiac MR and CT imaging for radiologists and cardiologists. Sponsored by the RSNA's Research and Education Foundation, the cardiovascular imaging fellowships allow radiologists to work with experienced cardiologists, radiologists, and technologists on state-of-the-art MR and multislice CT scanners in imaging centers that conduct thousands of cardiac exams a year. The Cleveland Clinic, for example, performs cardiac MR examinations on nearly 2000 patients and MSCT studies on more than 6600 patients per year. Stanford conducts about 15 CT studies a day.
As week-long educational efforts, Manhattan Project courses provide self-improvement opportunities for radiologists to begin building their knowledge of cardiac imaging, said Dr. Dieter Enzmann, chair of radiology at the University of California, Los Angeles.
But their short-term nature means these crash courses must leave out many intricacies of cardiac imaging. Participants get a sort of Evelyn Woods introduction to the subject and need more longitudinal follow-up to gain proficiency, said Dr. Richard D. White, head of cardiovascular imaging in the radiology department at the Cleveland Clinic.
"If somebody comes in with no prior knowledge of cardiac imaging and takes a five-day course or even a 10-day course, it doesn't matter. This person will just get an overview and get oriented. Let's add on a three-month course-he or she will be in a much better position to do at least 60% or 70% of the work. Is this person fully competent for complicated cases? Probably not. The individual would still need additional follow-up and practical training to solve all the problems associated with cardiac imaging," Wilke said.
For the most part, cardiologists and radiologists receive the same training. According to Wilke, 80% of the instruction at the University of Florida overlaps.
At the Cleveland Clinic, fellows in the cardiovascular imaging teaching program sit in on the same didactic lectures radiology residents receive on MR and CT. They participate in major general cardiovascular conferences, such as a local board review course, or major conferences on clinical issues, including atrial fibrillation and congestive heart failure. But the bulk of the training involves working with patients alongside skilled imaging teams and conducting related imaging-based research.
At Stanford, fellows participate in assessment of congenital heart disease, valvular disease, atherosclerosis of the coronary arteries, cardiomyopathies, cardiac masses, and pericardial disease. The fellows rotate though Stanford's 3D laboratory and work with five dedicated 3D imaging technologists who process more than 500 clinical cases a month. They learn how to operate 3D visualization and quantitative analysis hardware and software systems.
Fellowships in cardiac imaging are immensely popular. White fields calls almost every day from someone who wants to join the cardiovascular imaging program, but slots are limited by the lack of funding. In the first year of a cardiovascular tomography fellowship, the Cleveland Clinic was able to teach only three fellows: two cardiologists and a radiologist. Two fellows, both radiologists, are currently being trained.
Interest in cardiac imaging training is growing now that technological advancements have made MR and CT much more useful clinically. But cardiac imaging is no different from other areas of imaging in its educational demands.
"To be an expert in cardiac or cardiovascular imaging, the radiologists who perform the studies need to expand their clinical knowledge. But that's true for other radiology subspecialists, whether they are in pediatric, neurological, abdominal, chest, or musculoskeletal imaging," Enzmann said.
OBTAINING OPTIMAL STUDIES
Cardiac imaging is a developing and unfolding field. The imaging protocols that are best suited for capturing a dynamic aspect of cardiac function or evaluating myocardial damage or blood vessel patency are evolving. Although CT imaging tends to be more straightforward than MRI, questions persist about the best way to get optimal studies.
"Neither CT nor MRI is fully push-button. Cardiac imaging is not simply looking at a recipe or finding that if you follow a recipe closely, things will work out," Enzmann said.
Radiologists need to become acquainted, in particular, with techniques that will assure high-quality images, such as decreasing the patient's heart rate with intravenous or oral beta blockers.
Optimization of CT and MR imaging nevertheless tends to be relatively straightforward. More difficult is getting radiologists comfortable with viewing the moving heart, Yucel said. Because radiologists are used to viewing still images of anatomy, making a diagnosis from cine imaging of the heart in motion as well as its different segments takes some getting used to. It requires spending considerable time in an echocardiology lab looking at dozens of pictures of the moving heart to absorb all the issues and learn to recognize motion abnormalities.
Radiologists are accustomed to generating images in slices, but to make a diagnosis of coronary artery disease, they must obtain cross-sectional views along the course of arteries following circuitous paths that vary in every patient. Radiologists can't ask a technologist to generate 100 slices so they can go through them sequentially. They have to interact with a 3D data set on a workstation and view the coronary anatomy after multiplanar reconstruction to look for soft plaque and calcium.
CT scanners also spit out images at different parts of the cardiac cycle. An examination of the heart may consist of 10 sets of 200 pictures, each obtained at a different point in the cycle. While one of those sets of images may show all parts of the coronary arteries in a patient with a slow heart rate, viewing several large data sets on a 3D workstation may be necessary to clear all parts of the coronary artery in patients with irregular or more rapid heart rates, Yucel said.
To help radiologists learn to manipulate such large, multitemporal imaging databases, Yucel's cardiac imaging training program provides access to independent as well as vendor-specific workstation software. Radiologists can become familiar with software processing that matches their equipment at home or learn how to adapt processing to different computer software packages.
Understanding the roles of cardiac imaging modalities is a focus at the Cleveland Clinic's cardiac imaging fellowship program. Noninvasive coronary imaging is already a major application for cardiac CT in clinical practice, White said.
One benefit offered by cardiac CT is a strong negative predictive value, obviating catheterization for patients with no significant coronary artery disease who present with atypical chest pain and/or equivocal stress test results. Cardiac CT can also find early markers of atherosclerosis, such as soft plaque and remodeling, that would not be appreciated if the patient went directly to catheterization. And it can detect a high likelihood of significant stenotic disease that may not have been revealed by other modalities.
This growing niche for cardiac CT does not take business away from the cardiac cath lab. It enhances catheterization activity by confining the laboratory to diagnostic studies that precede interventions such as stenting or full diagnostic examinations necessary for later bypass grafting, White said.
Other roles for cardiac CT involve the evaluation of the venous anatomy in patients with a history of chronic atrial fibrillation who may be considered for a pulmonary vein isolation procedure, postprocedure assessment of venous stenoses, pre- and postoperative assessments of the thoracic aorta in patients undergoing stent-graft therapy, and examination of adult patients with congenital heart disease, pericardial problems, cardiac masses, or scar formation who cannot be studied by MR because of the presence of a defibrillator or pacemaker.
The Cleveland Clinic program stresses the importance of radiologists collaborating with other specialists in clinical teams. White points out that radiologists cannot afford to follow the more traditional route for radiology, which is to sit in their own departments and read scans. Radiologists engaged in cardiac imaging need to adopt the mindset of the clinician, rather than that of the imager, by interfacing with the clinical services when they are caring for patients and being aware of the referring physician's interest.
"The cardiologist doesn't want to be interrupted 30 times a day about a CT for pulmonary vein stenosis for the treatment of atrial fibrillation. Radiologists need to concentrate on the fundamental clinical issue that is being addressed and be ready to review the case when the referring physician comes down to radiology. And if there is something of great clinical concern, then radiologists need to seek out physicians and bring to their attention any bothersome sets of findings. So it's not just getting in the habit but getting the religion that being part of the clinical momentum is a key aspect of the radiologist's job," White said.
If radiologists want to be involved in cardiac imaging, they will have to become more in tune with the clinical implications of their work than they have in the past, he said. They have to be concerned less about doing the imaging and more about what imaging means.
"Cardiac imaging is the area that comes to the forefront right now because the pressures for clinical collaboration there are so vivid. But this is directly extendable to other areas of imaging, such as neurologic imaging, and I wouldn't be surprised if oncologic imaging is going to be feeling the same pressure," White said. "Cardiac imaging is taking the lead and showing that it's time for radiology to change its behavior pattern."