Cardiac CTA should stay with radiologists

As a practicing radiologist for 28 years, I was happy to see the Point/Counterpoint repartee between Dr. Carter Newton and Dr. David Dowe in Diagnostic Imaging (September 2006, pages 24 and 25) regarding cardiac CT angiography. It's time the radiology community and the medical community at large understand the difference between real imaging professionals and doctors who believe that cardiac imaging is some type of divine entitlement.

Newton claims that cardiac CT images are so accurate that the imaging process is "out of physicians' hands" and the "images speak for themselves." This is akin to having a professional photographer take photographs on a disposable camera and develop them at Fotomat. Obtaining computer-generated high-quality "pictures" is a small portion of the entire imaging process, and Newton's view of this endeavor is shortsighted and simplistic.

Frankly, his comments are an affront to a specialty that invented, pioneered, and nurtured medical imaging. The creation of images is just the first step in the process. Attention to the details of technique, radiation safety, imaging parameters, and injection dose and rate is essential to ensure proper anatomic coverage. Imagers must apply appropriate interactive reconstruction techniques, adjust window and level, and use the best imaging and filming algorithms. Innovations are ongoing.

Once the images are obtained, they need to be reviewed within the framework of the clinical question to be answered, pertinent clinical and lab data, patient history, and so on. All of this information must be integrated with the imaging physician's prior experience-his or her visual data bank and knowledge of medicine-to arrive at a set of findings and diagnoses that make sense in both the imaging and clinical context. Many of these factors are subtle, and while some observations are apparent instantaneously, the integration involved is complex.

I am sure that Newton is aware of these factors and issues, but he chose to ignore this vital part of the process in his comments. If he really believes, as he stated in the article, that reading CT images is "easy" and "does not require even a medical degree," then we should let any adolescent with a video toy take a crack at it. After all, most imaging software was developed by the computer gaming industry.

Clearly, there is more to performing any imaging study than looking at the pictures. The most important part of the process involves the neural connection between the retina and the brain, which Newton has completely ignored in his discussion. This oversight denigrates both radiology and cardiology and is typical of the belief held by many cardiologists that virtually anyone with the right equipment can be a radiologist. To them, cardiac CT is just another ancillary test that will automatically generate a computer printout correct answer, because the images "speak for themselves," much like the results of a serum troponin or automated hemogram. According to this reasoning, any junior high school kid (or radiologist) should be able to manage a patient with a myocardial infarction, after a few minutes of learning the appearance of ST elevation and the time sequence of cardiac enzyme elevation.

IMAGING CRAFT

Imaging, cardiac or otherwise, is a skill and craft that takes years to cultivate. When Newton indicates that the "world of x-rays and tomography has been our stock and trade for 25 years," he should be reminded that radiologists have plied that trade for over 100 years. Radiologists were originally responsible for every imaging modality in the cardiology armamentarium: radiography, echocardiography, cardiac angiography, nuclear imaging, CT, and MRI. In the interventional realm, we invented the technique of intraluminal angioplasty and subsequently developed vascular stents and transcatheter thrombolysis, all of which are now staples of the interventional cardiologist diet.

Radiologists were the ones who taught cardiologists how to perform cardiac catheterization and how to interpret the coronary artery images that it generated. Most catheters used in cardiac angiography are named after the radiologists who pioneered and perfected the technique. One of the most common coronary stents is named for a vascular interventional radiologist. In fact, it isn't much of an exaggeration to say that cardiologists didn't really know where the heart was (in terms of imaging) until radiologists showed them.

These are some of the arguments for cardiologists performing cardiac CTA:

• Only cardiologists know and understand coronary artery anatomy.

• Only cardiologists understand the cardiac physiology such as wall motion and valve function.

• Only cardiologists can assess the clinical significance of coronary artery lesions.

• Cardiologists have years of coronary artery imaging experience.

I offer my counter to these arguments:

• Radiologists imaged and learned coronary artery anatomy long before cardiologists. We taught them how to do it. Any competent radiologist, particularly one with interventional/angiography experience, can thoroughly learn coronary anatomy in a matter of hours. After all, there are only three vessels in the heart. Cerebral vascular anatomy is much more complex, and we have been doing that for 70 years.

• Radiologists have been imaging the heart in motion for years, by both ultrasound and nuclear techniques. Ultrasound and MRI have assessed valvular abnormalities for quite some time, and radiologists are capable of evaluating the valve lesions that are detectable by CT. Myocardial imaging, including evaluation of wall motion, ventricular aneurysms, and pseudoaneurysms, has long been performed by radiologists.

• 3Having imaged plaque, stenoses, aneurysms, and dissections throughout the vascular tree for decades, radiologists are well versed in the clinical significance of vascular abnormalities, including entities such as arteriovenous malformations and fistulae. In fact, radiologists pioneered both the ultrasound-guided compression technique and intravascular thrombin injection for occluding AV fistulae.

• Cardiac CTA is primarily a CT vascular imaging technique, not an angiographic one. This gives an overwhelming advantage to radiologists, who have 25 years of CT imaging experience combined with conventional angiographic imaging experience.

HOW DIFFERENT IS THE HEART?

Radiologists have performed vascular imaging in every part of the vascular system for 75 years. As Dowe states in the article, we are considered the experts in imaging atherosclerotic disease. Why is the heart different? The answer to that question is it's not. Cardiologists would have us believe that imaging the cardiovascular system requires a code for which only they have access. While the heart is clearly exquisitely important, its vessels follow the same imaging rules and demonstrate the same imaging characteristics as any other organ. All of the body's arteries contain the same intima, media, and adventitia, and all may demonstrate fibrous, fatty, and calcific plaque, stenoses, dissection, occlusion, and collateral flow.

I believe that what this argument is really about is the perceived loss of self-referred cardiac imaging business (exercise stress testing, nuclear imaging, and echocardiography) and coronary arteriography. This is why the American College of Cardiology so quickly formulated its credentialing criteria. It wanted cardiologists to be able to jump into an imaging modality with which they have virtually no experience or expertise.

The American College of Radiology has not seen a need to rewrite its credentialing standards, since it knows that radiologists don't need their foot in the door. We have been practicing CT imaging for three decades. As I recently said to a combined group of administrators and cardiologists who want to have exclusive imaging rights to cardiac CTA in my hospital, my group of 24 radiologists has over 350 combined years of CT and vascular imaging experience. We have interpreted approximately three million CT scans. The cardiologists at our hospital have zero CT experience and have yet to interpret a single scan. In legal parlance, this is referred to as res ipsa loquitor.

In general, cardiologists have precious little training or interest in radiation/imaging physics, radiation safety and protection, image production, reconstruction, image quality control, or postprocessing. They appear to ignore what lies at the heart of the imaging process. Since the beginning of our specialty, radiologists have realized the importance of radiation physics. Radiology residents spend four years learning the principles of physics and then apply them throughout their professional careers. Physics, with all of its ramifications, lies at the core of our discipline, and without understanding and applying its principles, there is no imaging!

Perhaps the coup de grace to the cardiologists' argument for dominance in this arena is the fact that, by their own admission, they are ill prepared for and totally untrained in the CT evaluation of any noncardiac structures in the chest, chest wall, and upper abdomen. These include, but are not limited to, the lungs, pleural spaces, mediastinum, trachea, esophagus, hila, aorta, pulmonary artery, aortic arch branches, bony thorax, axilla, adrenals, kidneys, liver, and spleen.

Their answer is to have radiologists overread the noncardiac portions of the exams. Our response is simple. Why should a physician perform a study when he or she can't interpret the entire examination? Multiple studies have confirmed that up to 40% of cardiac CT examinations contain significant noncardiac findings. Radiologists can interpret the entire exam and make all of the significant observations and diagnoses.

Patients with low to moderate risk of coronary artery disease-the ideal candidates for coronary CTA-have a much higher likelihood of having a noncardiac abnormality as the cause of their symptoms. It is clear that the physician who can evaluate only the organ that is less likely to be the cause of the symptoms is not acting in the patient's best interests.

By asking radiologists to overread their studies, cardiologists once again underestimate our value, relegating us to the role of backup in the event of potential liability. I think cardiologists are finding that their radiological colleagues are becoming very reluctant to enter into such relationships.

As radiologists, we have always striven to provide the best possible diagnostic and therapeutic imaging care and service to our patients and referring physicians. We have seen many other physicians try to do what we have been specially trained to do. Unfortunately, the quality of care provided often reflected their lack of training and expertise. Radiologists are in a unique position to deliver high-quality cardiac CT imaging, because we can evaluate and integrate all of the vascular and nonascular components within the imaging field. We feel that our patients deserve to have an imaging study performed and interpreted by a medical imaging specialist.

Dr. Spira is a radiologist practicing in Ft. Lauderdale, FL.