Innovations in imaging continue to advance field

Discussions on imaging technologies were a highlight at American College of Cardiology Foundation’s Integrated Cardiovascular Imaging Conference.

Issue: September 2005

SAN FRANCISCO — In recent years, advancements in imaging modalities have allowed for increased sophistication and more accurate pictures.

The American College of Cardiology Foundation’s first Integrated Cardiovascular Imaging Conference focused on the current state of cardiovascular imaging and future directions of this field. Four types of imaging — echocardiography, magnetic resonance, nuclear cardiology and computed tomography — were highlighted at the meeting.

Experts on the use of these technologies considered the current uses and looked ahead at probable innovations to come in the future.

Echocardiography

The use of echocardiography is widespread and is preferred by many doctors and patients because it is noninvasive, accessible and versatile.

Advancements and improvements in echocardiography are ongoing. James Thomas, MD, from the department of cardiology at the Cleveland Clinic Foundation, wondered what will drive innovation in echocardiography.

“We cannot change the laws of physics but we can improve data extraction,” he said. Advancements in echocardiography may include improved transducers and amplifier circuitry with less noise. Thomas said he expects to see smaller echocardiograph machines that offer the same features as current machines; he said smaller echocardiograph machines may increase functionality.

Other new developments in echocardiography include 3-D imagery, color Doppler quantification, new methods for measuring left ventricle function, contrast perfusion and targeted imaging. Wireless telemetry for real-time ultrasound review is also in development.

Magnetic resonance

Edward Martin, MD, director of cardiovascular MRI at the Oklahoma Heart Institute and clinical associate professor of medicine at the University of Oklahoma in Tulsa, spoke about the use of MRI. “The advantages of MRI include its high spatial and contrast resolution, its ability to obtain images in virtually any plane and large fields of view,” he said. “MRI also requires no ionizing radiation and is noninvasive and versatile.”

Cardiovascular MRI is beneficial for determining several parameters, including chamber size, global and regional left ventricle and right ventricle functions, volume and mass, cardiomyopathies, valvular function, pericardial disease, complex congenital heart disease and intracardiac shunts. “Cardiac MRI is a versatile imaging modality that can compete favorably with other more mature imaging modalities,” said Martin, adding that cardiac MRI can be thought of as a “one stop shop.”

Despite its benefits, MRI may not be optimal for all patients, including those with implanted cardiac devices such as pacemakers and implantable cardioverter defibrillators, neurostimulators, cochlear implants, bone growth stimulators, intracranial aneurysm clips, and women who are in the first trimester of pregnancy.

In the near future, advancements in MRI may include parallel imaging and real-time imaging.

Nuclear cardiology

According to guidelines from the ACC and AHA, nuclear cardiology can be used for general observations and may be particularly optimal for patients with chronic coronary artery disease.

Daniel Berman, MD, director of cardiac imaging and nuclear cardiology at Cedars-Sinai Medical Center in Los Angeles, said the use of nuclear cardiology imaging should be in patients with a likelihood of CAD and those who have an intermediate or high risk of cardiac death, as it may have higher sensitivity and specificity for determining these conditions. He recommended that patients be off anti-ischemic medications when undergoing nuclear cardiology evaluation.

Berman said studies have shown that nuclear cardiology imaging is equivocal to other methods of imaging for diagnostic or risk stratification purposes. “Nuclear cardiology imaging offers higher resolution and routine attenuation correction,” he said. “This method may also be optimal to determine a patient’s peak stress function and perfusion and may offer more data to determine the need for therapy.”

There are several limitations of nuclear cardiology imaging. Berman noted that it is not widely available and is more expensive than other methods of imaging.

Future developments of nuclear cardiology may include measurements of absolute myocardial blood flow, better image quality and improved efficiency.

Computed tomography

CT is beneficial for determining coronary calcifications, pulmonary embolism, pericardial disease, congenital heart disease, cardiac thrombi and tumors, global and regional function and valvular heart disease.

Matthew Budoff, MD, associate professor of medicine and program director of the division of cardiology at Harbor-UCLA Medical Center in Rottance, said there are five important uses of cardiac CT: “CT is used to screen patients with moderate Framingham risk, to identify patients who do not need further cardiac evaluation, to consider serial imaging as ongoing management tool, to improve compliance and as a noninvasive angiography,” he said.

CT is beneficial because of its high negative predictive power. “A negative test has a 98% chance of revealing normal coronary arteries on subsequent angiography,” Budoff said. “Thus, for lower probability cases, this test should provide a definitive answer most of the time.”

This method is also beneficial because it is fast and easy to perform and is noninvasive. CT offers good visualization of high-grade stenosis in proximal, medial and distal coronary segments and 93% of patients have good or excellent image quality. But CT often displays poor visualization of small vessels, especially those less than 1.5 mm. The radiation exposure may also be a negative aspect of this method.

Budoff said CT may be particularly beneficial following stress testing or after bypass surgery. – by Jay Lewis

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Presented at the American College of Cardiology Foundation’s Integrated Cardiovascular Imaging conference. Aug. 11-13, 2005. San Francisco.