Reflecting on a year of cardiac imaging

How do you measure a year's progress? While a difficult task, researchers from the Mayo Clinic in Rochester, Minn., attempted to put together a year in review for cardiac imaging, concluding that use of an integrated, multimodality approach still may be best for solving the majority of imaging’s clinical problems.

The review, published May 22 in the Journal of the American College of Cardiology, evaluated literature on myocardial perfusion imaging (MPI) with SPECT, PET, CT and MRI. Specifically, Raymond J. Gibbons, MD, of the Mayo Clinic, and colleagues looked at how patient safety has evolved, including how to stamp out radiation risk for SPECT patients.

The authors referenced a study by Berrington de Gonzalez et al on cancer risks from the current levels of SPECT scans in the U.S. While the lifetime risks varied by type of scan and age, it was estimated that the 9.1 million SPECT studies performed per year in the U.S. could result in 7,400 additional future cancers. The authors said that the cancer risk of an MPI scan should be balanced against the benefit of the test.

In addition, the review pointed to new CT research that used portable devices to evaluate patients with chest pain. The pilot study, performed on 102 patients, looked at the accuracy of evaluating coronary CT angiography (CCTA) with a mobile handheld phone device. Compared with traditional image review, image interpretation on the mobile device “showed a nonsignificant trend toward reduced specificity.”

The researchers also discussed two different studies on stress imaging for ischemia and CCTA. Van Velzen et al performed stress SPECT and CCTA imaging in 514 patients, 27 percent of whom had ischemia detected by SPECT. The presence of a 70 percent or more stenosis by CTA was associated with ischemia. In another study, Kajander et al performed PET and CTA in 107 patients and found that hybrid imaging with PET and CTA was more accurate than either CTA and PET alone.

The researchers also outlined the following points from this year’s cardiac imaging research:

• CT for vascular structure and function: Direct visualization of coronary artery plaque with CCTA may identify morphologic features that predict plaque rupture and help to identify previous rupture.
• CT for ventricular function: The higher temporal resolution of cardiac CT imaging with current scanners can permit better imaging of global and regional myocardial function.
• Diagnostic CAD and CT calcium score: Advocates of coronary calcium scoring (CAC) in asymptomatic individuals have suggested that it can improve the treatment of risk factors. For example, Rozanski et al found that having multiple risk factors showed favorable changes in the CAC group when compared with an existing practice group. Costs were also similar between the two groups.

“Within the past year, there have been multiple new and revised clinical practice guidelines, position statements, and appropriateness criteria published relating to the modalities covered in this review,” the authors wrote. However, they noted that the single most important may be the new American College of Cardiology Foundation and American Heart Association practice guidelines that spoke to the treatment of asymptomatic patients without coronary artery disease. The guidelines included Class IIa recommendations for CAC in patients with intermediate Framingham-risk scores and patients with diabetes.

The authors summed that they hoped the articles will help provide better imaging in everyday clinical practice. The review joins seven other reports that have highlighted important imaging research.