Significant technical and clinical innovations in CV CT continue to appear at a rapid pace, despite the struggling economy and continued pressure to reduce spending for medical imaging. Robust attendance at the July scientific meeting of the Society of Cardiovascular Computed Tomography in Denver suggested that enthusiasm was high for reports of new methods that reduce radiation dose and improve the diagnostic yield of cardiac CT.
Good payer news included an announcement from the Blue Cross Blue Shield (BCBS) Medical Advisory Panel, which concluded that patients with acute chest pain presenting the ED with low risk for acute coronary syndrome meet the BCBS Technology Evaluation Center’s criteria for CT angiography. This June 30, 2011, opinion clears the way for individual BCBS member companies to join many other payers in covering the use of cardiac CT for appropriate patients presenting the ED with chest pain.
Several presentations at the meeting addressed increasingly effective methods for reducing the amount of radiation delivered to patients during CV CT imaging. Using advances in detector design and image acquisition techniques, coupled with dramatically improved reconstruction algorithms employing intense digital processing for iterative reconstruction, General Electric, Philips, Siemens and Toshiba all now make systems that produce high-quality CT coronary angiograms using less than 1 mSv radiation — an almost inconsequential dose. Many of these protocols also use much lower volumes of iodinated contrast than traditional protocols, reducing both the expense and the risk for renal toxicity associated with cardiac CT. These new ultra-low radiation protocols may make CT perfusion imaging a clinical reality, as addressed in numerous scientific presentations at the meeting. Ricardo Cury, MD, of Baptist Hospital in Miami, is leading a large multicenter trial of CT myocardial perfusion. Constantly improving image quality also led to encouraging results from several investigators using CT to characterize the structure and quantity of atherosclerotic plaque.
Perhaps the most revolutionary new development at the meeting was a report by James Min, MD, of Cedars-Sinai Los Angeles and current president of the Society of Cardiovascular Computed Tomography, which compared calculation of fractional flow reserve (FFR) from standard CT coronary angiograms to FFR measured using an intracoronary pressure wire in the cardiac cath lab. Charles Taylor, PhD, formerly at Stanford University, has developed fluid dynamic models of the coronary circulation that can be processed using a supercomputer to produce FFR data strikingly similar to those measured in the cath lab. Min reported results of a recently completed multicenter feasibility trial comparing noninvasive CT-FFR measurements to invasive FFR. Further research is now under way to determine just how robust this method will be in routine clinical practice. Numerous recent trials have emphasized the need to assess the functional impact of coronary stenosis, not just visualization of the percent of luminal narrowing. Reliable and convenient assessment of FFR using standard coronary CT angiograms could revolutionize imaging in CHD, providing simultaneous assessment of anatomy and function, with significant reduction in the need for layered testing using stress nuclear, echo and CV MRI, as well as reducing the need for diagnostic catheter coronary angiography. FFR-CT could be a game-changer in this cost-conscious, evidence-demanding environment.
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