Health Imaging & IT - October 2008 - (Page 20)

special section cardiac imaGinG Advances in Cardiac CT & MRI [ two mixed plaques (arrowheads) and calcification (arrow) in left anterior descending (lad) artery are visible on Mdct angiography maximum-intensity-projection (MiP) image. ao = aorta. Mr angiography MiP image shows significant stenoses (arrowheads) at sites of two mixed plaques shown in a and mild stenosis (arrow) at site of calcification shown in a. image and caption courtesy of the american roentgen ray society. ] “We’re starting to see a departure in the journals from the feasibility studies that have marked the field of cardiac imaging. We’re looking into evidencebased medicine, cost-effectiveness, and the prognostic value of cardiac imaging studies.” uwe Joseph schoepf, Md, associate editor, radiology A pair of articles in AJR (December 2007) explored the targeted use of MR angiography (MRA) after 64-slice CT angiography (CTA) in assessing the severity of focal calcific coronary lesions. An international team from the United States and China found that coronary MRA has higher image quality for coronary segments with nodal calcification than for coronary segments with diffuse calcification. In addition, their results showed that coronary MRA has better diagnostic performance than coronary CTA for the detection of significant stenosis in patients with high calcium scores. “The results open the door for future studies about the use of MRA for targeted site-to-site comparison studies after coronary CTA stumbles onto a blind spot caused by a high focal concentration of calcium,” wrote Andre J. Duerinckx, MD, in a commentary on the study. In March, the AJR published results of a study comparing CT and intravascular ultrasound (IVUS) for the identification and quantification of coronary atherosclerotic plaques. The study, conducted in Beijing, found that 64-slice CT has a good ability to identify and quantify these plaques, compared with IVUS. “While the reliable differentiation of the composition of individual noncalcified plaques by CT is limited, it may be used to help riskstratify and monitor patients with suspected or known coronary atherosclerotic disease,” Colletti says, commenting on the study. The utilization of CT for cardiac imaging has received a great deal of attention from the lay press this year, Schoepf observes. Much of the attention has been focused on the radiation dose received by patients during these procedures. “We still need to do everything possible to keep the radiation dose as low as reasonably achievable in these patients,” Schoepf says. A pair of articles published this year in Radiology offered clinicians the results of studies that examined dose-lowering techniques for cardiac CT. A team of physicians from Fairfax Radiological Consultants in Fairfax, Va., retrospectively compared image quality, radiation dose and blood vessel assessability for CTA obtained with a prospectively gated transverse (PGT) CT technique and a 20 Health Imaging & IT | october 2008 retrospectively gated helical (RGH) CT technique in the March issue of Radiology. The PGT method takes advantage of the large 40-mm volume coverage available with a 64-detector CT scanner, which enables complete coverage of the heart in three or four incremental 40-mm acquisitions. “By using this technique, the table is stationary during image acquisition and then moves to the next location for another scan that is initiated by the subsequent cardiac cycle,” the authors wrote. “The result is very little overlap between the scans, substantial reduction in radiation dose, and more robust and adaptive ECG gating.” The researchers found that the use of PGT, compared with RGH, decreased the effective radiation dose to the patient during a CTA procedure by 83 percent. In addition, they reported that the PGT technique improved image quality. A study published by Radiology in August from Hiroshima, Japan, demonstrated that prospective CTA can reduce radiation dose (79 percent) below that of retrospective CTA with dose modulation, while maintaining image quality and the ability to assess luminal obstructions in patients with heart rates of less than 75 beats per minute. “We’re starting to see a departure in the journals from the feasibility studies that have marked the field of cardiac imaging,” Schoepf says. “We’re looking into evidence-based medicine, cost-effectiveness, and the prognostic value of cardiac imaging studies.” A recent study (August 2008) from St. Vincent’s University Hospital Elm Park in Dublin, Ireland, applied an evidence-based practice (EBP) model to cardiac CT. The team investigated currently published cardiac CT literature and evaluated the technical and diagnostic performance of the modality compared with invasive coronary angiography. “EBP principles applied to the literature involving cardiac CT show the current generation of cardiac CT to have a high sensitivity and specificity with satisfactorily narrow confidence intervals for the detection of hemodynamically significant coronary stenosis in patients with low and intermediate pretest probabilities,” the authors wrote. Healthimaging.com http://www.HealthImaging.com

Table of Contents Feed for the Digital Edition of Health Imaging & IT - October 2008

Health Imaging & IT - October 2008 Contents The Enterprise News Update Top Trends in Health Imaging & IT - Topping the Competition Advances in Cardiac CT & MRI CVIS Spurs Innovation Technology Outlook People & Technology In Practice Reader's Resource

Health Imaging & IT - October 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.