State-of-the-art imaging capabilities include the first hybrid 64-detector CT/PET scanner to be installed in the world
The Brigham and Women’s Hospital (BWH) Cardiovascular Imaging Center has recently upgraded its non-invasive imaging capabilities to include a state-of-the-art 64-detector CT scanner and the first hybrid 64-detector CT/PET scanner to be installed anywhere in the world.
These advanced imaging technologies will potentially play major roles in helping physicians evaluate patients with coronary artery disease (CAD). More detectors generally confer more speed, finer resolution, and the ability to visualize greater body volume in a single scan. With 64-detector CT angiography (CTA), it is possible to obtain clear pictures of all the coronary arteries,
including the smaller ones, and quantify atherosclerotic load. The addition of PET technology allows clinicians to assess the significance of coronary artery stenoses to make a diagnosis and management decisions. Marcelo F. Di Carli, MD, Co-Director of Cardiovascular Imaging at BWH says, “As powerful as these techniques are, it is not enough to be on the leading edge with the latest technology. It is also important to understand the best role for each technology and how to use imaging to benefit our patients.”
SPARC Trial
Dr. Di Carli is national principal investigator for a large prospective, multi-center observational study designed to elucidate the clinical value of four prominent diagnostic imaging modalities – SPECT, PET, PET/CT, and CT angiography – in the evaluation of CAD. The SPARC trial (Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles in CAD) will investigate these modalities with respect to post-test resource utilization and patient outcomes.
Approximately 4,000 patients with intermediate to high likelihood of coronary artery disease or known CAD who have been referred by their doctors for non-invasive imaging will be enrolled in the study. Patients will receive whichever form of imaging their doctors request, and additional testing or treatment as indicated by their imaging results. They will be followed for two years and surveyed at 90 days to determine whether catheterization or revascularization were required, and at two years to determine incidence of cardiac death or myocardial infarction.
Sharmila Dorbala, MD, Associate Director of Nuclear Cardiology at BWH and BWH site principal investigator for SPARC, has already recruited the first patients at the BWH study site. She says, “This is an easy trial for patients and their physicians. There are no investigational medications, and each patient receives only the imaging his or her doctor prescribes.”
Dr. Di Carli says, “SPARC’s large national data base will have sufficient power to allow us to examine the effects of geography on the utilization and effectiveness of different imaging modalities and the effectiveness of different techniques in diverse patient populations and sub-groups. We anticipate that it will provide important information about the benefits of each imaging modality to help physicians make informed clinical decisions and payers make appropriate reimbursement decisions.” For more information about referring a patient to the SPARC trial, please call (617) 732-0566 or visit www.sparctrial.org.
CTA
As the medical community awaits guidance from the SPARC trial, BWH clinicians are using their best judgment, based on extensive clinical experience and familiarity with the technology, to benefit patients. They are targeting 64-detector CTA as an evaluation tool for patients who present with chest pain and a low likelihood of an abnormal scan. The strength of CTA lies in its negative predictive value. A normal CTA excludes the presence of coronary artery disease, decreases the need for further testing, including catheterization, and serves as a guide for future medical management. CTA is not currently considered as a screening tool for asymptomatic patients.
PET/CT
A patient at moderate-to-high risk of CAD may benefit more from some form of hybrid imaging. Although CTA may pinpoint areas of atherosclerosis, it cannot determine whether these areas are causing cardiac ischemia. BWH physicians are targeting the PET/CT to patients whose evaluation is likely to require both anatomic and functional information. These may include patients who have had previous revascularization and are experiencing new, non-emergency symptoms, patients with congenital cardiac anomalies, and patients who exhibit discordance between imaging and symptoms.
Future directions
State-of-the art technology will take cardiovascular imaging into the molecular arena with the ability to visualize and target super-small structures. PET/CT can potentially detect both anatomic and biologic features of vulnerable plaque and, in the future, new radio-tracers may allow physicians to identify and treat these lesions before they rupture.
This development may also allow the use of PET/CT to assess early results of therapy. CT will reveal the landmarks from which biologic signals arise and PET imaging will read the signals to determine whether the therapy is working.
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