SAN FRANCISCO — The near future of nuclear cardiology will be a bright one, with several important developments expected within the next 3 years, Manuel D. Cerqueira, M.D., said at a cardiovascular imaging conference sponsored by the American College of Cardiology.
New technology and improvements to current technology will lead to more information and greater efficiencies, said Dr. Cerqueira of the Cleveland Clinic.
He highlighted a number of advances:
▸ Attenuation from the breast and diaphragm and scatter from the liver and gut are big problems, especially in women and obese patients. Scanners with combined single-proton emission computed tomography (SPECT) and CT are beginning to address these issues.
A combined, six-slice, SPECT/CT provides high-quality SPECT images with attenuation, scatter, and resolution correction. It also provides calcium scoring and CT coronary angiography.
But these scanners are expensive, quite large, and require shielding. “We had to basically take two imaging rooms and combine them to put this system in place,” Dr. Cerqueira said, adding that new, smaller systems will soon become available.
▸ PET scanners and combined PET/CT scanners will also make important contributions to cardiology. PET has much higher spatial resolution than SPECT, about 4–5 mm, vs. 16 mm. Attenuation correction can be quite accurate with these systems, and they can be used to make precise measurements of absolute myocardial blood flow and coronary flow reserve. This is important in the context of balanced disease, which is otherwise difficult to diagnose.
▸ Single acquisition rest/stress testing using two isotopes may soon become a reality. Dr. Cerqueira envisions a protocol involving an initial infusion of 4.5 mCi of thallium-201, followed 30 minutes later by a stress test. At the conclusion of the stress test would be an infusion of 9.0 mCi of technetium-99m, followed 30 minutes later by the acquisition of a rest image.
▸ Just a stress study, with no accompanying rest study, could be used to improve efficiency in certain patients. The best candidates would be patients judged to be of low risk on the basis of risk factors, calcium scoring, or biomarkers. If the stress study is normal, they wouldn't need a rest study, but if the stress study is abnormal, management decisions could be made on the basis of that study alone, or a rest study could be ordered.
▸ New systems to image vulnerable plaques may soon become a reality. Several constituents of vulnerable plaques provide inviting targets for radiotracers. These include LDL cholesterol, oxidized LDL cholesterol, HDL cholesterol, membrane components of macrophages such as metalloproteinases, G-protein signaling or tyrosine kinase from smooth muscle cells, and clotting components.