PET goes subcellular
By Catherine
Carrington
Nuclear cardiology has built its reputation on quantifying myocardial
perfusion and function. In coming years, however, its depiction of the heart
will be far more finely drawn.
“This is going to be an era driven by molecular biology and genetics,
just as the previous era was driven by physiologic principles of coronary flow
and physiology,” said Dr. Barry L. Zaret, cardiology chief and a professor
of diagnostic radiology at Yale University.
Using radiotracers linked to antibodies and other novel compounds, nuclear
imagers will be able to identify unstable plaque, track angiogenesis, assess
gene expression, and determine whether myocytes are ischemic, viable, or
undergoing programmed cell death, Zaret said.
Dr. Sam Gambhir, director of the Crump Institute for Molecular Imaging at the
University of California, Los Angeles, is developing a method that would use
radiolabeled protein probes to track the effects of gene therapy. Already being
tested in humans with cancer, the technique is poised to expand into cardiology.
It uses an innovative approach developed by Gambhir and colleagues in which an
engineered piece of DNA—a “reporter” gene—is linked to a
therapeutic gene. Once the therapeutic gene reaches its target, the reporter
gene spreads that news by producing a protein that mates with a radiolabeled
probe, which can be detected by PET. [Fig. 1]
Ultimately, Gambhir foresees cardiac molecular imaging becoming a form of
customized medicine.
“We will have individualized imaging,” he said. “We will have,
based on your exact genes (and) your exact heart disease, imaging probes for
you. And those probes will be customized for you.”
