MGH Martinos Center for Biomedical Imaging 2017 | Page 13

Good News for PET Researchers:
Radiotracer Binding Is Less Sensitive to
Blood Flow Than Previously Thought
In a Journal of Cerebral Blood Flow & Metabolism paper
published in August, the Martinos Center’s Christin
Sander and colleagues resolved a longstanding question
in positron emission tomography studies.
PET has played a crucial role in receptor binding
studies, shedding light on a range of biological ques-
tions and contributing in important ways to the devel-
opment of new drugs. But there has always been an
open question in these studies as to the potential effects
of changes in blood flow on the delivery and washout of
PET radiotracers. This is significant because any such
changes during measurements could, in theory, influ-
ence accurate quantification of receptor binding.
Researchers have used computer simulations to explore
the potential effects but, because so far it is has been
technically challenging to simultaneously track receptor
binding and blood flow, reliable experimental data has
proved elusive. Now, though, using the state-of-the-art
simultaneous PET-MR scanner in the Center, Sander
and colleagues have shown they can measure receptor
binding (using PET) and blood flow (using arterial spin
labeling [ASL]) at the same time. In doing this, they
were able to determine the effects of changes in blood
flow on receptor binding studies.
The impact of blood flow, as they reported in the JCBFM
paper, was so small that it was not even measurable.
This will be welcome news to PET researchers as it puts
to rest the debate as to whether flow affects the delivery
and washout of PET radiotracers. In effect, investigators
can now interpret findings from the studies with more
confidence than ever before.
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