Noninvasive imaging strategy detects dangerous blood clots in the body
Recent study verifies technique's potential in patients with atrial fibrillation.

Date:
November 1, 2021
Source:
Massachusetts General Hospital
Summary:
Investigators have developed and tested a targeted contrast agent
that can detect blood clots in the hearts of patients with atrial
fibrillation, or an irregular heartbeat. The strategy could be
used to find clots in other parts of the body as well, such as in
vessels that, when blocked, can lead to stroke.



FULL STORY ========================================================================== Atrial fibrillation -- an irregular and often rapid heart rate -- is a
common condition that can cause clots to form in the heart that may then dislodge and flow to the brain, potentially leading to a stroke. The
standard way to detect these clots requires patients to be sedated and
to have a fairly large tube inserted down the throat and esophagus for
a transesophageal ultrasound.

Investigators at Massachusetts General Hospital (MGH) have now developed
and tested a targeted contrast agent to detect and image these clots noninvasively.

They verified the potential of this strategy in a study published in JACC: Cardiovascular Imaging.


==========================================================================
The agent has a strong affinity for fibrin, a component of blood clots,
and is detected with a radioactive copper tag. "The idea behind the
technology is that the agent will find and bind to blood clots anywhere in
the body -- not just in the heart -- and make the clots detectable like
a bright star in the night sky," says senior author David Sosnovik, MD,
FACC, director of the Program in Cardiovascular Imaging within MGH's
Martinos Center for Biomedical Imaging and an associate professor of
Medicine at Harvard Medical School. "In some ways this is analogous
to doing a smart search with a search engine such as Google, where the
search terms one uses guide the search. We inject the agent into a small peripheral vein and it circulates throughout the human body on its search
for clots." If it doesn't find any clots, then it's rapidly excreted from
the body; however, if it finds a clot and binds to it, clinicians can
detect it with an imaging technique known as positron emission tomography.

Sosnovik and his colleagues first examined how the agent reacts
(specifically, its metabolism and pharmacokinetics) in eight healthy volunteers. After injection, the agent was initially stable within
the body and then was cleared from tissues within several hours,
suggesting that it was safe. Next, the team administered the agent to
patients with atrial fibrillation, some with clots in the heart and some without. Imaging tests of the heart revealed bright signals within the
clots that were not seen in patients without clots.

"Obviously much more work and many more studies will need to be done
before this changes routine clinical practice, but this first-in-human
study is an important step," says Sosnovik. "Importantly, this smart
or molecularly targeted agent can be used to detect clots anywhere in
the body." Sosnovik stressed that the multidisciplinary nature of this
project was critical to its success, with vital roles played by diverse scientists, including Peter Caravan, PhD, who invented and developed the study's agent and is the co-director of MGH's Institute for Innovation
in Imaging. "This probe was invented and optimized in my laboratory by
a dedicated team of chemists and biologists through the support of the
National Heart Lung and Blood Institute of the National Institutes of
Health," says Caravan. "It is extremely gratifying to see these years
of effort come to fruition with a fibrin-specific PET probe with the
potential to make a real impact on human health." Others playing a major
role in the study included David Izquierdo-Garcia, PhD, an assistant in Biomedical Engineering at MGH, and Ciprian Catana, MD, PhD, director
of Integrated MR-PET Imaging at MGH's Martinos Center for Biomedical
Imaging. Izquierdo-Garcia, the lead author on the paper, and Catana
both stressed the innovative nature of the imaging platform used in the
study. "Not only did we use a novel molecular imaging probe in humans
for the first time, but also, this is one of the first studies to fully
explore the synergies and advantages of integrated PET-MRI scanners,"
says Izquierdo-Garcia.

"It is a privilege to work at the Martinos Center for Biomedical Imaging
and be part of multidisciplinary teams that collaborate to develop and
apply cutting- edge imaging technologies," adds Catana. "We were the
first site in the U.S. to install a fully integrated PET-MRI scanner and
have played a major role in the advancement and clinical translation of
this technology." Additional co-authors include Pauline De'soge`re,
PhD, Anne L. Philip, MPH, Choukri Mekkaoui, PhD, Rory B. Weiner, MD,
Onofrio A. Catalano, MD, Yin-Ching Iris Chen, PhD, Doreen DeFaria Yeh,
MD, and Moussa Mansour, MD.

Funding for the study was provided by the National Institutes of Health.

========================================================================== Story Source: Materials provided by Massachusetts_General_Hospital. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. David Izquierdo-Garcia, Pauline De'soge`re, Anne L. Philip, Choukri
Mekkaoui, Rory B. Weiner, Onofrio A. Catalano, Yin-Ching Iris Chen,
Doreen DeFaria Yeh, Moussa Mansour, Ciprian Catana, Peter Caravan,
David E. Sosnovik. Detection and Characterization of Thrombosis
in Humans Using Fibrin-Targeted Positron Emission Tomography and
Magnetic Resonance.

JACC: Cardiovascular Imaging, 2021; DOI: 10.1016/j.jcmg.2021.08.009 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211101105402.htm

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