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Chapter 2
•
Cardiovascular Care
Individuals with any type of metal
device inside the body should not
have an MRI unless is certified as MRI
safe. These devices include:
•
Pacemakers and ICDs
•
Inner ear (cochlear) implants
•
Neuromuscular stimulators such as
those used for pain management
or muscle rehabilitation
•
Implanted drug infusion pumps
•
Intrauterine devices (IUDs)
•
Brain aneurysm clips that are not
approved for MRI
•
Some dental implants (check with
your dentist to make sure they are
not magnetic)
•
You should avoid MRI if you have
metal fragments in your body.
Metal fragments in the eyes can
be especially dangerous because
the magnet may move the metal,
causing eye damage or blindness.
Multiple-Gated Acquisition
Scanning
Radionuclide ventriculography (RVG,
RNV) or radionuclide angiography
(RNA) is often referred to as a
multiple-gated acquisition (MUGA)
scan. This test can view how well the
heart’s ventricles are pumping. During
a MUGA scan, a small amount of a
radioactive substance or tracer (called
a radionuclide) is put into the blood
which attaches to red blood cells. A
gamma camera takes pictures of the
heart. Pictures are taken at the same
time during each heartbeat (ECG-
gated) which is computer analyzed.
POSITRON EMISSION
TOMOGRAPHY
A positron emission tomography
(PET) scan of the heart is a
noninvasive nuclear imaging test.
It uses radioactive tracers (called
radionuclides) to produce pictures
of the heart and diagnose coronary
artery disease (CAD). PET scans can
show healthy and damaged heart
muscle and if there will be benefit
from a percutaneous coronary
intervention (PCI) such as angioplasty
and stenting, coronary artery bypass
surgery (CABG), or any other
procedure. PET scans use radioactive
material called tracers which mix with
blood and are taken up by the heart
muscle. A special “gamma” detector
that circles the chest picks up signals
from the tracer. A computer converts
the signals into pictures of the heart
at work. A PET scan determines if
the heart is getting enough blood
or if blood flow is reduced because
of narrowed arteries. It also shows
scaring from a prior heart attack.
A radioactive tracer is injected
into the bloodstream. The tracers
used for PET are mostly natural body
compounds such as glucose, water,
or ammonia, which are labeled or
“tagged” with a small amount of
radioactive material. Inside the body
the radioactive tracer produces a type
of energy called a gamma ray. Gamma
rays are detected by a gamma detector
and are used to produce a series of
clear images of your heart. Images of
thin slices made all the way through
the heart can be produced from
all different directions and angles.
Computer graphics can be used to
create a 3-dimensional image of your
heart from the thin-slice images.
Viable heart tissue will take in more
of the tracer than the tissue that is
no longer viable. Different colors or
degrees of brightness on the PET scan
show different levels of tissue function.