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| ANGIOGRAPHY |
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This is a technique for taking pictures of the arteries and veins which carry
the blood around the body. We mainly use it to find arteries narrowed by
atheroma - or hardening of the arteries. In the heart arteries atheroma causes
heart attacks and angina, in the neck arteries it causes symptoms of stroke,
such as temporary limb weaknes or intermitent loss of vision, and in the leg
arteries it causes leg pains with exercise and ulcers.
There are a number of other techniques for examining arteries, including
ultrasound, CT scan and MRI scan but angiography gives the best pictures.
An angiogram does not cause much discomfort, and most people find that it is
not as bad as they had imagined. The radiologist will numb the skin of your
groin with local anaesthetic and introduce a catheter into the groin artery.
The catheter is a soft 3mm plastic tube which is gently advanced through the
arterial system until its tip is in the artery we wish to examine. A clear
fluid which shows up well on xrays - called contrast material - is injected and
x-rays are taken as the dye flows rapidly through the arteries. The procedure
takes about an hour.
Sometimes atheroma causes narrow areas in the arteries which restricts the
blood flow. This can be treated by stretching the artery back to normal size
with a balloon catheter. This is called angioplasty.
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| SCINTIGRAPHY |
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Also known as nuclear medicine. This is a fascinating technique that relies on
the body’s own processes to help create the pictures.
For example a bone scan: In the laboratory a very small amount of a radioactive
tracer is chemically bonded to a substance that our body uses to repair bones.
This is injected into the blood stream and is absorbed by any bones which are
repairing themselves, such as a fracture, or a bone damaged by a cancer
deposit. We then make pictures of the body with a very sensitve camera (like a
sophisticated Geiger counter used to detect radioactivity) as you lie on a
table. The areas of damaged bone where the tracer has accumulated will show up
as "hot spots".
A bone scan is commonly used to check the bones of patients with cancer, and to
find tiny stress fractures which can not be seen on xrays in the feet or backs
of athletes.
Other types of scintigraphy reveal the action and structure of the thyroid
gland, and measure the function kidneys. We can also scan the heart to evaluate
the strength of the cardiac muscle. We check the heart with the patient
resting, and then stressing the heart with exercise. From this we can tell
which parts of the heart muscle are deprived of oxygen during exercise, and
therefore at risk of being damaged by a heart attack. The arteries supplying
the ‘at risk’ area can then be evaluated by a cardiac angiogram.
Some people worry about the word radioactivity, but the gamma rays from
radioactivity are very similar to the xrays we make with our xray machines. It
is just that with radioactivity the rays come from a chemical, which rapidly
breaks down to a harmless substance. The dose from these scintigraphy scans is
similar to the xray dose from our other tests.
As more tracers are developed we expect this type of scan to be very important.
Imagine if we could make a tracer that attached to very small breast cancers so
they would be visible even before mammography can see them.
Preparation: No special preparation. For a bone scan there is a 2 hour interval
between the injection and the scan so the tracer can circulate to the bones.
Other scans are taken straight after the injection.
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