Download 8533034_CT

Computed Tomography
(CT) &
CT Angiography
Maral Asmani 8533034
Computed tomographyWhat is it?!
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Computed Tomography (CT), more commonly known as a CAT
scan, is a form of medical diagnostic imaging
Joining separate images into one 3-D of graphical cross-section
Using X-rays beams that pass through the body to measure how
different tissues absorb different amounts of radiation
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Computed Tomography is commonly used in cancer, cardiovascular
disease, infectious disease, trauma and musculoskeletal
disorders diagnosis and treatment
Computed Tomography as a diagnostic imaging tool has huge
potential due to its ability to provide painless, quick and
detailed internal images of the body
History
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Tomography is from the Greek word "tomos" meaning
"slice" or "section" and graphia meaning "describing".
CT was invented in 1972 by British engineer Godfrey
Hounsfield of EMI Laboratories, England and by South
Africa-born physicist Allan Cormack of Tufts University,
Massachusetts. Hounsfield and Cormack were later
awarded the Nobel Peace Prize for their contributions to
medicine and science.
The first clinical CT scanners were installed between
1974 and 1976. The original systems were dedicated to
head imaging only, but "whole body" systems with larger
patient openings became available in 1976. CT became
widely available by about 1980. There are now about
6,000 CT scanners installed in the U.S. and about
30,000 installed worldwide.
What are some common
uses of the procedure?
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one of the best tools for studying the chest and abdomen
invaluable in diagnosing and treating spinal problems and
injuries to the hands, feet and other skeletal structures
measure bone mineral density for the detection of
osteoporosis
quickly identify injuries to the liver, spleen, kidneys or other
internal organs in cases of trauma
CT scanning can also be used to guide biopsies
How should I prepare for
the CAT scan?
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given a gown to wear during the procedure
Metal objects including jewelry, eyeglasses, dentures and
hairpins may affect the CT images
You may be asked not to eat or drink anything for several hours
beforehand, especially if a contrast material will be used in your
exam
Also inform your doctor of any recent illnesses or other medical
conditions
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Women should always inform their physician or
technologist if there is any possibility that they are
pregnant
Contrast Material
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They will be given a drink containing gastrografin,
an aniseed flavored X-ray dye, 45 minutes before
the procedure. This makes the intestines easier to
see on the pictures.
Sometimes a liquid X-ray dye is injected into the
veins during the test. This also makes it easier to
see the organs, blood vessels or, for example, a
tumor. The injection might be a little
uncomfortable, and some people also experience a
feeling of warmth in their arm
What does the equipment
look like?
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The CT scanner is typically a large machine with a
hole, or tunnel, in the center. A moveable
examination table slides into and out of this tunnel.
In the center of the machine, the x-ray tube and
electronic x-ray detectors are located opposite
each other on a ring, called a gantry, which rotates
around you. The computer that processes the
imaging information and monitor are located in a
separate room
How does a CT scanner
work?
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The X-rays from the beams are detected after
they have passed through the body and their
strength is measured.
Beams that have passed through less dense tissue
such as the lungs will be stronger, whereas beams
that have passed through denser tissue such as
bone will be weaker.
A computer can use this information to work out the
relative density of the tissues examined. Each set
of measurements made by the scanner is, in effect,
a cross-section through the body.
The computer processes the
results, displaying them as a
two-dimensional picture
shown on a monitor , CT
scans are far more
detailed than ordinary Xrays. The information
from the two-dimensional
computer images can be
reconstructed to produce
three-dimensional images
by some modern CT
scanners
Is a CT scan dangerous?
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Far more X-rays are involved in a CT scan than in
ordinary X-rays, so doctors do not recommend CT scans
without a good medical reason. Some patients may
experience side effects due to allergic reactions to the
liquid dye injected into the veins.
In very rare cases, this dye has been known to damage
already weakened kidneys. It is important to let the Xray doctors or technicians know if you have any allergies,
asthma or kidney trouble, prior to having the X-ray dye
injected.
Limitations!
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Not all diseases and medical conditions can be
identified by a CT scan. For example, hypertension
and diabetes must be tested by blood pressure and
blood sugar analysis, respectively. For this reason,
CT scans are ineffective as “general check-up”
methods and should only be used when a specific
condition in a specific region of the body is
suspected.
CT Heart Scan
CT heart scans give doctors a
3-dimensional visual image
that provides doctors with
detailed information about:
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heart disease
heart disease risk of arterial
blockage
presence of coronary artery
aneurysms
Coronary Artery Disease
the coronary arteries are responsible for supplying the heart
with the necessary amount of oxygen and nutrients.
Coronary artery disease occurs when these vessels
narrow.
Over time, the plaque builds. New cholesterol and fatty
deposits surround the existing plaque. Eventually, the
arteries harden, leading to a condition called
atherosclerosis, Coronary atherosclerosis often has no
symptoms, so heart attacks and death may occur
suddenly, with little or no warning.
plaque buildup narrows the vessel and restricts the flow of
blood to the heart. In some cases, the plaque buildup
completely blocks the artery. The reduced blood flow
means less oxygen goes to the heart. This lack of oxygen
can lead to:
 angina pectoris (Heart pain)
 myocardial infraction (heart attack)
Ways Of Diagnosis…..
Unfortunately, it can be difficult for doctors to detect
blocked heart arteries. They are small structures in
constant motion, and do not appear on x-ray images or
regular ultrasound techniques. Doctors typically “guess”
the existence of atherosclerosis by assesing risk factors
in a patient. Risk factors for atherosclerosis include:
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Cigarette smoking
High cholesterol
Diabetes
Age (women over 55; men over 45)
Family history of heart disease
Obesity
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Other tests exist to predict the existence of blocked
arteries, but these tests are not ideal,such tests cannot
detect blockages in their earliest stages, when they can
still be treated.for example,
Resting electrocardiogram (ECG or EKG)
Signal-averaged electrocardiogram (SAECG)
Chest X-ray
EB Angiography
Exercise stress test ...............
Angiography….
Angiography is performed using:
 x-rays with catheters
 computed tomography (CT)
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magnetic resonance imaging (MRI)
Angiography With
catheter…
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Coronary angiography is an X-ray examination of
the blood vessels or chambers of the heart. A very
small tube (catheter) is inserted into a blood
vessel in your upper thigh (groin area) or arm. The
tip of the tube is positioned either in the heart or
at the beginning of the arteries supplying the
heart, and a special fluid (called a contrast medium
or dye) is injected. This fluid is visible by X-ray,
and the pictures that are obtained are called
angiograms.
Another name for this test is coronary
arteriography.
CT Angiography……
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A small dose of contrast material may be injected
through the IV to determine how long it takes to reach
the area under study. Next, the table will then move
quickly through the scanner to determine the correct
starting position for the scans and a test image will be
taken. The table will then move slowly through the
machine as the actual CT scanning is performed. As the
images are being recorded, an automatic injector machine
connected to the IV will continue to inject contrast
material at a controlled rate. When the contrast dye is
used to visualize veins, the study is called a venogram,
and when it is used to visualize arteries, it is known as an
arteriogram.
How does it compare to
standard angiography?
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With regular angiography, a needle puncture is placed in
the groin and contrast material is injected. CT
angiography does not require the use of a large vessel for
injection and is an outpatient procedure. The complication
rates (bleeding, hematoma, emboli) after angiogram are
higher compared to CT angiography.
Physicians use the
procedure to:
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detect atherosclerosis disease in the carotid artery,
Aorta….
detect thrombosis (clots) in veins
Detect embolism in pulmonary
identify a small aneurysm or arteriovenous
malformation……
Benefits of a CT Heart Scan
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Fast
Painless
Non-invasive
Can detect the buildup of arterial plaque in its early
stages, while it is still treatable
Sources:
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www.americaheart.org
www.ctcardiac.com
www.radiologyinfo.com
www.lifescanuk.org.uk
www.medscape.com
www.patient.co.uk