Abdomen
CT procedures :-

1- Computed Tomography (CT) - Abdomen
What is CT Scanning of the Abdomen?
What are some common uses of the procedure?
How should I prepare for the CAT scan?
What does the equipment look like?
How does the procedure work?
How is the CAT scan performed?
What will I experience during the procedure?
Who interprets the results and how do I get them?
What are the benefits vs. risks?
What are the limitations of CT Scanning of the Abdomen?
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What is CT Scanning of the Abdomen?
Computed tomography (CT)—sometimes called CAT scan—uses special x-
ray equipment to obtain image data from different angles around the
body then uses computer processing of the information to show a
cross-section of body tissues and organs.

CT imaging is particularly useful because it can show several types
of tissue with great clarity, including organs like the liver,
spleen, pancreas and kidneys. Using specialized equipment and
expertise to create and interpret CT scans of the lower
gastrointestinal (GI) tract, the colon and the rectum, an
experienced radiologist can accurately diagnose many causes of
abdominal pain such as an abscess in the abdomen, an inflamed colon
or colon cancer, diverticulitis and appendicitis. Often, no
additional diagnostic workup is necessary and treatment planning can
begin immediately.

What are some common uses of the procedure?
Because it is a non-invasive procedure that provides detailed, cross-
sectional views of all types of tissue, CT is becoming the preferred
method for diagnosing many diseases of the bowel and colon,
including diverticulitis and appendicitis, and for visualizing the
liver, spleen, pancreas and kidneys. In cases of acute abdominal
distress CT can quickly identify the source of pain. When pain is
caused by infection and inflammation, the speed, ease and accuracy
of a CT examination can reduce the risk of serious complications
caused by a burst appendix or ruptured diverticulum and the
subsequent spread of infection. In cases where bowel obstruction is
suspected, CT may be the best imaging test.

CT is often the preferred method for diagnosing many different
cancers, including colon cancer, since the image allows a physician
to confirm the presence of a tumor and to measure its size, precise
location and the extent of the tumor's involvement with nearby
tissue. CT examinations of the lower GI tract can be used to plan
and properly administer radiation treatments for tumors and to guide
biopsies and other minimally invasive procedures. Many dedicated
shock-trauma centers have a CT scanner in the trauma department. CT
can also play a significant role in the detection, diagnosis and
treatment of vascular disorders that can lead to stroke, gangrene or
kidney failure.

How should I prepare for the CAT scan?
You should wear comfortable, loose-fitting clothing for your CT
exam. Metal objects can affect the image, so avoid clothing with
zippers and snaps. You may be asked to remove hairpins, jewelry,
eyeglasses, hearing aids and any removable dental work that could
obscure the images. You also may be asked to refrain from eating or
drinking anything for an hour or longer before the exam. Women
should always inform their doctor or x-ray technologist if there is
any possibility that they are pregnant.

What does the equipment look like?
The CT scanner is a large, square machine with a hole in the center,
something like a doughnut. The patient lies still on a table that
can move up or down and slide into and out from the center of the
hole. Within the machine an x-ray tube on a rotating gantry moves
around the patient's body to produce the images, making clicking and
whirring noises as the arm moves. Though the technologist will be
able to see and speak to you, you will be alone in the room during
the exam.

An example of the CT equipment that may be used is shown above.

How does the procedure work?
CAT scan: abdomen

CAT scan: appendix


CAT scan: kidneys
and ureters

In many ways CT scanning works very much like other x-ray
examinations. Very small, controlled amounts of x-ray radiation are
passed through the body while different tissues absorb the radiation
at different rates. With plain radiology, an image of the inside of
the body is captured when special film is exposed to the absorbed x-
rays. With CT, the film is replaced by an array of detectors that
measure the x-ray profile.

Inside the CT scanner is a rotating gantry that has an x-ray tube
mounted on one side and an arc-shaped detector mounted on the
opposite side. During each full rotation, as the fan-shaped x-ray
beam is emitted through the patient's body, an image of a thin
section is acquired. The detector records about 1,000 images—or
profiles—of the expanded x-ray beam with each rotation. The profiles
are then reconstructed by a dedicated computer into two-dimensional
images of the sections that were scanned. Multiple computers are
typically used to control the entire CT system.

You might think of it as looking into a loaf of bread by cutting the
bread into thin slices. When the image slices are reassembled by
computer the result is a very detailed, multidimensional view of the
body's interior.

With spiral—or helical—CT, refinements in detector technology
support faster, higher-quality image acquisition with less radiation
exposure. The current spiral CT scans are called multidetector CT
and are most commonly four- or 16-slice systems. CT scanners with 64
detectors are now available. These instruments should provide either
faster scanning or higher resolution images. Using 16-slice scanner
systems the radiologist can acquire 32 image slices per second. A
spiral scan can usually be obtained during a single breath hold.
This allows scanning of the chest or abdomen in 10 seconds or less.
Such speed is beneficial in all patients but especially in
populations in which the length of scanning was often problematic,
such as elderly, pediatric or critically-ill patients. The
multidetector CT also allows applications like CT angiography to be
more successful.

With conventional CT, small lesions may frequently go undetected
when a patient breathes differently on consecutive scans, as a
lesion may be missed by unequal spacing between scans. The speed of
spiral scanning and a single breath hold increase the rate of lesion
detection.

How is the CAT scan performed?
The technologist begins by positioning the patient on the CT table.
The patient's body may be supported by pillows to help hold it still
and in the proper position during the scan. As the study proceeds
the table will move slowly into the CT scanner. Depending on the
area of the body being examined, the increments of movement may be
so small that they are almost undetectable or large enough that the
patient feels the sensation of motion.

A CT examination of the gastrointestinal tract requires the use of a
contrast material (this may be barium, iodine or in some cases
water) to enhance the visibility of certain tissues. The contrast
material may be swallowed or administered by enema. Before
administering the contrast material the radiologist or technologist
may ask whether the patient has any allergies, especially to
medications or iodine, and whether the patient has a history of
diabetes, asthma, a heart condition, kidney problems or thyroid
conditions. These conditions may indicate a higher risk of reaction
to the contrast material or potential problems eliminating the
material from the patient's system after the exam.

A CT examination usually takes five minutes to half an hour. When
the exam is over, the patient may be asked to wait until the images
are examined to determine if more images are needed.

What will I experience during the procedure?
CT scanning causes no pain, and with spiral CT the need to lie still
for any length of time is reduced. For examinations of the abdomen
and lower gastrointestinal tract you may be asked to swallow either
water or a positive contrast material, a liquid that allows the
radiologist to better see the stomach, small bowel and colon. Some
patients find the taste of the contrast material mildly unpleasant,
but most can easily tolerate it. Your exam may require the
administration of the material by enema if the colon is the focus of
the study. Many patients also receive iodine intravenously (injected
into a vein) to help evaluate blood vessels and organs such as the
liver, kidneys and pancreas.

You will be alone in the room during the scan; however, the
technologist can see, hear and speak with you at all times. With
pediatric patients, a parent may be allowed in the room to alleviate
fear but will be required to wear a lead apron to prevent radiation
exposure.

Who interprets the results and how do I get them?
A radiologist, who is a physician experienced in CT and other
radiologic examinations, will analyze the images and send a signed
report with his or her interpretation to the patient's primary care
physician. The physician's office will inform the patient on how to
obtain their results. New technology also allows for distribution of
diagnostic reports and referral images over the Internet at some
facilities.

What are the benefits vs. risks?
Benefits
Viewing a CT scan an experienced radiologist can diagnose many
causes of abdominal pain with very high accuracy enabling faster
treatment and often eliminating the need for additional, more
invasive diagnostic procedures.
Unlike other imaging methods, CT scanning offers detailed views of
many types of tissue, including the lungs, bones, soft tissues and
blood vessels.
CT scanning is painless, noninvasive and accurate.
CT examinations are fast and simple. For example, in emergency cases
they can reveal internal injuries and bleeding quickly enough to
help save lives.
Diagnosis made with the assistance of CT can eliminate the need for
invasive exploratory surgery and surgical biopsy.
CT scanning can identify normal and abnormal structures, making it a
useful tool to guide radiotherapy, needle biopsies and other
minimally invasive procedures.
CT has been shown to be a cost-effective imaging tool for a wide
range of clinical problems.
Risks
CT does involve exposure to radiation in the form of x-ray, but the
benefit of an accurate diagnosis far outweighs the risk. The
effective radiation dose from this procedure is about 10 mSv, which
is about the same as the average person receives from background
radiation in three years. See the Safety page for more information
about radiation dose.
Women should always inform their doctor or x-ray technologist if
there is any possibility that they are pregnant. See the Safety page
for more information about pregnancy and x-rays.
Nursing mothers should wait for 24 hours after contrast material
(iodine) injection before resuming breast feeding.
The risk of serious allergic reaction to iodine-containing contrast
material is rare, and radiology departments are well-equipped to
deal with them.
What are the limitations of CT Scanning of the Abdomen?
The exam is not generally indicated for pregnant women.