Simple, safe, and swift… Computed Tomography (or CT scanning) is a
common radiologic test that has revolutionized the way doctors diagnose
and evaluate diseases, examine abnormalities, and detect internal
damage. CT scanning provides an unparalleled window to the inside of the
body by combining X-rays and computers. Using a highly focused X-ray
beam, CT scans create a set of wafer-thin, cross-sectional images of the
body's internal organs, tissues, and structures—much like slices of
bread. Accurate to within millimeters in resolution, these 2-dimensional
X-ray images are displayed in 3D on a computer screen for in-depth
Unmatched for detail, speed, and consistency, CT scanning is a vital
tool in the diagnosis and management of a host of medical problems. Main
Line Health Imaging utilizes GE LightSpeed 16-Slice CT Scanners. Unlike
the early CT scanners that required patients to lie still for long
periods, these newer devices can complete a head-to-toe body scan in
just 90 seconds (compared with 30 minutes on older machines).
At the Bryn Mawr Hospital Health Center, the Main Line Health Center in
Collegeville, and Paoli Hospital, new GE LightSpeed VCT 64-Slice CT
Scanners have been installed.
Even patients who are critically ill, in pain, are very young, or have
trouble holding still can undergo successful scans. The test is
completely painless (although patients having certain studies may be
injected with or be asked to drink a contrast material).
Data from the CT scanners is sent electronically to radiology reading
rooms at the three hospitals for every study. Through our Picture
Archiving and Communications System (PACS) all Main Line Health
hospitals and outpatient centers are digitally interconnected, allowing
radiologists across the Main Line Health System to consult with each
other to make the most accurate diagnosis.
With greater clarity than ever before, this advanced technology helps
physicians make a more accurate diagnosis, quickly. CT scanning is
performed of areas of the body such as the head, neck, chest, abdomen,
and pelvis. Very thin section CT imaging is also done of bones and
joints, as well of specialized areas of the body such as the base of the
skull and facial bones. With its ability to capture very fine details of
the human body, reduced diagnostic time, and excellent safety record,
the new generation of CT scanners at Main Line Health Imaging facilities
provide an indispensable diagnostic tool that radiologists expect will
eventually replace more and more invasive procedures.
Almost all CT scanning of the abdomen and pelvis require drinking an
oral contrast medium, which is a liquid solution of diluted barium.
Scanning is performed 1 hour after drinking the contrast to allow time
for it to pass into the intestine. While this may seem like an
inconvenience, the oral contrast can significantly improve the quality
of the CT study and often results in a more accurate diagnosis.
In addition, many CT scans require intravenous contrast. For these
scans, a technologist or nurse must place an IV before the examination.
During the scanning, iodine containing contrast is injected through the
IV. This IV contrast provides a dramatic improvement in overall quality
of the CT images, particularly when evaluating the abdominal organs such
as the liver, pancreas, and kidneys. Intravenous contrast is also often
used for CT scanning of the neck, chest, pelvis, and head. While
scanning of these areas can be done without the IV contrast, the lack of
contrast limits the quality of these scans.
The intravenous contrast material used at all imaging sites of Main Line
Health is universally the safest (non-ionic) agent available. However,
there are important factors that must be considered for all patients:
There is a potential risk of damage to the kidneys in patients
with renal insufficiency. The risk of damage is small but real
and increases with the severity of pre-existing kidney disease.
For these patients, a recent creatinine blood test may be
required before the CT examination. For high-risk patients, the
radiologist (often in consultation with the referring doctor)
makes a decision whether to administer or withhold the IV
Intravenous contrast rarely can cause an allergic response in
the patient. When it occurs, it is usually mild, such as itching
or hives. (Flushing or warmth during the injection is normal and
is not considered an allergic reaction.) Very rarely, an acute
allergic reaction may occur. In these instances, there is often
a history of a previous mild allergic reaction where the body
became sensitized to the contrast agent. Therefore, if you have
ever experienced a reaction to the IV contrast, you should
inform your doctor before the scan. CT technologists also
routinely ask patients about a prior contrast reaction before
the scan. If you do experience an allergic reaction, even a mild
one, you must take great care in the future to inform your
doctor before having any other IV contrast injection that
contains iodinated contrast.
For patients that have had an allergic contrast reaction in the
past, pre-medication with a short-term immunosuppressant can
greatly reduce the risk of another (and possibly more severe)
contrast reaction. This pre-medication preparation consists of 3
divided doses of oral steroid (Prednisone) given for 24 hours
before the IV contrast injection. Your doctor will write you a
prescription for the medication with more detailed instructions.
The oral anti-diabetic agent Glucophage poses a special problem.
There is a known risk of delayed allergic response for 48 hours
after having the IV iodinated contrast injection, and the
Glucophage must not be taken for these two days. The CT
technologist will also ask you if you take Glucophage before the
What Happens Next?
An experienced Main Line Health radiologist will analyze your CT scans
and send a report to your referring physician, who will inform you on
your test results. Results cannot be given directly to the patient or
For more information, call 1.866.CALL.MLH.