What is CT Scanning of the Head?
CT scanning also known as CT scan is a noninvasive, painless radiological test to evaluate many disorders of the brain. CT scan uses special x-ray equipment to produce multiple cross sectional images of the head- which are then analyzed by a computer and converted into a 3 dimensional picture. The CT scan is many times more sensitive then the plain x ray in imaging the brain.
What conditions of the head can CT scan be used for?
A head CT may be recommended if one has:
- Head injury or injury to the face or eyes
- Dizziness or problems with balance
- Skull fracture
- Sudden behaviors change
- Trauma to the e facial
- Repeat falls
- repeat sinus infections
- swelling in the head and face area
- suspected brain cancer
- spread of cancer to the brain
- Cysts in brain
- Congenital deformities
- suspected bleeding in the brain
- suspected aneurysm or AV malformations
- Infection of brain
- Hydrocephalus (brain swelling from excessive fluid)
- When performing biopsy of a brain lesion
- CT can be used to follow results of radiation therapy for cancer
What preparations are required for a CT Head scan?
One should not eat 2-3 hrs prior to the procedure. When arriving to the radiology suite, one should wear loose-fitting clothing to your exam or a gown can be provided.
All metal objects including jewelry, eyeglasses, dentures and hairpins can interfere with CT imaging an should be removed or left home prior to the CT scan.
Anyone with allergies/asthma should inform the technologist of this. Individuals with allergies/asthma are required to take some medications at least 24 hrs prior to the procedure.
Individuals with kidney/diabetes problems may be admitted the night before and hydrated with fluids.
Women should always inform their physician or technologist if there is any possibility that they are pregnant. Pregnancy is usually a contraindication to a CT scan, unless the benefits of the test override the risks.
What does the CT scan equipment look like?
The CT scanner is a large machine with tunnel housing 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- and rotate around the patient. The images generated are processed by a computer.
Recent advances in scanning technology allow new CT scanners to obtain multiple images in a single rotation. These scanners, called "multi slice CT" or "multidetector CT," allow thinner slices to be obtained in a shorter period of time, resulting in more detail and better resolution. These fast scanners are beneficial for critically ill patients and the elderly.
How is the CT scan performed?
You will be asked to lie down on a flat table which is mobile. An IV is usually started when contrast material is used in the study. After this, the table moves into the tunnel where the actual imaging is done. During the procedure, you may be asked to hold your breath for a few seconds to prevent any motion artifacts. Unfortunately, no one else is allowed in the CT scan room because of radiation exposure but you will be watched through a window by the technologist. The technologist will also speak to you via a microphone. Once the imaging has been completed, you can go home. The imaging takes about 15-20 minutes.
How does one feel during the procedure?
CT scan is a painless procedure. Today's fast speed scanners can complete the imaging in less than 5-10 minutes, thus reducing the time needed to lay flat and still.
The only discomfort of CT scanning is the lying down flat for a few minutes. This may be of no consequence to most individuals but can be discomforting to those with neck and back problems. In addition, the CT scan does tend to cause a claustrophobic feeling because of the closed space enclosure.
When contrast is used, the individual may feel warm all over the body during the injection. This is a transient painless feeling. Others may complain of a metallic taste in the mouth. The rare individual may develop an allergy which may be associated with hives and pruritis (itching).
When the contrast material is swallowed, it does have an unpleasant taste but tolerable. Most individuals complain of bloating after swallowing the dye- symptoms which rapidly subside.
When a child is having a CT scan, one of the parents or a nurse may be allowed into the room but is required to wear a lead apron to prevent radiation exposure.
After the CT scan, one can resume all normal activities. If contrast was administered, one is encouraged to drink lots of fluids.
Who interprets the results and how do I get them?
The Scans are always read by a radiologist. If prior arrangements have been made with the radiologist, then the results can be available 30 mins after the CT is done.
What are the advantages vs disadvantages of a CT scan of the head?
- CT scan is a painless non invasive procedure with good sensitivity to detect pathology of the head
- CT scan is far superior to an MRI when evaluating skull fractures
- Ct scan can provide detailed images of the brain nervous tissue
- CT is excellent for individuals involved in head trauma
- CT can rapidly identify the presence of a stroke early in evolution
- CT is excellent in making a diagnosis of bleeding in the brain (Subarachnoid hemorrhage)
- CT scan is much cheaper than an MRI an equally as fast
- The newer generation of CT scans can combine angiography and assess the blood supply to the brain
- The motion artifacts are less of a problem with a CT scan compared to an MRI.
- CT scan can be performed in patients with implanted medical devices.
- CT scan provides dynamic imaging and thus allows for needle biopsies to be performed simultaneously.
- unlike MRI, CT scan is associated with a radiation (this is about the same radiation exposure that a normal individual would get in about 12 months)
- CT scan should never be done in a pregnant female because of the exposure of radiation risk to the fetus
- The dye used in a CT is iodine based and is often a cause of allergy. The dye can also lead to kidney failure in individuals with diabetes
- Unlike adults, CT scan should not be repeated in children because of the repeat radiation exposure
- CT is not very good at identifying pathology of the soft tissues
- CT is not good at identifying areas of inflammation or infection of the brain compared to MRI
What are the limitations of CT Scanning of the Head?
An obese patient may not be able to fit in the machine.
For those who have partial renal failure, injection of contrast may not be possible because of the risk of inducing complete renal failure.
What is the cost of a CT scan?
The average cost of a CT scan of the head is about $200-$400.