The CAT scan, also known as CT (Computed Tomography) imaging, is a safe and non-invasive procedure which uses low radiation X-rays to create a computer-generated, three-dimensional image of the brain. It provides detailed information about the structure of the brain.

The CT scan uses a narrow beam of X-rays, which pass through the head and hit a detector on the opposite side. The beam moves around the head and the detector moves with it. Since different brain tissues have different densities, each will block the X rays from reaching the detector to different degrees. These may reveal abnormalities (blood clots, cysts, tumours, scar tissue, etc.) in the skull or brain which may be related to seizures.

This allows physicians to examine this structure, section by section, as the test is being conducted. The CAT scan helps point to where a person’s seizures originate. The CT scan only shows what the brain looks like, not how it works. The scanning period is brief, safe and painless.

Before a CAT Scan

• Dress your child in comfortable, loose-fitting clothing.
• Remove any metal objects such as jewellery, belts, hairpins, hearing aids or glasses before going to the test centre. These objects  may degrade the clarity of the images.
• If a contrast medium is going to be used, your child should not eat or drink anything four to eight hours before the test.
  • A contrast medium is a dye that may be given to your child orally or injected into his/her hand or arm. This fluid goes up to the brain and makes the scan easier to read.
  • Some people are allergic to particular contrast mediums. It is important to inform your doctor if your child has any allergies, especially to iodine.
    • You should also inform the doctor if your child has diabetes, asthma, a heart condition, kidney problems, or thyroid condition. These conditions may indicate a higher risk of iodine reactions.
  • Ensure your child knows to inform the technician if they feel any itching or shortness of breath after the administration of the contrast medium.
    • After the injection your child may feel flushed, have a metallic taste in his/her mouth, or feel nauseated.
    • Another mild reaction that can occur following the administration of iodine is itching over various parts of the body. This lasts from several minutes to several hours and is usually treated with medication.
    • More serious but less common reactions may include shortness of breath, swelling of the throat or other parts of the body. If your child has these reactions, they require immediate treatment.
  • A CAT scan still provides valuable information without administering a contrast agent. If your child is at risk of reaction to the contrast agent, the physician may decide not to administer it during a CAT scan.

During a CAT Scan

• After the administration of the contrast agent, your child will be asked to lie down on a scanning table.
• The technician will move to another room and then proceed to move your child into the scanner machine.
• A series of X-rays will be taken by a camera, which will rotate around your child’s head.
• It is important that your child lies completely still until the entire examination is complete.
  • Any movement will blur the image.
  • Your child may be asked to hold his/her breath during the scanning procedure to help to eliminate blurring of the images caused by the movements of breathing.
• During the examination, your child will hear some noise from the machine and the CT table may move slightly. This will not cause any discomfort.
• If your child has any questions or concerns throughout the examination, s/he can speak with the technologist via intercom.
• You cannot accompany your child during the scanning process because the CT scanner uses X-rays. Only your child should be in the CT scanner room during the procedure.
• The scan should be complete in about 15 to 20 minutes.

After a CAT Scan

• Your child can return to his/her usual daily activities and resume his/her regular diet immediately after the scan unless instructed otherwise by the doctor.
• If your child was given an injection and the injection site remains sore, you are encouraged to call your child’s physician.
• You may need to monitor your child while returning from the test centre as the effects of the sedative may not have worn off yet.
• A radiologist will interpret the images and send them to your child’s doctor who will review the results with you at a follow-up appointment. Additional tests or a treatment plan will be designed accordingly.

Important Considerations

• If your child has allergies or has experienced discomfort because of any contrast agent previously, inform the technologist and the doctor before the examination.

Personnel

• Radiologists
  • interpret the CT images
  • send a report to the referring physician
  • administer or observe the contrast injection
• CT technologists
  • operate computerized tomography scanner to produce cross sectional views of the body section being scanned
  • perform the examination under the supervision of the radiologist
  • may also administer the contrast injection

Payment

The CAT Scan is covered by the Ontario Health Insurance Plan (OHIP).

Click here to learn about other types of diagnostic tests.

Positron Emission Tomography is a scanning technique which detects chemical and physiological changes related to metabolism. This procedure produces three-dimensional images of blood flow, chemical reactions and muscular activity in the body as they occur. It measures the intensity of the use (metabolization) of glucose, oxygen or other substances in the brain.

More active brain areas have increased blood flow and consume more oxygen, thus detecting over- or under- activity in the brain. This allows the neurologist to study the function of the brain. By measuring areas of blood flow and metabolism, the PET scan is used to locate the site from which a seizure originates.

The information provided by a PET scan is valuable in the diagnosis of seizure type and in the evaluation of a potential candidate for surgery. The PET scan tests brain metabolism, chemistry or blood flow by injecting a small amount of radioactive substance into the body. When this substance reaches the brain during the scan, a computer uses the recorded signals to create images of specific brain functions.

A functional image of brain activity is important because functional changes are often present before structural changes in tissues. PET images may therefore demonstrate pathological changes long before they would be evident by other scanning techniques.

The limitations of PET:

• The session cannot last very long because it requires the injection of radioactive material.
• It takes time for active brain cells to absorb the radioactive material takes time to be absorbed. The scan images change too slowly to capture fast-changing brain events.

Before a PET Scan

• Your child should not eat or drink anything four to six hours prior to the exam.
• Dress your child in comfortable clothing.
• Your child should take all prescribed medication(s) as usual unless instructed otherwise by the physician.

During a PET Scan

• Before the scan, your child will either inhale or receive an injection of a small amount of radioactive tracer. The tracer is a compound such as sugar “labelled” with a short-lived radioisotope.
• Following the injection, your child will rest for approximately 30 to 45 minutes while the substance reaches the brain.
• The technologist will place your child on a scanner table.
• Your child will place his/her head in a special headrest. This immobilizes the head using foam blocks or a special mould shaped for your child.
• It is important for your child to lie completely still.
• The scanner table will slowly pass through the PET scanner. Your child’s head will be inside the large, doughnut-shaped machine. The scanner detects the radioactive material to produce a computer image of your child’s brain.
• Scanning time is approximately one to two hours.

After a PET Scan

• There are no after effects from the injection or the PET imaging.
• Your child can resume normal activity immediately after the PET scan is completed.
• A radiologist or nuclear medicine technologist will review the PET scan and report to your child’s physician. The physician will then make a follow-up appointment to discuss the results with you.

Personnel

• Nuclear Medicine Technologist
  • operates cameras which detect and map the radioactive tracer in the patient’s body to create an image on the computer monitor
  • explains test procedures to patients
  • prepares the radiopharmaceutical and administer it orally or through injection
• Doctors
  • interpret the results.

Important Considerations

• Pregnant women should not undergo a PET Scan because of the radioactive isotopes used.
• If your child is or may be pregnant, inform your doctor.

Availability

Clarke Institute of Psychiatry, Toronto, Ontario
416-535-8501
Research grants to the institute cover the cost of the test.

McMaster-Chedoke Hospital, Hamilton, Ontario
905-521-2100
The hospital covers the cost of the test.

Montreal Neurological Institute and Hospital, Montreal, Quebec
514-398-5358
You must pay $700 for the test, but the Ontario Health Insurance Plan (OHIP) will fully reimburse you.

University of British Columbia, Vancouver, British Columbia
604-822-2211 (general directory)

Epilepsy Foundation (of America) – for locations in the United States
301-459-3700
www.efa.org
You must pay approximately US$1700 for the test, which insurance does not cover.

Click here to learn about other types of diagnostic tests.

Electro refers to electricity; encephalo refers to the brain; gram refers to record.

A doctor may administer an EEG test to determine whether your child has epilepsy and in what form. The EEG allows the doctor see if there are any irregularities electrical activities occurring in the brain that may produce seizures.

An electroencephalogram is a non-invasive diagnostic test. It records electrical activity on the surface of the brain to identify the location of the abnormally firing neurons that cause seizures. An electroencephalograph is the instrument used to register this activity and record it on graph paper. A neurologist uses these recordings to help identify the location, severity and type of seizure disorder. This safe and painless procedure will not affect your child in any way.

It is important to remember that an abnormal EEG does not diagnose epilepsy nor does a normal EEG reading exclude epilepsy. An EEG can only measure abnormal electrical activity that occurs during the test period. Sometimes, the brain of the person with epilepsy functions perfectly normal during the test.

Tests that have been done on people with epilepsy commonly show uneven activity or large changes in the voltage of brain waves (spikes). Different patterns of activity from different spots on the scalp point to different kinds of epilepsy.

Before an EEGExpand Before an EEG Section