Imaging Tests: X-Ray, MRI, and CT Scan

Imaging tests are ways of taking pictures of the inside of the body. Different types of imaging are useful in different situations.

  • X-rays are a kind of radiation. X-rays passing through the body give a 2-dimensional picture of the inside of the body.
  • Magnetic resonance imaging (MRI) uses a strong magnet and radio signals to take pictures.
  • Computed tomography (CT) scans use X-rays and a computer to take cross-sectional pictures.
  • Sometimes a liquid called contrast medium is used to give more information or more detailed pictures of certain parts of the body.

Chest X-rays

What is a chest X-ray?

A chest X-ray is a picture of the heart, lungs, and bones of the chest. An X-ray is a type of radiation that passes through the body. It gives the doctor information on the size, shape, and location of the heart, in order to help diagnose a condition. It is also called chest radiography.

How is the X-ray done?

Your child, wearing a hospital gown, will be asked to stand next to the X-ray film in the hospital radiology department. Younger children may need to be restrained, while older children will be asked to hold still for 2 or 3 seconds, so the picture does not blur.

The X-ray machine is turned on for a fraction of a second. Beams of X-rays pass through the chest to make a picture on the film. Usually an X-ray is taken from the front and then the side. The X-ray film is developed in about 10 minutes.

Will the X-ray hurt my child?

Your child will not feel anything.

There is very little radiation released through the X-ray, so it will not cause damage to the body. Young children and pregnant women are more sensitive to X-rays, so they are sometimes given small protective shields made of lead to prevent the X-ray from going through certain parts of the body.

Magnetic resonance imaging (MRI)

Neurological Magnetic Resonance Imaging (MRI) Procedure
What is magnetic resonance imaging (MRI)?

Magnetic resonance imaging (MRI) is a way of taking pictures of the head and body without the use of radiation or X-rays. A magnet, radio signals, and a computer are used to create the pictures. An MRI scan is fairly noisy, but it does not hurt.

A number of short scans make up a complete MRI study. Each scan takes from 1 to 10 minutes. The total time for a complete MRI study is about 1 to 2 hours.

Tell the MRI team about any metal in your child's body

Because MRI involves a strong magnetic field, certain metal implants could injure your child. Tell the MRI team if your child has had any surgeries, procedures, or injuries that involved metal, such as metal rods, plates, screws, braces, clips, or body piercing. If your child does have any implants, please give the MRI team information about the type of device and the manufacturer. In some cases, your child may need an X-ray to confirm that it is safe for him to have an MRI. If you have any questions, please contact the MRI team.

Is there any preparation for MRI?

If your child is old enough and able to lie perfectly still for an hour, then no special preparation is usually needed for the scans. However, many children need medicine to help them sleep so they will lie still for the scan. This medicine may be a type of sedation or a general anaesthetic. Before having any sedation or general anaesthetic, your child will have to be careful about what he eats or drinks. The treatment team will tell you what to feed your child before the MRI.

What should I tell my child?

Tell your child exactly what will happen during the MRI scan. Explain what he will see, hear, and feel. Remember, MRI scans do not hurt!

Who will be doing the MRI study?

A team of 3 or 4 people will be involved in the MRI study:

  • A medical radiation technologist will do the MRI scans.
  • A nurse will prepare your child for the scans. If your child is having sedation, the nurse will give the sedation. If your child is having a general anaesthetic, the nurse will assist the anaesthesiologist.
  • The anaesthesiologist is the doctor who gives the general anaesthetic.
  • A radiologist or cardiologist will check and interpret each MRI scan to make sure that the study is complete.

Will my child be given any needles for the MRI study?

Children who are being sedated or are having a general anaesthetic will in most cases need to get a needle.

Some MRI scans give the doctor more information when they are done with a special liquid called a contrast medium. This liquid is put into the vein in the hand or arm using an intravenous line (IV). The IV is put in with a small needle. If needed, the IV will be inserted before the MRI scan.

Contrast medium is normally very safe, but it may produce a reaction in rare cases. The team will watch your child very closely during and after the MRI to see if your child has a reaction.

What happens before the MRI?

Before your child goes into the room, the staff will ask some questions. They want to make sure your child will have no problems being near the strong magnet in the MRI scanner. There are some metal devices and implants that make it impossible to have an MRI.

Your child will have to empty his pockets completely of everything, including coins, keys, pens, cell phones, wallets, and bank cards. He will also have to take off his watch. Your child cannot wear any makeup or jewellery. Your child will change into a hospital gown.

What happens during the MRI?

Your child will lie on a bed. The technologist will place him in the correct position for the MRI scan. The MRI scanner is a large machine with a wide tunnel in the centre.

When everything is ready, the bed will be moved into the tunnel. Most of your child's body will be inside the tunnel.

Your child must lie completely still for the whole time of each MRI scan.

The scanner makes a loud knocking or drumming sound during scanning. Everyone staying in the room will wear ear plugs or headphones to protect their hearing.

The technologist will talk to your child through a speaker. When the MRI scan is complete, the technologist will help your child off the table.

If your child does not need to be asleep during the study, you will be able to stay in the room with your child if you wish. If you wish to stay in the room, you will also need to be screened for metal implants.

What happens after the MRI?

If your child has had sedation or general anaesthetic, you must stay until he is awake. The MRI nurse will let you know when you can leave. A radiologist or cardiologist will review the MRI study, and a report will be sent to your doctor. Your doctor will discuss the results of the study with you at a follow-up appointment.

Computerized tomography (CT)

What is a computerized tomography (CT) scan?

A computerized tomography (CT) scan uses an X-ray and a complex computer to take cross-sectional pictures of your child. These pictures allow doctors to see the structures inside the body at different levels. A CT scan can be done on any body part.

Chest CT Scan
The length of your child’s CT scan depends on many things. A routine scan may take anywhere from 5 to 30 minutes, depending on the part of the body being scanned, the size of your child, and the amount of cooperation your child can give.

Is there any preparation for a CT scan?

If your child is old enough and able to lie completely still for up to an hour, he will not usually need any special preparation for a CT scan.

Movement during the scan creates blurry pictures that cannot give your doctor the information needed. Many children need mild sedation to help them sleep so they can lie still for the scan. The sedation may be given in a drink or by a needle in the muscle or vein. The type given depends on the age and size of your child as well as the kind of CT scan being done.

If your child needs sedation, you will be given instructions on how to prepare.

Tell your child exactly what will happen when the CT scan is being done: what she will see, hear, and feel. Remember, CT scans do not hurt.

Who will be doing the CT scan?

The CT scan will be done by a team of 3 people. A medical radiation technologist will take the pictures of your child and assist the nurse. The nurse will help you and your child throughout the scan and give your child sedation if needed. A radiologist will check your child’s scan before you leave to make sure it is complete. A radiologist is a doctor who specializes in reading diagnostic images made using X-rays.

Will my child be given any needles for the CT scan?

Children who are being sedated may be given a needle.

Some CT scans give the doctor more information when they are done with a special liquid called an X-ray contrast fluid. This is a clear, colourless liquid that is injected into a vein. This fluid makes the blood vessels inside the body show up better on the pictures. The liquid is quite safe. The nurse will look for your child’s best vein and use a small butterfly needle to put in the contrast liquid. The needle may sting a little when it goes in, but it will be taken out once all the contrast medium has been given.

A child who is having an abdominal CT scan will probably be asked to drink some juice or water with X-ray contrast fluid mixed into it. This helps make the stomach and intestines easier to see on the pictures. If your child has a favourite drink, you may bring it with you to mix with the fluid.

What happens during the CT scan?

One parent may stay in the room with the child during the scan. You will be given a lead coat to wear. When you enter the room, you will see a table and a large white box with a hole in the middle. This is the camera. The camera makes some noise when it takes a picture, but it will not touch your child.

Your child will lie on a narrow bed. The technologist will make sure that your child is lying on the table in the correct position for the CT scan. Your child will be held with a safety strap. If your child is having a CT scan of the head, the technologist may place little pillows beside your child’s ears and a headband over his or her forehead to keep his or her head still.

The bed moves up and into the CT machine, which looks like a big donut. The camera moves around inside the machine and takes many pictures. The camera makes some noise when it takes a picture, but the camera will not touch your child.

Your child needs to stay very still while the camera is taking pictures. Your child can sleep (or pretend to sleep), or you can read a story to help the time go faster.

The technologist will be able to hear, see, and speak to your child during the CT scan.

Depending on the body part we are scanning, the scan can take anywhere from 10 minutes to 30 minutes from start to end. When the scan is finished, the technologist or nurse will help your child off the table.

What happens after the CT scan?

If your child has had sedation, you must stay until he is awake. This can take up to 2 hours. The nurse will let you know when you can leave.

A radiologist will review the CT scan, and a report will be sent to your doctor. Your doctor will discuss the results of the scan with you at a follow-up appointment.

Andrew N. Redington, MD, FRCP (UK), FRCPC

 

12/11/2009


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