What is an MRI (magnetic resonance imaging) test?
Magnetic resonance imaging (MRI) is a procedure that uses strong magnetic fields and radio waves to produce cross-sectional images of organs and internal structures in the body. The signal detected by the MRI machine varies depending on the water content and local magnetic properties of different tissues or structures throughout the body, so they can be distinguished from one another in the MRI study. Each cross-section represents a “slice” of the part of the body being imaged. When viewed together these images provide a comprehensive view of the area imaged, with greater clarity and more detail than conventional X-ray images, and MRI provides different information about structures in the body than can be obtained using ultrasound or computed tomography (CT). An MRI exam of a joint such as the knee can provide detailed images of ligaments and cartilage, for example, which are not visible using other study types.
Doctors use MRI scans of internal organs, bones, soft tissue, and blood vessels to evaluate:
- organs of the chest and abdomen
- the brain
- pelvic organs including the bladder and the reproductive organs
- blood vessels and lymph nodes
- vascular anomalies
- bones and joints
MRI scans can help diagnose or monitor treatment for tumors; diseases and abnormalities of the liver, bile ducts, and pancreas; inflammatory bowel disease; heart problems, such as congenital heart disease; and malformations or inflammation of the blood vessels.
An MRI imaging system includes a scanner shaped like a tube, and a motorized table that slides in and out of the tube. Your child will lie on the table and while he/she is inside the scanner, information from many different angles will be collected. This information is sent to a computer, which reconstructs all of the individual "snapshots" into one or multiple cross-sectional images (slices) of the internal organs and tissues.
For some MRI exams we will give your child a magnetically active material (called a contrast agent) containing the element gadolinium, intravenously to make the organs and structures more visible in the images we create.
How should I help my child get ready for the test?
On the day of the test your child should wear comfortable clothes, and may be asked to change into a gown when you arrive at the MR exam site. If your child will be sedated or receive a contrast material for the MRI, we will give you more specific instructions before the exam.
What will happen during the test?
Because it is very important that your child lies still during the MRI exam we may require that he/she is sedated during the exam. If your child’s doctor has requested that your child have an MRI with contrast, we will first insert an IV, usually into his/her hand or arm. Rarely, a child develops itching and hives from the contrast, which we can relieve with medication. Even more rarely a child becomes light-headed or has difficulty breathing; these may indicate a more severe allergic reaction, and you should notify the technologist or nurse immediately. If your child is being sedated for the exam we will also insert an IV.
We will then take you and your child to the MRI exam room, and position him/her on the MRI table, usually on his/her back, but for some scans your child may have to lie on his/her stomach or side. Once your child is positioned properly the table will slide into the scanner, and a red light may shine on your child’s body, which helps ensure that he/she is properly positioned. MRI scanners make loud buzzing and clicking sounds, and we will give your child ear plugs to make him/her more comfortable. The MRI technologist will leave the room to perform the scan, but he/she will be able to see, hear, and speak with your child at all times.
The MRI scan can take from 30 minutes to one hour.
What can I do to help my child feel comfortable during this test?
Young children sometimes find the MRI scanner a bit frightening. You can remain with your child in the imaging area during the exam to offer comfort and reassurance. We can also arrange to have a child life specialist at your child's appointment to help your child better cope with the stress of the procedure.
Are there any risks?
MRI does not use ionizing radiation, the type of radiation used in x-rays and CT scans, and there are no known harmful side-effects associated with temporary exposure to the strong magnetic field used by MRI scanners. There is a slight risk that your child will develop an allergic reaction to the contrast agent.
After the test
After the exam most children can immediately resume their normal activities. If your child was sedated, though, we will ask you to wait in the imaging area after the exam until your child is reasonably alert.
A radiologist will analyze the MRI images and will share the results with the doctor who requested the exam. Your child’s doctor will then discuss the results with you.