What is an MRI scan?

An MRI (or magnetic resonance imaging) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner. The receiver information is processed by a computer, and an image is produced.

The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body. For some procedures, contrast agents, such as gadolinium, are used to increase the accuracy of the images.

How To Prepare

Before the CT scan, tell your doctor if you:

  • Are or might be pregnant.
  • Are allergic to any medicines, including iodine dyes.
  • Have a heart condition, such as heart failure.
  • Have diabetes or take metformin (Glucophage) for your diabetes. You may have to adjust your medicine for a day before and after the test.
  • Have had kidney problems.
  • Have asthma.
  • Have a medical device, such as a pacemaker or an insulin pump.
  • Have had multiple myeloma.
  • Have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. Barium and bismuth show up on X-ray films and make it hard to see the picture clearly.
  • Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.

When are MRI scans used?

An MRI scan can be used as an extremely accurate method of disease detection throughout the body. In the head, trauma to the brain can be seen as bleeding or swelling. Other abnormalities often found include brain aneurysms, stroke, tumors of the brain, as well as tumors or inflammation of the spine.

Neurosurgeons use an MRI scan not only in defining brain anatomy but in evaluating the integrity of the spinal cord after trauma. It is also used when considering problems associated with the vertebrae or intervertebral discs of the spine. An MRI scan can evaluate the structure of the heart and aorta, where it can detect aneurysms or tears.

It provides valuable information on glands and organs within the abdomen, and accurate information about the structure of the joints, soft tissues, and bones of the body. Often, surgery can be deferred or more accurately directed after knowing the results of an MRI scan.

What are the risks of an MRI scan?

An MRI scan is a painless radiology technique that has the advantage of avoiding x-ray radiation exposure. There are no known side effects of an MRI scan. The benefits of an MRI scan relate to its precise accuracy in detecting structural abnormalities of the body.

Patients who have any metallic materials within the body must notify their physician prior to the examination or inform the MRI staff. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner. Patients who have heart pacemakers, metal implants, or metal chips or clips in or around the eyeballs cannot be scanned with an MRI because of the risk that the magnet may move the metal in these areas. Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should not have MRI scanning.

During the MRI scan, patient lies in a closed area inside the magnetic tube. Some patients can experience a claustrophobic sensation during the procedure. Therefore, patients with any history of claustrophobia should relate this to the practitioner who is requesting the test, as well as the radiology staff. A mild sedative can be given prior to the MRI scan to help alleviate this feeling. It is customary that the MRI staff will be nearby during MRI scan. Furthermore, there is usually a means of communication with the staff (such as a buzzer held by the patient) which can be used for contact if the patient cannot tolerate the scan.

How does a patient prepare for an MRI scan and how is it performed?

All metallic objects on the body are removed prior to obtaining an MRI scan. Occasionally, patients will be given a sedative medication to decrease anxiety and relax the patient during the MRI scan. MRI scanning requires that the patient lie still for best accuracy. Patients lie within a closed environment inside the magnetic machine. Relaxation is important during the procedure and patients are asked to breathe normally. Interaction with the MRI technologist is maintained throughout the test. There are loud, repetitive clicking noises which occur during the test as the scanning proceeds. Occasionally, patients require injections of liquid (dye contrast) intravenously to enhance the images which are obtained. The MRI scanning time depends on the exact area of the body studied, but ranges from half an hour to an hour and a half.

How does a patient obtain the results of the MRI scan?

After the MRI scanning is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy) or burned to a CD. A radiologist is a physician who is specially trained to interpret images of the body. The interpretation is transmitted in the form of a report to the physician who requested the MRI scan. Your physician can then discuss the results with the patient and/or family.

MRI Scan At A Glance

  • MRI scanning uses magnetism, radio waves, and a computer to produce images of body structures.
  • MRI scanning is painless and does not involve x-ray radiation.
  • Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet.
  • Claustrophobic sensation can occur with MRI scanning.

What is Computed Tomography (CT)

A computed tomography (CT) scan uses X-rays to make detailed pictures of structures inside of the body.

During the test, you will lie on a table that is attached to the CT scanner, which is a large doughnut-shaped machine. The CT scanner sends X-rays through the body area being studied. Each rotation of the scanner provides a picture of a thin slice of the organ or area. All of the pictures are saved as a group on a computer. These images can be printed or burned to a CD.

In some cases, a dye called contrast material may be used. It may be put in a vein (IV) in your arm, to see those areas better. For some types of CT scans you drink the dye. The dye makes structures and organs easier to see on the CT pictures.

A CT scan can be used to study all parts of your body, such as the chest, belly, pelvis, or an arm or leg. It can take pictures of body organs, such as the liver, pancreas, intestines, kidneys, bladder, adrenal glands, lungs, and heart. It also can study blood vessels, bones, and the spinal cord.

How To Prepare

Before the CT scan, tell your doctor if you:

  • Are or might be pregnant.
  • Are allergic to any medicines, including iodine dyes.
  • Have a heart condition, such as heart failure.
  • Have diabetes or take metformin (Glucophage) for your diabetes. You may have to adjust your medicine for a day before and after the test.
  • Have had kidney problems.
  • Have asthma.
  • Have a medical device, such as a pacemaker or an insulin pump.
  • Have had multiple myeloma.
  • Have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medicine that contains bismuth (such as Pepto-Bismol) in the past 4 days. Barium and bismuth show up on X-ray films and make it hard to see the picture clearly.
  • Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.

Arrange for someone to take you home in case you get a medicine to help you relax (sedative) for the test.

If you have a CT scan of your belly, you may be asked to not eat any solid foods starting the night before your scan. For a CT scan of the belly, you may drink contrast material. For some CT scans, you may need a laxative or an enema before the test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form.

How It Is Done

The CT scan is performed by a radiology technologist and once the scan is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy) or burned to a CD. A radiologist is a physician who is specially trained to interpret images of the body. The interpretation is transmitted in the form of a report to the physician who requested the CT scan. Your physician can then discuss the results with the patient and/or family.

You may need to take off any jewelry. You will need to take off all or most of your clothes, depending on which area is studied. You may be able to wear your underwear for some scans. You will be given a gown to use during the test.

During the test, you will lie on a table that is attached to the CT scanner.

The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while the scanner takes pictures. You may hear a click or buzz as the table and scanner move. It is very important to lie still during the test.

During the test, you may be alone in the scanning room. But the technologist will watch you through a window. You will be able to talk to the technologist through a two-way intercom.

The test will take about 30 to 60 minutes. Most of this time is spent getting ready for the scan.

MRI Preparation Information

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