Cardiac CT Scan & MRI

 Procedure Overview (Cardiac CT Scan & MRI)

Computed tomography (CT or CAT scan) is a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than standard x-rays.
 

In standard x-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a standard x-ray, a lot of detail about internal organs and other structures is not available.
 

In computed tomography, the x-ray beam moves in a circle around the body. This allows many different views of the same organ or structure. The x-ray information is sent to a computer that interprets the x-ray data and displays it in a two-dimensional (2D) form on a monitor.
 

CT scans may be done with or without “contrast.” Contrast refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your physician will notify you of this prior to the procedure.
 

CT scans of the chest can provide more detailed information about organs and structures inside the chest than standard x-rays of the chest, thus providing more information related to injuries and/or diseases of the chest (thoracic) organs.
 

CT scans of the chest may also be used to visualize placement of needles during biopsies of thoracic organs or tumors, or during aspiration (withdrawal) of fluid from the chest. CT scans of the chest are useful in monitoring tumors and other conditions of the chest before and after treatment.
 

Other related procedures that may be used to assess the heart include resting or exercise electrocardiogram (ECG or EKG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest x-ray, echocardiogram, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, radionuclide angiography, and ultrafast CT scan. Please see these procedures for additional information.
 

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Reasons for the Procedure

The chest contains organs of the respiratory and cardiovascular systems, as well as the esophagus (hollow tube of muscle extending from below the tongue to the stomach). A CT scan of the chest may be performed to assess the chest and its organs for tumors and other lesions, injuries, intra-thoracic bleeding, infections, unexplained chest pain, obstructions, or other conditions, particularly when another type of examination, such as x-rays or physical examination, is not conclusive.
 

A CT scan of the chest may also be used to evaluate the effects of treatment of thoracic tumors. Another use of chest CT is to provide guidance for biopsies and/or aspiration of tissue from the chest.

There may be other reasons for your physician to recommend a CT scan of the chest.
 

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Risks of the Procedure

You may want to ask your physician about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of x-rays, so that you can inform your physician. Risks associated with radiation exposure may be related to the cumulative number of x-ray examinations and/or treatments over a long period of time.
 

If you are pregnant or suspect that you may be pregnant, you should notify your physician. Radiation exposure during pregnancy may lead to birth defects.
 

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications, contrast dye, iodine, or shellfish should notify their physician.
 

Patients with kidney failure or other kidney problems should notify their physician. In some cases, the contrast dye can cause kidney failure, especially if the person is taking Glucophage (a diabetic medication).
 

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.

Certain factors or conditions may interfere with the accuracy of a CT scan of the chest. These factors include, but are not limited to, the following:

• metallic objects within the chest, such as surgical clips or a pacemaker

• body piercings on the chest

• barium in the esophagus from a recent barium study

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Before the Procedure

• Your physician will explain the chest CT procedure to you and offer you the opportunity to ask any questions that you might have.

• If your procedure involves the use of contrast dye, you may be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear.

• Notify the technologist if you have ever had a reaction to any contrast dye, or if you are allergic to iodine or seafood.

• Generally, there is no fasting requirement prior to a CT scan, unless a contrast dye is to be used. Your physician will give you special instructions ahead of time if contrast is to be used and if you will need to withhold food and drink.

• Notify the technologist if you are pregnant or suspect you may be pregnant.

• Notify the technologist if you have any body piercing on your chest and/or abdomen.

• Dress in clothes that permit access to the area or that are easily removed.

• Based upon your medical condition, your physician may request other specific preparation.

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During the Procedure

A chest CT may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.

Generally, the chest CT follows this process:

1. You will be asked to remove any clothing, jewelry, or other objects that may interfere with the procedure.

2. If you are asked to remove clothing, you will be given a gown to wear.

3. If you are to have a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye. For oral contrast, you will be given a liquid contrast preparation to swallow.

4. You will lie on your back with your arms above your head on a scan table that slides into a large, circular opening of the scanning machine. Pillows and straps may be used to prevent movement during the procedure.

5. The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.

6. As the scanner begins to rotate around you,  x-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.

7. The x-rays absorbed by the body's tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.

8. It will be important that you remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.

9. If contrast dye is used for your procedure, you will be removed from the scanner after the first set of scans has been completed. A second set of scans will be taken after the contrast dye has been administered.

10. If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.

11. You should notify the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations.

12. When the procedure has been completed, you will be removed from the scanner.

13. If an IV line was inserted for contrast administration, the line will be removed.

14. You may be asked to wait for a short period of time while the radiologist examines the scans to make sure they are clear.

While the CT procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.
 

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After the Procedure

If contrast dye was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.
 

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician as this could indicate an infection or other type of reaction.
 

If you are given contrast by mouth, you may experience diarrhea after the procedure.
 

Otherwise, there is no special type of care required after a CT scan of the chest. You may resume your usual diet and activities unless your physician advises you differently.
 

Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.
 

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Procedure Overview (MRI)

What is magnetic resonance imaging (MRI) of the heart?

Magnetic resonance imaging (MRI) is a diagnostic procedure that uses a combination of a large magnet, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.
 

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How does MRI work?

The MRI machine is a large, cylindrical (tube-shaped) machine that creates a strong magnetic field around the patient. This magnetic field, along with a radiofrequency, alters the hydrogen atoms' natural alignment in the body. Computers are then used to form two-dimensional (2D) images of the heart's structure based on the activity of the hydrogen atoms. Cross-sectional views can be obtained to reveal further details. MRI does not use radiation, as do x-rays or computed tomography (CT scans).
 

A magnetic field is created and pulses of radio waves are sent from a scanner. The radio waves knock the nuclei of the atoms in the body out of their normal position. As the nuclei realign back into proper position, they send out radio signals. These signals are received by a computer that analyzes and converts them into an image of the part of the body being examined. This image appears on a viewing monitor. Some MRI machines look like narrow tunnels, while others are more open.
 

MRI may be used instead of a CT scan in situations where organs or soft tissue are being studied, because with MRI scanning bones do not obscure the images of organs and soft tissues, as does CT scanning.

Other related procedures that may be used to assess the heart include resting or exercise electrocardiogram (ECG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest x-ray, computed tomography (CT scan) of the chest, electrophysiological studies, myocardial perfusion scans, radionuclide angiography, and ultrafast CT scan. Please see these procedures for additional information.
 

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Reasons for the Procedure

MRI of the heart may be performed for further evaluation of signs or symptoms that may suggest:

• atherosclerosis - a gradual clogging of the arteries over many years by fatty materials and other substances in the blood stream

• cardiomyopathy - an enlargement of the heart due to thickening or weakening of the heart muscle

• congenital heart disease - defects in one or more heart structures that occur during formation of the fetus, such as a ventricular septal defect (hole in the wall between the two lower chambers of the heart)

• congestive heart failure - a condition in which the heart muscle has become weakened to an extent that blood cannot be pumped efficiently, causing buildup (congestion) in the blood vessels, lungs, feet, ankles, and other parts of the body

• aneurysm - a dilation of a part of the heart muscle or the aorta (the large artery that carries oxygenated blood out of the heart to the rest of the body), which may cause weakness of the tissue at the site of the aneurysm

• valvular heart disease - malfunction of one or more of the heart valves that may cause an obstruction of the blood flow within the heart

• cardiac tumor - a tumor of the heart that may occur on the outside surface of the heart, within one or more chambers of the heart (intracavitary), or within the muscle tissue of the heart

There may be other reasons for your physician to recommend an MRI of the heart.
 

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Risks of the Procedure

Because radiation is not used, there is no risk of exposure to radiation during an MRI procedure.
 

Due to the use of the strong magnet, MRI cannot be performed on patients with implanted pacemakers, intracranial aneurysm clips, cochlear implants, certain prosthetic devices, implanted drug infusion pumps, neurostimulators, bone-growth stimulators, certain intrauterine contraceptive devices, or any other type of iron-based metal implants. MRI is also contraindicated in the presence of internal metallic objects such as bullets or shrapnel, as well as surgical clips, pins, plates, screws, metal sutures, or wire mesh.
 

If you are pregnant or suspect that you may be pregnant, you should notify your physician. Due to the potential for a harmful increase in the temperature of the amniotic fluid, MRI is not advised for pregnant patients.

MRI generally is not advised for patients with epilepsy.
 

If contrast dye is used, there is a risk for allergic reaction to the dye. Patients who are allergic to or sensitive to medications, contrast dye, iodine, or shellfish should notify the radiologist or technologist.
 

MRI contrast may have an effect on other conditions such as allergies, asthma, anemia, hypotension (low blood pressure), and sickle cell disease.
 

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.
 

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Before the Procedure

• Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

• If your procedure involves the use of contrast dye, you will be asked to sign a consent form that gives permission to do the procedure. Read the form carefully and ask questions if something is not clear.

• Notify the technologist if you have ever had a reaction to any contrast dye, or if you are allergic to iodine or seafood.

• Generally, there is no special restriction on diet or activity prior to an MRI procedure.

• Notify the technologist if you are pregnant or suspect you may be pregnant.

• Before the examination, it is extremely important that you inform the technologist if any of the following apply to you:

  • you are claustrophobic and think that you will be unable to lie still while inside the scanning machine, in which case you may be given a sedative

  • you have a pacemaker or have had heart valves replaced

  • you have any type of implanted pump, such as an insulin pump

  • you have metal plates, pins, metal implants, surgical staples, or aneurysm clips

  • you have any metallic fragments anywhere in the body

  • you have permanent eye liner or tattoos

  • you are pregnant or suspect you may be pregnant

  • you ever had a bullet wound

  • you have ever worked with metal (e.g., a metal grinder or welder)

  • you have any body piercing

  • you have an intrauterine device (IUD)

• Sedative medication may be given if you have claustrophobia and/or anxiety that would make it difficult for you to remain still during the procedure.

• Based upon your medical condition, your physician may request other specific preparation.

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During the Procedure 

MRI may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician’s practices.

Generally, an MRI follows this process:

1. You will be asked to remove any clothing, jewelry, eyeglasses, hearing aids, hairpins, removable dental work, or other objects that may interfere with the procedure.

2. If you are asked to remove clothing, you will be given a gown to wear.

3. If you are to have a procedure done with contrast, an intravenous (IV) line will be started in the hand or arm for injection of the contrast dye.

4. You will lie on a scan table that slides into a large circular opening of the scanning machine. Pillows and straps may be used to prevent movement during the procedure.

5. The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You will have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.

6. A surface coil may be placed over the area to be examined.

7. You will be given earplugs or a headset to wear to help block out the noise from the scanner. Some headsets may provide music for you to listen to.

8. During the scanning process, a clicking noise will sound as the magnetic field is created and pulses of radio waves are sent from the scanner.

9. It will be important for you to remain very still during the examination, as any movement could cause distortion and affect the quality of the scan.

10. At intervals, you may be instructed to hold your breath, or to not breathe, for a few seconds. You will then be told when you can breathe. You should not have to hold your breath for longer than a few seconds.

11. If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line. These effects include coolness or discomfort at the IV site, and should only last for a few moments.

12. You should notify the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations.

13. Once the scan has been completed, the table will slide out of the scanner and you will be assisted off the table.

14. If an IV line was inserted for contrast administration, the line will be removed.

While the MRI procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

On occasion, some patients with metal fillings in their teeth may experience some slight tingling of the teeth during the procedure.
 

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After the Procedure

You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat for the length of the procedure.
 

If any sedatives were taken for the procedure, you may be required to rest until the sedatives have worn off. You will also need to avoid driving.
 

If contrast dye is used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast dye, such as itching, swelling, rash, or difficulty breathing.
 

If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician as this could indicate an infection or other type of reaction.
 

Otherwise, there is no special type of care required after a MRI scan of the heart. You may resume your usual diet and activities, unless your physician advises you differently.
 

Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.
 

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Online Resources

The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your physician. Please consult your physician with any questions or concerns you may have regarding your condition.
 

This page contains links to other Web sites with information about this procedure and related health conditions. We hope you find these sites helpful, but please remember we do not control or endorse the information presented on these Web sites, nor do these sites endorse the information contained here.
 

American College of Cardiology

American Heart Association

National Heart, Lung, and Blood Institute (NHLBI)

National Institutes of Health (NIH)

National Library of Medicine

Radiological Society of North America - Radiology Info

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