Frequently Asked Questions

+What do I need to do to prepare for an MRI?

Preparing for an MR scan is very easy. You can take all your normal medications and follow usual eating schedules unless your doctor gives you special instructions. The only unusual preparation for an MR scan is that all removable metallic objects must be left outside the scanning room, including removable hearing aids, dentures and other prosthetic devices. Credit cards cannot be brought into the scanner room since the magnetic codes on them can be affected by the magnet. For optimal image quality when performing head scans, all makeup must be removed since it may contain metallic powders which are magnetic and thus degrade image quality. You may be asked to wear a hospital gown, since clothes may have metallic fasteners or metallic fibers that can interfere with the imaging.

+What does the MR scanning center staff need to know about me to perform the scan?

Besides complete information about your medical history, your doctor and the MR staff must know if you have any metal in your body which cannot be removed, including: pacemakers, implanted insulin pumps, aneurysm clips, vascular coils and filters, heart valves, ear implants, surgical staples and wires, shrapnel, bone or joint replacements, metal plates, rods, pins or screws, contraceptive diaphragms or coils, penile implants, and permanent dentures. In most cases, you can be scanned even though you have metal implants. Nevertheless, the radiologist and MRI staff must be aware of them. Also, tell a member of the staff if you are pregnant or if there is a possibility you are pregnant. IMPORTANT: DO NOT ALLOW YOURSELF TO BE SCANNED IF YOU HAVE A PACEMAKER OR OTHER IMPLANTED MECHANICALLY, ELECTRICALLY OR MAGNETICALLY ACTIVATED DEVICE. UNLESS SPECIFICALLY ORDERED BY THE RADIOLOGIST, YOU WILL NOT BE SCANNED IF YOU HAVE METAL IMPLANTS IN THE HEAD REGION

+What will happen when I get scanned?

A trained MR professional will help you into position on the scanner bed. This narrow bed slides directly into the scanner. Ask for a blanket if you are cold. It may be necessary to place a special band or ring on the area to be scanned. This band or ring is actually a special antenna that enables the scanner to pick up signals with more clarity from that portion of anatomy that is being scanned. Once you are positioned, all you have to do is relax and lie as still as you can. You will be able to talk to a member of the staff in the next room who will be able to see and hear you during the entire scan. You can have a companion stay in the scanning room with you throughout the scan. In fact, whenever possible, parents are encouraged to be in the room with their children during the scan. The procedure will take from 20 to 60 minutes depending on your doctor’s instructions. After the scan, you can resume all normal activities immediately. Infrequently, certain types of scans require the use of an injected contrast agent. If your doctor ordered this type of scan, our staff member will explain the contrast agent to you and answer your questions.

+Isn’t an MRI scan basically the same as a CAT scan?

No, except for the fact that they both use computers and they are both used for medical diagnosis, they really have very little in common. One of the most important differences between a CAT scan and an MRI is the fact that CAT scans use X-ray radiation and MRI scans do not. In other words, CAT scans are nothing more than computerized X-rays. As you probably already know, X-rays can be harmful and it is important therefore to avoid unnecessary exposure to them. Although there are still some situations in which a CAT scan should be instead of an MRI-your physician will be able to tell you when this is the case and why-for the most part, MRI’s are diagnostically superior, especially if soft tissue is involved. If a CAT scan and an MRI are diagnostically equivalent in a particular situation, an MRI is the better choice because it will not subject you to any ionizing radiation. Instead, MRI’s use harmless radio waves. In addition to the superior portrayal of soft tissue, MRI’s provide much more flexibility in portraying cross-sectional planes of the body. Unlike a CAT scanner which is relatively limited to when it comes to plane selection, an MRI can provide a cross-sectional image taken at any plane in the human body.

+Do you need a prescription for an MRI?

Yes. If you have reason to believe that an MRI would be beneficial in diagnosing your physical condition more accurately, discuss it with your doctor. If your doctor agrees, he or she will refer you to a local MRI diagnostic center for a scan.

+If I have an MRI scan, how will I find out the results?

Typically, your MRI scan will be examined or ‘read’ by a radiologist who is specially trained in MRI technology. The radiologist in turn will report to your physician, and your physician will then discuss the findings with you.

+Can I choose the type of MRI scanner I want?

Yes, you can. Your physician may have a business relationship with a particular diagnostic center and therefore prefer sending you to that particular site. The imaging centers will have closed bore scanner or open type scanners. You could ask your doctor if both types are available in your area.

+Do I have to lie still when I have an MRI?

Yes, you can. Your physician may have a business relationship with a particular diagnostic center and therefore prefer sending you to that particular site. The imaging centers will have closed bore scanner or open type scanners. You could ask your doctor if both types are available in your area.

+When is an MRI called for?

Whenever your doctor requires top-quality anatomic portrayal, especially soft tissue, chances are that an MRI will be the modality of choice. Unfortunately, the decision to prescribe or not to prescribe an MRI will not always be made on the basis of diagnostic quality. Sometimes, in a well-meaning attempt to save money for the patient or the insurance company, a physician will choose a less-expensive procedure, hoping that he or she will receive sufficient information to make a correct diagnosis. If the less-expensive test proves inadequate, however, and an MRI is prescribed later, the attempt to save money will have been futile. Even worse, the condition may be inaccurately diagnosed using a less definitive, non-MRI procedure. Because MRI portrays soft tissue with such diagnostically-useful clarity, it is relied upon frequently for revealing abdominal abnormalities-mid-field scanners are clearly superior to high-field scanners in this regard-and a wide variety of other ills as diverse as malfunctioning temporomandibular joints (TMJs) in the jaw, pinched nerves in the spinal column, heart disease and multiple sclerosis. (Nothing is superior to MRI for revealing MS.) From the beginning, of course, one of the great strengths of MRI has been its ability to reveal tumors. The second largest application for MRI at present is musculoskeletal disease. Orthopedic physicians regularly refer patients for MRI’s for a wide variety of conditions. That’s why you hear so much, for example, about professional athletes getting MRI scans. Many MRI’s have a new development of a number of specialized MRI diagnostic methods used in sports medicine. These have led the way, for example, in providing anatomical motion studies. These studies enable technologists to electronically sequence a series of MRI images to create an accurate portrayal of how a malfunctioning joint in a patient is working dynamically. Individual MRI images reveal static conditions, just as a photo snapshot reveals a person’s likeness just for an instant of time, but misses the facial expression that occurred a second or two earlier and the one that followed immediately after. A dynamic portrayal of a joint helps a physician understand how a particular joint-a shoulder, a knee, a neck or a TMJ-functions in “real life.” Incidentally, open-environment MRI scanners are clearly superior for these motion studies as they provide the space required for a patient to move their arm, leg or neck through a wide range of positions. Magnetic resonance angiography (MRA) is a well-utilized procedure that will only increase in use by cardiologists in the future. Although CAT scans are better able to show calcified plaque that has built up in an artery, physicians will increasingly turn to MRA in the future to reveal the presence and severity of soft atherosclerotic plaque. In other words, it will reveal newer, more recent plaque which has formed, enabling physicians to view the extent of artery disease more accurately and to treat that disease more appropriately. Nothing is superior to an MRI for imaging breast implants. It shows the implants much more clearly than other modalities and it has the added advantage of not using X-rays, a particular concern when imaging the breast. MRI is also superior to ultrasound, X-ray mammograms or CAT scans when it comes to revealing malignancies in very dense breasts. This is still a developing area for MRI, one which will become much more dominant in the future. The MRI applications mentioned above are just a small portion of the applications for which MRI is the modality of choice. If you have further questions, discuss them with your physician or speak with a radiologist who specializes in MRI. MRI is still a developing modality whose diagnostic power is becoming more and more appreciated with time. Already, it has replaced a great number of X-ray-based procedures and it is certain to replace even more in the future

+What is a PET scan?

Positron emission tomography, also called PET imaging or a PET scan, is a diagnostic examination that involves the acquisition of physiologic images based on the detection of radiation from the emission of positrons. Positrons are tiny particles emitted from a radioactive substance administered to the patient. The subsequent images of the human body developed with this technique are used to evaluate a variety of diseases.

+How does a PET scan work?

Before the examination begins, a radioactive substance is produced in a machine called a cyclotron and attached, or tagged, to a natural body compound, most commonly glucose, but sometimes water or ammonia. Once this substance is administered to the patient, the radioactivity localizes in the appropriate areas of the body and is detected by the PET scanner. Different colors or degrees of brightness on a PET image represent different levels of tissue or organ function. For example, because healthy tissue uses glucose for energy, it accumulates some of the tagged glucose, which will show up on the PET images. However, cancerous tissue, which uses more glucose than normal tissue, will accumulate more of the substance and appear brighter than normal tissue on the PET images.

+Why are PET scans performed?

PET scans are used most often to detect cancer and to examine the effects of cancer therapy by characterizing biochemical changes in the cancer. These scans can be performed on the whole body. PET scans of the heart can be used to determine blood flow to the heart muscle and help evaluate signs of coronary artery disease. PET scans of the heart can also be used to determine if areas of the heart that show decreased function are alive rather than scarred as a result of a prior heart attack, called a myocardial infarction. Combined with a myocardial perfusion study, PET scans allow differentiation of nonfunctioning heart muscle from heart muscle that would benefit from a procedure, such as angioplasty or coronary artery bypass surgery, which would reestablish adequate blood flow and improve heart function. PET scans of the brain are used to evaluate patients who have memory disorders of an undetermined cause, suspected or proven brain tumors or seizure disorders that are not responsive to medical therapy and are therefore candidates for surgery.

+How do I prepare for a PET scan?

PET is usually done on an outpatient basis. Your doctor will give you detailed instructions on how to prepare for your examination. You should wear comfortable, loose-fitting clothes. You should not eat for four hours before the scan. You will be encouraged to drink water. Your doctor will instruct you regarding the use of medications before the test. Note: Diabetic patients should ask for any specific diet guidelines to control glucose levels during the day of the test.

+Are there any risks involved with PET scans?

Because PET allows study of body function, it can help physicians detect alterations in biochemical processes that suggest disease before changes in anatomy are apparent with other imaging tests, such as CT or MRI. Because the radioactivity is very short-lived, your radiation exposure is low. The substance amount is so small that it does not affect the normal processes of the body. The radioactive substance may expose radiation to the fetus in patients who are pregnant or the infants of women who are breast-feeding. The risk to the fetus or infant should be considered in relation to the potential information gain from the result of the PET examination. If you are pregnant, you should inform the PET imaging staff before the examination is performed.

+What will I experience during the PET exam?

The administration of the radioactive substance will feel like a slight pinprick if given by intravenous injection. You will then be made as comfortable as possible before you are positioned in the PET scanner for the test. You will be asked to remain still for the duration of the examination. Patients who are claustrophobic may feel some anxiety while positioned in the scanner. Also, some patients find it uncomfortable to hold one position for more than a few minutes. You will not feel anything related to the radioactivity of the substance in your body.

+What will I experience during the PET exam?

The administration of the radioactive substance will feel like a slight pinprick if given by intravenous injection. You will then be made as comfortable as possible before you are positioned in the PET scanner for the test. You will be asked to remain still for the duration of the examination. Patients who are claustrophobic may feel some anxiety while positioned in the scanner. Also, some patients find it uncomfortable to hold one position for more than a few minutes. You will not feel anything related to the radioactivity of the substance in your body.

+What is “contrast” used for in a PET scan?

Contrast is a radioactive substance is administered as an intravenous injection (although in some cases, it will be given through an existing intravenous line or inhaled as a gas). It will then take approximately 30 to 90 minutes for the substance to travel through your body and accumulate in the tissue under study

+When will I receive the results of the PET scan?

Patients undergo PET because their referring physician has recommended it. A radiologist who has specialized training in PET will interpret the images and forward a report to your referring physician. It usually takes one to three days to interpret, report and deliver the results. In order to facilitate interpretation, you may be asked to bring any previous radiological images with you, such as recent CT (CAT) scans or MRI images.

+What is a CT scan?

CT (computed tomography) angiography (CTA) is an examination that uses x-rays to visualize blood flow in arterial and venous vessels throughout the body, from arteries serving the brain to those bringing blood to the lungs, kidneys, and arms and legs. CT combines the use of x-rays with computerized analysis of the images. Beams of x-rays are passed from a rotating device through the area of interest in the patient’s body from several different angles to create cross-sectional images, which then are assembled by computer into a three-dimensional picture of the area being studied. Compared to catheter angiography, which involves placing a sizable catheter and injecting contrast material into a large artery or vein, CTA is a much less invasive and more patient-friendly procedure—contrast material is injected into a small peripheral vein by using a small needle or catheter. This type of exam has been used to screen large numbers of individuals for arterial disease. Most patients undergo CT angiography without being admitted to a hospital

+How does a CT scan work?

During the examination, the rotating device spins around the patient, creating a fan-shaped beam of x-rays, and the detector takes snapshots of the beam after it passes through the patient. As many as one thousand of these pictures may be recorded in one turn of the detector. The real work of CTA comes after the images are acquired, when powerful computer programs process the images and make it possible to display them in different ways, for instance, in cross-sectional slices or as three-dimensional “casts” of the blood vessels.

+Why are CT scans performed?

CTA is commonly used to: Examine the pulmonary arteries in the lungs to rule out pulmonary embolism, a serious but treatable condition. Visualize blood flow in the renal arteries (those supplying the kidneys) in patients with high blood pressure and those suspected of having kidney disorders. Narrowing (stenosis) of a renal artery is a cause of high blood pressure (hypertension) in some patients and can be corrected. A special computerized method of viewing the images makes renal CT angiography a very accurate examination. Also done in prospective kidney donors. Identify aneurysms in the aorta or in other major blood vessels. Aneurysms are diseased areas of a weakened blood vessel wall that bulges out—like a bulge in a tire. Aneurysms are life-threatening because they can rupture. Identify dissection in the aorta or its major branches. Dissection means that the layers of the artery wall peel away from each other—like the layers of an onion. Dissection can cause pain and can be life-threatening. Identify a small aneurysm or arteriovenous malformation inside the brain that can be life-threatening. Detect atherosclerotic disease that has narrowed the arteries to the legs. Detect thrombosis (clots) in veins, for example large veins in the pelvis and legs. Such clots can travel to the lungs and result in pulmonary embolism. CTA is also used to detect narrowing or obstruction of arteries in the pelvis and in the carotid arteries, which bring blood from the heart to the brain. When a stent has been placed to restore blood flow in a diseased artery, CTA will show whether it is serving its purpose. Examining arteries in the brain may help reach a correct diagnosis in patients who complain of headaches, dizziness, ringing in the ears or fainting. Injured patients may benefit from CTA if there is a possibility that one or more arteries have been damaged. In patients with a tumor, it may be helpful for the surgeon to know the details of arteries feeding the growth.

+How do I prepare for a CT scan?

Depending on the part of the body to be examined, you may be asked to take only clear liquids by mouth before CTA. You may be asked whether you have asthma or any allergies to foods or drugs, and what medications you are currently taking. If you are pregnant, you should inform the technologist before the procedure. You probably will not have to undress if you are undergoing an exam of the head, neck, arms or legs but you will have to remove any jewelry, hair clips, dentures and the like that could show up on the x-rays and make them hard to interpret.

+Are there any risks involved with CT scans?

There is a risk of an allergic reaction—which may be serious—whenever contrast material containing iodine is injected. If you have a history of allergy to x-ray dye, your radiologist may advise that you take special medication for 24 hours before CTA to lessen the risk of allergic reaction. Another option is to undergo a different exam that does not call for contrast material injection. CTA should be avoided in patients with kidney disease or severe diabetes, because x-ray contrast material can further harm kidney function. If a large amount of x-ray contrast material leaks out under the skin where the IV is placed, skin damage can result. If you feel any pain in this area during contrast material injection, you should immediately inform the technologist. If you are breastfeeding at the time of the exam, you should ask your radiologist how to proceed. It may help to pump breast milk ahead of time and keep it on hand for use after CTA contrast material has cleared from your body. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.

+What will I experience during the CT exam?

Overall, you can expect to be in or near the examining room for 20 to 60 minutes. You may feel warm all over when contrast material is injected, but you should not feel pain at any time. Any CT study requires that you remain still during the exam. Pillows and foam pads may help make it more comfortable. At the same time, the nurse or technologist may use pads or Velcro straps to keep an area of your body from moving. The examination table will move into and out of the scanner opening, but it is not enclosed, and only a small part of your body will be inside at any one time. You may be asked to hold your breath for 10 to 25 seconds to be sure that the images will not be blurred. During the time that no actual imaging is taking place, you are free to ask questions or talk to the technologist, but friends or relatives will not be allowed in the examining room. Once the needed images have been recorded, you will be free to leave. You can eat immediately, and it is a good idea to drink plenty of fluids in the hours after the exam to help flush contrast material out of the system.

+How long will the CT scan take?

CTA takes about 10 to 25 minutes from the time the actual examination begins.

+What is “contrast” used for in a CT scan?

Before the actual exam begins, you will have a dose of contrast material injected into a vein to make the blood vessels stand out. An automatic injector machine is used that controls the timing and rate of injection, which may continue during part of the time images are recorded.

+When will I receive the results of the CT scan?

A radiologist, who is a physician experienced in CTA and other radiology examinations, will analyze the images and send a report to your personal physician, who in turn will discuss the findings with you. Typically the results of CTA are available within 24 hours, although in complicated cases special computer analysis may take somewhat longer.