Department of Radiology,
Lister Hospital,
Stevenage,
Herts SG1 4AB

Email: Dr. Amerasekera
Tel: 01438 781 028
Fax: 01438 781 176

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The North Herts Radiology Group

MRI Scans

This service is available at the Lister Hospital and at Pinehill Hospital. At Pinehill Hospital scans are done one day a week.

Magnetic Resonance Imaging

Clinical MRI has been one of radiology's great success stories since its introduction in the mid-1980s. Few would dispute the enormous impact it's had on our ability to diagnose pathologic conditions of the brain, spine, and musculoskeletal system. Body MRI, on the other hand, has lagged behind the other applications. Whereas MRI has clear advantages over CT for central nervous system and musculoskeletal imaging, its superiority is less apparent in the abdomen. CT and ultrasound remain the dominant cross-sectional modalities for abdominal imaging. MRI is one of the latest medical technology that allows your doctor to "see" soft tissue muscles, fat, and internal organs without the use of X-rays, making it the safest and most comprehensive diagnostic scan available today. Using two natural,safe forces- magnetic fields and radio waves-this unique imaging technique can look "through" hard bones to examine underlying soft tissue. MRI can pinpoint brain lesions, problems of the spinal cord, abdomen, bone marrow and other organs and tissue-all without radiation. This is very useful in the early discovery and treatment planning for many conditions and diseases. Other advantages of our MRI system is the shorter scanning times, which minimize the patient discomfort and provide for quicker diagnosis, higher accuracy than other methods of imaging, and cost effectiveness as an out-patient procedure

What happens during the procedure?

The patient is comfortably positioned on a special table which slides into the MRI system opening where the magnetic field is created. Then the radiologist and technologist leave the room and the individual MRI sequences are performed. The patient will hear tapping noises during the examination. The tapping is created when magnetic field gradient coils are switched on and off to measure the MRI signal reflecting back out of the patient's body. The patient is able to communicate with the radiologist or technologist at any time using an intercom. Also, many MRI Units will allow a friend or, if a child is being examined, a parent, to stay in the room. Depending on how many images are needed, the examination will generally take from 15 to 45 minutes, although a very detailed study may take longer. You will be asked not to move during the actual imaging process, but between sequences some movement is allowed. Patients are generally required to remain still for only a few seconds to a few minutes at a time. Depending on the part of the body being examined, a contrast agent may be used to enhance the visibility of certain tissues or blood vessels. A small needle connected to an intravenous line is placed in an arm or hand vein. The contrast agent is injected about two-thirds of the way through the exam. When the exam is over the patient is asked to wait until the images are examined to determine if more images are needed

How do I prepare for the procedure?

Because the strong magnetic field used for MRI will pull on any ferromagnetic metal object implanted in the body, MRI staff will ask whether you have a prosthetic hip, an aneurysm clip in the brain, heart pacemaker (or artificial heart valve), intrauterine device (IUD), or any metal plates, pins, screws, or surgical staples in your body. In most cases, surgical staples, plates, pins and screws pose no risk during MRI if they have been in place for more than 4-6 weeks. Dyes used in tattoos and permanent eyeliner may contain metallic iron oxide and could heat up during MRI; however, this is rare. You will be asked if you have ever had a bullet or shrapnel in your body, or ever worked with metal. If there is any question of metal fragments, especially in the orbit, you may be asked to have an x-ray that will detect any such metal objects. Tooth fillings usually are not affected by the magnetic field, but they may distort images of the facial area or brain, so the radiologist should be aware of them. The same is true of braces, which may make it hard to "tune" the MRI unit to your body. You will be asked to remove anything that might degrade MRI images of the head, including hairpins, jewelry, eyeglasses, hearing aids, and any removable dental work. The radiologist or radiographer may ask if you have any drug allergies and whether you have undergone any surgery in the past. If you are or might be pregnant, mention it to the MRI staff. Some patients who undergo MRI in an enclosed unit may feel confined or claustrophobic. If you are not easily reassured, a sedative may be administered. Roughly 1 in 20 patients will require medication .

Gadolinium

This is an approved contrast agent for MRI. Gadolinium, or gadodiamide, provides greater contrast between normal tissue and abnormal tissue in the brain and body. Gadolinium looks clear like water and is non-radioactive. After it is injected into a vein, Gadolinium accumulates in the abnormal tissue that may be affecting the body or head. Gadolinium causes these abnormal areas to become very bright (enhanced) on the MRI. This makes it very easy to see. Gadolinium is then rapidly cleared from the body by the kidneys.

What does Gadolinium do?

Gadolinium allows the MRI to define abnormal tissue with greater clarity than ever before. Tumors enhance after Gadolinium is given. The exact size of the tumor and location are very important in treatment planning and follow up. Gadolinium is also helpful in finding small tumors by making them bright and easy to see.

Is Gadolinium safe?

Gadolinium has been used for years in adults and children in the United States, Europe and Japan, without any serious complications in thousands of patients. In USA the FDA declared Gadolinium safe for use in MRI in 1988. A few side effects, such as mild headache, nausea and local burning can occur. Very rarely (less than one in a thousand), patients are allergic to Gadolinium. If you have kidney problems, it must be used with caution. Gadolinium should be used in pregnant patients or nursing mothers only when the benefits outweigh the risk. Gadolinium used in MRI is many times safer than the iodine type contrast used in CT scans.

Side effects

The unwanted affects of the contrast agent injection include mild headache, nausea and local pain. Rarely (less than 1% of the time) low blood pressure and lightheadedness occurs. This can be treated immediately with intravenous fluids. Very rarely (less than one in one thousand), patients are allergic to the contrast agent. These effects are most commonly itchy eyes, but more severe reactions have been seen which result in shortness of breath.

What about breast feeding?

More data are available for Magnevist than for the other agents. Magnevist is excreted in very low concentrations (i.e., 0.011% of the total dose) in human breast milk over approximately 33 hours. The concentration of this contrast agent in breast milk peaks at approximately 4.75 hours and decreases to less than a fifth of this level (to less than 1 micromol/L) 22 hours after injection. For this reason, and as an extra precaution, it is recommended that nursing mothers express their breasts and not breastfeed for 36 to 48 hours after administration of an MR imaging contrast agent, to ensure that the nursing child does not receive the drug in any appreciable quantity."

Magnetic Resonance Angiography

(MRA) is a completely non-invasive imaging procedure used to detect and evaluate arterial vascular disease anywhere in the body. Non-invasive means no injections, catheters, incisions or dyes of any kind are used on the patient during MRA. A new application to high-tech MRI, MRA gives us the tools to easily perform comprehensive, routine vascular studies.

Magnetic resonance angiography, or MRA, uses the natural magnetic properties of the hydrogen atoms in our bodies to create (with the help of a computer) images of the blood vessels. It is a special type of magnetic resonance imaging (MRI) study and it is obtained by the same machine. Often, the patient having an MRI performed will have an MRA performed at the same time. Whereas MRI looks at the organs and soft tissues of the body, MRA looks specifically at the blood vessels. It is painless and the whole study takes less than an hour to perform. Who receives an MRA? If your doctor suspects you may have narrowing or other abnormalities of arteries or veins in your head or neck, MRA often can visualize them. MRA also can detect abnormal widenings, called aneurysms, of the arteries in your brain. Sometimes, it can be used to investigate abnormalities in the vessels of the body as well. MRA does not usually involve the use of needles and catheters, or the administration of x-ray contrast material or preparation. In many cases, MRA will provide the information needed and will make the x-ray angiogram unnecessary. As with MRI, patients with heart pacemakers, brain aneurysm clips, inner ear implants, or metal particles in or around their eyes should not have an MRA examination. Pregnant women are advised to delay having an MRA examination until after delivery, unless it is a medical emergency. MRA does not involve the use of x-rays.

How do I prepare for an MRA? Very little preparation is necessary. You should inform your doctor and the staff at the MRI center of any prior operations you have had (especially insertion of cardiac pacemakers) or if you have worked with or around sheet metal.

How is the MRA performed? As with MRI, you will lie on a patient table that will move slowly into the center of a tube-shaped machine. The bore of the tube is well-lit and well-ventilated. Although the machine itself does not move, it makes a continuous thumping sound while the images are being obtained. You will be able to hear and talk to the technologist performing the examination. It is important that you do not move while the images are being obtained.

How do you obtain the results of your exam? Your exam will be interpreted by a radiologist. The results are then sent to your physician (who ordered the study), who will discuss them with you.

Central Nervous System

MRI has experienced widespread use in diagnosing diseases of the central nervous system. Spinal cord deterioration and tumors of the brain are especially well visualized with MRI, and it was the first method used to visualize multiple sclerosis. A very common application of MRI is imaging of the entire spine for assessment of herniated slipped discs. MRI of the brain is performed to diagnose brain tumours, haemorrhages and infarctions. It helps in the diagnosis and assessement of the extent of involvement of the brain and spinal cord in Multiple Sclerosis. MRA shows the arteries and veins of the brain when looking for aneurysms,thrombosis and arterio-venous malformations. The coverings of the brain are called meninges. Meningeal disease may also be adequately demonstrated by MRI.

Meniscus

Torn meniscus

ACL and PCL

Musculo-Skeletal Radiology

Bone and Joint MRI is the only imaging modality to provide simultaneous, non-invasive visualization of cartilage, ligaments, bone, muscle, fat and menisci. Disorders of the bones, knees, temporomandibular joint (TMJ) and other joints may be diagnosed with results superior to currently employed methods such as conventional X-ray and arthrography. MRI provides the

first non-invasive technique to evaluate several common shoulder disorders. MRI demonstrates the effects of impingement syndrome prior to an actual rotator cuff tear and will detect most, if not all, complete and partial tears of the rotator cuff. Also, MRI is recommended for patients with knee pain when internal derangements like meniscus tear or ligamentous injury are suspected.

The parts of the musculoskeletal system that are most frequently imaged with MRI are the knee and shoulder. However, MRI has also been used to study almost every joint in the body, including the spine, hips, wrists, and hands. MRI requires specialized equipment and expertise and allows evaluation of some body structures that may not be as visible with other imaging methods

MRI of the Body

A rapidly growing area of Magnetic Resonance lies in the imaging of the chest and abdomen. Images can be acquired in a fashion that allows the physician to watch the heart in motion. Other applications of MRI where the imaging has proven to be extremely useful are studies of the liver, kidney adrenal glands, male and female pelvis, and abdominal blood vessels.

Abdominal MRI

Liver
MRI compares favorably with contrast-enhanced CT and sonography for non-invasive demonstration of liver tumors, both those originating in the liver and those metastasizing to the liver. CT is better for showing the extent of tumor spread outside the liver because of better demonstration of bowel. When a good bowel contrast agent for MRI becomes readily available, MRI will probably replace CT for this purpose. Although a few hepatic tumors, such as hemangiomas, can be specifically diagnosed by their MR appearance, most still require biopsy for definitive diagnosis. The same is true for most diffuse diseases of the liver cells, with the exception of haemochromatosis, a disorder of excess iron storage within the liver, which turns the liver black on MRI. MRI is the best single noninvasive preoperative study prior to liver transplantation. Not only can it establish whether or not the portal and hepatic veins are patent, but it can screen the liver for occult tumors. Sonography is the best initial test to evaluate patients for clots in the hepatic veins, portal vein or inferior vena cava, but MRI is often used if questions remain after the ultrasound exam.

Pancreas
Contrast enhanced CT is still the preferred method of evaluating patients with suspected pancreatic cancer, other pancreatic tumors, or pancreatitis. However, patients who cannot receive intravenous CT contrast should consider MRI to evaluate pancreatic cancer especially if a relatively new machine with rapid scanning capability and fat suppression capability is available. MRI can be a helpful adjunctive test when the CT is equivocal.

Cancer of the Stomach, Colon or Rectum
Imaging studies are not particularly accurate in staging these cancers except for the presence or absence of liver metastases. MRI currently does not have an advantage compared to CT except for local staging of rectal cancer. MRI using a coil placed in the rectum is more accurate than CT and may help the surgeon decide if a colostomy can be avoided.
Abdominal Aorta and Inferior Vena Cava
Both regular MRI and magnetic resonance angiography (MRA) are important non-invasive modalities for evaluating suspected aortic aneurysm, aortic dissection, postoperative aortic problems, renal and iliac arterial stenoses or aneurysms, and inferior vena caval thrombosis. CT angiography is also being studied for these applications. The preferable test is a now a function of local equipment capability and expertise.

Lymph Nodes
Contrast enhanced CT is preferable for diagnosing retroperitoneal lymphadenopathy. MRI is helpful in selected cases, especially when intravenous contrast cannot be used. When a good bowel contrast material for MRI becomes available, MRI will probably supplant CT for this indication.

Kidneys
Contrast enhanced CT is better than MRI for the diagnosis of renal mass lesions. MRI is better than non-contrast CT. The two methods are equivalent for staging known renal cancer. Contrast enhanced CT is generally preferred over MRI when an additional imaging test is required for urinary tract stone disease or medical renal disease or renal inflammations after sonography and intravenous urography. MRI is not that useful for evaluating renal transplants. A few centers have experience with a unique MR application--MR urography--in which MRI is used to quickly screen or serially evaluate the urinary tract for obstruction. This would replace the role formerly held by intravenous urography (IVU or IVP). It will be interesting to see over the next few years whether this application takes hold and spreads.

Adrenal Glands
CT remains the primary procedure for evaluating the adrenal glands. MRI is useful in evaluating adrenal masses in cancer patients since it can often tell physicians which masses are likely to be metastases and which are probably innocuous benign tumors. Pheochromocytoma is an unusual adrenal tumor which causes high blood pressure and is very bright on certain types of MRI scans. MRI is the best imaging test for diagnosing and staging pheochromocytoma. CT and nuclear medicine are also useful.
Other: Psoas Muscles, Ureters, Retroperitoneal Fibrosis
Although CT is usually used first, MRI is as good or better at imaging most diseases of these structures. An exception is small stones in the ureter for which CT is better.

MRI PELVIS

New equipment (coils) now available greatly improves imaging in the pelvis. In women, MRI of the pelvis is increasingly used to evaluate the uterus, cervix, ovaries and bladder. In men, MRI of the pelvis is increasingly used to evaluate the prostate, bladder, penis, and scrotum. Typical indications for a MRI of the pelvis include cancer staging, pain and palpable masses. MRI of the pelvis can help detect enlarged lymph nodes, fibroids, ovarian masses, prostate cancer staging, metastatic disease, testicular cancer, and structural abnormalities

CHEST MRI

Magnetic Resonance Imaging (MRI) is a noninvasive imaging technique. It is used to view organs, soft-tissue, bone, and other internal body structures. In a chest MRI, the person's body is exposed to radio waves while in a magnetic field. Cross-sectional pictures of the chest are produced by energy emitted from hydrogen atoms in the body's cells. An individual is not exposed to harmful radiation during this test.

Indications for the examination
· lung cancer
· heart and vascular disease
· disorders affecting the airways and chest wall
· diseases of the heart valves, chambers and muscle
· tears in the aorta, the body's largest artery

Excessive movement can blur MRI images. If you have difficulty lying still or are very anxious, you may be given a sedative. There is no recovery required (unless you have been sedated). After an MRI scan, you can resume normal diet, activity, and medications.

As the test begins, the person lies on a flat platform. The platform then slides into a doughnut-shaped magnet where the scanning takes place. To prevent image distortion on the final images, the person must lie very still for the duration of the test.

Commonly, a special substance called a contrast agent is administered prior to or during the test. The contrast agent is used to enhance internal structures and improve image quality. Typically, this material is injected into a vein in the arm.
Excessive movement can blur MRI images. If you have difficulty lying still or are very anxious, you may be given a sedative. There is no recovery required (unless you have been sedated). After an MRI scan, you can resume normal diet, activity, and medications.

The scanning process is painless. However, the part of the body being imaged may feel a bit warm. This sensation is harmless and normal. Loud banging and knocking noises are heard by the person during many stages of the exam. Earplugs are provided for people who find the noises disturbing.

After the test, the person is asked to wait until the images are viewed to see if more images are needed. If the pictures look satisfactory, the person is allowed to leave.

Frequently, the chest MRI will help to better evaluate diseases of the heart, lung and chest wall. Chest MRIs can reveal the size and location of tumors, blood vessel abnormalities, heart problems, hemorrhages and other tissue abnormalities. This technique is useful in studying disorders of the ribs and sternum.

How the test is performed:
The MRI scanner is in an area that has been shielded from outside magnetic fields. You are asked to lie on a narrow table that can slide inside a large tunnel-like tube within the scanner. The scanner creates a magnetic field around you, then pulses radio waves that are directed at the tissues in question. Several sets of images are usually required, each taking from 2 to 15 minutes. The complete scan takes about 1 hour; some scans take more than 90 minutes.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
· infant test or procedure preparation (birth to 1 year)
· toddler test or procedure preparation (1 to 3 years)
· preschooler test or procedure preparation (3 to 6 years)
· schoolage test or procedure preparation (6 to 12 years)
· adolescent test or procedure preparation (12 to 18 years)

How the test will feel:
There is no pain. The magnetic field and radio waves are not felt. The primary discomfort is the claustrophobic feeling that some people experience from being inside the scanner. The table may be hard or cold, but you can request a blanket or pillow. The machine produces loud thumping and humming noises. Ear plugs are usually given to reduce the noise. A technologist observes you during the entire procedure and may enter the room to speak to you or may speak with you through an intercom in the scanner.

Why the test is performed:
MRI provides detailed pictures of tissues within the chest cavity, without obstruction by overlying bone. It may be used to clarify findings from previous X-rays or CT scans. It can show the structures of the chest from multiple planes. It is useful in the diagnosis of abnormal growths, and can provide information for the staging (such as the size, extent, and spread) of thoracic tumors. MRI clearly shows lymph nodes and blood vessels, and is a noninvasive procedure that can evaluate blood flow. MRI can distinguish tumors or other lesions from normal tissues. MRI is sometimes used to avoid the dangers of angiography or of repeated exposure to radiation.

MR - CHOLANGIOGRAPHY (MRCP)

This examination is performed to find the cause of bile duct obstruction. The commonest cause of obstruction is gall stones. This examination also shows the pancreatic duct which may be obstructed due to a tumour or gall stones. The other examination performed to show the bile ducts is ERCP which is a more invasive procedure. For MRCP examinations no injections are necessary.

DIFFUSION MR IMAGING

Diffusion-weighted MR imaging has steadily evolved from a basic research tool to a clinical tool. Diffusion is a physical property of molecules referring to their ability to move randomly in relation to their thermal energy. The use of alteplase for intravenous fibrinolytic treatment of acute cerebrovascular thrombosis helps in the management of acute, nonhemorrhagic stroke. Clinical outcomes from alteplase, as well as other acute stroke therapies could be improved with better patient selection. For example, fibrinolytic therapy of patients who do not have vascular occlusive disease isn't likely to help. Likewise, patients with already completed major strokes might not benefit from any therapy. More advanced imaging techniques such as diffusion imaging is likely to improve triage of acute stroke patients into appropriate treatment, or non-treatment groups. Cancer patients who now endure months of treatment-and then weeks of anxious waiting to see whether it worked-may soon get word of their tumors' response within days of starting therapy, thanks to a new use for a widely available MRI technique. One of the biggest problems in dealing with many solid cancers is measuring their response to treatment in a timely way,. Diffusion MRI seems to provide a way to gauge that response faster and could individualize the clinical management of each patient. Even though cancer treatments such as chemotherapy or radiation kill tumor cells immediately, it often can be weeks before the body absorbs enough of the dead cells to produce a change in tumor size that's visible on an MRI scan. Already widely used to diagnose strokes, diffusion MRI can be done using nearly any closed MRI scanner, and it adds just a few minutes to a regular scan.

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