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Magnetic resonance imaging (MRI) | Diseases and conditions: Medical tests.

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What is an MRI

Magnetic resonance imaging (MRI) is a diagnostic test that results in images of the inside of the body. It is based on the processing of radio waves that pass through the patient, which is subjected to a strong magnetic field. Unlike the TAC or Plain radiographs do not use ionizing radiation (x-rays).
Magnetic resonance imaging allows to obtain very detailed images of the body, in two and three dimensions, and from any perspective. It can provide information on diseases that are not with other imaging such as ultrasound or CT techniques. It is also used when other imaging tests, are contraindicated to as for example in case of allergy to iodinated contrast used in CT.
To carry out the patient must get into a machine, that patients describe as a big washing machine, and must remain still in its interior for 30-60 minutes. RMNM devices exist to Open that can be used in people with claustrophobia. These devices are not available in many centers and images that are obtained have poorer quality than those obtained with the standard closed devices.

Why is a nuclear magnetic resonance

MRI is usually done on a specific part of the body in which suspected illness. The most common reasons why the realization of an MRI can be requested are:
In the head you can see tumors, abscesses, aneurysms, bleeding, heart attacks or nerve damage. It can also serve to study pathologies in the eyes and ear or brain degenerative diseases.
In the chest is widely used to study cardiac Anatomy or pathology of the coronary arteries. It is also used in the study of breast cancer or tumors of the lung.
Abdomen and pelvis allows you to study with great detail organs such as the pancreas, the kidneys or liver, the uterus and the ovaries in women, or the prostate in males. There you can find tumors, infections, malformations, etc.
The blood vessels are very well with the NMR. View thrombus, strokes, aneurysms, malformations, or bleeding.
MRI can diagnose many problems in bones and joints such as arthritis, fractures, ligaments, tendons and cartilage problems. In addition, as in other organs, tumors or infections can be. Used much to study problems of spine as the Herniated discs, as it allows to see in great detail the intervertebral discs, spinal cord and nerves that come out of the bone marrow. Also used frequently in the knee problems, to study their different ligaments or meniscus.
On many occasions, to perform this technique, it is necessary to manage a liquid called contrast that highlights the organs studied, and facilitates the interpretation of the images. The most widely used contrast is called gadolinium and unlike the contrast used to make a TAC, it is not composed of iodine, so it is unlikely that cause side effects or allergic. This contrast dye is administered intravenously.

Preparation for magnetic resonance imaging

These are the issues that you must consider when you undergo a magnetic resonance imaging:
Duration: the test is performed in about 30-60 minutes, although sometimes it can last more.
Entry: the test can be done on an outpatient basis.
Is necessary to be accompanied?: don't have to be accompanied by, although it might help if it makes you feel more relaxed. Where the test produce much anxiety, or if the patient cannot be still inside the appliance, are often a relaxing medication. In such a case, it will need to be accompanied by someone who can drive you home.
Drugs: is not necessary to take any prior medication.
Food: depends on the organ being studied. In some tests that include the abdomen or pelvis may be necessary to do not eat food or water for several hours before the test.
Clothing: you can wear any clothes you want, but it should be easy to remove. You don't want to carry metal objects (earrings, bracelets, etc.), because they will be asked to remove them during the test.
Documents: should be informed consent, which is a role where they explain you what is the test and its potential risks. You should read it carefully and take it signed. You must take the wheel of the test request.
Contraindications: You should not do a colonoscopy in the following cases:
  • If you are allergic to such as gadolinium MRI contrast media. In this case the test without contrast may be performed.
  • The presence of metallic material in the body, such as plates, screws, heart valves, pacemakers, shrapnel, etc. This is because all materials are attracted to the magnetic field which is created within the resonance apparatus and may be dangerous. However, many materials that are deployed today allow the realization of an MRI. This feature is reflected in the specifications of the product.
  • The use of intrauterine devices (IUDS), then the IUD may have metallic substances such as copper.
  • Patients with claustrophobia that not tolerated to be inside the device during the test. In these cases, you can perform a sedation of the patient or use open NMR devices.
  • Patients who can not remain still during the test. You can also solve this problem with sedation.
  • Very obese patients who do not climb on the appliance. In this case also open NMR devices can be used.
  • Patients with severe renal or hepatic insufficiency, or some diseases such as sickle cell anemia, in which the contrast can worsen the picture. In these cases, non-contrast test can be performed.
  • In some cases of recent surgery on a blood vessel.
  • Patients clinically "unstable", i.e., that are very serious and they may require some medication, or even urgent cardiopulmonary resuscitation maneuvers, then inside the machine not can be properly monitored and his attention can be complicated.
Pregnancy and lactation: risks that can have the test on the fetus are not known. Therefore, in general is not recommended testing during pregnancy, especially during the first trimester. The contrast used, gadolinium, crosses the placenta and the effect that may have on the fetus is unknown. However, if the benefits of the test outweigh the possible risks can be the MRI provided that the mother is sufficiently informed.
Regarding breastfeeding, medium contrast manufacturers indicate that it is you should not breast-feed the baby for 24-48 hours after administration. However, American and European Radiology societies consider that the amount of gadolinium which is excreted into milk probably does not have toxic effects on the baby. Therefore, based on available data, they suggest that there is no risk in continue breastfeeding. Anyway, those mothers who are concerned about the risk that your child may have this slight exposure to contrast, can avoid breastfeeding during the 24 hours following the completion of the procedure. During these 24 hours the mother can remove the milk through a pump and discard. In anticipation of this period that won't be breastfeeding, the mother can also remove milk before testing, and store enough to cover the child's needs 24 hours.

Other considerations

Not do exercise immediately before the test and be as relaxed as possible, because any movement can alter the result should.
In addition to all metal objects, should remove any patch that may have on the skin, as if they carry something metal content may result in Burns.

How magnetic resonance imaging

The unit in which the test is cubic-shaped and inside moves a stretcher that is where lies down the patient, usually face up. The stretcher is moved inside the hub and there remains throughout the test. In general, it is necessary to change the clothes by a hospital gown. They will make you take off all metal objects, since they interfere with the x-ray images and can move with the magnetic field. If it is necessary the administration of contrast you will pick up a venous pathway in the arm and introduced the contrast there moments before the test. They can also give you a medication to be more relaxed. Inside the device can hold you arms, head and chest with straps to prevent movement. Also put a device in the chest that detects the respiration and heart rate.
Inside the unit, you will hear the noise of a fan and you will feel air moving. You will also hear a noise rattling while the images are taken. Sometimes a headset with which you can listen to music provided him. This can help reduce noise and can help relax you.
During the procedure, a technician will be watching you from an adjoining room and will instruct you to not move. You can sometimes tell you that you do not breathe for a few seconds. You can contact the technician if he deems it necessary.
MRI is a very safe test. The magnetic field which applies does not have any detrimental effect on the body. Sometimes you can feel something hot or cold with the introduction of the contrast. Fortunately, the allergic reaction to the contrast used for MRI are very rare. Somewhat annoying can be remain still long on the couch and you can feel some claustrophobia. People who have fillings may feel a little tingling in the mouth. It is normal to feel some heat in the area that is being explored. You can contact the technician who is doing the test in case of any major discomfort.
The greatest risk of NMR is derived from a possible movement of any metallic object that has in the body due to the strong magnetic field. For this reason, it is very important to remove all metal objects or notify the technician about any materials you may have implanted. You must also remove any patch that may lead to the skin, because if you hold something metal may lead to Burns.
People with tattoos might experience some irritation on the skin.

Results of the magnetic resonance imaging

The images obtained by NMR can be seen immediately. However, their interpretation requires much expertise and is carried out by medical radiologists. This specialist will make a written report that will give you a few days of the test along with the images obtained.
The result report will include data on the technique used, if it was necessary the use of contrast, and the findings found. The type of discovery can vary greatly depending on the pathology and studied organ. Often benign or malignant, tumors, signs that indicate various infections such as abscesses, inflammation or pathology found in bones, such as fractures or malformations. In the spine can see Herniated discs and affectations of the spinal cord or nerve roots coming out of the bone marrow. In the knee, they will tell you if there is any ligament or the meniscus involvement. In relation to the vessels that irrigate the various organs, you can find thrombus, vascular infarcts (due to the blockage of an artery) or bleeding. In the liver, you can very well see the bile and detect if there are obstructions or tumors at that level.
It is sometimes necessary to repeat the test to see how evolve different injuries, either spontaneously or after any treatment. The doctor has asked the test will give you the results and will indicate the need to do any therapy or other complementary explorations.
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