If the patient feels uncomfortable during the procedure, they can speak to the MRI technician via the intercom and request that the scan be stopped. After the scan, the radiologist will examine the images to check whether any more are required.
If the radiologist is satisfied, the patient can go home. The radiologist will prepare a report for the requesting doctor. Patients are usually asked to make an appointment with their doctor to discuss the results. However, the contrast dye can cause nausea, headaches , and pain or burning at the point of injection in some people. Allergy to the contrast material is also seldom seen but possible, and can cause hives or itchy eyes. Notify the technician if any adverse reactions occur.
People who experience claustrophobia or feel uncomfortable in enclosed spaces sometimes express difficulties with undergoing an MRI scan. An MRI scanner contains two powerful magnets.
These are the most important parts of the equipment. The human body is largely made of water molecules, which are comprised of hydrogen and oxygen atoms. At the center of each atom lies an even smaller particle called a proton, which serves as a magnet and is sensitive to any magnetic field.
Normally, the water molecules in the body are randomly arranged, but on entering an MRI scanner, the first magnet causes the water molecules to align in one direction, either north or south. The second magnetic field is then turned on and off in a series of quick pulses, causing each hydrogen atom to change its alignment when switched on and then quickly switch back to its original relaxed state when switched off.
Passing electricity through gradient coils, which also cause the coils to vibrate, creates the magnetic field, causing a knocking sound inside the scanner. Although the patient cannot feel these changes, the scanner can detect them and, in conjunction with a computer, can create a detailed cross-sectional image for the radiologist.
The blood flow increases in areas where neurons are active. This gives an insight into the activity of neurons in the brain. This technique has revolutionized brain mapping, by allowing researchers to assess the brain and spinal cord without the need for invasive procedures or drug injections. Functional MRI helps researchers learn about the function of a normal, diseased, or injured brain. Standard MRI scans are useful for detecting anomalies in tissue structure.
However, an fMRI scan can help detect anomalies in activity. As such, doctors use fMRI to assess the risks of brain surgery by identifying the regions of the brain involved in critical functions, such as speaking, movement, sensing, or planning. In most other cases, it is usually not necessary to avoid food or drink prior to the scan.
However, be advised by your doctor. Claustrophobia — tell your doctor if you experience claustrophobia. Some patients find the confined space within the MRI scan unsettling. The doctor may offer you medication to help you relax during the procedure. Children — often children are given anti-anxiety medication prior to the procedure to help them relax. Talk to your doctor if you have any concerns about this. MRI scan procedure Generally, an MRI involves the following: You will be asked to remove all metal objects, including wristwatches, keys and jewellery.
These items must be left outside the scan room. In most cases, you are asked to undress and put on a cotton gown. The table then slides into the cylinder. An intercom inside the MRI scanner allows you to talk with the radiography staff. It is important to lie very still. Movement will blur or distort the pictures. While it is in operation, the MRI scanner makes noises such as knocks, loud bangs and clicks. You may be offered earplugs. In some cases, you can listen to music through headphones if you prefer.
The scanned area of your body may feel a little warm. The scan may take up to an hour, depending on the nature of the investigation. Immediately after the MRI You may be asked to wait while the radiographer checks the quality of the pictures. You will know when images are being recorded because you will hear and feel loud tapping or thumping sounds. The coils that generate the radio waves make these sounds when they are activated. You will be provided with earplugs or headphones to reduce the noise made by the scanner.
You may be able to relax between imaging sequences. However, you will need to keep the same position as much as possible without moving. You will usually be alone in the exam room. However, the technologist will be able to see, hear, and speak with you at all times using a two-way intercom. Many facilities allow a friend or parent to stay in the room if they have also been screened for safety.
Children will be given appropriately sized earplugs or headphones during the exam. Music may be played through the headphones to help pass the time. MRI scanners are air-conditioned and well-lit. In some cases, IV injection of contrast material may be given before the images are obtained.
The IV needle may cause you some discomfort and you may experience some bruising. There is also a very small chance of skin irritation at the site of the IV tube insertion. Some patients may have a temporary metallic taste in their mouth after the contrast injection.
If you do not require sedation, no recovery period is necessary. You may resume your usual activities and normal diet immediately after the exam. On very rare occasions, a few patients experience side effects from the contrast material. These may include nausea, headache, and pain at the site of injection.
It is very rare that patients experience hives, itchy eyes, or other allergic reactions to the contrast material. If you have allergic symptoms, tell the technologist. A radiologist or other doctor will be available for immediate assistance. A radiologist, a doctor trained to supervise and interpret radiology exams, will analyze the images.
The radiologist will send a signed report to your primary care or referring physician, who will share the results with you. You may need a follow-up exam. If so, your doctor will explain why. Sometimes a follow-up exam further evaluates a potential issue with more views or a special imaging technique. It may also see if there has been any change in an issue over time. Follow-up exams are often the best way to see if treatment is working or if a problem needs attention.
High-quality images depend on your ability to remain perfectly still and follow breath-holding instructions while the images are being recorded. If you are anxious, confused or in severe pain, you may find it difficult to lie still during imaging. A person who is very large may not fit into certain types of MRI machines.
There are weight limits on the scanners. Implants and other metallic objects can make it difficult to obtain clear images. Patient movement can have the same effect. A very irregular heartbeat may affect the quality of images. This is because some techniques time the imaging based on the electrical activity of the heart.
Breathing may cause artifacts , or image distortions, during MRIs of the chest, abdomen and pelvis. Bowel motion is another source of motion artifacts in abdomen and pelvic MRI studies. This is less of a problem with state-of-the art scanners and techniques. Present data show no convincing evidence that non contrast MRI harms the fetus of a pregnant woman.
However, if the need for the exam is not time sensitive your doctor may delay the exam until after delivery. MRI gadolinium contrast agents are generally avoided during pregnancy except in very specific circumstances. Your doctor will discuss the benefits and risks of any MRI procedure with you. Doctors may perform MRI after the first trimester to assess the fetus for findings that are not fully evaluated by ultrasound. MRI may not always distinguish between cancer tissue and fluid, known as edema.
An MRI exam typically costs more and may take more time than other imaging exams. Talk to your insurance provider if you have concerns about the cost of MRI. Please type your comment or suggestion into the text box below. Note: we are unable to answer specific questions or offer individual medical advice or opinions. Some imaging tests and treatments have special pediatric considerations.
The teddy bear denotes child-specific content. Please contact your physician with specific medical questions or for a referral to a radiologist or other physician.
To locate a medical imaging or radiation oncology provider in your community, you can search the ACR-accredited facilities database.
This website does not provide cost information. On the day of your MRI scan, you should be able to eat, drink and take any medication as usual, unless you're advised otherwise. In some cases, you may be asked not to eat or drink anything for up to 4 hours before the scan, and sometimes you may be asked to drink a fairly large amount of water beforehand.
This depends on the area being scanned. When you arrive at the hospital, you'll usually be asked to fill in a questionnaire about your health and medical history. This helps the medical staff to ensure you have the scan safely. Read more about who can and can't have an MRI scan. Once you have completed the questionnaire, you'll usually be asked to give your signed consent for the scan to go ahead. As the MRI scanner produces strong magnetic fields, it's important to remove any metal objects from your body.
Depending on which part of your body is being scanned, you may need to wear a hospital gown during the procedure. If you don't need to wear a gown, you should wear clothes without metal zips, fasteners, buttons, underwire bras , belts or buckles. Some MRI scans involve having an injection of contrast dye. This makes certain tissues and blood vessels show up more clearly and in greater detail.
It's also possible for contrast dye to cause tissue and organ damage in people with severe kidney disease. If you have a history of kidney disease, you may be given a blood test to determine how well your kidneys are functioning and whether it's safe to proceed with the scan. You should let the staff know if you have a history of allergic reactions or any blood clotting problems before having the injection.
0コメント