As the nuclei realign back into proper position, the nuclei send out radio signals. These signals are received by a computer that analyzes and converts them into a two-dimensional 2D image of the body structure or organ being examined.
Magnetic resonance MRI may be used instead of computed tomography CT in situations where organs or soft tissue are being studied, because MRI is better at telling the difference between normal and abnormal soft tissue.
New uses and indications for MRI have contributed to the development of additional magnetic resonance technology. Magnetic resonance angiography MRA is a new procedure used to evaluate blood flow through arteries in a noninvasive the skin is not pierced manner. MRA can also be used to detect intracranial within the brain aneurysms and vascular malformations abnormalities of blood vessels within the brain, spinal cord, or other parts of the body.
Magnetic resonance spectroscopy MRS is another noninvasive procedure used to assess chemical abnormalities in body tissues, such as the brain.
MRS may be used to assess disorders such as HIV infection of the brain , stroke , head injury , coma, Alzheimer's disease , tumors, and multiple sclerosis. Functional magnetic resonance imaging of the brain fMRI is used to determine the specific location of the brain where a certain function, such as speech or memory, occurs.
The general areas of the brain in which such functions occur are known, but the exact location may vary from person to person. During functional resonance imaging of the brain, you will be asked to perform a specific task, such as recite the Pledge of Allegiance, while the scan is being done. By pinpointing the exact location of the functional center in the brain, doctors can plan surgery or other treatments for a particular disorder of the brain.
The spinal column, also called the vertebral or spinal canal, is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas. The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back.
The spinal cord is surrounded by the bones of the spine and a sac containing cerebrospinal fluid. The spinal cord carries sensory and movement signals to and from the brain, and controls many reflexes. The central nervous system CNS consists of the brain and spinal cord. The brain is an important organ that controls thought, memory, emotion, touch, motor skills, vision, respirations, temperature, hunger, and every other process that regulates our body. The cerebrum supratentorial or front of brain is composed of the right and left hemispheres.
Functions of the cerebrum include: initiation of movement, coordination of movement, body temperature, touch, vision, hearing, judgment, reasoning, problem solving, emotions, and learning. The brainstem midline or middle of brain includes the midbrain, the pons, and the medulla. Functions of this area include: movement of the eyes and mouth, relaying sensory messages such as hot, pain, and loud , hunger, respirations, consciousness, cardiac function, body temperature, involuntary muscle movements, sneezing, coughing, vomiting, and swallowing.
The cerebellum infratentorial or back of brain is located at the back of the head. Its function is to coordinate voluntary muscle movements and to maintain posture, balance, and equilibrium. A deep part of the brain, located in the brainstem, the pons contains many of the control areas for eye and face movements. The lowest part of the brainstem, the medulla is the most vital part of the entire brain and contains important control centers for the heart and lungs.
Spinal cord. A large bundle of nerve fibers located in the back that extends from the base of the brain to the lower back, the spinal cord carries messages to and from the brain and controls many reflexes. Frontal lobe. The largest section of the brain located in the front of the head, the frontal lobe is involved in personality characteristics and movement.
Parietal lobe. The middle part of the brain, the parietal lobe helps a person to identify objects and understand spatial relationships where one's body is compared to objects around the person. The parietal lobe is also involved in interpreting pain and touch in the body. Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision. Temporal lobe. The sides of the brain, these temporal lobes are involved in memory, speech, and sense of smell.
Subdural hematoma an area of bleeding just under the dura mater, or covering of the brain. Hydrocephalus , or fluid in the brain. Help plan surgeries on the spine, such as decompression of a pinched nerve or spinal fusion.
MRI can also help to identify the specific location of a functional center of the brain the specific part of the brain controlling a function, such as speech or memory to assist in treatment of a condition of the brain. Because radiation is not used, there is no risk of exposure to ionizing radiation during an MRI exam.
Some facilities also provide goggles or headsets so the child can watch a movie during the exam. This helps the child stay still and allows for good quality images. The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet.
You will lie on a table that slides into a tunnel towards the center of the magnet. Some MRI units, called short-bore systems , are designed so that the magnet does not completely surround you. Some newer MRI machines have a larger diameter bore, which can be more comfortable for larger patients or those with claustrophobia.
They are especially helpful for examining larger patients or those with claustrophobia. Open MRI units can provide high quality images for many types of exams.
Open MRI may not be used for certain exams. For more information, consult your radiologist. Instead, radio waves re-align hydrogen atoms that naturally exist within the body. This does not cause any chemical changes in the tissues. As the hydrogen atoms return to their usual alignment, they emit different amounts of energy depending on the type of tissue they are in. The scanner captures this energy and creates a picture using this information.
In most MRI units, the magnetic field is produced by passing an electric current through wire coils. Other coils are inside the machine and, in some cases, are placed around the part of the body being imaged.
These coils send and receive radio waves, producing signals that are detected by the machine. The electric current does not come into contact with the patient.
A computer processes the signals and creates a series of images, each of which shows a thin slice of the body. The radiologist can study these images from different angles. MRI is often able to tell the difference between diseased tissue and normal tissue better than x-ray, CT, and ultrasound.
The technologist will position you on the moveable exam table. They may use straps and bolsters to help you stay still and maintain your position. The technologist may place devices that contain coils capable of sending and receiving radio waves around or next to the area of the body under examination.
MRI exams generally include multiple runs sequences , some of which may last several minutes. Each run will create a different set of noises. If your exam uses a contrast material, a doctor, nurse, or technologist will insert an intravenous catheter IV line into a vein in your hand or arm. They will use this IV to inject the contrast material. You will be placed into the magnet of the MRI unit.
The technologist will perform the exam while working at a computer outside of the room. You will be able to talk to the technologist via an intercom. If your exam uses a contrast material, the technologist will inject it into the intravenous line IV after an initial series of scans. They will take more images during or following the injection. When the exam is complete, the technologist may ask you to wait while the radiologist checks the images in case more are needed. The technologist will remove your IV line after the exam is over and place a small dressing over the insertion site.
Depending on the type of exam and the equipment used, the entire exam is usually completed in 30 to 50 minutes. Most MRI exams are painless. However, some patients find it uncomfortable to remain still. Others may feel closed-in claustrophobic while in the MRI scanner. The scanner can be noisy. It is normal for the area of your body being imaged to feel slightly warm. If it bothers you, tell the radiologist or technologist.
It is important that you remain perfectly still while the images are being taken. This is typically only a few seconds to a few minutes at a time. 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.
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. 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. 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. 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. 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.
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. At intervals, you may be instructed to hold your breath or to not breathe, for a few seconds, depending on the body part being examined.
You will then be told when you can breathe. You should not have to hold your breath for longer than a few seconds. If contrast dye is used for your procedure, you may feel some effects when the dye is injected into the IV line.
These effects usually last for a few moments. You should notify the technologist if you feel any breathing difficulties, sweating, numbness, or heart palpitations. Once the scan is complete, the table will slide out of the scanner and you will be assisted off the table.
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.
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.
Otherwise, there is no special type of care required after an MRI scan of the bones, joints, and soft tissues. 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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