MRI


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magnetic resonance imaging

 (MRI)
a noninvasive nuclear procedure for imaging tissues of high fat and water content that cannot be seen with other radiologic techniques. The MRI image gives information about the chemical makeup of tissues, thus making it possible to distinguish normal, cancerous, atherosclerotic, and traumatized tissue masses in the image.

The patient having an MRI procedure lies in the bore of the cylindrical magnetic resonance machine; therefore, the test can induce claustrophobia. Furthermore, the person must lie motionless during the test, which can last from 15 to 90 minutes. If patients are susceptible to claustrophobia or cannot tolerate the tedium of lying still in a confined space, a sedative can be given without compromising test results.
Magnetic resonance imaging. The patient enters a cylinder, which serves as a magnet. Radiofrequency coils within the cylinder emit signals that are transformed into an image of a display unit.
Coronal view from magnetic resonance imaging (MRI). The MRI study provides anatomical information about the osseous and soft tissue extent of a tumor. From Thrall and Ziessman, 2001.

MRI

Abbreviation for magnetic resonance imaging.

MRI

magnetic resonance imaging.

MRI 1

(ĕm′är′ī′)
n. pl. MRIs
1. An image produced by magnetic resonance imaging.
2. The act or process of producing such an image.

MRI 2

abbr.
1. machine-readable information
2. magnetic resonance imaging

MRI

abbreviation for magnetic resonance imaging.

MRI

Abbreviation for;
magnetic resonance imaging (see there)
Medical Research Institute
moderate renal insufficiency

MRI

Magnetic Resonance Imaging, see there.

MRI

Abbreviation for magnetic resonance imaging.

imaging

(im'a-jing)
The production of a picture, image, or shadow that represents the object being investigated. In diagnostic medicine the classic technique for imaging is radiographic or x-ray examination. Techniques using computer-generated images produced by x-ray, ultrasound, or magnetic resonance are also available.

black blood magnetic resonance imaging

Abbreviation: BB-MR
Imaging of arterial walls with magnetic resonance for evidence of atherosclerosis. Blood flow normally gives off a bright signal during magnetic resonance imaging but can be made to appear dark to distinguish it from the walls of the surrounding blood vessels. This enhancement in magnetic resonance imaging can be used noninvasively to show where arteries are obstructed and to determine the components of the plaque in those arteries.

cerebral blood pool imaging

Radionuclide brain imaging performed after a tracer molecule is injected angiographically into a blood vessel that supplies the brain and the tracer allowed to equilibrate (achieve a steady state) in the brain's arteries and veins.

diffusion tensor imaging

Abbreviation: DTI
An imaging technique in magnetic resonance imaging to identify the unique directional movement of molecules, esp. water molecules, along muscle and neural tracts. One of its uses is to identify the linkages and structures of white matter tracts in the brain.

diffusion weighted imaging

In magnetic resonance imaging, the use of changes in the movement of water through tissues as a contrast medium. Diffusion weighted imaging has been used in the diagnosis of strokes and other neurological diseases as well as abdominal and musculoskeletal injuries and diseases.

digital imaging

The capture and production of an image of an object, either on film or on a computerized display, where it can be reformatted and analyzed. Commonly used imaging modalities include x-rays, ultrasound, and magnetic resonance.

digital subtraction imaging

In radiology, the use of electronic means to subtract portions of the radiographic image in order to better visualize the object.

duplex imaging

A form of ultrasonography that incorporates both gray-scale imaging for the architecture of the tissue and a color Doppler signal for flow or movement within the tissue.

echo planar imaging

Abbreviation: EPI
A fast magnetic resonance imaging technique in which an image is acquired after a single radiofrequency excitation.

electrical source imaging

Abbreviation: ESI
A means of mapping the electrical activity of organs such as the brain or heart to diagnose or treat diseases such as seizures or dysrhythmias. ESI relies on the collection via external sensors of the electrical activity generated by multiple tissue sites within an organ, and the mathematical manipulation of that data to localize areas where patterns of electrical conduction are blocked or excessively active.

functional magnetic resonance imaging

Abbreviation: fMRI
The identification of metabolic activities during MRI studies of the brain. During an fMRI, magnetic resonance images of the brain are made while the subject performs specific tasks, e.g. using certain fingers or saying particular words. The study helps identify changes in blood flow during these activities, as well as changes in brain chemistry or the movement of water molecules in neural tissues. It is used to study brain injuries caused by cancer, multiple sclerosis, strokes, and trauma.

fusion imaging

Any combination of radiological technologies for generating images of body structures. Fusion imaging includes positron emission tomography-computed tomographic (PET-CT) scanning, CT–magnetic resonance fusion imaging, and single photon emissions computed tomographic (SPECT) fusion imaging.

gated blood pool imaging

Radioisotopic imaging of the heart, esp. of the muscular contraction of its walls and of its ejection fraction. Red blood cells are withdrawn and labeled with an isotope of technetium. A sequence of images is taken immediately after the radiolabeled blood is reinjected into a peripheral vein and allowed to circulate. The images are timed to begin with each ventricular depolarization (with each R wave of the electrocardiogram). Normally the ejection of blood from the heart occurs at the same time and with the same strength from all muscle segments. Areas of the heart affected by infarction may not move normally (they may be akinetic or hypokinetic) or they may move paradoxically (they may be dyskinetic, as when a ventricular aneurysm is present).
Synonym: gated blood pool study
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MAGNETIC RESONANCE IMAGING: MRI of the cervical spine, sagittal view.
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MAGNETIC RESONANCE IMAGING

magnetic resonance imaging

Abbreviation: MRI
Imaging that uses the characteristic behavior of protons when placed in powerful magnetic fields to make images of tissues and organs. Certain atomic nuclei with an odd number of neutrons, protons, or both are subjected to a radiofrequency pulse, causing them to absorb and release energy. The resulting current passes through a radiofrequency receiver and is then transformed into an image. This technique is valuable in providing soft-tissue images of the central nervous and musculoskeletal systems. Imaging techniques allow visualization of the vascular system without the use of contrast agents. Agents such as gadolinium are available for contrast enhancement but must be used with caution in patients with renal insufficiency.

CAUTION!

Magnetic resonance imaging is contraindicated in patients with cardiac pacemakers or ferromagnetic aneurysmal clips in place. Metal may become damaged during testing; therefore, health care providers must establish whether the patient has magnetizable metal anywhere on or in the body. Patients should not wear metal objects, e.g., jewelry, hair ornaments, or watches. Patients who have had surgical procedures after which magnetizable metal clips, pins, or other hardware remain in the body should not have this imaging. Some patients with tattoos or permanent cosmetics should also avoid MRI because of the risk of burns.

Patient care

During imaging, the patient lies on a flat surface that is moved inside a tube encompassed by a magnet (the bore of the gantry). The patient must lie as still as possible. No discomfort occurs as a result of the MRI. Sounds heard during the imaging come from the pulsing of the magnetic field as it scans the body. Confinement during the 30 to 90 min required for scanning may frighten the patient, but the patient can talk to staff by microphone. Relaxation techniques may help claustrophobic patients endure MRI. Comfort measures and analgesics (as necessary and prescribed) should be provided before beginning the scan to offset the discomfort related to prolonged positioning in the scanner. Claustrophobic patients may require a mild sedative, or be better managed in an open MRI scanner which is less confining, however open MRI devices, which use weaker magnetic fields than closed systems may take longer to obtain images and may reveal less detail. Right angle eyeglasses, which divert the patient's gaze outside the bore of the MRI gantry, provide a helpful diversion for some patients. Most patients, however, are able to tolerate the close confinement of the gantry. A nurse or MRI technologist should maintain verbal contact with the patient throughout the procedure. An IV line with no metal components should be in place if the patient’s condition is unstable. See: illustration; brain for illus.; positron emission tomography

illustration

myocardial perfusion imaging

Abbreviation: MPI
The use of radioactive isotopes, such as 201Tl or 99mTc sestamibi, to gauge the blood supply and viability of the regions or walls of the heart. MPI is frequently used to assess patients with coronary artery disease, often in conjunction with exercise tolerance tests. A patient with a coronary artery that is almost totally blocked may take up only a small quantity of radioisotope during exercise but much more of the tracer after several hours of rest. By contrast, heart muscle that is fed by a completely blocked artery will take up no radioisotope either during or after exercise.

near-infrared fluorescence imaging

Abbreviation: NIRI
Imaging of tissues within the body after they are bound by fluorescent molecules and stimulated with light in the 700-900 nm wavelength range. NIRI is used to provide images of solid cancers, bone and joint inflammation, and blood flow to tissues.

nuclear magnetic resonance imaging

Abbreviation: NMRI
See: magnetic resonance imaging

perfusion weighted imaging

In radioisotopic imaging, the use of differences in blood flow through organs as a means of diagnosing diseases such as strokes or malignancies.

physiological imaging

Imaging of the functions of an organ, i.e., of its blood flow, electrical activity, metabolism, oxygen uptake, or working receptors.

polarized helium imaging

A means of assessing asthma in which a magnetic resonance image is made of the lungs after a patient inhales polarized helium gas. Asthmatics have ventilation defects in the lungs that are not present in nonasthmatics.

radionuclide reflux imaging

Imaging to determine whether an infant has gastroesophageal reflux. Radioactively labeled milk is given to the child orally, and the progress of the milk through the upper gastrointestinal tract (and in reflux, into the lungs) is monitored. The scan is typically used if an infant has had more than one episode of aspiration pneumonia.

retinal vascular imaging

Measurement of the caliber of the blood vessels in the retina as risk markers for coronary and cerebrovascular disease. Narrowing of retinal arterioles has been correlated with an increased risk of diabetes mellitus and coronary artery disease. Dilation of retinal venules has been associated with an increased risk of stroke.

volumetric brain imaging

Measurement of the size of specific structures within the brain with magnetic resonance imaging or other devices. It is used to diagnose and identify brain diseases noninvasively. Atrophy of certain anterior brain structures is found in patients with frontotemporal dementia. In schizophrenia, the hippocampus and amygdala are reduced. Other findings have been demonstrated in depression, fragile X syndrome, Rett's disease, Tourette's syndrome, and other neurological disorders.
Synonym: volumetric neuroimaging
Enlarge picture
MAGNETIC RESONANCE IMAGING: MRI of the cervical spine, sagittal view.
Enlarge picture
MAGNETIC RESONANCE IMAGING

magnetic resonance imaging

Abbreviation: MRI
Imaging that uses the characteristic behavior of protons when placed in powerful magnetic fields to make images of tissues and organs. Certain atomic nuclei with an odd number of neutrons, protons, or both are subjected to a radiofrequency pulse, causing them to absorb and release energy. The resulting current passes through a radiofrequency receiver and is then transformed into an image. This technique is valuable in providing soft-tissue images of the central nervous and musculoskeletal systems. Imaging techniques allow visualization of the vascular system without the use of contrast agents. Agents such as gadolinium are available for contrast enhancement but must be used with caution in patients with renal insufficiency.

CAUTION!

Magnetic resonance imaging is contraindicated in patients with cardiac pacemakers or ferromagnetic aneurysmal clips in place. Metal may become damaged during testing; therefore, health care providers must establish whether the patient has magnetizable metal anywhere on or in the body. Patients should not wear metal objects, e.g., jewelry, hair ornaments, or watches. Patients who have had surgical procedures after which magnetizable metal clips, pins, or other hardware remain in the body should not have this imaging. Some patients with tattoos or permanent cosmetics should also avoid MRI because of the risk of burns.

Patient care

During imaging, the patient lies on a flat surface that is moved inside a tube encompassed by a magnet (the bore of the gantry). The patient must lie as still as possible. No discomfort occurs as a result of the MRI. Sounds heard during the imaging come from the pulsing of the magnetic field as it scans the body. Confinement during the 30 to 90 min required for scanning may frighten the patient, but the patient can talk to staff by microphone. Relaxation techniques may help claustrophobic patients endure MRI. Comfort measures and analgesics (as necessary and prescribed) should be provided before beginning the scan to offset the discomfort related to prolonged positioning in the scanner. Claustrophobic patients may require a mild sedative, or be better managed in an open MRI scanner which is less confining, however open MRI devices, which use weaker magnetic fields than closed systems may take longer to obtain images and may reveal less detail. Right angle eyeglasses, which divert the patient's gaze outside the bore of the MRI gantry, provide a helpful diversion for some patients. Most patients, however, are able to tolerate the close confinement of the gantry. A nurse or MRI technologist should maintain verbal contact with the patient throughout the procedure. An IV line with no metal components should be in place if the patient’s condition is unstable. See: illustration; brain for illus.; positron emission tomography

illustration
See also: imaging

MRI

Abbrev. for MAGNETIC RESONANCE IMAGING.

MRI (magnetic resonance imaging)

The abbreviated term for magnetic resonance imaging. MRI uses a large circular magnet and radio waves to generate signals from atoms in the body. These signals are used to construct images of internal structures.

MRI

magnetic resonance imaging

MRI

magnetic resonance imaging.

Patient discussion about MRI

Q. Anybody to tell me more about MRI scan? had an MRIscan and this has snown adenocarcinoma of endometrium early stage There is no lymphatic involvement but is it possible an MRIscan to miss some tumor?

A. MRI is a very effective machine but it has it's limits. it has a great resolution but will not see very small tumors. therefore- it can miss metastasis sometime. but if your adenocarcinoma is in early stage- it might not sent metastasis. they did a biopsy? that can give you some idea what to expect.

Q. Can I have a MRI of the knee if I have hemostatic clips in the brain?(also called aneurysm clips)?

A. How about a CAT scan of the knee?, I wonder if it would be an appropriate diagnostic tool, I suspect problems with a lateral meniscus.

Q. i lost a lot of hearing in my ears a couple of years ago,and i had a mri done,the mri said i had ETD, the ETD caused my eushation tube to close,its very uncomfortable,i dont feel the wind or air in my ears no more,i also feel fluid behind my ear drum,i lost a lot of inner hearing,its hard to hear my own voice,and nothing sounds clear,i also feel presser behind my ear drum from the fluid,i went to several doctors for this and i tryed medican and nothing worked,i tryed steriods for the influmation in my ears,that didnt work,i asked many doctors to drain my ears and give me venteling tubes,no doctor will do it,is there anyone out there that has the same ear problem that i do,and the doctors wont give them the tubes?why are the doctors not puting tubes in ears anymore?is it just me.or is everyone getting turned down for the tubes in there ears?i just feel so alone in this does anyone have the same problem and if they do could you share your experence,it would be nice to talk to someone that has the ETD ear problem like me,im in content discomfort,and i dont understand why nobody will help.

A. from some reason it did not upload the picture...here it is:
http://www.usfamily.net/web/lucky/ear.jpg

More discussions about MRI
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