Magnetic resonance imaging (mri)

M

agnetic resonance imaging (MRI) also called magnetic resonance tomography (MRT) is a method of creating images of the inside of opaque organs in living organisms as well as detecting the amount of bound water in geological structures. It is primarily used to demonstrate pathological or other physiological alterations of living tissues and is a commonly used form of medical imaging. MRI has also found many novel applications outside of the medical and biological fields such as rock permeability to hydrocarbons and certain non-destructive testing methods such as produce and timber quality characterization.

MRI was developed from knowledge gained in the study of nuclear magnetic resonance. The original name for the medical technology is nuclear magnetic resonance imaging (NMRI), but the word nuclear is almost universally dropped. This is done to avoid the negative connotations of the word nuclear, and to prevent patients from associating the examination with radiation exposure, which is not one of the safety concerns for MRI. Scientists still use an NMR when discussing non-medical devices operating on the same principles. Unfortunately the devices themselves are very expensive with several hundred thousands dollars per year upkeep costs.

In clinical practice MRI is used to distinguish pathological tissue (such as brain tumor) from normal tissue. One of the advantages of an MRI scan is that, according to current medical knowledge, it is harmless to the patient. It utilizes strong magnetic fields and non-ionizing radiation in the radio frequency range. Compare it to CT scans and traditional X-rays which involve doses of ionizing radiation and may increase the chance of malignancy, especially in children receiving multiple examinations.

The typical MRI examination consists of 5-20 sequences, each of which are chosen to provide a particular type of information about the subject tissues. This information is then synthesized by the interpreting physician. The presence of a ferromagnetic foreign body in the subject, or a metallic implant (like surgical prostheses, or pacemakers) can present a (relative or absolute) contraindication towards MRI scanning: interaction of the magnetic and radiofrequency fields with such an object can lead to: trauma due to the shifting of the object in the magnetic field, thermal injury from radiofrequency induction of heating of the object, or failure of an implanted device.

Because of MRI’s superior imaging of soft tissues, it is now being utilized to specifically locate tumors within the body in preparation for radiation therapy treatments. For therapy simulation, a patient is placed in specific, reproducible, body position and scanned. The MRI system then computes the precise location, shape and orientation of tumor mass, correcting for any spatial distortion inherent in the system. The patient is then marked or tattooed with points which, when combined with the specific body position, will permit precise triangulation for radiation therapy.

II. Read the text and answer the questions.

1	What is MRI?
2	Why is the word “nuclear” almost universally dropped from the name of this medical technology?
3	What are common uses of MRI in clinical practice?
4	How is the procedure performed?
5	Are there any limitations of MRI?

III. Using information from the text name advantages of the MRI procedure.

IV. Read the text and describe a typical MRI examination.

V. Give the main points of the text in 5-6 sentences.

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