NMR - chest
Key points
- A chest MRI uses powerful magnets and radio waves to construct pictures of the body.
- Since MRI makes use of radio waves very close in frequency to those of ordinary FM radio stations, the scanner must be located within a specially shielded room to avoid outside interference.
- No preparatory tests, diets, or medications are usually needed.
- The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust.
Alternative names
Nuclear magnetic resonance - chest; Magnetic resonance imaging - chest; Chest MRI; MRI of the thorax
Definition
A chest MRI uses powerful magnets and radio waves to construct pictures of the body.
Unlike conventional radiography and Computed Tomographic (CT) imaging, which make use of potentially harmful radiation (X-rays) that pass through a patient to generate images, magnetic resonance imaging (MRI) is based on the magnetic properties of atoms.
A powerful magnet generates a magnetic field roughly 10,000 times stronger than the Earth's. A very small percentage of hydrogen atoms within the body will align with this field. Radio wave pulses are broadcast towards the aligned hydrogen atoms in tissues of interest, returning a signal of their own. The subtle differing characteristics of that signal from different tissues enables MRI to differentiate between various organs, and potentially, provide contrast between benign and malignant tissue.
Any imaging plane, or "slice", can be projected, and then stored in a computer or printed on film. MRI can easily be performed through clothing and bones, however, certain types of metal in or around the area of interest can cause significant errors in the reconstructed images.
How the test is performed
Since MRI makes use of radio waves very close in frequency to those of ordinary FM radio stations, the scanner must be located within a specially shielded room to avoid outside interference. The patient will be asked to lie on a narrow table which slides into a large tunnel-like tube within the scanner.
If contrast dye is used, it will be injected into a small vein of the hand or forearm. A technologist will operate the machine and observe you during the entire study from an adjacent room.
Several sets of images are usually required, each taking from 2 to 15 minutes. A complete scan, depending on the sequences performed, and need for contrast enhancement, may take up to one hour or more. Newer scanners with more powerful magnets utilizing updated software and advanced sequences may complete the process in less time.
How to prepare for the test
No preparatory tests, diets, or medications are usually needed. An MRI can be performed immediately after other imaging studies.
Because of the strong magnets, certain metallic objects are not allowed into the room. Items such as jewelry, watches, credit cards, and hearing aids can be damaged. Pins, hairpins, metal zippers, and similar metallic items can distort the images. Removable dental work should be taken out just prior to the scan. Pens, pocketknives, and eyeglasses can become dangerous projectiles when magnet is activated and should not accompany the patient into the scanner area.
Written and revised by
Andrey Nailor, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.