Final answer:
An MRI uses magnetism and radio waves to produce detailed images of the body's organs and tissues. The technique involves aligning proton spins and detecting their resonant frequencies to create a map of the body without radiation exposure.
Step-by-step explanation:
Magnetic Resonance Imaging (MRI) uses magnetism to create detailed images of the organs and tissues inside the body. To generate these images, MRI exploits the physical phenomenon where nuclei in a magnetic field absorb and reemit radio frequencies. Specifically, it uses radio waves that are broadcast through the body and a powerful magnetic field to align the spin of protons within the body, particularly those in hydrogen atoms. The varying resonant frequencies of these protons based on their positions are detected and used to construct a map of the tissue. This allows MRI to provide highly detailed two- and three-dimensional images of internal structures without exposing patients to ionizing radiation, unlike some other imaging techniques such as X-rays or CT scans.
The level of detail in an MRI is achieved by the imaging receiver gathering information point by point, which is then reconstructed into 'slices' or cross-sections of the body that are several millimeters thick. These scans are particularly sensitive to the density and chemical environment of the nuclei, which helps differentiate between various types of tissues and can be crucial in identifying abnormalities such as tumors. The relaxation times, or the time it takes for protons to return to their initial state after the magnetic field is turned off, vary between different types of tissues, providing additional contrast in images.
While MRI offers superior imaging for specific tissue types and poses no radiation hazards, it is less effective than X-rays for imaging certain conditions such as bone fractures. Moreover, the cost of MRI scans can be higher compared to simple X-ray images. Some patients may also experience discomfort due to claustrophobia in the enclosed space of traditional MRI machines, although open-MRI machines are available to alleviate this issue.