How MRI's Function - By: Seymour23

Magnetic Resonance Imagining (MRI) has become a critical tool in modern medicine. Developed in the late 1970’s, an application for this diagnostic imaging has rapidly developed. MRI uses no radiation in contrast to Computerized Tomography (CT) and conventional x-rays. This provides an extremely safe diagnostic medium for both patients and technologists.

The basic physics behind the functioning of a MRI has to do with hydrogen ion spins. Most of the body is comprised of or contains water molecules, H2O. The properties of hydrogen in the body’s water molecules can be altered and measured. This is accomplished by a magnetic field.

Hydrogen is the simplest molecule in nature. It consists of a single negatively charged electron circling a positive nucleus. When two hydrogen’s are attached to oxygen, making a water molecule, the hydrogen’s are called a dipole. The dipole has two energy levels, resting, and excited. It takes energy to excite the dipole and when that energy is discontinued, the dipole returns to the resting energy state, releasing the absorbed energy as a photon. The released photons can be identified and converted into an image by a computer. Because different tissues in the body require different amounts of energy to excite their dipoles, their differences are reflected in the images.

The MRI machine uses a strong magnetic field to align the hydrogen ion spins and then utilizes a short burst from a radio frequency transmitter to excite the dipoles. The energy this generates is called the resonance energy, hence the name magnetic resonance imaging.

Because of MRI’s mechanism, differentiating between tissue types makes it an excellent choice for the brain, heart and tumor identification. There are several unique applications available with MRI. Contrast may be used to highlight vessels or injected into joints for detailed pictures of the anatomy. 3D pictures can be generated giving enhanced evaluation of size and function. There are functional MRI’s that diagnose the activity of certain organs. There are many other unique diagnostic applications.

While MRI is an extremely safe examination, because of the strong magnetic field the patient is subjected to, certain individuals cannot undergo this form of imaging. Anyone with metal contained within their body can be potentially harmed. This includes patients with pacemakers, certain cochlear implants, non-titanium orthopedic hardware or recently placed coronary artery or vascular stents. Patients with retained shrapnel or bullet fragments may also be at risk.

There has been no evidence to suggest any harm to a developing fetus in pregnant women undergoing MRI. The general recommendation is still to proceed only if extremely necessary, particularly during the first trimester. Claustrophobia is another concern; however, there are several means to improve the experience. The noise generated as a result of the machine generating the magnetic field can be improved by earplugs or non-metallic earphones with music.

MRI has revolutionized the medical field. In the past, radiology was used to support a clinical diagnosis, now it is relied on often to establish the diagnosis and assist treatment.

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