How MRI Machines Work & What They Can Scan and Image in the Human Body

Magnetic resonance imaging (MRI) is an imaging technique that can provide a detailed visualization of soft tissues. The MRI allows for detailed images of the brain, cardiovascular system, cancer(s) and musculoskeletal system. The MRI scanner is a large circular tube that contains a circular magnet (Healthwise 2007).

When the large magnet is turned on, a magnetic field is created that positions the protons and hydrogen atoms in alignment so they can become exposed to radio waves. When the radio waves come into contact with the protons and hydrogen atoms, a receiver on the MRI scanner receives a signal that is sent back and a computerized image can be developed. The type of signal received back is important. The reason for this is that a cancerous tissue has a different type of signal than a healthy tissue. Thus, this is how pictures of organs and structures inside the body are developed (Healthwise 2007).

Once a person is placed on the table and positioned inside the MRI's circular opening, the MRI is turned on and air movement will be generated. To help ease the noise from the machine, a person will wear earplugs or headphones. It is possible to speak with a technologist via an intercom. The length of an MRI scan is dependent on the reason for the MRI scan. Some MRI tests can be done as quickly as 30 minutes and some more than two hours long.

The MRI doesn't give off any ionizing radiation like an x-ray or CT scans do. Instead, an MRI machine uses a magnetic field, radio waves and computers to enhance the image of the soft tissues.

MRI imaging of soft tissues in the human body is performed to evaluate abnormalities that include the following;

Organs that surround the chest, abdomen and pelvis. The specific organs can include the heart, lungs, liver, kidney, spleen and pancreas. Some of the conditions tested for can include breast or lung cancer; and also cancers of the liver, kidney and pancreas (Schiel).

Organs that surround the pelvic region. These organs can include the prostate, testicles, uterus and ovaries (Schiel).

Organs of the circulatory system. An MRI test can detect problems with arteries, veins, aneurysms, blood clots, and damage to blood vessels (Schiel).

Conditions of the brain. An MRI test can detect for brain tumors, aneurysm, internal bleeding in the brain, nerve damage and degeneration, damage caused by a stroke, damage to optic nerves and auditory nerves (Schiel).

Bones and joints. For bones and joints, an MRI can detect arthritis, bone marrow problems, tumors, cartilage damage-commonly used for imaging damage to the knee and shoulders (Schiel).

An MRI is ordered by a physician to exam, diagnose or monitor treatment. Some of the specific conditions that can be found include tumors, coronary artery disease, and lesions of the liver or any other organ. In addition, an MRI can help examine the size of the chambers of the heart, tissue damage from a heart attack and congenital defects of the cardiovascular system.

References:

Healthwise. Magnetic Resonance Imaging (MRI). June 22,2007

Shiel, William. MedicineNet. Magnetic Resonance Imaging (MRI Scan). MedicineNet.