Diagnostic medical imaging refers to the process of obtaining images of parts of the human body for examination and diagnosis of illness or injury. The process may include x-rays, magnetic resonance imaging (MRI), ultrasound, computerized tomography (CT), or positron emission tomography (PET). The information derived from diagnostic medical imaging often allows health care professionals to examine the inside of a patient’s body in a non-invasive way.
The term x-ray refers to X-radiography. X-rays use short wave radiation to expose film. Soft tissue does not absorb the high energy waves, so they pass through. Dense objects, such as bones and tendons, absorb the rays. The resulting image shows less dense structures as gray or black, and dense structures as lighter gray or white.
MRI, another type of diagnostic medical imaging, provides detailed visualization of the inside of the body. Using powerful magnets and radio waves, an MRI takes advantage of the magnetic properties of atoms to create clear images. An MRI is useful because the radiologist can modify the exam so that it provides the clearest image of the required area. With this, anything from ligaments to blood flow may be observed.
Ultrasound examinations send high-frequency sound waves into tissue and then utilize the returning echoes to create images of the area. Ultrasounds are frequently used to assess the status of a fetus during pregnancy. Echocardiography, another form of ultrasound, is often used to examine heart function and blood flow through the heart. This type of diagnostic medical imaging may be used to assist in diagnosing many conditions, including thyroid tumors, gallstones, or blood clots.
A CT scan uses a rotating x-ray mechanism and a computer to provide cross-sectional images of organs or other body parts. This type of diagnostic medical imaging is commonly used to quickly distinguish trauma-related injuries in the chest or abdomen. It is also useful in determining the size, location, and spread of tumors.
PET scans construct three-dimensional images from gamma rays emitted by a tracer introduced into the body. The radiotracer is broken down by the body, and the resulting images reveal how the involved body parts work. PET scans are commonly used to study the brain in epilepsy patients, and for detailed examination of different areas of the heart.
Some diagnostic medical imaging examinations require the use of a contrast medium. These substances may be given by injection, enema, or orally. Generally iodine or barium-based, a contrast medium enhances the visibility of the tissues being examined. A doctor should closely monitor a patient who has received contrast media to observe for allergic reactions.
