Imaging tests provide pictures of bones, organs (such as the
liver, pancreas, or intestines), tissues, and other structures (such as blood
vessels) inside the body. These tests are used to help diagnose medical
Imaging tests include:
X-rays, which use a radiation beam. X-rays can detect bone injuries or
abnormal growths or changes in bone structure or size.
Ultrasound. This uses reflected sound waves to produce an image.
Ultrasound is most useful for looking at organs and structures that are either
uniform and solid (like the liver) or that contain water (like the
gallbladder). Mineralized structures (like bones) or air-filled organs (like
the lungs) do not show up well. Echocardiography is a type of ultrasound that
produces an image of the heart. It is used in heart conditions.
Computed tomography (CT or CAT). This uses a series of X-ray
pulses through the body to obtain information about almost any body organ,
blood vessels, the abdominal cavity, bones, and the spine.
Magnetic resonance imaging (MRI). This uses a magnetic field and
pulses of radio-wave energy to detect changes in the normal structure and
characteristics of organs or tissues. An MRI can provide information that
cannot be obtained from an X-ray, ultrasound, or CT scan. MRI is most effective
at providing pictures of tissues that contain water, such as ligaments and
muscles. An MRI is not as useful in looking at structures that do not contain
water, such as bones.
Nuclear medicine scans, which use a camera to take pictures of
certain tissues in the body after a radioactive tracer (radionuclide or
radioisotope) is put into the body. The radioactive tracer helps make the
tissues visible on the scanning pictures. Each type of tissue that may be
scanned (including bones, organs, glands, and blood vessels) uses a different
radioactive compound as a tracer.
Positron emission tomography (PET). This combines computed
tomography and nuclear scanning. PET has been used primarily in heart and brain
conditions and cancer.
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Adam Husney, MD - Family Medicine & Martin J. Gabica, MD - Family Medicine