X-rays are the radiation tests we are all familiar with; you have probably taken one at the dentist if you had your wisdom teeth removed. They show bony structures, so they are best for diagnosing bone injuries and cannot be used to diagnose soft tissue injuries.

CT scan, sometimes known as a CAT scan, is short for computerized tomography. A CT scan uses multiple x-rays taken in a circle around the same point to build a better picture than one x-ray could provide alone, using a computer to combine them.

MRI is short for magnetic resonance imaging. If you undergo an MRI, the doctors will ask you to lie down in a large tube that uses harmless magnetic radiation to look at soft tissues of the body. Sometimes they will also ask you to drink or have an injection of a substance that makes those tissues easier to see. Because this technology uses magnets, you cannot use it if you have a pacemaker or other metal implanted in your body.

PET scan is often used in tandem with a CT scan. In a PET scan, the patient is injected with a harmless substance that can be seen by the scanner using radioactivity. Unlike CT scans, PET scans show your body’s metabolic activity rather than just structures of the body. The images they produce are also three-dimensional.

Ultrasound tests use high-frequency sound waves that bounce off internal structures of the body to build an image. The image it builds is not as detailed as images from other methods, but because it does not use radiation, it may be the best choice for people with certain conditions. It is also less expensive than an MRI. Doctors may use ultrasound studies to look at internal organs, connective tissue, bones, blood vessels and eyes.

Nerve conduction study is an electrical test that can detect problems with your nerves. In this test, one electrode is placed over the nerve being tested, while another is placed in a “downstream” area of the nervous system. The speed it takes for the electricity to travel between them determines whether there is nerve damage.

Electromyograph study (EMG) shows muscles’ activity by measuring the electrical current they produce when they are in motion. This might be used for people with nerve damage, muscle weakness or the conditions that might cause them. EMG involves doctors either inserting a thin needle into the muscle being tested or placing an electrode over the area, then measuring the electrical impulses of the muscle.

Endoscopy uses a flexible tube with a light and a camera to look inside natural openings in your body, such as the throat. This study is most commonly associated with tests of the stomach or colon, but can be used in any area with a natural opening.