Radiology imaging incorporates a number of different types of scanning technologies. They all do the same thing – take pictures of the inside of your body in a noninvasive way for diagnostic or treatment purposes or to guide biopsies, catheterization, or other procedures. But how they work varies.

Some imaging is used by itself, while in other cases two or more scans might be used together.

Here’s a look at some of the most common types of imaging and how they work:

A test that uses X-rays to show your blood vessels. Dye is injected into blood vessels, and an X-ray machine or fluoroscopy takes a quick series of images, which are called angiograms. The dye helps enhance the images to show blockages or injuries. Angiograms can be used to look at the vessels of the heart, brain, head, neck, arms, legs, chest, back, or abdomen.
Bone density
An enhanced form of X-ray that measures bone density. It’s often used to diagnose osteoporosis, as well as measure the effects of osteoporosis treatment. The test sends low-dose X-rays with two distinct peaks into specific bones. One peak is absorbed by soft tissue, the other by bone. Subtracting the soft tissue amount from the total tells how dense the bone is. There are several types of bone density tests, depending on the bones or body region being studied.
Computed tomography (CT)
Combines a series of X-rays from different angles and computer processing to create cross-sectional images of the bones and soft tissues in your body. Images appear on a computer screen as slices that your doctor can view individually or in groups. CT scans provide much more information than X-rays and have a number of uses. It can be used on the abdomen, chest, urinary tract, pancreas, liver, gallbladder, pelvis, spleen, arm, and leg. Also, it’s often used to guide the needle placement for biopsies.
An imaging test that shows a continuous X-ray image on a monitor, like an X-ray movie. It’s used to treat patients by displaying the movement of a body part, an instrument, or dye through the body. It has many uses but is often used in orthopaedic surgery to show fractures, to study blood flow, and to examine the skeletal, urinary, digestive, respiratory, and reproductive systems. It can help evaluate bones, joints, muscles, heart, lungs, or kidneys. It is also used to locate foreign objects in the body.
Magnetic resonance imaging (MRI)
A procedure that uses a strong magnetic field and radiofrequency waves to produce detailed pictures of organs or tissues inside your body. During the test, the magnetic field aligns the body’s water molecules and the radio waves cause those molecules to give off faint signals, creating the cross-sectional images. The machine can also produce 3-D images that can be viewed from many angles.
A low-dose X-ray used to screen for and diagnose breast diseases. During a mammogram, each breast is positioned between two plastic plates as you stand in front of the imaging machine, and the X-ray energy passes through the breast, creating a digital image. Pictures are taken from different angles. You’ll be required to hold very still as each image is taken. The procedure can be uncomfortable, but it usually takes just a few minutes.
Positron emission tomography (PET)
This procedure uses a radiopharmaceutical to target abnormal metabolism in soft tissue or bone which may be associated with cancer. The combination with CT provides excellent localization of the processes.
Radiography (X-ray)
The oldest type of imaging, X-rays are a quick procedure that pass energy into the body to take a picture of the structures inside the body. X-rays can be done on most body parts, including teeth, chest, abdomen, and bones.
Ultrasound, also called sonography
This procedure uses high-density sound waves to produce precise images of the soft tissue structures inside the body. An ultrasound can be used for a variety of diagnostic purposes. Ultrasound is done with a transducer usually placed on the outside of the body, but some procedures require placing the transducer inside the body. An ultrasound is safe, using no radiation.