Diagnostic imaging lets doctors look inside your body for clues about a medical condition. A variety of machines and techniques can create pictures of the structures and activities inside your body. The type of imaging your doctor uses depends on your symptoms and the part of your body being examined.

Many imaging tests are painless and easy. Some require you to stay still for a long time inside a machine. This can be uncomfortable. Certain tests involve exposure to a small amount of radiation.

Below is a list of the most common diagnostic imaging procedures.

X-rays

What are X-rays?

x rayX-rays use invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs on film or digital media. Standard X-rays are performed for many reasons, including diagnosing tumors or bone injuries. X-rays are made by using external radiation to produce images of the body, its organs, and other internal structures for diagnostic purposes. X-rays pass through body structures onto specially-treated plates (similar to camera film) or digital media and a “negative” type picture is made (the more solid a structure is, the whiter it appears on the film).

When the body undergoes X-rays, different parts of the body allow varying amounts of the X-ray beams to pass through. The soft tissues in the body (such as blood, skin, fat, and muscle) allow most of the X-ray to pass through and appear dark gray on the film or digital media.  A bone or a tumor, which is more dense than soft tissue, allows few of the X-rays to pass through and appears white on the X-ray. When a break in a bone has occurred, the X-ray beam passes through the broken area and appears as a dark line in the white bone.

X-ray technology is used in other types of diagnostic procedures, such as arteriograms, computed tomography (CT) scans, and fluoroscopy.

Radiation during pregnancy may lead to birth defects. Always tell your radiologist or doctor if you suspect you may be pregnant.

How are X-rays performed?

X-rays can be performed on an outpatient basis, or as part of inpatient care.

Although each facility may have specific protocols in place, generally, an X-ray procedure follows this process:

  1. The patient will be asked to remove any clothing or jewelry which might interfere with the exposure of the body area to be examined. The patient will be given a gown to wear if clothing must be removed.
  2. The patient is positioned on an X-ray table that carefully positions the part of the body that is to be X-rayed–between the X-ray machine and a cassette containing the X-ray film or specialized image plate. Some examinations may be performed with the patient in a sitting or standing position.
  3. Body parts not being imaged may be covered with a lead apron (shield) to avoid exposure to the X-rays.
  4. The X-ray beam will be aimed at the area to be imaged.
  5. The patient must be very still or the image will be blurred.
  6. The technologist will step behind a protective window and the image is taken.
  7. Depending on the body part under study, various X-rays may be taken at different angles, such as the front and side view during a chest X-ray.

Computerized tomography (CT)

What is a CT or CAT scan?

ct scan

A CT or CAT scan is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, organs, and blood vessels. CT scans are more detailed than standard X-rays.

In standard X-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle, and other tissue. While much information can be obtained from a regular X-ray, a lot of detail about internal organs and other structures is not available.

In computed tomography, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure, and provides much greater detail. The X-ray information is sent to a computer that interprets the X-ray data and displays it in two-dimensional form on a monitor. Newer technology and computer software makes three-dimensional (3-D) images possible.

CT scans may be done with or without contrast. “Contrast” refers to a substance taken by mouth or injected into an intravenous (IV) line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.

CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage.

You may want to ask your doctor about the amount of radiation used during the CT procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous CT scans and other types of X-rays, so that you can inform your doctor. Risks associated with radiation exposure may be related to the cumulative number of X-ray examinations and/or treatments over a long period of time. If you are pregnant or suspect that you may be pregnant, you should notify your doctor.

Advances in computed tomography technology include the following:

  • High-resolution computed tomography. This type of CT scan uses very thin slices (less than one-tenth of an inch), which are effective in providing greater detail in certain conditions such as lung disease.
  • Helical or spiral computed tomography. During this type of CT scan, both the patient and the X-ray beam move continuously, with the X-ray beam circling the patient. The images are obtained much more quickly than with standard CT scans. The resulting images have greater resolution and contrast, thus providing more detailed information. Multidetector row helical CT scanners may be used to obtain information about calcium build-up inside the coronary arteries of the heart.
  • Ultrafast computed tomography (