Diagnostic ultrasounds use sound waves to make pictures of the body. Ultrasound, also called sonography, shows the structures inside the body. The images can help guide diagnosis and treatment for many diseases and conditions.

These images show how ultrasound can help guide a needle into a tumor (left), where material is injected (right) to destroy tumor cells.

These images show how ultrasound can help guide a needle into a tumor (left), where material is injected (right) to destroy tumor cells.

Ultrasound is a valuable tool, but it has limitations. Sound waves don't travel well through air or bone. This means ultrasound isn't effective at imaging body parts that have gas in them or are hidden by bone, such as the lungs or head. Ultrasound also may not be able to see objects that are located very deep in the human body. To view these areas, your healthcare professional may order other imaging tests, such as CT or MRI scans or X-rays.

Most ultrasounds are done using a device outside the body. However, some involve placing a small device inside the body.

A trained technician, called a sonographer, uses a small, hand-held device called a transducer. The technician presses the transducer against the area being studied and moves it as needed to capture the images. The transducer sends sound waves into your body and collects the ones that bounce back. The images appear on a computer.

Wear loose clothing to your ultrasound appointment. You may be asked to remove jewelry during your ultrasound. It's a good idea to leave any valuables at home.

Gel is applied to your skin over the area being examined. It helps prevent air pockets, which can block the sound waves that create the images. This safe, water-based gel is easy to remove from skin and, if needed, clothing.

Ultrasound is usually painless. However, you may experience mild discomfort as the sonographer guides the transducer over your body. It may not be comfortable if you're required to have a full bladder or the transducer is inserted it into your body.

When your exam is complete, a doctor trained to interpret imaging studies, called a radiologist, analyzes the images. The radiologist sends a report to your healthcare professional who will share the results with you.

During a transvaginal ultrasound, a healthcare professional or technician uses a wandlike device called a transducer. The transducer is inserted into your vagina while you lie on your back on an exam table. The transducer emits sound waves that generate images of your pelvic organs.

Sometimes, ultrasounds are done inside the body. In this case, the transducer is attached to a probe that's inserted into a natural opening in the body. Examples include:

During a transvaginal ultrasound, a healthcare professional or technician uses a wandlike device called a transducer. The transducer is inserted into your vagina while you lie on your back on an exam table. The transducer emits sound waves that generate images of your pelvic organs.