diagnostic medical imaging radiology


Ultrasound uses high-frequency sound waves to make images of organs and structures inside the body.

How the Test is Performed

An ultrasound machine creates makes images so that organs in the body to be examined. The machine sends out high-frequency sound waves, which reflect off body structures. A computer receives the waves and uses them to create a picture. Unlike with an x-ray or CT scan, this test does not use ionizing radiation.

The test is done in the ultrasound or radiology department.

  • You will lie down for the test.
  • A clear, water-based gel is applied to the skin on the area to be examined. The gel helps with the transmission of the sound waves.
  • A handheld probe called a transducer is moved over the area being examined. You may need to change position so that other areas can be examined.

How to Prepare for the Test

Your preparation will depend on the part of the body being examined:

  • Abdomen: Nothing to eat or drink 4-5 hours prior to the exam.
  • Pelvic: Drink 32 oz of water 1 hour prior and hold the water in.
  • OB (under 24 weeks): Drink 32 oz of water 1 hour prior and hold the water in.
  • Retro/Kidneys/Bladder: Drink 16 oz of water 1 hour prior and hold the water in.
  • Breast: Needs to have a recent mammogram if over the age of 35.

For all other parts of the body, St. Helena Hospital Medical Imaging will give you instructions for how to prepare for your test when you schedule an appointment.

How the Test Will Feel

Most of the time, ultrasound procedures do not cause discomfort. The conducting gel may feel a little cold and wet.

Why the Test is Performed

The reason for the test will depend on your symptoms.


There are no known risks. The test does not use ionizing radiation.


We are located at Adventist Health St. Helena
10 Woodland Road
St. Helena, CA 94574

Please check in at the admissions office. Walk into the front entrance of the medical center and turn left at the front desk. Follow signs for admissions.

To learn more, please call us at (707) 963-6570.