How Does Ultrasound Work?

Ultrasound imaging uses the principles of sonar developed for ships at sea. As sound passes through the body it produces echoes, which can identify distance, size and shape of objects inside.  During the ultrasound examination, a machine called a transducer is used to view the target organ and produce pictures for study. The transducer emits sound and detects the returning echoes when it is placed on or over the body part being studied.  When the emitted sound encounters a border between two tissues that conduct sound differently, some of the sound waves bounce back to the transducer, creating an echo.  The echoes are analyzed by a computer in the ultrasound machine and transformed into moving pictures of the organ or tissue being examined.

Ultrasound Process 

Ultrasound waves pass easily through fluids and soft tissues, making the procedure especially useful for examining fluid-filled organs such as the uterus in pregnancy, as well as the gallbladder, and soft organs like the liver.  The ultrasound waves do not pass through bone.

Bone not Penetrated by Ultrasound Waves 

What Should I Expect?

Most ultrasound examinations are painless, fast and easy. A technologist will position you on the table, apply warm gel on your skin (over the area being imaged), and will then press on the skin with a hand-held transducer to obtain the necessary images.  The images are then analyzed and interpreted by the radiologist.

Abdominal Examinations
Patient must go without food and drink for six hours prior to an abdominal study.
Necessary medications may be taken with a small amount of water only. No chewing gum please.
Pelvic Ultrasound
Patients must have a full bladder before the pelvic exam can be performed. Patients should finish drinking 36 ounces of water one hour before their appointment time. Patients should not empty their bladder once they have started drinking.

Obstetrical Ultrasound
First Trimester – Please follow preparation for pelvic exam as seen above.
Second and third trimester – No patient preparation is necessary.

Endovaginal Ultrasound
A brief, conventional pelvic ultrasound exam is performed prior to an endovaginal exam to evaluate the entire pelvis and adnexa, therefore patients should follow the same prep required for a conventional pelvic ultrasound exam.

Thyroid Ultrasound
No preparation is required for this exam.

Breast Ultrasound
No preparation is required for this exam.

Scrotal Ultrasound
No preparation is required for this exam.

How do I Get the Exam?

The exam must be ordered by your doctor, but you can choose where to have the exam performed.  Simply ask your doctor to refer you to Comprehensive Diagnostic Imaging.