sonogram
Meaning of sonogram: Sound bounces back wherever one tissue meets another, so the picture is assembled from echoes rather than from shadows.
Definition of sonogram
A sonogram is the picture of internal structures produced by ultrasound, in which high frequency sound is sent into the body and the echoes returning from tissue boundaries are converted into an image. Because it forms in real time and involves no ionizing radiation, the examination can be repeated as often as needed and can show structures in motion, such as a beating heart.
How is the picture built?
The handheld probe does two jobs in alternation. It sends a pulse of sound into the body, then falls silent and listens. Every boundary between tissues of different density reflects part of that pulse, and the machine uses the delay before an echo returns to work out how deep the boundary lies, and the strength of the echo to decide how bright to draw it. Fluid reflects almost nothing and appears black, which is why a cyst filled with fluid looks so different from a solid lump. Bone and gas reflect nearly everything and appear brilliantly white, with a blank shadow behind them. A separate mode measures the change in pitch of echoes returning from moving blood, and displays flow and its direction in color laid over the gray image.
What does it do well, and badly?
| Strong | Weak |
|---|---|
| Telling a fluid filled cyst from a solid mass | Anything lying behind bone or behind gas |
| Stones in the gallbladder and lumps in the thyroid | The adult brain, the spine, the lungs and gas filled bowel |
| Watching a needle enter tissue as it happens | Deep structures in a larger body, where the sound weakens |
| Blood flow, direction and speed | Reproducibility, since results depend heavily on the operator |
One trade off sits behind much of this. Higher frequency sound draws fine detail but penetrates only a short distance, while lower frequency reaches deep structures with a coarser picture, so the probe is chosen for the depth of the target rather than for image quality alone.
Sonogram or ultrasound: which word is right?
Both, for different things. Ultrasound names the sound waves themselves and the technique that uses them. Sonography is the act of performing the examination, and the person performing it is a sonographer. The sonogram is the image that results. In conversation the words are swapped freely, and no confusion follows in practice, though the distinction is kept in writing. Related words follow the same pattern, so a study of the heart is an echocardiogram and a study performed during pregnancy is often just called a scan. Whatever it is called, the absence of ionizing radiation is what allows the examination to be repeated through a pregnancy or to follow a lump over months without accumulating any exposure.
Also known as
Used in a sentence
A sonogram of the abdomen was obtained to evaluate the gallbladder.
Good to know
The terms sonogram and ultrasound are frequently used interchangeably in conversation, though sonogram refers specifically to the resulting image rather than the sound-wave technique itself.
Word origin
Where “sonogram” comes from
Formed from sonus, Latin for sound, and -gram, from Greek gramma, meaning something written or recorded.