Interchanging the terms doesn’t mean they’re the same.
The terms “ultrasound” and “sonogram” are used interchangeably and reference the same exam, but don’t mean exactly the same thing.
An ultrasound uses high-frequency sound waves to scan an anatomic area and create a picture (sonogram) of the structures. In short, the ultrasound is the procedure used to produce a sonogram, which is the actual image.