Sonogram
There are no documented risks. No ionizing radiation exposure is involved.
Most ultrasound examinations are performed in the manner described. However, certain circumstances require that the ultrasound probe be inserted into the body, rather than simply passing it over the skin. Consult your health care provider to determine the specifics of your test.
Cosgrove DO, Meire HB, Lim A, Eckersley RJ. Ultrasound: general principles. In: Grainger RC, Allison D, Adam, Dixon AK, eds. Diagnostic Radiology: A Textbook of Medical Imaging. 4th ed. New York, NY: Churchill Livingstone; 2001:chap 3.