Answer to Question #11479 Submitted to "Ask the Experts"
Category: Medical and Dental Patient Issues
The following question was answered by an expert in the appropriate field:
I realize ultrasound doesn't emit radiation, but I am hoping you can help calm my fears. I had a transvaginal ultrasound today to look at my ovarian follicles, and the technician spent an unusually long time examining each ovary (about 10 minutes on each side). I read that overheating can be an issue with ultrasound. Now I am very worried that the examination damaged my tissue or eggs, and I will have trouble conceiving. Is there cause for my concern?
Ultrasound has been in use for decades, having been introduced in the late 1950s. Transvaginal ultrasound has been in use for over a decade. There have been no reported cases of adverse reactions from the performance of medical ultrasounds on humans (Orenstein 2011). As recently as December 2014, the U.S. Food and Drug Administration (FDA) stated that there is a lack of evidence of any harm due to ultrasound imaging (FDA 2014).
Newer equipment (manufactured since about 1992–1993) has a thermal index indicator so that the ultrasound operator can get real-time feedback on the screen about the acoustic output of the unit in terms of heat generation (Abramowicz 2015). This has been an FDA requirement for new ultrasound equipment since the late 1990s.
The ovaries are small, and it does take time to locate and image them among the intestines and other pelvic structures. An imaging time of 10 minutes per side is not unusual.
During the examination, ultrasound operators start and stop the ultrasound, so there are periods during the study when no ultrasound energy is being emitted. The probe and ultrasound beam are moved, and not focused on one area any longer than necessary. Ultrasound operators are trained to use the shortest dwell time consistent with obtaining the diagnostic information.
In addition, the body can cool tissue via blood flow to and from the area. (This is something that occurs naturally such as during times of fever, etc.) It is not possible to calculate with absolute certainty how much tissue heating occurred during any ultrasound procedure as it is influenced by so many factors including the specific equipment, the mode of operation, the acoustic output, the operator's experience, the dwell time, the individual patient's anatomy, etc.
Aggie Barlow, CHP
- Abramowicz JS. Bioeffects of obstetric ultrasound for the clinician: How to keep it safe. Institute of Advanced Medical Education online course; 2015. Available at https://iame.com/online-courses/physics/bioeffects-of-obstetric-ultrasound-for-the-clinician-how-to-keep-it-safe1. Accessed 8 February 2016.
- FDA. Avoid fetal "keepsake" images, heartbeat monitors. FDA consumer update; 2014. Available at http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm095508.htm. Accessed 5 February 2016.
- Orenstein BW. The ALARA principle and sonography. Radiology Today 12(11):10; 2011.