As Low As Reasonably Achievable (ALARA) Principle

May 19, 2020

The potential benefits and risks of each examination should be considered. The as low as reasonably achievable (ALARA) principle should be observed when adjusting controls that affect the acoustic output and by considering both the transducer dwell time and overall scanning time. Practicing ALARA requires that users do all of the following:

1. Apply correct examination presets if built into the diagnostic ultrasound device. The review of manufacturer default presets for appropriateness is encouraged.

2. Adjust the power to the lowest available setting that provides diagnostic-quality images. If appropriate, reduce power at the end of each examination so the next user will start with the lowest acoustic output setting.

3. Monitor the mechanical index (MI) and thermal index (TI). Know the recommended upper limit of the MI, TI, and related duration limitations for the type of examination being performed. 1,2

4. Move/lift the transducer when stationary imaging is not necessary to reduce the dwell time on a particular anatomic structure.  When possible, avoid fields of view that include sensitive tissues such as the eye, gas-filled tissues (lung and intestines), and fetal calcified structures (skull and spine).

5. Minimize the overall scanning time to that needed to obtain the required diagnostic information.



1. American Institute of Ultrasound in Medicine. Recommended maximum scanning times for displayed thermal index (TI) values. American Institute of Ultrasound in Medicine website. Approved October 30, 2016.

2. American Institute of Ultrasound in Medicine. Medical Ultrasound Safety. 3rd ed. Laurel, MD: American Institute of Ultrasound in Medicine; 2014.

Approved: 03/16/2008; Reapproved: 04/02/2014, 05/19/2020