Due to the absorption of ultrasound, heating of tissue (including bone) can occur. For this reason, the sonographer should follow the ALARA principle to minimize the potential for ultrasonic heating of tissue during for example M-mode ultrasound. The thermal effect of Doppler ultrasound flow examinations is significantly greater.

See also Thermal Index and Ultrasonic Power.

The ultrasonic power is the total amount of sound energy emitted by the transducer per unit of time.

See also Ultrasonic Heating.

Ultrasonography is another term[aka: sonography] used to describe the practice of using ultrasound technology for diagnostic imaging. It is synonymous with sonography and signifies the process of capturing ultrasound images, regardless of the body part or condition being examined. Ultrasonography is widely utilized in various medical imaging specialties, including obstetrics and gynecology, cardiology, radiology, urology, and many others. It has proven to be particularly valuable in obstetric imaging, allowing healthcare providers to monitor the growth and development of a fetus during pregnancy.
Ultrasonography uses the reflections of high-frequency sound waves to construct an image of a body organ. These ultrasonic waves are generated by a quartz crystal and are reflected at the interface between different tissues. The transmission and reflection of these high-frequency waves are displayed with different types of ultrasound modes.
See also sonogram, sonography, ultrasound imaging.

(US) Ultrasound is very high frequency sound above about 20,000 Hertz. Any frequency above the capabilities of the human ear is referred to as ultrasound.
Diagnostic ultrasound imaging uses much higher frequencies, in the order of megahertz. The frequencies present in usual sonograms can be anywhere between 2 and 13 MHz. The sound beam produce a single focused arc-shaped sound wave from the sum of all the individual pulses emitted by the transducer.

See also Medical Imaging.

Ultrasound biomicroscopy utilizes high frequency (10 - 50 MHz) diagnostic ultrasound to examine living tissue at a microscopic level and allows to image the skin with extremely high resolution to a depth of 2-3 centimeters. Ultrasound biomicroscopy images provide detailed anatomical information that can lead to better and more accurate treatments and avoid a biopsy.
Ultrasound biomicroscopy improves also the spatial resolution of US images of the anterior segment of the eye. US biomicroscopy of the eye operates in the 50 MHz range with a possible axial resolution on the order of 30 μm. In this frequency range, tissue penetration of only approximately 5 mm is attainable. Both continuous wave Doppler and high-frequency pulsed Doppler can be used.

See also Ultrasound Imaging Procedures, A-Scan, B-Scan and C-Scan.