Urology>>>>>Imaging and Principles of Uro-Radiology
Question 1#

Which of the following statements about diagnostic ultrasonography is INCORRECT?

A. At lower ultrasound frequencies, there is better penetration but worse resolution
B. At higher ultrasound frequencies, there is worse penetration but better resolution
C. Acoustic impedance influences the amount of energy reflected from tissue interfaces
D. Diagnostic medical ultrasound frequencies are typically between 2 and 18 KHz, which is above the audible range of normal human hearing
E. Fat appears echo-bright on ultrasound

Correct Answer is D

Comment:

Answer D

Ultrasound can be used as a diagnostic medical imaging technique that utilises the interaction between sound waves and different tissues. Alternative current is applied to crystals of a piezoceramic plate in a transducer. Expansion and contraction of these crystals produce longitudinal waves, typically at a frequency varying between 2 and 18 MHz. In humans, the audible range of sound wave frequency is between 20 and 20,000 Hz. As the sound waves travel through tissues some are reflected back and are converted from their mechanical form to electrical energy by the transducer to produce an image.

Artefacts occur due to acoustic shadowing, distal enhancement, edging and reverberation.