Beam hardening occurs when an ultrasound beam passes through a strongly attenuating structure, causing the lower-frequency components of the beam to be absorbed more than the higher-frequency components. This effectively changes the average frequency of the remaining beam and reduces its intensity, which can affect the accuracy of the image beyond that structure. The concept is more commonly discussed in CT imaging, but it applies to ultrasound as well, particularly when the beam passes through dense structures like calcifications or bone. Sonographers compensate for this effect using time-gain compensation controls and by adjusting their scanning technique to find better acoustic windows around highly attenuating structures.
Sonography Term