What does diffraction refer to in ultrasound physics?

Diffraction in ultrasound physics refers to the spreading out of the ultrasound beam when it encounters an obstacle or aperture that is comparable in size to the wavelength of the sound. This phenomenon occurs because the wavefront of ultrasound is altered as it passes through or around these structures, leading to a change in direction and distribution of the ultrasound energy.

As the sound waves propagate, they bend and spread, especially when passing through small openings or around edges. This can influence the resolution and imaging qualities in ultrasound, as it can lead to the interaction of waves and affect how reflections from different interfaces are received. Understanding diffraction is crucial because it can impact the interpretation of ultrasound images, including the spatial relationships of structures being evaluated.

In contrast, concepts like concentration of the beam, reflection, and absorption relate to different physical principles and do not accurately describe the effect characterized by diffraction. Concentration of the beam typically involves focusing techniques, reflection pertains to the return of sound waves from interfaces, and absorption concerns the energy loss of sound as it travels through tissue.