What effect does increasing frequency have on the quality of ultrasound images?

Increasing the frequency of the ultrasound waves enhances the axial resolution of the images produced. Axial resolution refers to the ability to distinguish between two points that are close together along the direction of the ultrasound beam. Higher frequencies produce shorter wavelengths, which naturally leads to improved detail and the ability to resolve smaller structures.

However, this improvement in axial resolution comes at the cost of tissue penetration. Higher frequency ultrasound waves are absorbed more readily by tissues and scatter more than lower frequency waves. As a result, while detailed imaging is enhanced, the overall depth of penetration into the body is reduced. This means that at higher frequencies, there is a limit to how deeply the ultrasound can effectively image.

Understanding this trade-off is essential in sonography. For example, when imaging superficial structures like the thyroid or arteries, higher frequencies are beneficial for obtaining clear images. Conversely, when examining deeper structures, such as organs within the abdominal cavity, a lower frequency would be preferable to achieve adequate tissue penetration, even if it results in slightly lower axial resolution.