Beam width refers to the cross-sectional size of the ultrasound beam as it travels through tissue. The beam is narrowest at the focal zone, where the transducer has been focused, and widens both before and after this point. Narrow beam width at the focal zone produces better lateral resolution, meaning the ability to distinguish two side-by-side structures as separate. Structures located outside the focal zone are imaged with a wider beam and therefore appear less sharp. Sonographers adjust the focal zone to the depth of the structure they are most interested in examining, ensuring the best possible image quality at that level.
Sonography Term