Of all imaging modes discussed so far, the Sectorial scan is unique to phased array equipment. In a linear scan, all focal laws employed a fixed angle with sequencing apertures. Sectorial scans, on the other hand, use fixed apertures and steer through a sequence of angles.
Two main forms are typically used. The most familiar, very common in medical imaging, uses a zero degree interface wedge or shoe to steer longitudinal waves at relatively low angles, creating a pie-shaped image showing laminar and slightly angled defects.