Ultrasound in the diagnosis of maxillary and frontal sinusitis.

Sinus ultrasound (3 MHz ultrasound wave) is ideal for detecting maxillary and frontal sinusitis as it propagates well through bone, soft tissues and fluids but not through air. Ultrasound is sent towards the bony back wall of a sinus cavity and the reflected echoes correlate to the depth of the tissue boundaries. A healthy sinus cavity, containing only air, reflects from the anterior wall of the sinus, whilst an infected sinus cavity, filled with fluid, reflects from the posterior wall.