The top row displays attenuation-corrected PET data; the bottom row shows non-attenuation-corrected PET data.

In physics, attenuation (in some contexts also called extinction) is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated while passing through seawater.

In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, as well as in air (radio waves).

Basically, attenuation is a way of reducing brightness or making a display look darker than it appears.