What phenomenon is referred to as pin cushion distortion?

Pin cushion distortion is a specific type of optical distortion that occurs in imaging systems, often seen in radiographic systems. This phenomenon results in the outward bending of the edges of an image, creating a shape that resembles the surface of a pin cushion. As a result, straight lines at the periphery appear curved or distorted towards the center of the image, leading to inaccuracies in representation.

This distortion is primarily caused by the geometrical arrangement and design of the imaging system, and its effects can be especially noticeable in specific modalities or under certain conditions. Understanding pin cushion distortion is crucial for professionals in the field, as it impacts image accuracy and diagnostic capabilities.

The other options describe different types of image issues. Increased brightness in the center pertains to a different type of illumination distortion, blurring during rapid camera movement concerns motion artifacts rather than distortion related to geometry, and loss of image color at the edges refers to color fringing which is unrelated to pin cushion distortion.