What term refers to the phenomenon where the middle of the image appears darker than the periphery?

The term that describes the phenomenon where the middle of an image appears darker than the periphery is known as cupping artifact. This artifact results from variations in density and attenuation coefficients within the imaged object, often related to the way the CT scanner processes the data.

In CT imaging, when an object—like soft tissue or bone—is scanned, the x-ray photons may pass through different densities, causing discrepancies in the resulting image. The central region may receive fewer photons due to scatter or other factors, while the edges might appear lighter. This effect usually leads to a gradient in image brightness from the center towards the edges, manifesting as a darkened central area compared to the outer margins.

Understanding cupping artifact is crucial for radiologists and technicians as it can affect diagnostic accuracy. Being aware of this phenomenon helps in image interpretation and in taking necessary precautions to minimize its occurrence during the scanning process, ensuring a clearer and more accurate representation of anatomical structures.