What does a high deviation index indicate in radiography?

A high deviation index in radiography indicates that there has been excessive exposure during the imaging process. The deviation index is a measurement that compares the amount of radiation exposure received by the image receptor to the amount that is considered optimal for that particular examination.

When the deviation index is high, it shows that the actual exposure is greater than the target exposure levels recommended for achieving a diagnostic-quality image. This can result in overexposure, which can lead to increased patient dose and may affect the overall image quality by causing issues such as saturation of the image, loss of detail in bright areas, and poor contrast.

In contrast, a low deviation index would suggest inadequate exposure, where the image may be underexposed and lack sufficient information for proper diagnosis. An optimal deviation index indicates that the exposure was within the recommended range, leading to the potential for high-quality images, while poor image quality can result from various factors unrelated to the deviation index itself, such as motion artifacts or technical errors during the image acquisition process.