What does a higher penumbra in fixed fields indicate?

A higher penumbra in fixed fields indicates increased image blur. Penumbra refers to the zone of transition between the fully illuminated area and the fully shadowed area produced by the radiation beam. When the penumbra is larger, it creates a less defined boundary, leading to more blurriness in the resulting image. This can occur due to factors such as poor focus, increased distance from the source, or a wide beam profile.

Higher penumbra often suggests that there is a degradation in image sharpness, making it harder to distinguish fine details. This is particularly relevant in fluoroscopy, where clarity is crucial for accurate diagnosis and treatment. Hence, recognizing that an increase in penumbra correlates with decreased image quality is vital for interpreting fluoroscopic images effectively.