Entry #6: Artifacts from Image Intensification

Even though the image intensifier has done some wonderful things to improve diagnostic imaging, it still has problems from time to time. Here's a quick list at some things that can occur that may produce less than stellar images:

• Lag: An image remains after utilizing x-ray stimulation. This essentially creates a "ghost" image.

• Vignetting: Brightness of the image is reduced around the edges. This is caused by pincushion distortion or scatter light inside of the optical coupling device between the II and the optical recording device.

• Pincushion distortion: The outside edges curve in towards the center of the image. This happens when the input screen is curved and the output screen is planar (flat). Alignment occurs at the center but not at the peripheral edges. This will warp the image.

• Veiling glare: The contrast between structures on the image is reduced, making differentiation difficult.

• S Distortion: Some sort of electromagnetic force pulls on the electrons in the image intensifier, distorting the image into these characteristic "S" waves. The entire image becomes warped.