What to do if lines appear on the digital x rays?

That depends:

- If You see straight paralell lines (shadows) one close to another (filling all the screen) You may see the antiscatter grid shadow. This could mean that the grid isn't moving or the exposure time is too short to move the grid. Try to use less current to increase exposure time and check if the grid mechanism is ok.

- If You see curved lines or repeating patterns that are visible if the image isn't 1:1 zoomed - it may be moire effect. It's the output of adding 3 spatial frequencies: grid density , scanning resolution and monitor resolution. Consult it with Your CR/DR service. Sometimes it's possible to add filters or change the parameters of image.

- If You see some lines through all the image (like scratches) something is wrong with CR reader. Consult service.