What radiology scans have white backgrounds and which ones have black backgrounds?

Interesting question: Xray, ct scan, MRI scan, ultrasound have black backgrounds. Nuclear medicine scans such as bone scans, pet/ct scans, and gallbladder scans have white backgrounds.

All of them: Digital imaging allows you to look at the images either way.

Nuclear Medicine: In general, scans done in nuclear medicine traditionally have a white "background" (in other words, air is white). Pretty much all other studies traditionally have a black background (air is black). But these are all read on computers and can be switched easily.

All types: Most digital images can be inverted and printed both ways. Most images have black backgrounds. Angiograms and fluoroscopy is often a white background.

Can be either way: Historically most studies are read with a black background due to the nature of film developing process. However most images are digital and black on white and white on black can be changed with a click of the mouse. Most radiologists prefer white on black, with the exception of live fluoroscopy