In this video Dirk Steiner compares two examples of scans at 550mm vs 1100mm detector distance using a micro-focus tube to illustrate how scan speed can be increased, and he shows the impact on image quality and dimensional deviation. 
 

Thanks to most recent developments, computed tomography (CT) is now an affordable and efficient
technology for non-destructive testing of workpieces made of a vast variety of materials. While digital radiography provides two-dimensional fluoroscopic images, computed tomography typically rotates the object between the X-ray tube and the flat-panel detector 360° and captures several hundred to well over a thousand X-ray images from various angles.