X-rays are rays along the electromagnetic spectrum that have variable success in passing through human tissue.  The greater the density of the tissue the less success it has in passing through.

X-ray machines use this principle to produce a two dimensional map of the density of a human body.  Effectively, the machine consists of a tube that produces x-rays, and a detector the other side of the human area being imaged.  Areas of high density (e.g. bone) allow lesser amounts of x-rays to pass, and areas of lower density allow more x-rays to pass.

If the detector were able to represent the x-rays hitting it in a black and white image with white representing lesser amount of x-rays passing through it, then the image is recognisable as today’s x-ray film.

Traditionally, the detectors were photographic film, and producing visible pictures involved dark rooms, chemical and processing.  Modern machines are digital, and the pictures are taken by a digital detector.

The quality of an x-ray machine is determined by the resolution of its detector, the size of the detector plate and its sensitivity (the greater the sensitivity, the lesser the amount of x-ray radiation a patient has to be exposed to).  In addition, the more manoeuvrable, and flexible a system is, the better able radiographers are to get the exact image needed for a diagnosis.

MDI chooses digital x-rays that have the best flexibility and dose reducing features.