AP chest x-rays are harder to read than PA x-rays and are therefore generally reserved for situations where it is difficult for the patient to get an ordinary chest x-ray, such as when the patient is bedridden. In this situation, mobile X-ray equipment is used to obtain a lying down chest x-ray (known as a supine film).
An MRI system requires helium to keep its magnet cool, especially when imaging a patient, and continues to consume helium to remain cool when the magnet is idling. An MRI system must be cooled to 4.2 K, or -452Â° F, and liquid helium is the most effective way to sufficiently cool the magnet to that temperature.
The mixture of helium and oxygen with a 0% nitrogen content is generally known as Heliox. This is frequently used as a breathing gas in deep commercial diving operations, where it is often recycled to save the expensive helium component. Analysis of two-component gases is much simpler than three component gases.