What alkali metals is usually used for x-ray?

Lithium is the alkali metal most commonly used in X-ray applications, particularly in the form of lithium fluoride (LiF) crystals. These crystals are utilized as scintillators and in radiation detectors due to their favorable properties, such as high efficiency and low atomic number. Sodium and potassium can also be involved in certain X-ray applications, but lithium is the primary choice for high-quality X-ray imaging and detection.