The Derivation of Approximate X-ray Spectral Distributions and an Analysis of X-ray “Quality” Specifications

Part I considers methods of deriving and specifying approximate X-ray spectral distributions if either the time or facilities are not available for obtaining complete spectra. Tables are provided which simplify the representation of an X-ray beam by three monoenergetic components when the transmission curve of the radiation in a suitable absorber is known. In another approach three components are fitted graphically to the attenuation data. The various methods are compared. Part II considers the amount of information regarding an X-ray spectrum which can be derived from the various forms in which radiation quality may be expressed. The specifications examined are: (i) HVT only, (ii) HVT and kilovoltage, (iii) first and second HVT, (iv) first and second HVT and kilovoltage, and (v) full attenuation curve and kilovoltage. From these are derived representations by means of one, two or three monoenergetic components, and by approximate or accurate spectral distributions. The various methods are compared with each other and with those of Part I.