What percentage of the beam is characteristic above 70 kVp?

The percentage of the beam that is characteristic above 70 kVp is accurately identified as 15%. In radiography, "characteristic radiation" is produced when electrons from the cathode collide with the target material, typically tungsten, and eject inner shell electrons from the atoms. When these inner shell vacancies are filled by higher energy electrons, characteristic photons are emitted.

At tube potentials over 70 kVp, the majority of the x-ray beam produced consists of bremsstrahlung radiation, which is generated by the deceleration of electrons as they approach the nucleus of the target atoms. However, characteristic radiation still contributes a notable fraction. Research and empirical data suggest that it accounts for approximately 15% of the total x-ray beam in this range, making it an important consideration in imaging scenarios.

This concept helps technicians understand the contributions of different types of radiation in their imaging, which can be crucial in optimizing exposure and maximizing the quality of the diagnostic image.