Principles of radiological imaging: The cathodic tube

This chapter focuses on the working principles and principal components and issues of the cathodic tube, essential part of powerful medical imaging techniques such analog and digital radiography and computed tomography. Cathodic tube emits X-rays photons, which hit the patient body and are partially attenuated. The transmitted X-rays are detected by image plates or solid state detectors in order to represent the density of human body tissues and organs. Energies of the emitted X-rays usually range between 20 and 150 keV, depending on the specific application of the medical imaging technique and are determined by power supply applied to the cathodic tube and by the target material. Peculiar characteristics of the cathodic tube (such as the "heel effect") will be exploited along this chapter along with the physical phenomena ruling the X-ray production.