X-Ray Production and Control

Mind Map

Learning Guide

Learning Activities

Visuals for
Class Discussion



Objectives and Learning Activities

  • Sketch a cross-section of a basic x-ray tube and label the components. 
  • Describe and explain the concept of the two electrical quantities, KV and MA, that are associated with x-ray production.
  • Describe the events that occur within an x-ray tube that lead to x-ray production.
  •  Describe a focal spot, what is it? where is it?
  • Name the material used as the x-ray tube anode for general x-ray imaging and explain why it is used.
  • Name two materials used as the x-ray tube anode for mammography and explain why each is used.
  • Lookup in a reference the atomic number (Z) of the two anode materials used for mammography and describe the significance of Z with respect to x-ray production.
  • Describe the filament and focusing cup (i.e., the cathode assembly) of an x-ray tube, including the purpose of two filaments in some x-ray tubes and the purpose of the focusing cup. 
  • Name and briefly describe the process by which electrons are liberated from a heated filament at the cathode of an x-ray tube. 
  • Describe the principle factor that determines the kinetic energy attained by electrons as they strike the x-ray tube anode. Can it be changed or adjusted? 
  • Discuss at least two functions of the x-ray tube housing.
  • Describe the process of bremsstrahlung production and sketch a typical spectrum.
  • Sketch and compare the three bremsstrahlung spectra for the following factors:
        50 kV and 50 mA
        100 kV and 50 mA
        100 kV and 100 mA
  • Describe the production of characteristic radiation and sketch a typical spectrum.
  • Sketch and compare the characteristic x-ray spectra for a molybdenum anode operating at 25 kV and 35 kV.
  • Sketch and compare the characteristic x-ray spectra for a molybdenum anode and a rhodium anode both operating at 30 kV.
  • Identify the adjustable operating factor(s) that determine(s) the maximum energy of x-ray photons emitted from an anode. 
  • Explain why K x-rays emitted by an atom have higher energies than L or M x-rays from the same atom.
  • Explain why a high Z element produces some characteristic x-rays with energy greater than that of x-rays from a lower Z element, even though both elements are bombarded by 100 keV electrons.
  • Define the expression "efficiency" of  x-ray production and identify the principle factors that affect efficiency , and estimate its value for a diagnostic x-ray tube. 
  • Describe how the efficiency is related to the electron accelerating voltage (KV).
  • Describe the general relationship between x-ray production efficiency and the atomic number of the anode material. 
  • Sketch typical graphs and describe the variation in output (i.e., exposure rate) of an x-ray tube as a function of: 1. tube voltage (KV) 2. tube current (MA).  What is the type of mathematical relationship for each?
  • Estimate the skin entrance exposure to a 23 cm thick patient for a PA chest radiograph performed at 72 inches using a technique of 120 kVp and 15 mAs. Use appropriate references as necessary to obtain typical x-ray tube output data.
  • Estimate the increase in x-ray tube output exposure when the tube potential (KV) is increased from 60 to 75 kVp.  Explain how you arrived at the answer.