RTCA 218 Xray Production Bushong Chapter 8 Xray

RTCA 218 X-ray Production Bushong, Chapter 8

X-ray Production Abstract: This section will deal with the two primary methods of producing radiation. Special emphasis will be placed on characteristic and bremsstrahlung radiation and the probability of each occurring in a typical x-ray beam. Included also will be a discussion on the x-ray emission spectrum and the factors affecting that spectrum. Objectives: At the end of this section, the student should be able to: § discuss and describe the function of the x-ray tube. § define and describe characteristic radiation. § define and describe bremsstrahlung radiation. § describe the x-ray emission spectrum. § discuss the relationship between wavelength and x-ray energy. § discuss the characteristic and bremsstrahlung radiation spectrum. § list and discuss the factors that affect the x-ray emission spectrum.

X-ray Production § § § Electron-Target Interaction Primary function of the x-ray tube is to ________ electrons from the cathode to the anode Convert electrical energy into _________ (x-radiation) energy KE = ½m v 2

X-ray Production § Increasing k. Vp increases electron _______ energy – increases intensity (m. As) and energy (k. Vp) of x-ray beam § Heat production – ____% of kinetic energy is converted to heat – less than ___% results in x-ray production

X-ray Production § radiation produced isotropically – with equal _______ in all directions § only the radiation that is directed through the ________ is considered useful – primary beam

X-ray Production § radiation other than that which is directed through the window is absorbed by the protective ________ or oil inside the x-ray tube § any radiation that emerges from the x-ray tube other than through the window is called _______ radiation

X-ray Production § § § Characteristic Radiation Interaction of projectile electrons with the _______ shell electron of the target atom Interaction must be sufficiently violent to _____ the target atom Energy of the projectile electron must be equal to or greater than the EBE of the target atom

X-ray Production § _______ shell electron fills the vacancy of the inner shell resulting in the production of an x-ray photon § photon energy equal to the difference between the inner shell _____ and the ______ of the electron that filled the vacancy

X-ray Production § K Xrays – Characteristic radiation produced as a result of ionization of inner (K) shell – only form of characteristic radiation that is _______ in radiology § All other characteristic radiation (L, M, N. . . ) have energy levels too _____ to be of use

X-ray Production Characteristic X-ray of W & Their Energies Electron Transition from Shell Characteristic L-shell K 57. 4 L M N O M-shell 66. 7 9. 3 N-shell 68. 9 11. 5 2. 2 O-shell 69. 4 12. 0 2. 7 0. 52 P-shell 69. 5 12. 1 2. 8 0. 6 0. 08 Eff. Ener. 69 12 3 0. 6 0. 1

X-ray Production § Since a K-shell electron of a W atom has an EBE of 69 ke. V, no characteristic radiation can be produced unless the PE contains at least _____ ke. V § This means that no characteristic radiation is produced on exposures using _________ 69 k. Vp § k. Vp setting determines the peak level of any single x-ray photon in an exposure, as well as the energy level of the PE passing from the cathode to the anode

X-ray Production § § § Bremsstrahlung Radiation German word for “breaking” or “______” Projectile electron _______ the orbital electrons Interact with the nucleus of the target atom

X-ray Production § Projectile electron 1) slows down, 2) changes _______ , and 3) loses some or all of its ________ energy § X-ray photon energy produced equals the amount of energy lost by the projectile electron

X-ray Production § If P. E. has 75 ke. V, and it interacts with the target nucleus and loses 75 ke. V of energy, the brem. radiation equals _____ ke. V § if it loses 60 ke. V, the brem. radiation equals 60 ke. V § if it loses ____ ke. V, no brem. radiation is produced

X-ray Production § Brem. radiation can have an energy range from 0 ke. V to the ________ energy level of the P. E. § Maximum energy of the P. E. is determined by the _____ setting § In the diagnostic range, ______ x-rays are produced in the brem. fashion

X-ray Production X-ray Emission Spectrum § determines the number of x-rays produced at various _______ levels

X-ray Production Characteristic X-ray Spectrum § have precisely _______ energies § those energies are totally dependent on the type of ________ material used – characteristic of the target atom

X-ray Production Characteristic X-ray Spectrum § represented by _______ lines for each of the orbital shells that can produce radiation

X-ray Production Characteristic X-ray of W & Their Energies Electron Transition from Shell Characteristic L-shell K 57 L M N O M-shell 67 9 N-shell 68. 9 11. 5 2. 2 O-shell 69. 4 12. 0 2. 7 0. 52 P-shell 69. 5 12. 1 2. 8 0. 6 0. 08 Eff. Ener. 69 12 3 0. 6 0. 1

X-ray Production Bremsstrahlung X-ray Spectrum § has a ______ curve appearance § _________ x-ray photon energy available equals the k. Vp set on the x-ray unit – kilovoltage peak

X-ray Production Bremsstrahlung X-ray Spectrum § greatest number of x-rays produced have energies about ______ of the maximum energy

X-ray Production § Factors influencing the shape of the brem. spectrum: 1. peak kinetic ______ of the projectile electron 2. thickness of the target material 3. absorption of _____ energy photons 4. external filtration

X-ray Production Factors Affecting the X-ray Emission Spectrum § m. A – ________ proportional to the amplitude of the spectrum at all energy levels

X-ray Production Factors Affecting the X-ray Emission Spectrum § k. Vp – increase in k. Vp increases amplitude of the spectrum and shifts it to the right – _____% rule

X-ray Production Factors Affecting the X-ray Emission Spectrum § Added Filtration – ________ effective (average) energy of x-ray beam, ________ quantity – results in decreasing amplitude and a shift to the right

X-ray Production Factors Affecting the X-ray Emission Spectrum § Target material – as atomic number ________, efficiency of brem. radiation increases – results in increase in amplitude and slight shift to the _____

X-ray Production Factors Affecting the X-ray Emission Spectrum § Voltage Waveform – Single phase to 3 Phase equals 12% increase in k. Vp or nearly _______ m. As – results in _________ in amplitude and shift to the right

X-ray Production § X-ray intensity and energy increase as voltage increases § Peaks at the peak energy and decreases thereafter § 3 -phase and HF units require half exposure factors compared to single phase