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• 1. rays


  • Produced ISOTROPICALLY and has EQUAL INTENSITY to all directions
  • Size is VARIABLE by using x-ray beam collimators
  • Intercepted by MATTER & TISSUE
• 1. ray production


  1. Using a HIGH VOLTAGE and an ELECTRIC CURRENT

  2. Fast moving electrons coming from the cathode interacts with the target in the anode
• Primary Beam


  • X-rays emitted through the window of the x-ray tube are called the USEFUL BEAM or PRIMARY BEAM
  • Transmitted from the x-ray tube to the image receptor
  • The quality and quantity of the primary beam can be determined by the kVp and mAs
  • It should never be directed at the radiologic technologist, other personnel, or the control booth
  • The actual x-ray beam that is intercepted by the patient
• Central Ray


  • Imaginary line in the useful beam
  • Centermost part of the x-ray beam
  • Should be aligned to the center of the structure being imaged and grid if being used
  • Particularly important in radiographic positioning and reducing image distortion
• If the intensity of the central ray is 100%, then the x-ray intensity on the cathode side may be as high as 120% and the anode side as low as 75%
• Exit/Remnant Beam


  • The part of the x-ray beam that exits the patient after interaction
  • Interact with the patient and are scattered away
• Leakage Radiation


  • Any x-rays that escape the protective housing of the X-ray tube
  • Contributes nothing in the way of diagnostic information and results in unnecessary exposure of the patient and radiologic technologist
  • Must not exceed 100 mR/hr at 1 meter
• Off-Focus/Stem Radiation


  • Also known as Extrafocal X-rays
  • X-rays tubes are designed so that the projectile electrons from the cathode interacts with the target only at the focal spot
  • Some electrons bounce off the focal spot and land on other areas of the target causing x-rays to be produced from outside of the focal spot
  • Undesirable because it extends the focal spot size increasing the skin dose unnecessarily
  • Can reduce the radiographic image contrast
  • Can be a reason that tissue that was meant to be excluded, appear on the radiograph
  • Can also be reduced by the use of metal enclosures which extract and conduct the reflected electrons
  • Reduced by using a fixed diaphragm inside the x-ray tube near its window
• Radiography is the process of producing images using ionizing radiation.
• Kinetic Energy


  • Energy in motion
  • Electrons with high kinetic energy focused toward a small spot on the anode are necessary for x-ray production
• Kinetic Energy Equation


  • KE = (1/2)(mv^2)
  • M - mass in kg
  • V - velocity in meters per second
  • KE - kinetic energy in joules
• Kilo electron volts


  • What energy of x-rays are expressed as
  • 1 keV = 1.6 x 10^-16 J
• 1. ray imaging system


  Primary function is to accelerate electrons from cathode to anode
• 1 cm - distance of the filament to the target
• Heat


  Most of the projectile electrons' kinetic energy is converted into this
• Thermal Energy


  99% of projectile electron interaction is converted into this
• Projectile Electrons


  • Interact with outer shell electrons which causes excitation then return to the original state
  • Constant excitation and return to normal state - responsible for most heat generated in the Anode
• Factors affecting the production of Anode Heat

  • Tube Current = increase mAs, increase anode heat
  • Tube Voltage = increase kVp, increase anode heat
• 1% - percentage of anode heat used in x-ray production
• 1. ray tube - considered to be an ineffective device
• Projectile Electrons


  • Electrons traveling from the cathode to anode
  • When electrons hit the anode, they transfer their kinetic energy to the target atoms
  • These electrons interact with the orbital electrons or the nuclear field of the target atoms
  • These results in the formation of thermal energy and electromagnetic energy in the form of infrared and x-rays
  • Interact with an inner shell electron and ionizes it leaving a void to be filled by an outer shell electron
• Characteristic Radiation


  • Produced when an outer shell electron fills an inner shell void
  • Emission of x-ray occurs as the outer shell electron fills the inner shell
  • Any other outer shell electron can fill in an inner void
• K x-rays


  Occurs when radiation is produced by any other outer shell electron filling a K shell vacancy
• 1. characteristic x-rays of tungsten - only ones useful in x-ray imaging as all other outer shell electron binding energy is lower than of a K-shell electron
• 1. shell x-rays - require an x-ray tube with a potential of 69 kVp and up since the K-shell electron of a tungsten target has an effective energy of 69 KeV
• Bremsstrahlung


  German word meaning "slowed down"
• Bremsstrahlung Radiation


  • Results from the braking of projectile electrons by the nucleus of an atom
  • Where the projectile electrons completely avoids the orbital electrons as it passes through the target atom and may come close enough to the nucleus to interact with its electric field
• Nuclear Force Field


  Where projectile electron loses its kinetic energy as it interacts with this then changes direction
• Electromagnetic energy


  What lost kinetic energy is converted into
• Electrostatic force of attraction

  • Causes the "braking" down of electrons
  • Occurs between nucleus of atom and projectile electrons
• Nucleus of an atom is positively charged
• Projectile Electrons are negatively charged
• Low energy bremsstrahlung x-rays

  Results when the projectile electrons barely interact with the nuclear force field
• In diagnostic range, most x-rays are Bremsstrahlung x-rays
• In bremsstrahlung radiation, energy produced can be 1 keV up to 70 keV
• An electron with kinetic energy of 70 keV can lose ALL, NONE, or ANY intermediate level of that kinetic energy
• Computed Tomography (CT) uses multiple views of the same area to create cross sectional images of the human body.