REVIEW Review of Science, Math Review of X-Tube Construction
Review of Science and Math Self Quiz Convert 1/7 into a decimal. Convert .11 into a fraction Multiply: Solve for x: 5x2=45 Solve for x:
Review of Science and Math What is an atom? smallest particle of an element What are the parts of an atom? nucleus-protons, neutrons electrons What is Atomic Number? What is the electrostatic law of attraction? un-like charges attract, like charges repel
Review of Atom BOHR model of the atom Electrons orbit around a nucleus (center)
Differences in Binding Energy Remember this for later…
Review of Tube Construction vacuum vacuum
Review of X-ray Tube Stators Rotors mA current High voltage current Focal track
Electromagnetic Spectrum What the heck are those squiggly lines????
Electromagnetic Spectrum • Spectrum • Continuous range of energy • Although there are precise ranges defined, they often overlap • 3 most important to Radiologic technology: • Visible light • X-radiation • Radiofrequency
Electromagnetic Spectrum Ionizing Radiation Has same properties as all EM radiation, has properties unique to ionizing radiation, has wavelength and frequency unique to ionizing radiation
Electromagnetic Spectrum Wavelength Frequency Inversely proportional
Wavelength and Frequency Distance
Wavelength • Wavelength is the difference between: • Crest to Crest • Valley to Valley
Frequency • Frequency is the number of wavelengths passing a point of observation per second
Wavelength and Frequency INVERSELY PROPORTIONAL
Wavelength and Frequency • Wavelength & frequency are inversely proportional • As Wavelength increases frequency decreases • As wavelength decreases frequency increases • Frequency and wavelength are closely associated with the relative energy of electromagnetic radiation. • More energetic radiations have shorter wavelengths and higher frequency.
EMS-Ionizing Radiation General Characteristics of EMSX-ray photons: • Have no mass or physical form • Travel in a linear path (until interaction occurs) • Dual nature: wave vs. particle • Unaffected by • electric or magnetic fields • gravity
Tube Interactions • Heat = 99% • X-ray = 1% • Bremsstrahlung (Brems) = 80% • Characteristic = 20%
X-ray production begins at the atomic levelEnergy (photons) are released when the electron collides with another electron,or passes close to the nucleus of the atom –the change in energy of the shells –produces photons
Self Test • True or False • X-ray production begins as the electrons stream begins toward the anode. • The energy production in the x-ray tube is 90% heat, 80% brems, 20% characteristic. • Heat results from a mild ionization. • As wavelength increases, the frequency also increases. • The smallest packet of electromagnetic energy is called a photon. • Thoughtful challenge question: What is the most frequent ionizing tube interaction?
Heat • Most kinetic energy of projectile e- is converted into heat – 99% • Projectile e- interact with the outer-shell e- of the target atoms but do not transfer enough energy to the outer-shell e- to ionize
8 p+ + 8e- = neutral atom • Projectile electrons from cathode • Pass by the electrons in the target • Causing the electrons to vibrate (excitation) • Excitation produces small amounts of heat HEAT e e
Things to Remember About Diagnostic Radiation Production • Diagnostic radiation production happens in the x-ray tube • Two kinds of diagnostic radiation production: characteristic and bremsstrahlung • Incoming electron • Interacts with: • inner shell electron = characteristic radiation • nuclear force field = bremsstrahlung radiation
Bremsstrahlung brems animation
Bremsstrahlung The closer the Electron passes To the nucleus, The more energetic The resulting x-ray Photon.
Brems The incoming electron passes near enough to the nucleus to be affected by the law of electrostatic attraction. The electron starts to slow down and veer toward the nucleus but never hits the nucleus or another electron. The slowing down motion changes the direction of the incoming electron and release some of the energy of that electron. The form of energy released is x-ray radiation. Brem radiation 2 http://youtu.be/q-cTw1x7TzA
Characteristic Radiation • Projectile e- with high enough energy to totally remove an inner-shell electron of the tungsten target • All tube interactions result in a loss of kinetic energy from the projectile e- • Characteristic x-rays are produced when outer-shell e- fills an inner-shell void
Characteristic Radiation animation of characteristic
It is called characteristic because it is characteristic of the target element in the energy of the photon produced
Characteristic characteristic radiation -1 characteristic radiation-2
Electron hits inner shell e in orbit – knocked out & creates a hole Other E’s want to jump in Energy released as PHOTONS CHARACTERISTIC (in tube)
Summation of Tube Interactions Radiation Interaction in the Tube