medical imaging

• What is the first focus of the video?

  The x-ray tube
• What is required to accelerate electrons in an x-ray tube?

  A high voltage power supply
• What happens when electrons hit the target in an x-ray tube?

  X-rays are emitted
• What is the efficiency of x-ray production in an x-ray tube?

  Only 1% of kinetic energy is converted
• How do you calculate the minimum wavelength of an x-ray with 150 kilovolt potential?

  Use the formula $\lambda =$$\frac{hc}{eV}$
• What is the value of Planck's constant?

  $6.63 \times 10^{-34} \text{ J s}$
• What is the speed of light?

  $3 \times 10^{8} \text{ m/s}$
• What is the minimum wavelength calculated for 150 kilovolt potential?

  $8.3 \times 10^{-12} \text{ m}$
• How do you calculate the maximum frequency of an x-ray with 150 kilovolt potential?

  Use the formula $f =$$\frac{eV}{h}$
• What is the maximum frequency calculated for 150 kilovolt potential?

  $3.6 \times 10^{19} \text{ Hz}$
• What happens to an x-ray with energy below the work function?

  It is simply scattered
• What is Compton scattering?

  An x-ray removes an electron and scatters
• What is produced in pair production?

  A positron-electron pair
• How do you calculate the minimum energy for pair production?

  Use $\Delta E =$$\Delta mc^2$
• What is the change in energy for pair production?

  $1.6 \times 10^{-13} \text{ J}$
• What is the photoelectric effect?

  An x-ray is absorbed, releasing an electron
• What does the x-ray attenuation coefficient represent?

  How much x-rays are absorbed by tissue
• What is the equation for x-ray intensity attenuation?

  $I =$$I_0 e^{-\mu x}$
• How do you rearrange the attenuation equation for the attenuation coefficient?

  $\mu =$$\frac{\ln(I_0/I)}{x}$
• What are the k lines in x-ray characteristics?

  Peaks in the intensity-wavelength graph
• What happens when electrons bombard the target in an x-ray tube?

  High energy photons are released
• How do you estimate the maximum accelerating potential from the minimum wavelength?

  Use <latex{V = \frac{hc}{e\lambda}}}</latex>
• What is the estimated maximum accelerating potential for a minimum wavelength of $2.5 \times 10^{-11} \text{ m}$?


  Approximately 50,000 volts
• How does increasing the accelerating potential affect x-ray characteristics?

  Increases maximum energy and decreases minimum wavelength
• What is the purpose of contrast media in x-rays?

  To improve resolution of soft tissue images
• What are common contrast media used in x-rays?

  Barium and iodine
• How does the atomic number affect x-ray absorption?

  Higher atomic number increases absorption
• What is a CAT scan?

  A rotating x-ray tube for imaging
• What shape is the x-ray beam in a CAT scan?

  A thin fan-shaped beam
• What is the advantage of a CAT scan over a standard x-ray?

  Produces 3D images for diagnosis
• What is a disadvantage of CAT scans compared to x-rays?

  More harmful due to radiation exposure
• What is the limitation of x-rays in diagnosing soft tissue?

  They have similar attenuation coefficients
• What imaging technique is used for soft tissue examination?

  MRI or medical tracers
• What type of images can be taken as the x-ray moves?

  Images of slices or cross-sectional areas
• What is a typical advantage of an x-ray scan compared to a CT scan?

  X-ray scans are quicker and cheaper
• Why might a CT scan be considered more harmful than an x-ray?

  CT scans involve multiple x-ray images
• What imaging technique is used to look at soft tissue?

  MRI or medical tracers
• What is a medical tracer?

  A radioactive substance for diagnosis or treatment
• What type of radiation must medical tracers be?

  Gamma sources
• Why do medical tracers need a long enough half-life?

  To be detected but not stay long