1 / 27

X-Rays in Medicine

X-Rays in Medicine. Tyler Bradshaw- Fall 2008. Discovery of X-Rays . -W ilhelm Conrad Roentgen-1895 -E lectrical discharges in a vacuum tube -C aused a phosphored screen to fluoresce -F ormed an image of bone -F irst x-ray photograph of wife’s hand/ring . X-rays in Medicine.

anoki
Download Presentation

X-Rays in Medicine

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. X-Rays in Medicine Tyler Bradshaw- Fall 2008

  2. Discovery of X-Rays -Wilhelm Conrad Roentgen-1895 -Electrical discharges in a vacuum tube -Caused a phosphored screen to fluoresce -Formed an image of bone -First x-ray photograph of wife’s hand/ring

  3. X-rays in Medicine • One year later British doctors were already using x-ray imaging. • Prolonged exposure to x-rays caused tissue burns. • Wounds were abnormal- took time before appearing.

  4. Electro-Magnetic Spectrum • X-rays are electro-magnetic radiation. • Same as radio waves, sunlight, or microwaves. • The difference is in the wavelength/frequency Radio Waves: ~3 km 10000 Hz Microwave: ~ 1 cm 1010 Hz Visible Light: ~0.000005 mm 1015 Hz X-Rays: ~ 10-10 m 1018 Hz *Not to scale. Not even close.

  5. ENERGY

  6. PHOTONS -The energy of a light-wave is carried by packets called photons -The energy of a photon depends on the light’s wavelength -Smaller wavelengths have larger energies

  7. ENERGY Photon energies are usually given in units of electron volts (eV) 1 eV = 1.602x10-19 Joules Need 56,000,000,000, 000,000,000,000 eV to cook an egg.

  8. How do you create x-rays? • Bremsstrahlung • Fluorescence

  9. Creating X-rays: Bremsstrahlung • Charged particles emit photons when decelerating. • To form x-rays it must be very abrupt. • An electron arcs around the nucleus, emits an x-ray photon

  10. Creating X-rays: Bremsstrahlung Heavy Atom High speed electron Energy released depends on the electron’s speed and proximity to the nucleus.

  11. Creating X-rays: Fluorescence Characteristic X-rays • Electron-electron collision • Both leave atom, leaving a vacancy in the inner orbital • Vacancy filled by an outer electron • Transition releases high energy photon High speed electron Heavy Atom

  12. BremsstrahlungvsX-ray Fluorescence Both methods occur in an x-ray machine Bremsstrahlung: • Photon energies vary: 10,000-90,000 eV. • Lower energy x-rays are more common. Fluorescence: • Specific energies per atom. • Higher energy. • More useful.

  13. X-Ray Machines *Electron beam collides with a spinning tungsten disk *Electrons interact with the tungsten atoms *Both Bremsstrahlung and flourescence occur *Filter absorbs low energy x-rays X-Ray Machine Video

  14. Uses of X-rays 1) Imaging 2) Killing diseased/cancerous tissue X-rays are used because of their unique interaction with tissue and bone. There are four types of interactions…

  15. 1st: Elastic Scattering • Absorbs x-ray, bounces up and down • Re-emits x-ray • No effect on the atom • Bends the x-ray’s path (fuzziness)

  16. 2nd: Photoelectric Effect • X-ray photon is absorbed • Electron shoots away from the atom. • Larger atoms are more likely to absorb an x-ray than smaller atoms.

  17. Bone (Ca) absorbs x-rays • Tissue (C, H, O, N) transmit x-rays

  18. Photoelectric effect: useful in imaging • When treating cancer, however, you must avoid harmingsurrounding tissue • To target the tumor, another type of interaction is used… 3rd: Compton Scattering

  19. Compton Scattering -1,000,000+ eV photons used -Photon collides with an electron -Both bounce off like billiard balls

  20. Compton scattering affects only a fraction of the tissue. To target the tumor it must be treated from many different angles.

  21. When a 1,000,000 eV photon collides with an atom, another type of interaction occurs… 4th: Electron-positron Pair Production

  22. E=mc2 Einstein postulated that energy can become mass, and mass can turn into energy. A small amount of mass can create a lot of energy.

  23. Electron-Positron Pair Production e- Electron e+ Positron

  24. Antimatter: Symmetry in the universe. Almost all particles have an antimatter… Proton Antiproton Neutron Antineutron ElectronPositron

  25. Matter-antimatter collisions turn mass into energy, and create an explosion. e+ e- “Annihilation”

  26. *These electron-positron pairs are formed in radiation treatment. *The newly formed positron quickly “annihilates” another electron. *Helps kill tumors.

More Related