1 / 39

Patient Interactions

Patient Interactions. Photoelectric Classic Coherent Scatter Compton Scattering Pair Production Photodisintegration. Interaction in The body begin at the atomic level Atoms Molecules Cells Tissues Organ structures. X-ray photons can change cells.

harriets
Télécharger la présentation

Patient Interactions

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. Patient Interactions • Photoelectric • Classic Coherent Scatter • Compton Scattering • Pair Production • Photodisintegration

  2. Interaction in The body begin at the atomic level Atoms Molecules Cells Tissues Organ structures

  3. X-ray photons can change cells

  4. Some radiations are energetic enough to rearrange atoms in materials through which they pass, and can therefore he hazardous to living tissue. 1913

  5. EM Interactions with Matter • General interactions with matter include • scatter (w or w/o partial absorption) • absorption (full attenuation)

  6. No interaction: X-ray passes completely and get to film Complete absorption: no x-rays get to film Partial absorption with scatter Interactions of X-rays with matter

  7. Photoelectric effect • Low energy (low kVp) x-ray photon ejects inner shell electron (energy absorbed) • Leaving an orbital vacancy. As vacancy is filled a photon is produced • More likely to occur in absorbers of high atomic number (eg, bone, positive contrast media) • Contributes significantly to patient dose, • As all the photon energy is absorbed by the patient (and for the latter reason, is responsible for the production of short-scale contrast).

  8. CASCADE

  9. Photoelectric – Absorption

  10. PHOTOELECTRIC ABSORBTION IN THE PATIENT (CASCADE OF ELECTRONS)

  11. PHOTOELECTRIC ABSORBTION IS WHAT GIVES US THE CONTRAST ON THE FILM

  12. 8 p+ + 8e- = neutral atom CLASSICAL SCATTER IN PATIENT INCOMING PHOTONS FROM TUBE Pass by the ELECTRONS IN THE PATIENT Do not interact with e– Causes them to VIBRATE – RELEASING SMALL AMOUNTS OF HEAT

  13. Classical (Coherent) Scattering • Excitation of the total complement of atomic electrons occurs as a result of interaction with the incident photon • No ionization takes place • Electrons in shells “vibrate” • Small heat is released • The photon is scattered in different directions • Energies below 10K keV

  14. Coherent / Classical Scatter

  15. Classic Coherent Scatter

  16. Compton scatter • High energy (high kVp) x-ray photon ejects an outer shell electron. • Energy is divided between scattered photon and the compton electron (ejected e-) • Scattered photon has sufficient energy to exit body. • Since the scattered photon exits the body, it does not pose a radiation hazard to the patient. • Can increase film fog (reduces contrast) • Radiation hazard to personnel

  17. Compton Scatter

  18. COMPTON SCATTERING – OUTER SHELL ELECTRON IN BODY – INTERACTS WITH X-RAY PHOTON FROM TUBE

  19. (WAVY LINE IN = PHOTON MUST BE INTERACTION IN THE BODY)

  20. During Fluoro – the patient is the largest scattering object

  21. XXXXX

  22. Differential Absorption • Results from the differences between x-rays being absorbed and those transmitted to the image receptor • Compton Scattering • Photoelectric Effect • X-rays transmitted with no interaction

  23. Compton and Differential Absorption • Provides no useful info to the image • Produces image fog, a generalized dulling of the image by optical densities not representing diagnostic information • At high energies

  24. Photoelectric and Differential Absorption • Provides diagnostic information • X-rays do not reach film because they are absorbed • Low energies (more differential absorption) • Gives us the contrast on our image

  25. No interactions with Image Receptor and Differential Absorption • No interaction • Usually high kVp • Goes through body • Hits image receptor • Usually represents areas of radiolucency (low atomic numbers) • Results in dark areas on the film

  26. The probability of radiation interaction is a function of tissue electron density, tissue thickness, and X-ray energy (kVp). • Dense material like bone and contrast dye attenuates more X-rays from the beam than less dense material (muscle, fat, air). • The differential rate of attenuation provides the contrast necessary to form an image.

  27. Pair Production

  28. Photodisintegration

  29. Remember….When reviewing diagrams What is coming in (e or photon? Where is it occurring (the tube or body?) Keep practicing – you will get it

More Related