Patient Interactions

1. Patient Interactions Fall 2009 FINAL

2. Patient Interactions • ______________ • ______________ • ______________ • ______________ • ______________

4. Interaction in the body begin at the atomic level • _______________ • _______________ • _______________ • _______________ • _______________

5. X-ray photons can change cells

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

7. EM Interactions with Matter General interactions with matter include: • ______________ • With or without partial absorption • ______________ • Full attenuation

8. ________________: X-ray passes completely and get to film ________________: no x-rays get to film ________________________________ Interactions of X-rays with matter

9. 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).

11. CASCADE

12. Photoelectric – Absorption

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

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

15. 8 p+ + 8e- = neutral atom CLASSICAL SCATTER IN PATIENT • Incoming photons form tube • Pass by the electrons in the patient • Do not interact with e– • Causes them to vibrate- releasing smnall amounts of heat

16. 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

17. Coherent / Classical Scatter

18. Classic Coherent Scatter

21. 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

24. Compton Scatter

25. COMPTON SCATTERING • ______ shell electron in body • Interacts with x-ray photon from the _________

27. (WAVY LINE IN = ________ MUST BE INTERACTION IN THE BODY)

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

29. XXXXX

30. Differential Absorbtion • Results from the differences between xrays being abosorbed and those transmitted to the image receptor • ____________________________ • ____________________________ • ____________________________

31. Compton and Differential Absorbtion • Provides ____ useful info to the image • Produces image ________ • dulling of the image • NOT representing ___________ information • At ____________ energies

32. Photoelectric and Differential Absorbtion • Provides _________________ information • X-rays do not reach film because they are __________________ • ______ energies (more differential absorbtion) • Gives us the ______________ on our image

33. No interactions with Image Receptor and Differential Absorbtion • No interaction • Usually ____________ kVp • Goes ______________ body • Hits ____________ ________________ • Usually represents areas of __________ • _____atomic numbers • Results in __________ areas on the film

34. 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.

36. Pair Production

38. Photodisintegration

40. 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