1. Patient Interactions Photoelectric Classic Coherent Scatter
Compton Scattering
Pair Production
Photodisintegration
These are the type of interactions after the photons leave the tube and interact with the bodhy.

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

4. X-ray photons can change cells
If the photon hits the nucleus it can kill the cell. The nucleus carries DNA.

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

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

7. Interactions of X-rays with matter
No interaction: X-ray passes completely and get to film
Complete absorption: no x-rays get to film
Partial absorption with scatter
No interaction; X-ray passes completely through tissue and into the image recording device.
Complete absorption; X-ray energy is completely absorbed by the tissue. No imaging information results.
Partial absorption with scatter; Scattering involves a partial transfer of energy to tissue, with the resulting scattered X-ray having less energy and a different trajectory. Scattered radiation tends to degrade image quality and is the primary source of radiation exposure to operator and staff.

8. 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).
Low kVp- increase patient dose. A relatively low energy (low kVp) x-ray photon uses all its energy (true absorption) to eject an inner shell electron,
leaving an orbital vacancy.
An electron from the shell above drops down to fill the vacancy and, in doing so, gives up energy in the form of a characteristic ray.
The photoelectric effect is more likely to occur in absorbers of high atomic number (eg, bone, positive contrast media)
and 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).

9. Total absorbtion interaction of the incident x-ray.
Electron that is removed from k-shell is called a photoelectron.
This constitutes the greatest hazard to the patient in diagnostic radiology.
FIG. 9–3 Photoelectric absorption interaction.
(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: Fax )

10. Sine wave coming into the body.
CASCADE

11. Photoelectric – Absorption

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

13. PHOTOELECTRIC ABSORBTION IS WHAT GIVES US THE CONTRAST ON THE FILM
Photoelectric provides diagnostic information to the image receptor because they not do not reach the image receptor. These x-rays are representative of anatomic structures with a high anatomic number, high absorbtion characterisitcs, such structures are radiopaque. This is the areas that the film is light (white).

14. 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
8 p+ + 8e- = neutral atom
What does this look very similar to?
heat interaction within the tube.

15. 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
WE can tell the difference between the heat and coherent because it is a photon incoming and exiting.
The incoming photon comes in with a energy and changes direction leaving with the same amount of energy.
Not useful in diagnostic radiology. Sometimes causes fog on the film. At a higher kVp a few of the classic coherent can add fog to the film.

16. Coherent / Classical Scatter

17. Classic Coherent Scatter

19. FIG. 9–2 Classic coherent scatter interaction.
(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: Fax )

20. 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
A fairly high energy (high kVp) x-ray photon ejects an outer shell electron.
Though the x-ray photon is deflected with somewhat reduced energy (modified scatter),
it retains most of its original energy and exits the body as an energetic scattered photon.
Since the scattered photon exits the body, it does not pose a radiation hazard to the patient.
It can, however, contribute to film fog and pose a radiation hazard to personnel (as in fluoroscopic procedures).

22. Scatter provides no useful information
Scatter provides no useful information. It adds unifrom density or fog to the film.
FIG. 9–4 Compton scatter interaction.
(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: Fax )

23. Compton Scatter
Overall it degrades the image, can affect technolgist. Does not contribute to a quality image.

24. OUTER SHELL ELECTRON IN BODY –
COMPTON
SCATTERING –
OUTER SHELL ELECTRON IN BODY –
INTERACTS WITH
X-RAY PHOTON
FROM TUBE
Outer shell rather than inner shell electron .

26. (WAVY LINE IN = PHOTON MUST BE INTERACTION IN THE BODY)
The differnce between coherent and comptoon is that compton has enough energy to make it out of the patient to exit the patient.
Where as coherenet is low energy and usually does not exit the patient and increases the dose to the patient.

27. During Fluoro – the patient is the largest scattering object
SO this is why we are behind the lead or the doctor.
It is an exposure hazard in radiography and fluoroscopy . Large amount of scatter is produced by the patient in fluoroscopy. This exposure is the source of most of the occupational radiation exposure that radiologic technologists receive.
During radiography if the radiologic technologist stays in the rooom they will need to shield themselves.

28. XXXXX
Compton

29. Differential Absorbtion
Results from the differences between xrays being abosorbed and those transmitted to the image receptor
Compton Scattering
Photoelectric Effect
X-rays transmitted with no interaction

30. Compton and Differential Absorbtion
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

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

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

33. 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.

34. Very high energy…not used in diagnostic radiology
Very high energy…not used in diagnostic radiology. It has enough energy to hit the nucleus and break off two parts of the nucleus: 1 positron and a negatron.
This is bad because the nucleus contains DNA. But it is good for cancer, because it kills the cell.
Incoming photon must possess a minimum of 1.02 mEv. (million electron volts). Interacts with nuclear electric field and causes it to dissapear. In its place we get two elecgtrons : one positron and one negatron.
Electron eventaully will filla vacancy. Positron unites with a free e- and the mass of the both particles is converted to energy ina process called annihnilation radiation.
We don’t use this in diagnostic radiology.

35. Pair Production

36. FIG. 9–5 Pair production interaction.
(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: Fax )

37. Photodisintegration
Very high energy, this is also for cancer treatements. High incidnet photons hits the nucleus and gets 1 large fragment. It kills the cell or it changes the structure of the cell.
Energies above 10 mEv. Absorbed directly by nucleus. When this occurs the nucleus is raised to an excitaion state and instantly emits a nuclear fragment. Not used in diagnostic radiology.

38. FIG. 9–6 Photodisintegration interaction.
(Modified from Carlton RC, Adler AM: Principles of radiographic imaging, an art and a science, ed 4, Thomson Delmar Learning, 2006, Albany, NY. Reprinted with permission of Delmar Learning, a division of Thomson Learning: Fax )

39. 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