1. Biological response and radiation safety practices

2. Biological response and radiation safety practices
X-ray interactions in the patient
Radiation exposures
Radiation measurement units
Methods of detecting radiation
Biological effects of radiation exposure
Acute Radiation Syndrome
Sub-syndromes-hemopoietic, GI, CNS
Radiation Protection
ALARA
Biological response and radiation safety practices

3. Terminology NCRP R, roentgen, coulombs/kg rad rem Gray Sievert
Curie, Becquerel
Effective does
Quality factor
Threshold
ALARA
OSL
Film badge
TLD
Pocket dosimeter
Field survey instruments
Geiger-Müller counter
Cutie pie
Somatic effect
Genetic effect
Acute Radiation Syndrome(ARS)
Terminology

4. Radiation Exposure Units of measure International units British Units
Exposure Measurements
Methods of Measuring
Units of measure
International units
British Units
Unit conversions
Film badge
OSL
TLD
Pocket dosimeter
Field Survey Instruments
Radiation Exposure

5. What happens to our x-ray?
Primary beam is the radiation that exits the x-ray tube. The Exit radiation is the radiation that builds our radiograph. The exit radiation is the x-ray photons that exit the patient.

6. Patient Interactions Classical Compton Photoelectric Pair Production
Photodisintegration

7. Classical (Coherent) Scattering
Patient Interactions
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 10kV
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.

8. Compton scattering COMPTON SCATTERING Outer shell electron in body
Patient Interactions
Compton scattering
COMPTON SCATTERING
Outer shell electron in body
Interacts with x-ray photon from the tube
3. Moderate energy electron
Outer shell rather than inner shell electron .

9. Photoelectric effect Patient Interactions photoelectron
Incoming photon interacts with inner shell electron. The “knocked-out” electron is called a photoelectron. The energy of the incoming photon is absorbed.

10. Pair Production Patient Interactions
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.

11. Patient Interactions
Photodisintegration

12. X-rays interact with Patient’s body to cause changes in cells.
Interaction in the body begin
at the atomic level

13. Patient Interactions: Interactions of X-rays with matter
No interaction: X-ray passes completely and get to image receptor
Complete absorption: no x- rays get to image receptor
Partial absorption with scatter-some x-rays get to image receptor but some get scattered
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.

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

15. To Keep Ourselves Safe:
Radiation Exposures
To Keep Ourselves Safe:
Measure exposure
Determine levels at which damage occurs

16. Measuring Exposure Units of Measure International Units British Units
C/kg3
Gray
Sieverts
Becquerel
British Units
Roentgen
Rad
Rem
Curie

17. Exposure: Measured in air

18. Absorbed Dose

19. Radiation Equivalent

20. RADS REMS rads Grays Patient absorbed dose rems Sieverts Employee
(technologists) =
In diagnostic radiology:
1 roentgen = 1 rad = 1 rem

21. Comparison of Units Exposure R C/kg 1R=2.58x10-4 C/kg Absorbed Dose
rad
Gray
1rad=.01Gray
1Gray=100rad
Dose Equivalent
rem
Sievert
1rem=.01Sv
1Sv=100rem
In diagnostic radiology:
1 roentgen = 1 rad = 1 rem

22. Unit Conversions:
A normal chest x-ray exposes the patient to approximately 15mR. How many roentgens is that?
A CT examination results in a patient dose of 4000 mrad. How many gray is that?
Annual exposure dose for a technologist is 5 rems. What is that in Sieverts? mSv?
You Receive ~620 millirem per year. According to stats from the US Nuclear Regulatory Commission average yearly exposure is roughly 620 millirem--half of which comes from natural sources (cosmic radiation, from the soil, radon, etc) and half comes from manmade sources. Note that geography can play a big part in that. In Colorado, for example, natural radiation exposure can be 1000 mrem per year due to higher altitude.
What is your exposure in mSv?
What is your exposure in mSv if you live in Colorado?
A patient left a head of lettuce in the x-ray exam room. The lettuce received a dose of 10mrad. How many Gr is that?

23. Permissible Occupational Dose
Annual dose :
5 Rem/year 50mSv/year
5000 mrem
Cumulative Dose
1 rem x age or 10mSv x age

24. PUBLIC EXPOSURE NON MEDICAL EXPOSURE
10 % of Occupational exposure
0.5 rad or 500 mrad or 5mGray
Under age 18 and Students
0.1 rem

25. Pregnancy & Embryo Mother occupational worker Baby 5 rem .5 rem/ year
.05 rem/month

26. Methods of Measuring

27. Summary of Monitoring Devices

28. Exam 2 Next Week:
ALARA- As Low As Reasonably Achievable