1. HEALTH PHYSICS

2. TERMS
RAD (Gy)
mRad R mR
Rem
ALARA
NCRP

3. mR/mAs mAs=# of x-rays in useful beam=radiation quantity
Radiation=intensity of radiation-mR
I1 =mAs1
I2 =mAs2
As mAs increase, so does mR

4. Try this problem
If the exposure factors of 85 kVp, 400 mA and .12 sec yield an output of 150mR, what is the mR/mAs?
150mR/48 = 3.12 mR/mAs

5. HISTORICAL FACT Clarence Daly-First American fatality from radiation\
Thomas Edison’s assistant
Thomas Edison is credited for discovering…..
Fluoroscopy

6. HEALTH PHYSICS PROVIDING RADIATION PROTECTION FOR OCCUPATIONAL WORKERS AND TO THE PUBLIC

7. CARDINAL PRINCIPLES OF RADIATION PROCEDURES DESIGNED TO MINIMIZE RADIATION EXPOSURE TO PATIENTS AND PERSONNEL

8. TIME Exposure as short as possible
Dose to patient/occupational worker directly related to duration of exposure
Exposure = Exposure rate X time
Fluoro-Radiologists trained to turn switch on and off
5 minute reset button

9. TRY THIS PROBLEM
If a certain exam is calculated to have an exposure rate of 225mR per hour, what is the total exposure per 36 minutes?
X(exposure) = 225mR x 36/60
x = 135 mR

10. DISTANCE Isoexposure lines exposure areas calculated at waist level
As distance increases, radiation intensities to the occupational worker and other personnel decreases
X-ray tube target is considered a point source of radiation
Scatter from patient is considered an extended area source
Isoexposure lines
exposure areas calculated at waist level
patient an extended source of radiation

11. SHIELDING
Thickness or amount of shielding can be estimated if the HVL or TVL of barrier is known
TVL=tenth value layer
1 TVL = 3.3 HVL
See questions on page 553

12. Effective dose Partial body exposure
Risks are based on whole body exposure
Stochastic response is based on effective dose which is calculated as
The weight of the dose x the weight of the tissue (NCRP Report 116)

13. DL FOR OCCUPATIONAL PERSONS SHOULD NOT EXCEED SPECIFIED LIMITS
Dose limits (occupational)
Current DL is 100mRem (mSv) per week
Annual = 50mSv (5000mrem or 5 rem)
eye = 150mSv(15000mrems)
organs= 500 mSv (50,000 mrems)
pregnancy = 5mSv(500 mrem) not to exceed .5mSv per month
cumulative 10 mSv x age in years

14. RT effective dose
10% of monitor dose…why?

15. Radiologic Terrorism
Rescue and medical emergencies priority over radiologic concerns
RED
RDD
IND

16. Intro to radiation protection
Bushong pg 516, figure 33-4
DL is based on linear nonthreshold dose response relationship
E = Wr x Wt
LET
Conversion factor of .3 applied to collar-monitor value

17. PUBLIC EXPOSURE Annual 5mSv per year (500mrem)
1mSv (100mrem)non-RT hospital workers
1mSv is unit physicists use for thickness in protective barriers

18. MISCELLANEOUS DL NOTES
Student radiographers under the age of 18 may receive no more than 1 mSv during the duration of their educational activities
There is a movement underway to lower DL for occupational workers to 20 mSv