1. Patient & Occupational radiation dose management Chapter 37 & 38
RTMR 284 – Radiation Protection & Biology
WINTER 2013

2. 3 ways patient dose from diagnostic x-rays is reported:
Entrance Skin Exposure (ESE) or Entrance Skin Dose (ESD)
Most often reported & referred to as pt. dose , easy to measure
Ave Fluoro ESE can be est. at 40 mGy/min
(hard to estimate)
Gonadal Dose-GSD Genetically Sig. Dose
Important due to genetic responses, easy to measure
Bone Marrow Dose
Mean Marrow Dose is the ave radiation dose to the entire active bone marrow
Important due to rad-induced leukemia, est. from ESE and cannot be directly measured.

3. TLD’s Thermoluminescence Dosimters are used most often to measure ESE.
Response is proportional to exposure dose
Very accurate to within 5%
Can be used to measure all levels experienced, even low doses
Not used in most occupational monitoring due to no permanent record or re-readability is provided and an immediate, on the job readout is not possible.

4. Pt. Dose in Special Exams
Mammography:
ESE ~ 800mR/view
Glandular does Dg ~ 15% of ESE
Adverse biological response is small
Screening should be kept to two views for lower doses to pt.
CT Imaging:
Slices in CT produce much higher skin doses
Est. 10% of x-ray exams are CT w/ 70% of dose!
Dose ~ 50% of the ESE for body CT
Narrow, well collimated beams reduces dose
The higher the multislice value, the lower the dose

5. A 64 slice CT scanner will result in lower pt
A 64 slice CT scanner will result in lower pt. dose than fewer slices because a lower contribution is made from the pnenumbra for the same volume tissue.

6. Additional pt. dose savings occur when the same beam width is imaged with combined pixel rows because the mA can be reduces without compromising resolution.

7. Patient Dose Reduction
Unnecessary Examinations
Mass screening for TB
Hospital Admission
Pre-Employment physicals
Periodic Health Examinations
ER CT
Repeat Exams *** ???
Technique (kVp)
Positioning
Shielding-contact/shaped, shadow

9. Pregnant Patient Physical and Emotional land minds Time Frame 2 to 10
Talk to patients & work w/ dr.
Always ask…
Pt. Information
Elective booking
Questionnaire
Posting

10. Pt dose trends NCRP- National Council on Radiation Protection

11. Occupational Dose
Recommended dose limit for radiologic personal is 0.5 Sv/yr (5000 mrem/yr)
NORMAL exposure in diagnostic radiology for personal should not exceed 1 mSv/yr (100 mrem/year)
Effective Dose (E) = Radiation Weighting Factor (Wr) { = 1 for xray} x Tissue Weighting Factor (Wt) x Absorbed Dose
Fluoroscopy
Interventional Radiology
Mammography CT
Surgery
Mobile

12. Radiologic SI (customary) Units
Quantity Name Symbol
RadioActivity Becquerel Bq
(curie) (Ci)
Absorbed dose Gray Gy
(rad) (rad)
Dose Equivalent Sievert Sv
(rem) (rem)
Exposure Coulumb/kg C/kg
(roentgen) (R)
See conversion factors on inside cover!
1R/rad/rem = 100 Si units ex mrem = 1 mSv

13. Dose Limits
DL imply that if received annually, the risk of death would be less than 1 in 10,000
Based on Linear, non-threshold dose response
Basic annual = 50 mSv or 5000 mrem
Lens of eye = 150 mSv/yr or 15 rem/yr
Organs/Skin/Extremities = 500 mSv/yr or 50 rem/yr
Cumulative whole-body DL is 10 mSv times age in years
During Pregnancy DL = 5 mSv or 500 mrem (table 38-4)
After declared DL/month < 0.5 mSv or 50 mrem
Public /Students <18yo DL = 1 mSv/yr or 100 mrem/year
DL established for non-occupationally exposed persons is 1/10 of that established for the radiation worker

14. Reduction of Occupations Exp
In Diag Radiology 95% of Technologists occupational dose comes from Fluoro and mobile exams.
How to reduce your exposure? (x3 pg.588)
Portable apron, 2m cord, beam direction
Monitoring-Film Badges / TLD / OSL
During fluoro exp to collar region is 20
times greater than truck of body!
Protective Apparel ( mm Pb eq % attenuation at 75kVp)
Position , Holding, Pregnant Tech rules, Management Principles, Education

15. Final Next Week Monday 1-3 pm
75 Questions Total worth 150 points
MC Questions
Covers: Chapter 33-38
BOOK BASED QUESTIONS !!!
Chapter 33 Deterministic Effects………….19%
Chapter 34 Stochastic Effects …………...13%
Chapter 35 Health Physics ……………….13%
Chapter 36 Rad Protection Design ………21%
Chapter 37 Pt Rad Dose …………………15 %
Chapter 38 Occup Rad Dose………….. 19%