1. 2/20/2016Chapter N*31 Radiation Exposure, Dose and Quantity Exposure is an index of the ability of a radiation field to ionize air. Dose is a measure of the energy imparted to matter, per unit mass, when an ionizing radiation field interacts with matter. OR: (The amount of energy deposited per unit mass) Quantity of radioactive material is expressed as “activity”, the number of nuclear disintegrations that occur in a sample per second.

2. 2/20/2016Chapter N*32 Units of Exposure and Quantity Roentgen (R) Curie (Ci)Becquerel (Bq) 2.58 x 10 -4 coulombs / kg dry air at STP Disintegrations per second in 1 gm radium (3.7 x 10 10 dps) Systeme Internationale unit: one dps

3. 2/20/2016Chapter N*33 Roentgen Pronounced rent’gen with a hard “g” Limitations – only applies to photons – only applies in air – only applies to energies less than 3 MeV l Named after Wilhelm C. Roentgen (thus the abbr... is capital “R”)

4. 2/20/2016Chapter N*34 Curie (Ci) Radiation hazard does not solely depend on the activity. It also depends on the type of decay (alpha, beta, photon, etc.) l Named in honor of Pierre Curie

5. 2/20/2016Chapter N*35 Units of Absorbed Dose rad Gray (Gy) radiation absorbed dose (100 erg/gm) S.I. unit: 1.0 J/kg (100 rads)

6. 2/20/2016Chapter N*36 Concept of Equivalent Dose For the same absorbed dose (deposited energy), different forms of ionizing radiation can have different biological effects. “Equivalent Dose” attempts to normalize these differences.

7. 2/20/2016Chapter N*37 Equivalent Dose Equivalent Dose is the product of the dose and a modifying factor called the quality factor (QF), which reflects the relative biological effectiveness of the radiation: H T = D x QF

8. 2/20/2016Chapter N*38 Quality Factors (QF) QF are indices of the “relative biological effectiveness” (RBE) of a radiation. RBE is a complicated function of type of radiation, energy and the biological system under consideration. QF are not measured. They are determined by a committee. تعريف RBE & QF مستثنى

9. 2/20/2016Chapter N*39 Quality Factors (QF) RadiationQuality Factor Photons, electrons, betas, X-ray 1 Thermal Neutrons5 Alphas, Fast neutrons, Protons 20

10. 2/20/2016Chapter N*310 Effective Dose Equivalent Effective Dose Equivalent (EDE) is intended to reflect the total biological effect of a given exposure on a human. It is a weighted average of the individual doses to a number of important tissues: H E =  (H T x W T ) (sum is over all tissues)

11. 2/20/2016Chapter N*311 Effective Dose Equivalent EDE is a concept, not a measurable quantity. Applies to situation where irradiation of organs and tissues is non-uniform. EDE yields the same “radiation detriment” as a numerically-equivalent whole-body dose. W T values are assigned by a committee.

12. 2/20/2016Chapter N*312 Units of Equivalent Dose and EDE roentgen equivalent man (rad x quality factor) S.I. unit: Gy x quality factor Rem (rem) Sievert (Sv)

13. 2/20/2016Chapter N*313 rem Dose in health record is in units of rem 1 rem = 1 Roentgen l Roentgen Equivalent Man

14. 2/20/2016Chapter N*314 SI Radiation Protection Units Becquerel (Bq) for Curie – 1 Ci = 3.7 x 10 10 Bq Gray (Gy) for rad – 1 Gy = 100 rad Sievert (Sv) for rem – 1 Sv = 100 rem

15. 2/20/2016Chapter N*315 Units of Radioactivity Curie (Ci) = 2.22 E12 dpm or 3.7E10 dps Becquerel (Bq) = 1 dps (Annual) Maximum Dose/year = 5 REM or 50 mSv for Public Maximum Dose/year for Declared Pregnant Woman & Minors= 0.5 REM or 5 mSv

16. 2/20/2016Chapter N*316 Half Life Calculation

17. 2/20/2016Chapter N*317 Dose Response Relationships 0-150 rem—No or minimal symptoms 150-400 rem—Moderate to severe illness 400-800 rem—Severe illness deaths start above 500 rem Above 800 rem—Fatal ***Acute whole body doses

18. 2/20/2016Chapter N*318 Sources of Ionizing Radiation Cosmic rays and naturally-occurring radioactive elements Medical X-rays and nuclear medicine studies Man-made radioactive materials and radiation sources

19. 2/20/2016Chapter N*319 Estimated Exposure To The National Population Between 320 – 360 mr/yr

20. 2/20/2016Chapter N*320 Sources of Radiation Natural Sources – Cosmic Radiation Effects of Altitude –0.2 mSv/yr at sea level –1 mSv/yr at 10,000 ft – Terrestrial Sources Uranium & Thorium and their daughter products. – Radioactivity within the body Potassium 40 (Half-Life 1.3 x 10 9 years: 0.2 mSv/yr) Dependant on location, diet, and habits of the person.

21. 2/20/2016Chapter N*321 Spill Response On Skin—flush completely On Clothing—remove If Injury—administer first aid Radioactive Gas Release—vacate area, shut off fans, post warning Monitor all persons and define the area of contamination

22. 2/20/2016Chapter N*322 ALARA As Low As Reasonably Achievable—means making every reasonable effort to maintain exposures to radiation as far below the dose limits

23. 2/20/2016Chapter N*323 Radiation Protection Decrease Time Increase Distance Increase Shielding

24. 2/20/2016Chapter N*324 Time Minimize time spent near radiation sources Radiation Protection Reducing Radiation Exposure Distance Maintain maximal practical distance from radiation source Shielding Place radioactive sources in a lead container To Limit Caregiver Dose to 5 rem Distance Rate Stay time 1 ft 12.5 R/hr 24 min 2 ft 3.1 R/hr 1.6 hr 5 ft 0.5 R/hr 10 hr 8 ft 0.2 R/hr 25 hr

25. 2/20/2016Chapter N*325

26. 2/20/2016Chapter N*326

27. 2/20/2016Chapter N*327

28. 2/20/2016Chapter N*328

29. 2/20/2016Chapter N*329 The radiated energy can be considered to be spread over a sphere of area 4  r 2 at any distance r from the source. Since the radiation intensity is equal to the energy per unit area : If the radiation intensity is I 0 at a distance r 0 from the source, the intensity I at any other distance r will be given by : Since the radiation dose is proportional to the intensity, the dose D can be calculated by the same type of relationship :

30. 2/20/2016Chapter N*330 Example 1 If a nurse received a radiation dose of 100 millirems(0.1rem) by spending one hour at a distance of 2ft from a radioactive implant in a patient, how much would she have received at a distance of 4ft? At a distance of 20ft? ( 1 ft=30.48cm) Example 2 If a patient has received 100 millicuries of cobalt-60 as a therapeutic measure, the dose received by an attendant at a distance of one foot from the patient might be on the order of 200 millirems per hour. How long could the attendant spent at this distance in a week’s time? How long could he spent at 2ft? At 10 ft?

31. 2/20/2016Chapter N*331