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.

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

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”)

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

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)

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.

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

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

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

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)

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.

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)

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

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

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

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

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

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

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

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.

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

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

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

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

2/20/2016Chapter N*325

2/20/2016Chapter N*326

2/20/2016Chapter N*327

2/20/2016Chapter N*328

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 :

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?

2/20/2016Chapter N*331