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Everything You Need to Know About Radiation Protection Kelli Haynes, MSRS, RT(R) Program Director & Associate Professor.

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Presentation on theme: "Everything You Need to Know About Radiation Protection Kelli Haynes, MSRS, RT(R) Program Director & Associate Professor."— Presentation transcript:

1 Everything You Need to Know About Radiation Protection Kelli Haynes, MSRS, RT(R) Program Director & Associate Professor

2 Radiation Protection 45 questions of the 200 will be radiation protection (22.5%) 10 -Biological Aspects of Radiation 15-Minimizing Patient Exposure 11-Personnel Protection 9-Radiation Exposure and Monitoring

3 Biological Aspects of Radiation 10 Questions

4 Cell Radiosensitivity Cells and tissues vary in their degree of radiosensitivity Immature cells are nonspecialized- rapid cell division Mature cells are specialized-divide slower if at all DNA-most radiosensitive part of cell


6 High Low Lymphocytes Spermatogonia Erythroblasts Intestinal crypt cells Muscle cells Nerve cells Chondrocytes

7 Dose Response Relationships Graphic representation of the relationship between the amount of radiation absorbed (dose) and the amount of damage (response) Linear or nonlinear Threshold or nonthreshold

8 Response Dose Linear NonThreshold Linear Threshold

9 Response Dose NonLinear Threshold NonLinear Nonthreshold

10 Relative Tissue Radiosensitivities LET RBE OER

11 Linear Energy Transfer (LET) Photons deposit or transfer energy as they travel The average energy deposited per unit of path length Assesses potential tissue and organ damage

12 LET High-LET Radiation Alpha particles Beta particles Low-LET Radiation Gamma rays X-rays

13 Relative Biologic Effectiveness Measures biologic effectiveness of radiations having different LET’s Influenced by radiation type, cell or tissue type, physiologic condition, and biologic result

14 Oxygen Enhancement Ratio Response to radiation is greater when irradiated in the oxygenated state Radiation dose required to cause response w/o O2 OER= Radiation dose required to cause response w/ O2

15 Cell Survival and Recovery LD 50/30 Adults-3-4 Gy ( rad) Recovery may occur

16 Somatic Effects Biologic damage sustained by living organisms as a consequence of exposure to ionizing radiation Classified as either early (acute) or late

17 Short-term vs. Long-term Nausea Fatigue Redness of skin Loss of hair Intestinal disorders Fever Blood disorders Shedding skin Cancer Embryologic effects (birth defects) Formation of cataracts

18 Carcinogenesis The production or origin of cancer Experiments have shown that radiation induces cancer

19 Cataractogenesis Cataracts-opacity of the eye lens 2 Gy results in partial or complete vision loss Threshold, nonlinear dose-response relationship

20 Sterility Female sterility based on age of the subject-more radiosensitive when younger Temporary sterility-2 Gray (200rad) Permanent sterility-5 Gray (50 rad)


22 Hematopoietic Syndrome Whole-body doses ranging from 1 to 10 Gy (100 to 1000 rad) Reduction of blood cells in circulation results in a loss of the body’s ability to clot blood and fight infection

23 Gastrointestinal Syndrome Appears at a threshold dose of approx. 6 Gy (600 rad) and peaks after a dose of 10 Gy (1000 rad) Without treatment, a dose of 6-10 Gy may cause death in 3-10 days

24 Cerebrovascular Syndrome Doses of 50 Gray (5000rad) Death within 2 hours or up to 2 days

25 Embryonic and Fetal Risks Fetus is very sensitive Fetal radiosensitivity decreases as gestation progresses

26 Genetic Effects GSD-used to assess the impact of gonadal dose Dose equivalent to the reproductive organs that would bring genetic injury to the total population


28 Coherent Scattering Photon of low energy interacts with atom. No net energy has been absorbed by the atom. Low-energy photons,1-50 kVp Contributes to fog

29 Compton Scattering Moderate energy x- rays, kVp Interaction with outer shell electron Electron ejected, Atom is ionized Photon loses energy and recombines with an atom Fog and Scatter

30 Compton Scattering FIGURE 2-6 Compton scattering is responsible for most of the scattered radiation produced during a radiologic procedure. (From Radiobiology and radiation protection: Mosby’s radiographic instructional series, St. Louis, 1999, Mosby.)

31 Photoelectric Absorption Most important interaction between x-ray photons and the atoms of the pt’s body for producing useful images Higher energy x-rays ( kVp), more likely to penetrate & not interact Interaction b/t photon and inner shell electron X-ray is absorbed Electron ejected

32 Attenuation Process that decreases the intensity of the beam Refers to both absorption and scatter processes Thickness of body part (mass density) Type of tissue (atomic number)

33 Minimizing Patient Exposure 15 Questions

34 Exposure Factors kVp mAs

35 Shielding Protects gonads when w/i 5 cm of collimated beam Females receive more exposure due to location of organs

36 Types of Shields Flat contact shields Shadow shields Shaped contact shields Clear lead

37 Beam Restriction Purpose-confine useful beam Reduce scatter Types Cones Collimators


39 Filtration Effect on skin and organ exposure Effect on beam energy

40 NCRP Report #102 The useful beam shall be limited to the smallest area practicable and consistent with the objectives of the radiological or fluoroscopic examination.

41 Exposure Reduction Patient positioning AEC Patient Communication ALARA

42 Image Receptors Film-screen systems Intensifying screens Digital Image receptors CR and DR Film speed

43 Image Receptors Digital CT, CR, DR, DF, NM, MR, & US Photons on a detector Electronic image Matrix Patient dose Film Intensifying screens convert photons and expose film Analog image Patient dose

44 Grids As grid ratio increases patient dose increases Increases contrast Absorbs Compton scatter Improves quality Increases patient dose

45 Fluoroscopy Pulsed or Intermittent Exposure factors Positioning Fluoroscopy time

46 Personnel Protection 11 Questions

47 Sources of Radiation Exposure (3) Primary x-ray beam Secondary radiation 1. Scatter 2. Leakage Patient

48 Basic Methods of Protection

49 Protective Devices Protective structural shielding Primary Barriers Secondary Barriers Lead Shields

50 Protective Devices Aprons Gloves Thyroid shields Protective glasses

51 Portable (mobile) units Lead apparel Exposure cord Stand at right angles to the patient

52 Fluoroscopy Protective curtain Bucky slot cover Cumulative timer

53 NCRP Report #102 Fluoroscopy Exposure Rates General Purpose: 10 R per minute Non-image Intensified: 5 R per minute High Level Control: 20 R per minute Exposure Switch Guidelines Switch must be of the dead-man type

54 Radiation Exposure and Monitoring 9 Questions

55 Units of Measurement

56 Dosimeters

57 Film Badge Economical Parts Monitors x and gamma rays Temperature and humidity can cause fog

58 Pocket Ionization Chambers Most sensitive Must be charged to zero Accurate from mR

59 OSL Dosimeter Aluminum oxide detector Optically stimulated luminosity occurs when struck by laser light Accurate reading as low as 1mrem

60 TLD’s Look similar to film badge Lithium fluoride Ionization causes crystal to change

61 NCRP #116 Annual occupational effective dose- 50 mSv (5rem) Public Exposure- 1 mSv Embryo/fetus exposure- 50 mSv/month Dosimetry records

62 NCRP #160 Typical effective dose per exam; varies from 0.1 mSv for a chest xray to 1.5 for a lumbar spine Interventional- ~3mSv CT- range from 2mSv for a head to 10 mSv for a spine

63 That’s All Folks!

64 Review Questions What is the most radiosensitive part of the cell? Which is more radiosensitive, immature or mature cells?

65 This is a picture of what?

66 Review Questions What is LET? What is LD 50/30? What is an example of an early somatic effect? Late somatic effect? What is carcinogenesis?

67 Review Questions What is the threshold dose for cataracts? What is the threshold dose for temporary sterility? What is the threshold dose for permanent sterility? What is the threshold dose for cerebrovascular syndrome?

68 Review Questions What is the threshold dose for hematopoietic syndrome? What is the threshold dose for gastrointestinal syndrome? What are some types of shields? What is filtration? What does NCRP Report # 102 state?

69 Review Questions Why do we use a grid? What are the 3 sources of radiation exposure? What is the SI unit of measurement for exposure? What is the SI unit of measurement for absorbed dose?

70 Review Questions What is the traditional unit of measurement for dose equivalent? What is the sensing material in an OSL dosimeter? What is the sensing material in a TLD dosimeter? What does NCRP # 116 state?

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