-
2. Radiation with sufficient energy to separate an electron from its atom:
Ionizing Radiation
-
3. What do alpha particles consist of?
- 2 protons and 2 neutrons (a helium nuclei)
- Charge: +2 Atomic Mass: 4
-
4. What are alpha particles emitted from?
- o Unstable heavy nuclei
- ie. radon, radium
-
5. Alpha particles: High or Low LET?
- o Alpha particles are High LET
- o Can only travel short distances & can be stopped by a sheet of paper.
-
6. Alpha particles are hazardous if:
Ingested or Inhaled
-
8. Beta Particles: Charge? Atomic Mass?
- o Beta Particles:
- o Charge Atomic Mass
- o Negatron (B-) -1 0
- o Positron (B+) +1 0
-
9. What is the origin of beta particles?
- Beta particles are electrons emitted by the nucleus.
- o Can carry one unit of negative charge Negatron (B-)
- o or
- o carry one unit of positive charge Positron (B+)
-
10. Whenever beta particles are emitted, they are accompanied by a small, massless, chargeless particle known as a:
Neutrino
-
11. ___________ are not stable and can only exist for short periods of time
Positrons are not stable and can only exist for short periods of time.
-
High energy (1MeV) Beta particles may have range as long as _______ in soft tissue.
2cm
-
13. What is Bremsstrahlung radiation more likely to occur with?
Beta particles
-
What are the most common types of ionizing radiation used in XRT?
X-rays, Gamma rays & Electrons
-
18. What is the secong leading cause of lung Ca in the US? (behind smoking)
Radon
-
19. note: 1 Gy = 100 cGy = 100 rad
100 rad = 1 Gy = 100 cGy
-
The amount of ionization produced by photons in air per unit mass of air:
Exposure
- traditional: roentgen (R)
- SI: 2.58 x 10-4 C/kg
-
What are the units of measure for exposure?
- Traditional: roentgen (R)
- SI: C/kg (Coulomb of charge per kilogram of air)
- 1R = 2.58 x 10-4 C/kg
-
23. What are the units of measure for absorbed dose?
- Traditional: rad
- SI: Gy
- 1Gy = 100 rad
-
What takes in to account the fact that different types of radiation produce different amounts of biologic damage?
Dose Equivalent
100rem = 1Sv
-
25. Each type of radiation is assigned a _________ _________ to account for the different biologic effects & responses
Quality Factor (QF)
-
26. Quality Factor (QF) is also known as
Weighing factor
-
27. What are the units of measure for dose equivalent?
- Traditional: rem
- SI: sievert (Sv)
100rem = 1Sv
-
28. What are the units of measure for activity?
- Traditional: curie (Ci) 3.7x1010 disintegrations per second
- SI: becquerel (Bq) 1 disintegration per second
1Ci = 3.7 x 1010 Bq
-
The rate at which a radioactive isotope undergoes nuclear decay:
Activity
1Ci = 3.7x1010 Bq
-
The energy absorbed per unit mass of any material:
Absorbed Dose
1 Gy = 100 rad = 100 cGy
-
32. Quality Factor (QF) of x-rays & gamma rays:
1
-
33. Quality Factor (QF) of beta particles, positrons & muons?
1
-
34. Quality Factor (QF) of high energy external protons:
1
-
35. Quality Factor (QF) of protons, other than recoil protons & energy 2 Mev
2
-
36. Quality Factor (QF) of thermal neutrons:
5
-
37. Quality Factor (QF) of fast neutrons:
20
-
38. Quality Factor (QF) of alpha particles:
20
-
39. Quality Factor (QF) of fission fragments & other heavy nuclei:
20
-
What are two types of gas-filled detectors?
- o Ionization Chamber
- o Geiger-Muller Detecter (GM)
-
41. What is the sensitivity of a gas filled detector dependant upon?
The mass of the gas within the chamber (chamber volume) & the Applied Voltage
-
42. A type of detector that consists of two electrodes within a gas filled chamber, an applied voltage accross the electrodes & electronics and a meter to amplify & measure the electrical signal
o Ionization Chamber (the simplest kind)
-
43. When ionization chambers are properly calibrated, their accuracy approaches _____%, which makes them suitable for the measurement of radiation output of therapy machines.
2% accuracy
-
What is a form of ionization chamber used for personnel monitoring?
Pocket Dosimeter
-
Are ionization chambers suitable for the detection of very low levels of radiation or contamination?
No
-
Are GM detectors suitable for detection of very low levels of radiation or contamination?
Yes
-
Should a GM detector be used to measure the high energies of a LINAC?
o NO The GM counter can overload & produce a reading of zero if placed in a high level radiation field
-
48. What kind of gas-filled detector can detect individual ionization events & responds defferently to different photon energies?
Geiger-Muller (GM) Detector (strongly energy dependent)
-
49. What kind of detector gives off light when heated?
- o Thermoluminescent Dosimeters
- o (TLDs)
-
51. What is the atomic number of Lithium Fluoride similar to?
- The atomic number of LiF is close to that of TISSUE
- Li-3 F-9
-
52. What is the accuracy rate of TLDs?
If proper care is taken, doses can be measured with an accuracy of approx: 5%
-
53. TLDs: The more radiation absorbed by the crystal, the more _______ will be in the traps & the more _______ will be released when the crystal is heated later.
The more radiation absorbed by the crystal, the more ELECTRONS will be in the TRAPS and the more CHARACTERISTIC PHOTONS will be released when the crystal is heated later.
-
54. TLDs: The amount of ________ is a measure of the dose received by the crystal.
Light
-
What kind of detector can store the dose info for hours, days, or even weeks?
- Thermoluminescent Dosimeter
- all info is lost if heated in transit
-
56. What kind of detector can be used for mailed intercomparison of therapy unit calibration, in ring badges for personnel and/or for measurements of environmental levels of radiation?
TLDs
-
57. After development, x-ray film turns black. The level of blackness is called the:
Optical Density
-
61. What is the primary task of advisory agencies?
To analyze the existing data related to radiation exposure & to assess the radiobiological risks associated with those exposures.
-
62. Which agencies develop reccomendations for dose limits?
Advisory agencies
-
64. What is the role of regulatory agencies?
To license users of radioactive materials & radiation producing equipment, inspect these users, and enforce laws.
-
65. Who is responsible for enforcing the laws regarding radioactive material & radiation producing equipment?(advisory or regulatory)
Regulatory Agencies
-
72. LD50/30
4.5 Gy (450 rads)
Lethal Dose for 50% of the population / 30 days of the event
-
74. What are the two general classifications of long term effects related to radiation exposure?
- NONSTOCHASTIC
- o A threshold exists; Severity of effects increases with dose.
- STOCHASTIC
- o Non-threshold; Probability of occurence is a function of dose
-
75. Effects for which a threshold exists and for which the severity of the effect increases with dose.
Nonstochastic
-
76. Effects that have no threshold and for which the probability of occurrence is a function of dose.
Stochastic
-
77. Examples of Nonstochastic effects:
- o Nonstochastic:
- o Erythema (skin reddening)
- o Epilation (loss of hair)
- o Cataract Formation
- o Infertility
-
78. Examples of Stochastic effects:
- o Stochastic:
- o Cancer induction
- o Genetic effects
- o Embryologiceffects
- o Teratogenic effects (malformations of embryo or fetus)
-
79. Which type of effects are of more concern at low levels of exposure?
Stochastic
-
80. As a model for radiation protection guidelines, a risk of ____ in _____ per Sv has been assigned for the occurence of severe hereditary effects.
o 1 in 100 per Sv (1 in 10,000 per rem)
-
81. The NCRP assigned an overall risk estimate of ____ in ____per Gy for the probability of radiation effects on the fetal brain & possiblity of childhood cancer induction.
o 4 in 10 per Gy (4 in 1000 per rem)
-
82. Thresholds are related to _____ age and are estimated to be 0.12 to 0.23 Gy for ____ weeks after conception and 23 Gy for _____ weeks after conception.
- Thresholds are related to GESTATIONAL age.
- 0.12 to 0.23 Gy (12-23rem) for 8-16 wks
- 0.23 Gy (23rem) for 16-25 wks
-
83. The overall risk of exposure is approx ____ in ____ person per rem.
7 in 10,000 persons per rem
-
84. Nominal lifetime somatic risk for adults
- 1 in 100 per Sv
- (1 in 10,000 per rem)
-
What takes in to account the effect of irradiation of only part of the body or the effect of nonuniform irradiation of the body?
Effective Dose Equivalent
(100rem = 1Sv)
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