Dosage, Biology and Protection

Question 1

Rad

Answer 1

Units of Dose (radiation absorbed dose)

o measures dose to a specific tissue

Question 2

Rem

Answer 2

Dose Equivalents (Roentgen equivalent in man)
o        used to measure occupational dose and population dose
o        useful when several types of radiation is involved

Question 3

Roentgen

Answer 3

Units of Exposure (R

o measurement of the ionization of dry air

Question 4

Sievert

Answer 4

SI units of rem; 1 Sv = 100 rem

Question 5

Gray

Answer 5

SI unit of rad; 1 Gy = 100 rad

Question 6

Which are conventional and which are SI units?

Answer 6

· Conventional: Roentgen, rad, rem, Curie

· SI: coulombs per kilogram (C/kg), Gray (Gy), Sievert (Sv), Becquerel

Question 7

Conversion for rad to gray.

Answer 7

1 Gy = 100 rad

Question 8

What is the “quality factor”?

Answer 8

·         Quality Factor (QF) is derived from Relative Biological Effectiveness (RBE) measurement
·         x-ray photons = 1
·         Gamma photons = 1
·         Beta particles = 5
·         Thermal neutrons = 5
·         Fast neutrons = 20
·         Alpha particles = 20

Question 9

What is ESE?

Answer 9

· Entrance Skin Exposure
· patient dose is usually calculated according to the exposure level at the skin
· because the 1 R = 1 rad of x-ray exposure, the readings obtained from the graph may be interpreted as mrads ESE

Question 10

What did Bergonie and Tribondeau discover?

Answer 10

· Law of Radiosensitivity à law stating that the resistance or sensitivity to radiation depends on the metabolic state of a cell, tissue, or an organ

Question 11

What is the product of indirect hit?

Answer 11

· Ionization of water in the cell produces free radicals that may damage DNA directly or produce toxic substances that affect DNA, causing biological damage

Question 12

What is a direct hit?

Answer 12

· Interaction of photon with DNA molecule may sever one or more strands, causing point mutations

Question 13

What are stochastic and non-stochastic effects?

Answer 13

· Types of radiation effects
· Stochastic: probabilistic, random
· Non-stochastic: deterministic, predictable; severity proportional to dose, generally occur only after larger doses

Question 14

Examples of stochastic effects

Answer 14

o        cancer, leukemia
o        mutagenesis (damage to reproductive cells before conception)

Question 15

Examples of non-stochastic effects?

Answer 15

o        cataract formation
o        fibrosis
o        organ atrophy
o        loss of parenchymal cells
o        reduced fertility, sterility

Question 16

What occurs at higher doses?

Answer 16

Non-stochastic effects

Question 17

What is the meaning of ALARA?

Answer 17

As Low As Reasonably Achievable

Question 18

What are low dose factors?

Answer 18

· Fastest screens and films consistent with acceptable resolution
· Highest kVp consistent with acceptable contrast
· Minimum 40” SID
· Minimum 2.5 mm Al equiv. Filtration
· Maximum developer temperature consistent with acceptable fog levels

Question 19

Dose management requires:

Answer 19

o     Commitment to dose reduction policy and procedure
o     A basic plan to reduce dose
o     Proper equipment
o     Correct decisions
o     Caution to avoid repeats
o     Use of low dose techniques above
o     Proper collimation and shielding

Question 20

What is the whole-body dose equivalent for adult (non-pregnant)?

Answer 20

· Effective Dose Equivalent (EDE) Limits for an adult non-pregnant worker is 5 rem/year (limited to 1.25 rem per calendar quarter)