This document defines and explains various quantities and units used in radiation protection. It discusses physical radiation quantities like particle fluence, flux density, exposure, absorbed dose, kerma and activity. It also covers biological quantities like relative biological effectiveness, quality factor, equivalent dose and effective dose. Various units are defined for these quantities, including gray, sievert and becquerel. Tissue weighting factors are provided to calculate effective dose. The document also discusses concepts like dose commitment, radon concentration and linear energy transfer.

1. Fundamental of Radiation Protection
Quantities and Units 1
Lecture 1
QUANTITIES AND UNITS
Lamarsh 9.2

2. 2
General Terms
(That do not denote quantities)
 Directly ionizing particles
 Indirectly ionizing particles
 Ionization radiation
 Nuclide
 Energy imparted
Fundamental of Radiation Protection
Quantities and Units

3. 3
Radiation
 Radiation is a transport of energy through space
 In traversing material, radiation is absorbed
Directly Ionizing Particles
 Charged particles (e’s, p’s, ’s, etc.) having
sufficient kinetic energy to produce ionization by
collision
Indirectly ionizing particles
 Uncharged particles (n’s, ’s, etc.)
Ionizing radiation
 Any radiation consisting of directly or indirectly
ionizing particles or a mixture of both
Fundamental of Radiation Protection
Quantities and Units

4. Nuclide
 A species of atom having specified number of
neutrons and protons in its nucleus denoted as
e.g.
Energy imparted
 The energy imparted by ionizing radiation to the
matter in a vacuum is the difference between the
sum of the energies of all the directly and indirectly
ionizing particles which have entered the volume
and the sum of the energies of all those which
have left it, minus the energy equivalent of any
increase in rest mass that took place in nuclear or
elementary particle reactions within the volume
X
A
Z
U
235
92
Fundamental of Radiation Protection
Quantities and Units 4

5. General types of quantities of
interest
 Physical radiation quantities
 Biological radiation quantities
 Material radiation quantities
Fundamental of Radiation Protection
Quantities and Units 5

6. PHYSICAL RADIATION QUANTITIES
Definition
 The quantities that are proportional to the amount of
radiation received or the rate at which it is delivered
Quantities
 Particle fluence or fluence
 Particle flux density of flux density
 Energy fluence
 Energy flux density of intensity
 Kerma and kerma rate
 Exposure and exposure rate
 Absorbed dose and dose rate
 Activity
Fundamental of Radiation Protection
Quantities and Units 6

7. Particle fluence or fluence ()
 For particle, particle fluence or fluence is
 where N is the number of particles which enter a
sphere of cross sectional area a
a
N




Fundamental of Radiation Protection
Quantities and Units 7

8. Particle flux density or flux density
()
 For particles, the particle flux density or flux density
is
 where  is the particle fluence in time t
t





Fundamental of Radiation Protection
Quantities and Units 8

9. Exposure (X)
 The exposure is defined as
 where Q is the sum of the electrical charges on all
the ions of one sign produced in air when all the
electrons (negatrons and positrons), liberated by
photons in a volume element of air whose mass is
m, are completely stopped in air
Exposure rate
m
Q
X



t
X
X




Fundamental of Radiation Protection
Quantities and Units 9

10. Units of exposure
SI unit: Exposure unit (X-unit)
1 X-unit = 1 C/kg air
Old unit: Roentgen (R)
1 R = 1 esu / cm3 of dry air
1 R = 2.58x10-4 C/kg
Fundamental of Radiation Protection
Quantities and Units 10

11. Nuclide
 A species of atom having specified number of
neutrons and protons in its nucleus denoted as
e.g.
Energy imparted
 The energy imparted by ionizing radiation to the
matter in a vacuum is the difference between the
sum of the energies of all the directly and indirectly
ionizing particles which have entered the volume
and the sum of the energies of all those which
have left it, minus the energy equivalent of any
increase in rest mass that took place in nuclear or
elementary particle reactions within the volume
X
A
Z
U
235
92
Fundamental of Radiation Protection
Quantities and Units 11
Dr. Muhammad Tufail
(T.B., I.F., T.I.)

12. Absorbed dose (D)
 The absorbed dose is defined as
 where ED is the energy imparted by ionizing
radiation to the matter in a volume element, m is
the mass of the matter in that volume element
Absorbed dose rate
m
E
D D



t
D
D




Fundamental of Radiation Protection
Quantities and Units 12

13. Units of Absorbed dose
SI unit: gray (Gy)
1 Gy = 1 joule/ kg
Old unit: rad (radiation absorbed dose)
1 rad = 100 ergs/ gm
1 rad = 0.01 Gy
The gray is universally applicable to all types of
ionizing radiation.
Fundamental of Radiation Protection
Quantities and Units 13

14. Kerma (K)
 It is defined as
 where EK is the sum of the initial kinetic energies
of all the charged particles liberated by indirectly
ionizing particles in a volume element of the
specified material, m is the mass of the matter in
that volume element
Kerma Rate
m
E
K K



t
K
K




Fundamental of Radiation Protection
Quantities and Units 14

15. RBE (Relative biological effectiveness)
 Absorbed dose from different types of radiations have
different biological effectiveness
 The RBE of one type of radiation in relation to a
reference type of a radiation is the inverse ratio of the
absorbed doses of two radiations needed to cause the
same degree of the biological effect for which the RBE
is given
Quality factor (Q)
 The whole number rounded value of RBE
Fundamental of Radiation Protection
Quantities and Units 15

16. Activity (A)
 The activity of a quantity of a radionuclide is
 where N is the number of nuclear transformations
which occur in this quantity in time t
Units
 SI unit: becquerel (Bq)
1 Bq = 1 dis/sec
 Special unit: curie (Ci)
1 Ci = 3.7x1010 Bq
t
N
A



Fundamental of Radiation Protection
Quantities and Units 16

17. Radioactivity
 Denote phenomenon of radioactive disintegration
 It is not synonym for activity
Fundamental of Radiation Protection
Quantities and Units 17

18. Dose equivalent
conti.
Quality factors for various types of radiations
Types of radiation Q
x and  rays 1
 rays 1
 particles 10
Heavy recoil nuclei 20
Neutrons
Thermal to many MeV 2–10
Fundamental of Radiation Protection
Quantities and Units 18

19. Dose equivalent
conti.
Dose equivalent (H)
H = Q x D
Unit
rem (Roentgen equivalent man)
Fundamental of Radiation Protection
Quantities and Units 19

20. Equivalent dose (HT)
 Equal amounts of energy of different radiations can cause
different amounts of damage (biological effect)
 Equivalent dose introduced to quantify the portable bio-
effect
 Equivalent dose in a tissue T is given by:
where w signifies the relative biological effectiveness of a
given type of radiation, R; DR,T is the physical deposited
dose by a given radiation, R, in tissue type T


R
T
R
R
T D
w
H ,
Fundamental of Radiation Protection
Quantities and Units 20

21. Equivalent dose (HT)
…..Conti
 The so-called radiation weighting factor assumes different
values of different radiations, as follows:
 WR = 1 for X,  and  radiation (i.e. low LET radiation)
 WR > 1 for high LET radiation, the associated dose
deposition density having the capacity to cause greater
biological effects than low LET radiations
Units
SI unit: sievert (Sv)
Fundamental of Radiation Protection
Quantities and Units 21

22. Radiation Weighting Factors (WR)
Based on ICRP-60 (old Values)
Type and Energy of Radiation WR
Photons, all energies 1
Electrons and muons, all energies 1
Neutrons, energy  10 keV 5
10 keV to 100 keV 10
 100 keV to 2 MeV 20
 2 MeV to 20 MeV 10
 20 MeV 5
Protons 5
-particles, fission fragments, heavy nuclei 20
22

23. Recommended radiation weighting
factors Based on ICRP-103 (New Values)
Radiation Type Radiation weighting factor,
WR
Photons 1
Electrons and muons 1
Protons and charged pions 2
Alpha particles, fission
fragments, heavy ions
20
Neutrons 2 to 20
A continuous function of neutron
energy.
23

24. Effective dose
 A measure of biological harm in a given tissue type,
since different tissues and organs have different
sensitivity to radiation
 Effective dose
where wT is the tissue weighting factor, HT equivalent
dose
 Substituting HT of previous equation
Units
SI unit: sievert (Sv)


T
T
T H
w
E



R
T
R
R
T
T D
w
w
E ,
Fundamental of Radiation Protection
Quantities and Units 24

25. Tissue weighting factor (wT)
Organ or tissue wT
Whole body 1
Gonads 0.2
Red bone marrow, Colon, Lung, Stomach 0.12
Bladder, Breast, Liver, Oesophagus, Thyroid gland 0.05
Skin, Bone surface 0.01
Remainder: All organs and tissues not listed above
collectively, including the adrenal gland, brain,
extra-thoracic airway, small intestine, kidney,
muscles, pancreas, spleen, thymus and uterus
0.05
Fundamental of Radiation Protection
Quantities and Units 25

26. Population dose
Definition
 Product of effective dose (in Sv) per member of
population and population size
where E is effective dose and N is the population size
Units
 Unit is man-Sv


i
i
i
pop E
N
E
Fundamental of Radiation Protection
Quantities and Units 26

27. Tissue Weighting Factors (WT)
Based on ICRP-60 (old values)
Tissue or organ WT
Gonads 0.20
Bone marrow (red) 0.12
Colon 0.12
Lung 0.12
Stomach 0.12
Bladder 0.05
Breast 0.05
Liver 0.05
Oesophagus 0.05
Thyroid 0.05
Skin 0.01
Bone surface 0.01
Remainder 0.05
27

28. Recommended tissue weighting factors
Based on ICRP-103 (New values)
Tissue WT ∑ WT
Bone marrow (red), Colon,
Lung, Stomach, Breast,
Remainder tissues
0.12 0.72
Gonads 0.08 0.08
Bladder, Oesophagus, Liver,
Thyroid
0.04 0.16
Bone surface, Brain, Salivary
glands, Skin
0.01 0.04
Total 1.00
28

29. Effective dose commitment
 This is the integral over infinite time (or for specified
period) of the average, per caput, dose rate to a
specified population, often world population
resulting from the event
 The dose commitment has been particularly useful
in assessing the long-term consequences of events
occurring within a limited time
Units
sievert (Sv)



0
dt
E
E 
Fundamental of Radiation Protection
Quantities and Units 29

30. Radon concentration
 The potential  energy concentration of radon/
decay products in air is expressed in
 J/m3 (SI unit)
 working level WL (older unit)
1 WL = 2.08x10-3 J/m3
WL
 It is defined as any combination of the short lived
daughters of 222Rn in 1 liter of air that will ultimately
emit a total of 1.3x105 MeV in  energy
 For radon in equilibrium with its decay products
1 WL = 3700 Bq/m3 = 100 Bq/L
Fundamental of Radiation Protection
Quantities and Units 30

31. Radon concentration
conti.
Exposure to radon decay products
 The amount of inhaled decay products of radon,
taking into account their potential to emit radiation
energy, is the product of time during which the
decay products were inhaled and their
concentration in the inhaled air.
 Exposure is expressed in
 Bq h/ m3 in SI units
 Working level month (WLM) in older units
 Working month for miners = 170 h
Fundamental of Radiation Protection
Quantities and Units 31

32. Mutual relations of quantities
Conversions
1 X-unit = 3877 R
1 Gy = 100 rad
1 Sv = 100 rem
Exposure-Dose relationship
1 X-unit = 34 Gy (in air)
1 X-unit = 37 Gy (in tissue)
1 R = 0.877 rad (in air)
1 R = ____ rad (in tissue)
Fundamental of Radiation Protection
Quantities and Units 32

33. Linear energy transfer (L)
 For charged particles, the linear energy transfer is
 where dEL is the average energy locally imparted to
the medium by a charged particle of specified
energy in traversing a distance dl
L
dE
L
dl

Fundamental of Radiation Protection
Quantities and Units 33

34. Average energy (W) expended in a
gas per ion pair formed
 For a charged particle, the average energy
expended in a gas per ion pair formed is
 where NW is the average number of ion pairs formed
when a charged particle of initial kinetic energy E is
completely stopped by the gas
W
N
E
W 
Fundamental of Radiation Protection
Quantities and Units 34