This document discusses various units used to measure radiation and its effects. It introduces electromagnetic radiation and defines ionizing and non-ionizing radiation. It then explains the importance of measurement units and defines common units like becquerels, curies, grays, rads, sieverts and rems used to quantify radioactivity, radiation dose, and biological dose equivalents. The document also discusses concepts like kerma, equivalent dose and effective dose which account for different tissue sensitivities to different radiation types.

1. Understanding the
Radiation units
Presented by;
Niroj Sandha(PCL)
RADIOGRAPHY 2ND YR
KAHS

2. Contents
1. Introduction to Electromagnetic radiation
2. Importance of measuring system
3. Units of radioactivity
4. Units of radiation dose
5. Equivalent dose
6. KERMA
7. Effective dose
• Units of exposure
• Units of Absorption

4. Introduction to Electromagnetic Radiation
• Electromagnetic radiation is the form of energy formed by oscillating
electric and magnetic feild distrubance.
• It is a movement of electrically charged particles travelling through a
vaccum.
• Wavelength: 0.01 to 10nm
• Frequency:3×10^6Hz to 3×10^19Hz
• Energy:100ev to 100kev
• Types;
1. Non-Ionizing radiation
2. Ionizing radiation

5. 1. Non-Ionizing radiation
• Refers to the EMR that does not carry enough energy per
quantum(photon energy) to ionize atoms or molecules , that is to
completly rove the charge particles from an atom or molecule.
• Radiation with the particle or photon energy less than 100ev is
considered as Non-Ionizing .
• Eg;UV rays ,visible light ,Infrared,Microwaves ,Radiowaves etc

7. 2.Ionizing radiation
• Refers to the EMR that carry enough wnwrgy per quantum (photon energy
) to ionize the atoms pr kolecules in the medium through which it passes.
• It is categorized by the nature of EMR waves that create the ionizing effect;
i)Directly( charged particles)
ii)Indirectly (Neutral)
i)Directly:
It depositsenergy in the medium through direct coulomb interaction
between directly ionizing charge particles and orbital electrons of atom in
the medium.
Eg ;Alpha,Beta,Gamma

8. ii)Indirect :
Deposits energy into the medium through two process ;
1st step: charged particles released in the medium (photon release
electrons or positrons , neutrons releases protons or heavier ions).
2nd step :Charge particles deposits energy to the medium through
direct coulomb interaction with orbital electrons of the atoms in the
medium .
eg ; Neutrons

9. Importance of Measuring Units
In 1928 ,International commision on Radiation Units
(ICRU)adopted a Roentgen as a measuring unit of X & Y radiation.
When trying to measure radiation there
are two things being measured ,activity and exposure .Activity is how much
radiation is coming out of something while exposure measures the effect of
that radiation on any thing that absorbs it.
Radiation units are confusing for three or four reasons ;
• There are diffrent units depending on whether you’re measuring how
much radiation is being emitted or recived .
• There are diffrent ways of quantifying the amount of radiation recived
depending upon whether you’re doing physics or biology.
• For each of these measurements there are traditional units and SI units.

10. If you’re not familiar with scientfic units , a fourth source of
confusion is the prefix of various powers of 10:milli, micro etc.

11. The amount of radioactivity emitted by a source is measured in
Becqurels or Curies (named after Henri Becquerel and Marrie curie).The SI
unit is Becquerel(Bq),one decay per second .The traditional units Curie (Ci)
is 3.7×10^10Bq and is about radioactovity of gram of radium.
The amount of radiation recived by a source is measured in
grays or rads.The SI unit Gray(Gy) corresponds to one joule of energy
absorbed by one kilogram of matter (J/Kg).The traditional unit is Rad
(0.01Gy).
1 Rad =0.01 Gy
Or, 100Rads =1Gy
The biological effect of radiation is measured in seiverts
or Rems .Biologically effective dose is amount of radiation recived and
multiplied by relative biological effectiveness of the type of radiation
source .For x-rays RBE is 1.For Alpha rays RBE is 20 .The SI unit of
effective dose is seivers (si) which corresponds to one gray of x rays . A
rem is 0.01sev

12. Units of Radioactivity
Radioactivity /Radioactive decay/Nuclear decay is the phenomenon of
spontaneous emission of rays such as Alpha , Beta , Gamma by heavvy
elements having atomic number greater than 82.It isthe process by which
an unstable atomic nucleus loses energy by emitting radiation
• Conventional unit: Curie(Ci)
• SI unit:Becquerel(Bq)
One curie is defined as the activity of material which has
3.7×10^10dps.It is non – SI unit of radioactivity named after Marrie and
perrie curie.
1Ci=3.7×10^10dps
One cuire is equivalent to the 1gm of Radium isotopes^226R.

13. 1Bq can be defined as the activity of a radioactive material in which
one nucleus decays per second .Any radioactive material has an activity
of 1 Bq , if its Disintegration rate is 1 second .
1Bq =1dps=2.7×10^11Ci

14. Units of radiation dose

15. i)Units of Exposure
• Its is measure of ionization produced in air by photons .
• SI unit is C/Kg
• Traditional unit is Roentgen (R)
• Measures ionization in air only
• Cannot measure photon energies >3Mev
Limitations of Roentgen;
• For X and Gamma rays only
• Electrons liberated must give up all their energies before being collected
• Air must dry
• Photon energy less than 3 Mev

16. • 1Roentgen(R)=Amount of X or Gamma radiation that produces
ionization resulting in 1 electrostatic unit of charge in 1 cm3 of dry air
.
1ESU=3.333×10^-10c and 1cm3 of air at STP weighs 1.293×10^-6kg
.°.1R=2.58×10^-4C/Kg(air).
ii)Unit of Absorption
• Physical dose or Biologically significant affect of ionizing radiation
• Amount of radiation dose /energy deposited in a unit mass of human
tissue or medium.
• Traditional unit:Rad
1Rad=100erg/gm=10^-2J/Kg
• SI unit:Gray
1Gray=1J/kg=100rad

19. Equivalent dose
• Equal doses of all types of radiation are not harmful.
• Alpha partickes produce greater harm tha Beta ,Gamma and X rays for a given
absorbed dose .
• To account for this ,diffrence radiation dose is expressed as equivalent dose in
units in seiverts(Sv).
• The dose in Sv is equal to Absorbed dose multiplied by the radiation
weighting factor .
Dose in Sv=Absorbed dose ×radiation weighting factor (Wr)
Dose in rem=absorbed dose in rad × radiation conversion factor(QF)/(Wr)
• SI unit=Seivert(Si)
• Old unit=Rem
• 1 rem=10msv=1R
• 0.7Sv =1Gy

21. KERMA
• Acronym of Kinetic Energy Released per unit Mass.
• K(KERMA)=sum of all charged particles liberated by ionizing radiation
• Per unit weight of matter.
• K=dE÷dM
• unit=J/kg
• SI unit =Gray
• Special unit=Rad
• 1Gy=1J/Kg=10^4ergs/gm=100rad

22. Effective dose(E)
• It is a product of equivalent dose and tissue weighting factor
• Since all tissues dosen’t have same sensitivity towards radiation , so
each tissue is given a factor based on response to radiation.
• SI unit=Sv
Effective dose =Absorbed dose × Wr×Wt
Tissue weighting factor (Wt)
Radiation weighting factor(wr)

27. THANK YOU