Radiation is energy traveling through space in the form of waves or particles.
▪ It comes from many different sources including: ➢ X-rays
➢ Lasers
➢ Sunrays
➢ Microwaves
➢ Electric and magnetic fields
➢ Nuclear substances (radioactive materials)

Ionizing Radiation
It has sufficient energy to ionize (remove electrons from) atoms or molecules
Examples:
x-ray, gamma rays, alpha particles, beta particles, and neutrons
Non-ionizing Radiation
It does not have sufficient energy to ionize atoms or molecules. Instead, the energy is converted to heat
Examples:
Light, laser, heat, microwaves, and radar
Radiation

Ionizing Radiation
 It consists of subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, ionizing them.
 The occurrence of ionization depends on the energy of the impinging individual particles or waves, and not on their number (intensity).
 Roughly speaking, particles or photons with energies above few electron volts (eV) are ionizing.
 Examples:
Charged Particles
Electromagnetic Waves
Uncharged Particles
Alpha particles (α+) Beta particles (β+ , β- )
X-rays Gamma rays
Neutrons (n)

Ionizing Radiation
 Ionizing radiation comes from different sources:
▪ X-ray tubes.
▪ Radioactive materials decay (unstable nucleus). ▪ Particle accelerators.
▪ Nuclear fission and nuclear fusion. ▪ Environments.
 It is invisible and not directly detectable by human senses, so instruments such as Geiger counters or scintillation detectors are used to detect its presence.
 It has many practical uses in medicine, research, construction, and other areas; but presents health hazards if used improperly.

Nuclear Radiation

Nuclear Radiation

X-Rays
 X-rays are electromagnetic radiation caused by:
▪ deflection of electrons from their original paths, or
▪ inner orbital electrons that change their orbital levels.
 X-rays can travel long distances through air and most other materials like gamma rays, but they differ in their origin.

Interaction of Ionizing Radiation with Matter
➢ Direct Ionization
Charged particles (e.g. alpha and beta) interact strongly with matter and produce negatively-charged electrons and positively-charged ions along their path.
➢ Indirect Ionization
Photons and neutrons (have no charge) release charged particles in matter which are themselves directly ionizing.

Degree of Penetration for Different Ionizing Radiation Types
▪ Gamma rays need thicker shielding than X-ray because they have greater penetrating power

Radiation Measurement Units
النشاط الإشعاعي )Radioactivity (A ➢
It is the spontaneous emission of radiation from unstable atomic nuclei. It is measured as the number of nuclei that decay per unit time.
Radioactivity = decays/second = disintegrations/second Unit → Becquerel (Bq) or Curie (Ci)
(SI unit)
1 Bq = 1 decay/s = s-1
1 Ci = 3.7 × 1010 Bq (decay/s) 1Bq = 2.7×10-11 Ci

Radiation Measurement Units
التعرض الإشعاعي Radiation Exposure ➢
It is a measure of ionization of air caused by photons (γ- and x-rays).
It is defined as the electric charges freed by such radiation in a specified volume of air divided by the mass of that air.
Unit → Coulomb/kilogram (C/kg) or Rontgen (R) (SI unit)
1C/kg=3876 R 1R = 2.58×10-4 C/kg

Radiation Measurement Units
الجرعة الممتصة )Absorbed Dose (D ➢
It is defined as the energy imparted to a defined mass of tissue.
It is applied to all radiation exposures, all types of ionizing radiation, any absorbing medium.
Unit → Joule/kilogram (J/kg) ≡ Gray (Gy) or rad (SI unit)
1Gy=100 rad
1rad = 0.01 Gy
= 0.01 J/kg = 100 erg/gm

Radiation Measurement Units
الجرعة المكافئة )Equivalent Dose (H ➢
It takes into account the relative biological effectiveness (RBE) of different forms of ionizing radiation.
Equivalent
Absorbed
W
Dose
R
or rem
1 Sv = 100 rem 1 rem = 0.01 Sv
Weighting
Factor
Dose
H= D

×
x
Radiation
Unit →
Sievert (Sv)
(SI unit)

Radiation Measurement Units
الجرعة الفعالة )Effective Dose (E ➢
It takes into account the type of radiation the person was exposed to (equivalent dose) as well as what part of the body was irradiated.
Effective dose = Equivalent dose x Tissue Weighting Factor
E= H or rem
1 Sv = 100 rem 1 rem = 0.01 Sv
×
W
T
Unit →
Sievert (Sv)
(SI unit)

Ionizing Radiation Effects
 Exposure to ionizing radiation can be:
External → The source of radiation is outside the body (e.g. X-ray machine)
Internal → The source is taken into the body through ingestion, inhalation, or skin contact (e.g. I-131 taken orally by the patient)
 Exposure to ionizing radiation can cause damage to living tissues: High Doses → Skin burns, radiation sickness, and death
Low Doses → Cancer, tumors, and genetic damage
 Some early observations of the effects of ionizing radiation: 1897 → First cases of skin damage reported
1902 → First report of x-ray induced cancer
1911 → First report of leukemia in humans and lung cancer from occupational exposure 1911 → 94 cases of tumor reported in Germany (50 being radiologists)
1920s → Bone cancer among radium dial painters was linked with ingestion of radium

Ionizing Radiation Effects
تأثيرات عشوائية Stochastic Effects تأثيرات حتمية Deterministic Effects
▪ Due to cell death ▪ Due to cell change (DNA)
▪ There is threshold for effect (below: no effect) ▪ No dose threshold
▪ Severity increases with dose above threshold ▪ Probability of effect increases with dose ▪ Example: skin erythema, sterility, epilation ▪ Example: cancer, heritable disorders

Ionizing Radiation Effects
˂ 1Sv 1 - 2 Sv 2 - 10 Sv ˃ 10 Sv
1 Sv 2 - 5 Sv ˃ 3Sv
• produce nothing other than blood changes
• cause illness but will rarely be fatal
• will likely cause serious illness with poor outlook at the upper end of the range
• are almost invariably fatal
• causes nausea
• causes epilation or hair loss, hemorrhage and will cause death in many cases
• will lead to LD50/30 or death in 50% of cases within 30 days
• survival is unlikely

• Acute dose → received in a relatively short time, up to about one hour
  ˃ 6Sv
  Acute Dose

Ionizing Radiation Effects
Amount of Exposure
Rate of Exposure
Area of Exposure Type of Radiation (WR)
Sensitivity of Tissue (WT)
Biological Effect

Radiation Protection

 Radiation protection, sometimes known as radiological protection, is the science of protecting people and the environment from the harmful effects of ionizing radiation.
 Radiation protection can be divided into:
Occupational radiation protection Medical radiation protection
[Workers]
Public radiation protection [Individual members of the public]
[Patients]

Radiation Protection
 There are four major ways to control radiation exposure of workers or population:
Amount Time
Distance Shielding

Radiation Protection
➢ Time
▪ Decrease your exposure time to radiation source.
▪ Dose is directly proportional to exposure time. 𝐷𝑜𝑠𝑒 = 𝐷𝑜𝑠𝑒 𝑟𝑎𝑡𝑒 × 𝑇𝑖𝑚𝑒
𝐷𝑜𝑠𝑒 ∝ 𝑇𝑖𝑚𝑒
Amount Time
Distance Shielding

Radiation Protection
➢ Distance
▪ Increase your distance from radiation source.
▪ Dose is inversely proportional to (distance)2. 𝐷𝑜𝑠𝑒 = 𝑘
𝐷𝑜𝑠𝑒 ∝ 1 (𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒)2
𝑑2
Amount Time
Distance Shielding

Radiation Protection
➢ Shielding
▪ More shielding means less exposure.
▪The proper shielding for each type of ionizing
radiation must be chosen with proper thickness. ▪ Dose falls exponentially with increasing thickness.
𝐷 = 𝐷 𝑒−𝜇𝑥 𝑜
Amount Time
Distance Shielding

Radiation Protection
 The three fundamental principles of the international system of radiation protection are:
Justification
التبرير
Optimization
َ الأمثلة
Dose Limitation
حدود الجرعات
Minimum risks and maximum benefits should be achieved in a practice which included ionizing radiation.
Benefits ˃ Risks
Doses should be ‘‘as low as reasonably achievable” or ‘‘as
low as reasonably practicable’’
ALARA or ALARP principle
Dose limits are established to avoid deterministic effects and minimize stochastic effects.
(e.g. 20 mSv/y for workers and 1 mSv/y for public)

Radiation Protection
➢ General Working Rules for X-ray Machines

1. A room must not be used for more than one x-ray procedure simultaneously.


2. Persons not essential to the radiologic procedure must not be in the room during
   patient exposure.


3. Operators should not be in the room at the time of exposure.


4. If parents or escorts are called to assist, appropriate shielding should be worn by
   those people.


5. The x-ray housing should not be held by the operator during operation.


6. Under normal circumstances, there should be no radiation recorded on the
   dosimeter badge.

Radiation Protection
➢ General Working Rules for Radioactive Sources

1. Remove the source from the storage only when ready to use it.


2. Never pick up radioactive sources except with the tweezers/tongs.


3. There should be no eating or drinking in the laboratory where sources are in use.


4. Be sure that the sources are returned to the storage before you leave the
   laboratory.


5. Decrease your time exposure to the source.


6. Increase your distance from the source.


7. More shielding means less exposure.


8. Wear proper personnel radiation monitoring