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Radiation Hazards and Protection
30 January 2015 1Dr Saad Wahby Al Bayatti
X- ray Dose Measurements
X- ray Dose Units
30 January 2015 2Dr Saad Wahby Al Bayatti
Radiation Absorbed Dose
• This is a measure of the amount of energy
absorbed from the radiation beam per unit mass of
tissue
• Unit of measurement:
• SI unit : Gray, (Gy) measured in joules/kg
• original unit : rad, measured in ergs/gm
• 1 Gray = 100 rads
30 January 2015 3Dr Saad Wahby Al Bayatti
Equivalent Dose
• A measure which allows comparison between
different types of radiation in regard to their
absorbed doses in the body (RBE radiobiological
effectiveness)
• Unit of measurement (SI unit) : Sievert (Sv)
• subunits : millisievert (mSv) ( ×1/1 000)
• : microsievert ( µSv) ( ×1/1 000 000)
• original unit : rem
• 1 Sievert = 100 rems
30 January 2015 4Dr Saad Wahby Al Bayatti
Quality Factor (Q)
• Represents the biological effects of each
type of radiation:
• X- rays, gamma rays and beta particles
Q = 1
• Fast neutrons protons Q = 10
• Alpha particles Q = 20
30 January 2015 5Dr Saad Wahby Al Bayatti
Equivalent Dose
• equivalent dose = radiation absorbed dose (Gy)×
Q
• Since Q for x -ray = 1, then
equivalent dose = radiation absorbed dose
(Sv) = (Gy)
30 January 2015 6Dr Saad Wahby Al Bayatti
Effective Dose
• Each body tissue is affected differently by
radiation
• Effective dose: This is a measure that allows doses
from different investigations of different parts of
the body to be compared , by converting all doses
to an equivalent whole body dose
30 January 2015 7Dr Saad Wahby Al Bayatti
Weighing Factor (W)
• Measures the radiosensitivity, i.e.the risk of
the tissue being damaged by radiation.
• The higher the damage, the higher is W
30 January 2015 8Dr Saad Wahby Al Bayatti
Weighing factors for different body tissues
Tissue Weighing factor
Testes and ovaries 0.20
Red bone marrow, colon, lung,
stomach
0.12
Breast, bladder, liver, thyroid 0.05
Bone surfaces , skin 0.01
Remainder 0.01
30 January 2015 9Dr Saad Wahby Al Bayatti
Effective Dose
• Effective dose = equivalent dose × weighing factor
= radiation absorbed dose(Gy)×Q ×W
• SI unit : Sievert (Sv)
• subunit : millisievert (mSv)
• Effective dose (whole body) = sum of W
30 January 2015 10Dr Saad Wahby Al Bayatti
Absorbed dose
Multiplied by a factor to reflect harm by a specific radiation
Equivalent dose
Multiplied by a factor to reflect sensitivity of a specific tissue
Effective dose, commonly called “dose”
30 January 2015 11Dr Saad Wahby Al Bayatti
Effective doses
X -ray examination
X- ray exam. Effective dose (mSv)
• CT cest 8.0
• barium meal 7.7
• lumbar spine 2.2
• CT head 2.0
• skull 0.1
• chest 0.04
• OPG 0.007
• 2 intra oral films (E speed) 0.002
30 January 2015 12Dr Saad Wahby Al Bayatti
The frequency of taking films is based on
the following factors:
1. Patient’s oral hygiene
2. Caries activity
3. Dental history
4. Reliability of patient
5. ADA Guidelines
ADA Guidelines
Full-mouth Series
1 - 5 years
Bitewings
6 months - 3 years
Panoramic
1 - 5 years
Biological Effects of X-ray
30 January 2015 15Dr Saad Wahby Al Bayatti
Radiobiology
The response of living systems to
ionizing radiation
Biological Effects of X-ray
• X-Rays interact with living tissues and can cause
biological changes.
• These changes are mediated directly by excitation
or ionization of atoms or indirectly as a result of
chemical changes occurring near the cells.
• Affected cells may be damaged or killed.
30 January 2015 17Dr Saad Wahby Al Bayatti
Biological Effects of X-ray (cont’d)
• Genetic effects involve chromosomal damage or
mutation in the reproductive cells and will affect
future generations.
• Somatic effects involve damage to other tissues and
result in changes within the individual’s lifetime
(e.g. radiation burns, leukemia).
• Radiation is a particular hazard because its effects
are painless, latent and cumulative
30 January 2015 18Dr Saad Wahby Al Bayatti
Incoming
photon
Excited electron
Excitation
30 January 2015 19Dr Saad Wahby Al Bayatti
Incoming
photon
Ejected electron
Photon
Positive Ion
Ionization
Photon
30 January 2015 20Dr Saad Wahby Al Bayatti
Ionization
The process of removing an electron from an electrically
neutral atom to produce an ion. An ion is an atom or
subatomic particle with a positive or negative charge.
Ionization negative ion
positive ion
Attenuation
Reduction of x-ray beam intensity (that
reaches film) by interaction with matter.
1. Coherent scattering
2. Compton scattering
3. Photoelectric absorption
Coherent Scattering
Low-energy x-ray interacts with outer-
shell electron and causes it to vibrate
briefly. Scattered x-ray of same energy
as primary x-ray is then emitted, going
in a different direction than primary x-
ray. Electron not ejected from atom. (No
ionization).
Coherent Scattering
Compton Scattering
Outer shell electron ejected
(Ionization)
Scatter radiation results
Occurs majority of the time
30% of scatter exits head
recoil electron
scattered x-ray
Compton Scattering
primary x-ray
The primary x-ray strikes an outer-shell electron,
knocking it out of its orbit (ionization). The primary x-
ray loses some of its energy and continues in a different
direction as a scattered x-ray.
Inner-shell electron ejected
(Ionization)
Complete absorption
Photoelectric Absorption
photoelectron
primary x-ray
Photoelectric Absorption
The primary x-ray strikes an inner-shell electron,
knocking it out of its orbit (ionization). The x-ray loses
all of its energy and disappears. There is no scatter.
Dose-Response Curves
threshold
linear
non-linear
non-threshold
Response
Dose
Linear: the response is directly
related to the dose.
Non-linear: the response is not
proportionate to the dose.
Threshold: the dose at which effects
are produced; below this dose, there
are no obvious effects.
Non-threshold: any dose produces a
response.
Critical Molecule
(Target)
DNA
Hazards & protection
Radical
Atom or molecule that has an
unpaired electron in the valence
shell, making it highly reactive.
(Most damaging).
Mutations
Cell death
Sublethal injury
Biologic Effects
DNA altered; cell function
altered or development
changed. It is unclear which
critical lesion/s in DNA may
lead to cancer.
Mutation
Normal
Mutation
Loss of capacity for mitosis
Cell Death
Cellular Repair
1. Damage to biologic molecules
(single-strand break of DNA)
2. Removal of damaged section by
cell enzymes
3. Placement of new material by
other cell enzymes
Radiation Effects Influenced by:
Total dose
Dose rate
Total area covered
Type of tissue
Age
Sources of Radiation
30 January 2015 39Dr Saad Wahby Al Bayatti
Sources of Radiation
• Natural background radiation
- cosmic rays
- gamma rays from rocks & soil 87%
- ingested radioisotops in certain foods
- radon decay products (granite )
• Artificial background radiation
- fallout from nuclear explosions > 1%
- radioactive waste
• Medical and dental diagnostic radiation 12%
• Occupational exposure > 1%
30 January 2015 40Dr Saad Wahby Al Bayatti
30 January 2015 41Dr Saad Wahby Al Bayatti
Biologic Effects Of Ionizing Radiation
Stochastic
• The probability of occurrence
of the change, rather than its
severity, is dose dependant
• All or non, the person either has
the condition, or not
• No threshold
e.g.
• Radiation induced cancer,
greater exposure of population
to radiation increases cancer
probability, but not its severity
Deterministic
• The severity of response is
proportional to the dose
• Occur in all people when the
dose is large enough
• There is a dose threshold below
which the response is not seen
e.g.
• Oral effects after radiation
therapy
• Radiation sickness after whole
body radiation
30 January 2015 42Dr Saad Wahby Al Bayatti
Radiation Hazards
30 January 2015 43Dr Saad Wahby Al Bayatti
Radiation Hazards
Nuclerar boms
nueclear reactors leaks
Whole body
radiation
Medical
(diagnostic & theraputic)
Dental
X- rays
Specific area
radiation
Radiation exposure
30 January 2015 44Dr Saad Wahby Al Bayatti
Specific Versus Whole-Body Radiation
30 January 2015 45Dr Saad Wahby Al Bayatti
Radiation Hazards
Indirect Direct
Somatic
Affects individual
No effect on offspring
Genetic
Do not affect individuial
Offspring is affected
Radiation damage
30 January 2015 46Dr Saad Wahby Al Bayatti
Radiation Hazards
Direct Damage
RH +Radiation R
+
+ H
+
+ e
-
R
+
Dissociation
R
+
X + Y
Cross-linking
R
+
+ S RS
30 January 2015 47Dr Saad Wahby Al Bayatti
Radiation Hazards
Direct Damage
Radiation
• DNA /RNA molecule nuclear acid
breakdown
• Nuclear acid breakdown
Somatic cells radiation induced
malignancy
Genetic cells radiation induced
congenital abnormality
30 January 2015 48Dr Saad Wahby Al Bayatti
Radiation Hazards (indirect damage)
Water Hydrolysis
• H 2 O H
+
+ OH
-
• H
+
+ H
+
H2
• OH
-
+ OH
-
H 2 O 2
Radiation
30 January 2015 49Dr Saad Wahby Al Bayatti
• H2O2 + DNA Molecular
breakdown
• H2O2 + Proteins
• Molecular breakdown Cell damage
Radiation Hazards (indirect damage)
Water Hydrolysis
30 January 2015 50Dr Saad Wahby Al Bayatti
Radiation Hazards
Direct
DNA /RNA hit
Radiation induced malignancy
Indirect
H2O2 formation
TOXIC
breakdown of large molecules(protiens/DNA)
Somatic
Radiation damage
30 January 2015 51Dr Saad Wahby Al Bayatti
Radiation Hazards
Direct
DNA/RNA hit
Radiation induced congenital
abnormality
Indirect
H2O2 formation
TOXIC
breakdown large molecules ( proteins/ DNA)
Genetic
Radiation damage
30 January 2015 52Dr Saad Wahby Al Bayatti
30 January 2015 53Dr Saad Wahby Al Bayatti
30 January 2015 54Dr Saad Wahby Al Bayatti
Factors Affecting Radiosensitvity
• Dose: the amount of radiation
received. The higher the dose,
the greater is the effect
(consider the threshold)
• Dose rate: the rate of exposure.
e.g. a total dose of 5Gy can be
given as
- 5Gy/min (single dose) is more
destructive
- 5mGy/min(fractionized), less
destructive, injured cells can
recover
• Oxygen: the higher the O2 level
in irradiated cells, the greater is
the damage. (H2O2 formation)
• Linear Energy Transfer
(LET): the rate of loss of
energy from a particle as it
moves in its track through
matter (tissue)
e.g. alpha particles vs. X-ray
30 January 2015 55Dr Saad Wahby Al Bayatti
X- ray Protection
30 January 2015 56Dr Saad Wahby Al Bayatti
X- ray Protection
Follow ALARA , keep exposure
A = As
L = Low
A = As
R = Reasonably
A = Achievable
30 January 2015 57Dr Saad Wahby Al Bayatti
Patient Staff public
X- ray protection
30 January 2015 58Dr Saad Wahby Al Bayatti
X- ray Protection
Patient
• Radiographs are only taken when necessary
• Number, frequency and type of radiographs is the
responsibility of the dentist
• Use high output DC x- ray generators
• Minimum kilovoltage should be 60kV
• Minimum milliamperage should be 8 mA
• Minimum filtration should be 1.5 mm Al
30 January 2015 59Dr Saad Wahby Al Bayatti
X- ray Protection
Patient
• Maximum Beam diameter should be 7 cm
(circular beams)
• Use rectangular collimation for intra oral films
• Minimum target – skin distance should be 20 cm
• Accurate timer
• Use open- ended lead lined cylindrical cones
(PID)
• Do not use close ended pointed plastic cones
30 January 2015 60Dr Saad Wahby Al Bayatti
X- ray Protection
Patient
• Use high speed films (D or E )
• Use film holders and beam-aiming devices
• Avoid retakes, master radiographic
techniques
• Avoid retakes, master film processing
techniques
• Use lead aprons
• Use thyroid collars30 January 2015 61Dr Saad Wahby Al Bayatti
Lead Aprons
30 January 2015 62Dr Saad Wahby Al Bayatti
Lead Apron/Thyroid Collar
Psychology
Protection
Adult Patient’ s Lead apron
with a thyroid collar
Separate thyroid collar
30 January 2015 64Dr Saad Wahby Al Bayatti
Child Patient’ s Lead apron
with and without thyroid collar
30 January 2015 65Dr Saad Wahby Al Bayatti
Operator’s Lead apron
30 January 2015 66Dr Saad Wahby Al Bayatti
Proper placement of the Lead
apron with a thyroid collar
30 January 2015 67Dr Saad Wahby Al Bayatti
Correct way of hanging
the Lead apron
30 January 2015 68Dr Saad Wahby Al Bayatti
Lead apron
Without a thyroid collar
30 January 2015 69Dr Saad Wahby Al Bayatti
Correct way of hanging lead apron and thyroid collars
30 January 2015 70Dr Saad Wahby Al Bayatti
Lead apron
hangers
30 January 2015 71Dr Saad Wahby Al Bayatti
X- ray Protection
Staff
• Never hold the x- ray head during exposure
• Never hold the film during exposure
• Never stand in the path of the primary beam
• Stand behind a lead barrier (2 mm thickness)
• Watch the patient through leaded glass during
exposure
• Stand minimum 2 M from the x-ray beam behind
the patient’s head
30 January 2015 72Dr Saad Wahby Al Bayatti
X- ray Protection
Public
• Warning/Informative signals to indicate
hazardous x- radiation
• Patients should be seated away from x- ray
rooms
• Patients are not allowed to wait in corridors
next to x- ray rooms
30 January 2015 73Dr Saad Wahby Al Bayatti
30 January 2015 74Dr Saad Wahby Al Bayatti
Open –ended cylindrical
Close ended plastic
7 cm
7 cm
30 January 2015 75Dr Saad Wahby Al Bayatti
Mobile lead barriers
30 January 2015 76Dr Saad Wahby Al Bayatti
Open-end cylindrical coneClose-end pointed cone
√X
30 January 2015 77Dr Saad Wahby Al Bayatti
Rectangular modifications for an
Open-end cylindrical cone
30 January 2015 78Dr Saad Wahby Al Bayatti
30 January 2015 79Dr Saad Wahby Al Bayatti
Rectangular collimatorsCircular collimators
Area of exit of the x-ray beam
Area of exit of
the x-ray beam
Metal shield
30 January 2015 80Dr Saad Wahby Al Bayatti
Long cylindrical Open-end cone
Short cylindrical Open-end cone
Long rectangular cone
Short rectangular cone
30 January 2015 81Dr Saad Wahby Al Bayatti
Patient
90-135
o o
90-135
X- ray
head
90
o
90
o
180
o
Operator
Safe position
Operator
Safe position
Scattered rays Scattered rays
DangerDanger
Safe operator’s position
No barrier used
30 January 2015 82Dr Saad Wahby Al Bayatti
Patient
90-135
o
o
90-135
90
o
90
o
180
o
Operator’s
Safe position
Operator
Safe position
Scattered rays
Scattered rays
Danger
Danger
Safe operator’s position
No barrier used
30 January 2015 83Dr Saad Wahby Al Bayatti
Hazards & protection
30 January 2015 85Dr Saad Wahby Al Bayatti
1 M
2 M
A
B
Source
Inverse square law
I 1/D
Intensity of radiation at B =1/4 at A
2
30 January 2015 86Dr Saad Wahby Al Bayatti
Inverse-square law states that the
intensity (quantity) of X-ray is inversely
proportional to the square of the
distance from the source of radiation
30 January 2015 87Dr Saad Wahby Al Bayatti
2 M
minimum .
Operator `
Patient
Danger
X -ray
Safe operator’s position
30 January 2015 88Dr Saad Wahby Al Bayatti
Operator `
Lead barrier
Using a lead barrier allows less than
2 M distance
X- ray
Patient
Danger
30 January 2015 89Dr Saad Wahby Al Bayatti
Patient
Operator `
Leaded wall room
Leaded
glass
Danger
X- ray
30 January 2015 90Dr Saad Wahby Al Bayatti
Patients’
Waiting rooms
X- ray room
X- ray room
Restricted areas
Restrictedareas
Safe patients waiting rooms
30 January 2015 91Dr Saad Wahby Al Bayatti

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Hazards & protection

  • 1. Radiation Hazards and Protection 30 January 2015 1Dr Saad Wahby Al Bayatti
  • 2. X- ray Dose Measurements X- ray Dose Units 30 January 2015 2Dr Saad Wahby Al Bayatti
  • 3. Radiation Absorbed Dose • This is a measure of the amount of energy absorbed from the radiation beam per unit mass of tissue • Unit of measurement: • SI unit : Gray, (Gy) measured in joules/kg • original unit : rad, measured in ergs/gm • 1 Gray = 100 rads 30 January 2015 3Dr Saad Wahby Al Bayatti
  • 4. Equivalent Dose • A measure which allows comparison between different types of radiation in regard to their absorbed doses in the body (RBE radiobiological effectiveness) • Unit of measurement (SI unit) : Sievert (Sv) • subunits : millisievert (mSv) ( ×1/1 000) • : microsievert ( µSv) ( ×1/1 000 000) • original unit : rem • 1 Sievert = 100 rems 30 January 2015 4Dr Saad Wahby Al Bayatti
  • 5. Quality Factor (Q) • Represents the biological effects of each type of radiation: • X- rays, gamma rays and beta particles Q = 1 • Fast neutrons protons Q = 10 • Alpha particles Q = 20 30 January 2015 5Dr Saad Wahby Al Bayatti
  • 6. Equivalent Dose • equivalent dose = radiation absorbed dose (Gy)× Q • Since Q for x -ray = 1, then equivalent dose = radiation absorbed dose (Sv) = (Gy) 30 January 2015 6Dr Saad Wahby Al Bayatti
  • 7. Effective Dose • Each body tissue is affected differently by radiation • Effective dose: This is a measure that allows doses from different investigations of different parts of the body to be compared , by converting all doses to an equivalent whole body dose 30 January 2015 7Dr Saad Wahby Al Bayatti
  • 8. Weighing Factor (W) • Measures the radiosensitivity, i.e.the risk of the tissue being damaged by radiation. • The higher the damage, the higher is W 30 January 2015 8Dr Saad Wahby Al Bayatti
  • 9. Weighing factors for different body tissues Tissue Weighing factor Testes and ovaries 0.20 Red bone marrow, colon, lung, stomach 0.12 Breast, bladder, liver, thyroid 0.05 Bone surfaces , skin 0.01 Remainder 0.01 30 January 2015 9Dr Saad Wahby Al Bayatti
  • 10. Effective Dose • Effective dose = equivalent dose × weighing factor = radiation absorbed dose(Gy)×Q ×W • SI unit : Sievert (Sv) • subunit : millisievert (mSv) • Effective dose (whole body) = sum of W 30 January 2015 10Dr Saad Wahby Al Bayatti
  • 11. Absorbed dose Multiplied by a factor to reflect harm by a specific radiation Equivalent dose Multiplied by a factor to reflect sensitivity of a specific tissue Effective dose, commonly called “dose” 30 January 2015 11Dr Saad Wahby Al Bayatti
  • 12. Effective doses X -ray examination X- ray exam. Effective dose (mSv) • CT cest 8.0 • barium meal 7.7 • lumbar spine 2.2 • CT head 2.0 • skull 0.1 • chest 0.04 • OPG 0.007 • 2 intra oral films (E speed) 0.002 30 January 2015 12Dr Saad Wahby Al Bayatti
  • 13. The frequency of taking films is based on the following factors: 1. Patient’s oral hygiene 2. Caries activity 3. Dental history 4. Reliability of patient 5. ADA Guidelines
  • 14. ADA Guidelines Full-mouth Series 1 - 5 years Bitewings 6 months - 3 years Panoramic 1 - 5 years
  • 15. Biological Effects of X-ray 30 January 2015 15Dr Saad Wahby Al Bayatti
  • 16. Radiobiology The response of living systems to ionizing radiation
  • 17. Biological Effects of X-ray • X-Rays interact with living tissues and can cause biological changes. • These changes are mediated directly by excitation or ionization of atoms or indirectly as a result of chemical changes occurring near the cells. • Affected cells may be damaged or killed. 30 January 2015 17Dr Saad Wahby Al Bayatti
  • 18. Biological Effects of X-ray (cont’d) • Genetic effects involve chromosomal damage or mutation in the reproductive cells and will affect future generations. • Somatic effects involve damage to other tissues and result in changes within the individual’s lifetime (e.g. radiation burns, leukemia). • Radiation is a particular hazard because its effects are painless, latent and cumulative 30 January 2015 18Dr Saad Wahby Al Bayatti
  • 21. Ionization The process of removing an electron from an electrically neutral atom to produce an ion. An ion is an atom or subatomic particle with a positive or negative charge.
  • 23. Attenuation Reduction of x-ray beam intensity (that reaches film) by interaction with matter. 1. Coherent scattering 2. Compton scattering 3. Photoelectric absorption
  • 24. Coherent Scattering Low-energy x-ray interacts with outer- shell electron and causes it to vibrate briefly. Scattered x-ray of same energy as primary x-ray is then emitted, going in a different direction than primary x- ray. Electron not ejected from atom. (No ionization).
  • 26. Compton Scattering Outer shell electron ejected (Ionization) Scatter radiation results Occurs majority of the time 30% of scatter exits head
  • 27. recoil electron scattered x-ray Compton Scattering primary x-ray The primary x-ray strikes an outer-shell electron, knocking it out of its orbit (ionization). The primary x- ray loses some of its energy and continues in a different direction as a scattered x-ray.
  • 28. Inner-shell electron ejected (Ionization) Complete absorption Photoelectric Absorption
  • 29. photoelectron primary x-ray Photoelectric Absorption The primary x-ray strikes an inner-shell electron, knocking it out of its orbit (ionization). The x-ray loses all of its energy and disappears. There is no scatter.
  • 30. Dose-Response Curves threshold linear non-linear non-threshold Response Dose Linear: the response is directly related to the dose. Non-linear: the response is not proportionate to the dose. Threshold: the dose at which effects are produced; below this dose, there are no obvious effects. Non-threshold: any dose produces a response.
  • 33. Radical Atom or molecule that has an unpaired electron in the valence shell, making it highly reactive. (Most damaging).
  • 35. DNA altered; cell function altered or development changed. It is unclear which critical lesion/s in DNA may lead to cancer. Mutation Normal Mutation
  • 36. Loss of capacity for mitosis Cell Death
  • 37. Cellular Repair 1. Damage to biologic molecules (single-strand break of DNA) 2. Removal of damaged section by cell enzymes 3. Placement of new material by other cell enzymes
  • 38. Radiation Effects Influenced by: Total dose Dose rate Total area covered Type of tissue Age
  • 39. Sources of Radiation 30 January 2015 39Dr Saad Wahby Al Bayatti
  • 40. Sources of Radiation • Natural background radiation - cosmic rays - gamma rays from rocks & soil 87% - ingested radioisotops in certain foods - radon decay products (granite ) • Artificial background radiation - fallout from nuclear explosions > 1% - radioactive waste • Medical and dental diagnostic radiation 12% • Occupational exposure > 1% 30 January 2015 40Dr Saad Wahby Al Bayatti
  • 41. 30 January 2015 41Dr Saad Wahby Al Bayatti
  • 42. Biologic Effects Of Ionizing Radiation Stochastic • The probability of occurrence of the change, rather than its severity, is dose dependant • All or non, the person either has the condition, or not • No threshold e.g. • Radiation induced cancer, greater exposure of population to radiation increases cancer probability, but not its severity Deterministic • The severity of response is proportional to the dose • Occur in all people when the dose is large enough • There is a dose threshold below which the response is not seen e.g. • Oral effects after radiation therapy • Radiation sickness after whole body radiation 30 January 2015 42Dr Saad Wahby Al Bayatti
  • 43. Radiation Hazards 30 January 2015 43Dr Saad Wahby Al Bayatti
  • 44. Radiation Hazards Nuclerar boms nueclear reactors leaks Whole body radiation Medical (diagnostic & theraputic) Dental X- rays Specific area radiation Radiation exposure 30 January 2015 44Dr Saad Wahby Al Bayatti
  • 45. Specific Versus Whole-Body Radiation 30 January 2015 45Dr Saad Wahby Al Bayatti
  • 46. Radiation Hazards Indirect Direct Somatic Affects individual No effect on offspring Genetic Do not affect individuial Offspring is affected Radiation damage 30 January 2015 46Dr Saad Wahby Al Bayatti
  • 47. Radiation Hazards Direct Damage RH +Radiation R + + H + + e - R + Dissociation R + X + Y Cross-linking R + + S RS 30 January 2015 47Dr Saad Wahby Al Bayatti
  • 48. Radiation Hazards Direct Damage Radiation • DNA /RNA molecule nuclear acid breakdown • Nuclear acid breakdown Somatic cells radiation induced malignancy Genetic cells radiation induced congenital abnormality 30 January 2015 48Dr Saad Wahby Al Bayatti
  • 49. Radiation Hazards (indirect damage) Water Hydrolysis • H 2 O H + + OH - • H + + H + H2 • OH - + OH - H 2 O 2 Radiation 30 January 2015 49Dr Saad Wahby Al Bayatti
  • 50. • H2O2 + DNA Molecular breakdown • H2O2 + Proteins • Molecular breakdown Cell damage Radiation Hazards (indirect damage) Water Hydrolysis 30 January 2015 50Dr Saad Wahby Al Bayatti
  • 51. Radiation Hazards Direct DNA /RNA hit Radiation induced malignancy Indirect H2O2 formation TOXIC breakdown of large molecules(protiens/DNA) Somatic Radiation damage 30 January 2015 51Dr Saad Wahby Al Bayatti
  • 52. Radiation Hazards Direct DNA/RNA hit Radiation induced congenital abnormality Indirect H2O2 formation TOXIC breakdown large molecules ( proteins/ DNA) Genetic Radiation damage 30 January 2015 52Dr Saad Wahby Al Bayatti
  • 53. 30 January 2015 53Dr Saad Wahby Al Bayatti
  • 54. 30 January 2015 54Dr Saad Wahby Al Bayatti
  • 55. Factors Affecting Radiosensitvity • Dose: the amount of radiation received. The higher the dose, the greater is the effect (consider the threshold) • Dose rate: the rate of exposure. e.g. a total dose of 5Gy can be given as - 5Gy/min (single dose) is more destructive - 5mGy/min(fractionized), less destructive, injured cells can recover • Oxygen: the higher the O2 level in irradiated cells, the greater is the damage. (H2O2 formation) • Linear Energy Transfer (LET): the rate of loss of energy from a particle as it moves in its track through matter (tissue) e.g. alpha particles vs. X-ray 30 January 2015 55Dr Saad Wahby Al Bayatti
  • 56. X- ray Protection 30 January 2015 56Dr Saad Wahby Al Bayatti
  • 57. X- ray Protection Follow ALARA , keep exposure A = As L = Low A = As R = Reasonably A = Achievable 30 January 2015 57Dr Saad Wahby Al Bayatti
  • 58. Patient Staff public X- ray protection 30 January 2015 58Dr Saad Wahby Al Bayatti
  • 59. X- ray Protection Patient • Radiographs are only taken when necessary • Number, frequency and type of radiographs is the responsibility of the dentist • Use high output DC x- ray generators • Minimum kilovoltage should be 60kV • Minimum milliamperage should be 8 mA • Minimum filtration should be 1.5 mm Al 30 January 2015 59Dr Saad Wahby Al Bayatti
  • 60. X- ray Protection Patient • Maximum Beam diameter should be 7 cm (circular beams) • Use rectangular collimation for intra oral films • Minimum target – skin distance should be 20 cm • Accurate timer • Use open- ended lead lined cylindrical cones (PID) • Do not use close ended pointed plastic cones 30 January 2015 60Dr Saad Wahby Al Bayatti
  • 61. X- ray Protection Patient • Use high speed films (D or E ) • Use film holders and beam-aiming devices • Avoid retakes, master radiographic techniques • Avoid retakes, master film processing techniques • Use lead aprons • Use thyroid collars30 January 2015 61Dr Saad Wahby Al Bayatti
  • 62. Lead Aprons 30 January 2015 62Dr Saad Wahby Al Bayatti
  • 64. Adult Patient’ s Lead apron with a thyroid collar Separate thyroid collar 30 January 2015 64Dr Saad Wahby Al Bayatti
  • 65. Child Patient’ s Lead apron with and without thyroid collar 30 January 2015 65Dr Saad Wahby Al Bayatti
  • 66. Operator’s Lead apron 30 January 2015 66Dr Saad Wahby Al Bayatti
  • 67. Proper placement of the Lead apron with a thyroid collar 30 January 2015 67Dr Saad Wahby Al Bayatti
  • 68. Correct way of hanging the Lead apron 30 January 2015 68Dr Saad Wahby Al Bayatti
  • 69. Lead apron Without a thyroid collar 30 January 2015 69Dr Saad Wahby Al Bayatti
  • 70. Correct way of hanging lead apron and thyroid collars 30 January 2015 70Dr Saad Wahby Al Bayatti
  • 71. Lead apron hangers 30 January 2015 71Dr Saad Wahby Al Bayatti
  • 72. X- ray Protection Staff • Never hold the x- ray head during exposure • Never hold the film during exposure • Never stand in the path of the primary beam • Stand behind a lead barrier (2 mm thickness) • Watch the patient through leaded glass during exposure • Stand minimum 2 M from the x-ray beam behind the patient’s head 30 January 2015 72Dr Saad Wahby Al Bayatti
  • 73. X- ray Protection Public • Warning/Informative signals to indicate hazardous x- radiation • Patients should be seated away from x- ray rooms • Patients are not allowed to wait in corridors next to x- ray rooms 30 January 2015 73Dr Saad Wahby Al Bayatti
  • 74. 30 January 2015 74Dr Saad Wahby Al Bayatti
  • 75. Open –ended cylindrical Close ended plastic 7 cm 7 cm 30 January 2015 75Dr Saad Wahby Al Bayatti
  • 76. Mobile lead barriers 30 January 2015 76Dr Saad Wahby Al Bayatti
  • 77. Open-end cylindrical coneClose-end pointed cone √X 30 January 2015 77Dr Saad Wahby Al Bayatti
  • 78. Rectangular modifications for an Open-end cylindrical cone 30 January 2015 78Dr Saad Wahby Al Bayatti
  • 79. 30 January 2015 79Dr Saad Wahby Al Bayatti
  • 80. Rectangular collimatorsCircular collimators Area of exit of the x-ray beam Area of exit of the x-ray beam Metal shield 30 January 2015 80Dr Saad Wahby Al Bayatti
  • 81. Long cylindrical Open-end cone Short cylindrical Open-end cone Long rectangular cone Short rectangular cone 30 January 2015 81Dr Saad Wahby Al Bayatti
  • 82. Patient 90-135 o o 90-135 X- ray head 90 o 90 o 180 o Operator Safe position Operator Safe position Scattered rays Scattered rays DangerDanger Safe operator’s position No barrier used 30 January 2015 82Dr Saad Wahby Al Bayatti
  • 83. Patient 90-135 o o 90-135 90 o 90 o 180 o Operator’s Safe position Operator Safe position Scattered rays Scattered rays Danger Danger Safe operator’s position No barrier used 30 January 2015 83Dr Saad Wahby Al Bayatti
  • 85. 30 January 2015 85Dr Saad Wahby Al Bayatti
  • 86. 1 M 2 M A B Source Inverse square law I 1/D Intensity of radiation at B =1/4 at A 2 30 January 2015 86Dr Saad Wahby Al Bayatti
  • 87. Inverse-square law states that the intensity (quantity) of X-ray is inversely proportional to the square of the distance from the source of radiation 30 January 2015 87Dr Saad Wahby Al Bayatti
  • 88. 2 M minimum . Operator ` Patient Danger X -ray Safe operator’s position 30 January 2015 88Dr Saad Wahby Al Bayatti
  • 89. Operator ` Lead barrier Using a lead barrier allows less than 2 M distance X- ray Patient Danger 30 January 2015 89Dr Saad Wahby Al Bayatti
  • 90. Patient Operator ` Leaded wall room Leaded glass Danger X- ray 30 January 2015 90Dr Saad Wahby Al Bayatti
  • 91. Patients’ Waiting rooms X- ray room X- ray room Restricted areas Restrictedareas Safe patients waiting rooms 30 January 2015 91Dr Saad Wahby Al Bayatti