RADIATION PROTECTION AND BIOLOGY FINAL pdf.pdf

RADIATION PROTECTION

1. RADIATION PROTECTION AND
BIOLOGY
Chairperson: Dr. Pradeep Patil
Co-Chairperson: Dr V VHattiholi
Presenter: Dr. Harshita
Date: 12.08.2024

2. CONTENTS
BASIC MEASUREMENT UNITS
RADIATION MONITERING
DEVICES
RADIATION HEALTH EFFECTS
RADIATION PROTECTION
RADIATION AND PREGNANCY

3. As per,
The International commission of Radiation protection (ICRP)
An independent, international organization that advances for the public benefit the science of
radiological protection, in particular by providing recommendations and guidance on all
aspects of protection against ionizing radiation.

4. MEASUREMENTS
RADIATION UNITS

5. EXPOSURE
Roentgen(R) -unit of radiation exposure
1 R = 2.58 ×10
–4
C/kg of air
DEFINITION: Electrical charge produced by ionization created by the incident
X rays (radiations) in unit mass of air

6. ABSORBED DOSE
SI unit: Gray(Gy) = 1 joule/kg
Conventional Unit : rad (Radiation absorbed dose)
1 Gy= 100 rads
WHY DO WE NEED THIS?
It is a measurable physical quantity.
DEFINITION : Amount of energy deposited by interacting ionization radiation
with unit mass of matter

7. DOSE EQUIVALENT
Measurement of biological impact of radiation on person receiving
occupational or environmental exposures
Dose equivalent (Sv) = Absorbed dose (Gy) x radiation weighting factor(WR)
Rem= RADS x WR
SI unit: Sievert (Sv)
Conventional unit: rem (roentgen equivalent man)
1 Sv= 100 rem
BUT, NOT ALL TYPES OF RADIATIONS PRODUCE SAME EFFECT EVEN IF ABSORBED DOSE IS EQUAL.
TYPE OF
RADIATION
RADIATION
WEIGHTING
FACTOR
XRAY, GAMMA
RAYS, BETA
PARTICLES,
ELECTRONS
1
PROTONS 5
NEUTRONS 5-20
ALPHA PARTICLES
20

8. EFFECTIVE DOSE EQUIVALENT
BUT, NOT ALL THE BODY TISSUES HAVE SAME RADIOSENSITIVITY EVEN FOR THE SAME EQUIVALENT DOSE
Weighting factor (w
T):
•Different areas and organs are
assigned tissue weighting factor (w
T)
values.
•Represents the risk of radiation
exposure to that tissue with respect
to whole body radiation exposure
TISSUE
TISSUE
WEIGHTING
FACTOR
BONE MARROW,
COLON, LUNG,
BREAST, STOMACH
0.12
GONADS 0.08
BLADDER, LIVER,
ESOPHAGUS,
THYROID
0.04
SKIN, BONE
SURFACE, BRAIN,
SALIVARY GLANDS
0.01
PURPOSE: to relate exposure to risk

9. For a specific organ or body area, the effective dose equivalent is:
Effective Dose Equivalent (Sv) = Dose Equivalent (Sv) ×Wt
SI unit: Sievert (Sv)
Conventional unit: rem (roentgen equivalent man)
1 Sv= 100 rem
If >1 area has been exposed:
Total body effective dose = sum of the effective doses for each exposed area

11. RADIATION MONITERING
DEVICES

12. Dosimetry: is the determination of quantity of radiation exposure or dose to
the individuals exposed during their course of work and the radiation
measuring devices are called dosimeters
Purpose:
To monitor and control individual dose
Report and investigate over exposure
Maintain lifetime cumulative dose record

13. PERSONAL MONITERING DEVICES
Thermoluminescenc
e dosimeter
Optically
stimulated
luminescence
Film batch
Digital electronic
dosimeter
Pocket
dosimeter

14. THERMOLUMINESCENT DOSIMETER
•Thermoluminescence: Emission of light by a thermally stimulated crystal
following irradiation.
•Measures 100mSv to 10 Sv

15. PARTS OF TLD
TLD CASETTE TLD CARD

16. TLD CASETTE
Card holder
Made up of impact
plastic
Contains 3 filters:
1.Metal filter
2.Plastic filter
3.Open filter
1.Metal filter: contains
aluminium and
copper of thickness
1mm each
2. Plastic filter: thick
plastic filter of
thickness 1.5 mm
3. Open filter

17. TLD CARD
Contains 3 CaSO4: Dy-
Teflon TLD discs
mechanically clipped
over 3 symmetrical
circles on a nickel
plated aluminium plate
V Cut Disk Al
plate

18. WORKING OF TLD BADGE
DISC 1-Sandwiched between a pair of filter combination of 1.0 mm thick Al and
1.0 mm thick Cu
Measures x rays and gamma rays
DISC 2-Sandwiched between a pair of 1.5 mm thick plastic filters
Measures beta rays, x rays and gamma rays
DISC 3-placed under the circular open window
Measures all types of radiations

19. WORKING OF TLD BADGE
Step 1: TLD exposed to ionizing radiation interact with the phosphor
crystal and deposits its incident energy.
After absorbing incident energy, some atoms get ionized producing
free electrons
These electrons gets trapped in the crystal itself
TLD cards are changed every monitoring period
TLD badges are then sent to laboratory for dose assessment

20. HOW IS RADIATION CALCULATED
Step 2 (READING): Badge is heated uptospecific
temperature in TLD reader
On heating the crystal vibrates the crystal
releasing the trapped electrons
On returning to the ground state, these electrons
produce energy which is emitted as light
Light is recorded by the Photo-emitter tube
Emitted light is read on the “glow curve chart”

22. WHY TLD BATCH?
ADVANTAGESover other personnel monitors
•Sensitivity to low dose
•It is reusable
DISADVANTAGES
•No permanent record or re readability
•Immediate readout is not possible

23. WEARING THE DOSIMETER
During Radiography
During radiography (when no protective lead apron is worn), the personnel dosimeter is
worn at one of two regions:
1.On the trunk of the body at the level of the waist.
2.On the upper chest region at the level of the collar area.
At these positions, the dosimeter readings represent an estimate of exposure at two different
levels, i.e.
•the whole body exposure = trunk level badge
•exposures dose to internal organs like thyroid = collar level badge

24. During Fluoroscopy:

25. STORAGE OF TLD BADGE
Personnel TLD badges to be stored when not working with radiation
Badge must not be left in an area where it could receive a radiation exposure when not
worn by the individual (e.g. On a lab coat or left near a radiation source)
Lost or damaged badges should be reported immediately to the radiation safety officer
and a replacement badge will be issued

26. OPTICALLY STIMULATED LUMINESCENCE DOSIMETER
OSL uses Aluminium oxide (Al2O3) as the radiation
detector.
Working mechanism similar to TLD except the light
emission is stimulated by LASER light i.eoptical
stimulation
OSL has advantages over TLD, especially as applied to
occupational radiation monitoring.
•OSL is more sensitive than TLD
•Other features of OSL include reanalysis for confirmation
of dose, and excellent long-term stability

27. FILM BATCH
PARTS
Batch holder
Photographic
film
Filters

28. FIRST WINDOW
•Without anyfilter
•detects alpha
particles
•Due to minimum
penetration power of
alpha particles no
metallic filter is used
SECOND WINDOW
•Madeof plastic , Thickness
1mm
•Light white color
•Detects beta particles
THIRD WINDOW
•Made of cadmium, Thickness
1mm
• Yellow in color
• detects thermal neutrons
FOURTH WINDOW
•Madeof thin copper , Thickness
0.15mm
•Green color
•Detects low energy X rays
FIFTH WINDOW
•Madeof thick copper ,
Thickness 1mm
•Pink color
•Detects high energy X-rays
SIXTH WINDOW
•Madeof lead , Thickness
1mm
•Black color
•Detects gamma rays

29. Radiation exposes thefilm and cause formation of
latent image
Latent image has regions of different density
under the different filters due to their different
penetration power
After each month it is returned to agency where
film is processed and optical density under
different filters are measured by densitometer
WORKING:

30. POCKET DOSIMETER
Worn in pocket
Provides with an immediate reading of exposure
Consists of an ionisation chamber with
Eyepiece
Transparent scale
Hollow charging rod
Movable fibre
ADVANTAGES DISADVANTAGES
Accurate Limited range (upto
2mSv)
Immediate reading Expensive
Easily damaged

31. POCKET DOSIMETER
WORKING:
•Has two electrodes which are charged through an external connection.
Since they are same charge, they repel each other
•As ionizing radiation pass between the electrodes and the electrically
conductive case, the charge on electrode is neutralized
•When the charge reduces, an electrode moves away from the zero
calibration. The magnifier displays the motion against the scale

32. ELECTRONIC DOSIMETER
•Direct reading dosimeter
•Contains 3 silicon diode detectors. Each detector feeds a
chain of dedicated amplifiers and counter circuits to
measure soft gamma rays, hard gamma rays and beta
rays
•Can provide immediate reading
•Sensitivity: 50-200x TLD
•Can be reset by user without deleting permanent record
DISADVANTAGES:
Higher cost
Battery to be renewed every year

33. WHY DO WE NEED PROTECTION?

34. RADIOSENSITIVITY
RADIOSENSITIVITY = Probability of a
cell, tissue or organ of suffering an
effect per unit of dose.
The law states that the radiosensitivity
of living tissue varies with maturation
and metabolism
Stem cells are radiosensitive;
mature cells are radioresistant.
Younger tissues and organs are
radiosensitive.
Tissues with high metabolic
activity, high proliferation rate are
radiosensitive.
Law of Bergonieand Tribondeau

35. RADIATION HEALTH EFFECTS
TYPES OF EFFECTS
CELL DEATH
CELL
TRANSFORMATION
GENETIC EFFECT

36. TYPES OF EFFECTS
CELL DEATH
CELL
TRANSFORMATION
GENETIC EFFECT
STOCHASTIC
EFFECTS
DETERMINISTIC
EFFECTS

37. DETERMINISTIC EFFECTS STOCHASTIC EEFECTS
Also referred to as harmful tissue reactionsThese include the cancer and heritable effects
Appear as an early response (within few days-
weeks)
Appear as a late radiation response years later
Non linear threshold dose-response relationship Linear non-threshold dose-response relationship

38. Usually follow high-dose radiation exposure. Do
not occur below a threshold dose.
Usually follow low radiation exposure
Severity of response increases with radiation dose
Increased radiation dose : Increased Incidence, Not
severity!
No deterministic effects would be expected
below anabsorbed doseof 100 mGy (above
thenatural background exposure), and thresholds
for most effects are much higher.
Because of this, deterministic effects are rare,
although they can occur as a result of accidents.
There is reliable scientific evidence
thatdosesabove 100 mSv can increase the risk of
cancer.
Below this dose the evidence is less clear, but for
purposes of radiological protection it is assumed
that even small doses might result in small
increased risk.
In extremely rare cases, such as in severe
accidents, very high doses received in a very
short time can lead to acute radiation syndrome
and even death.
An extraeffective doseof 200 mSv increases the
risk of fatal cancer from the typical worldwide
average of about 25% to about 26%.

39. DETERMINISTIC EFFECTS
ACUTE RADIATION
SYNDROME
LOCAL TISSUE DAMAGE

40. Acute Radiation Syndrome
The sequence of events that follow high-level radiation total body exposure leading to death
within days or weeks is called the acute radiation syndrome.
3 separate syndromes that are dose related and follow distinct course of clinical
responses
Hematologic Death GI Death CNS Death

41. Acute Radiation Syndrome

42. Local Tissue Damage
When only part of the body is irradiated, in contrast to whole-body irradiation, a higher dose
is required to produce a response
The effect is cell death, which results in shrinkage of the organ or tissue. This effect can lead
to total lack of function for that organ or tissue, or it can be followed by recovery
oSkin effects
oGonad effects
oHematologic effects
oLens of eye

43. •Skin:the basal epidermis is the most radiosensitive and the first direct effect is
erythema,. These are levels which can be encountered in the medical environment in
areas such as radiotherapy and fluoroscopic procedures in interventional radiology.
•Lens of the eye is also sensitive to radiation exposures, and coagulation of proteins
within the lens. This causes opacities within the lens, which are cumulative, and over
time can lead to vision impairment due to cataracts

44. Effects on Gonads
oOvaries: The most radiosensitive cell during female germ cell development is the oocyte in
the mature follicle.
oIrradiation of the ovaries early in life reduces their size (atrophy) through germ cell death.
After puberty, such irradiation also causes suppression and delay of menstruation.
oThe spermatogonia stem cells signify the most sensitive phase in the gametogenesis of the
spermatozoa.
oAfter irradiation of the testes, maturing cells, spermatocytes, and spermatids are relatively
radioresistant and continue to mature.

45. Hematologic effects
•The principal response of
the hemopoietic system
to radiation exposure is a
decrease in the numbers
of all types of blood cells
in the circulating
peripheral blood. Lethal
injury to the stem cells
causes depletion of
these mature circulating
cells.

46. Radiation Induced Malignancy
•Various malignancies: Thyroid, Bone, Skin, Breast, Lung, Liver (Thorotrast)
•The overall absolute risk for induction of malignancy is approximately 8 cases/100 Sv, with the
at-risk period extending for 20 to 25 years after exposure.
STOCHASTIC EFFECTS

47. SO…WE NEED RADIATION
PROTECTION

48. OBJECTIVES OF RADIATION
PROTECTION:
Prevention of deterministic effects
Limiting the probability of stochastic effects

49. PRICIPALS OF RADIATION PROTECTION
JUSTIFICATION OPTIMIZATION
DOSE
LIMITATION

50. JUSTIFICATION
Practice that entails exposure to radiation should only be adopted if its yields
sufficient benefit to the exposed individuals or to the society to outweigh the
radiation detriment it causes or could cause

51. OPTIMIZATION AND ALARA
Protection should be optimized in relation to
Magnitude of exposure
likelihood of exposures
the numbers of individuals exposed
For all social and economic strata of patients

52. As
Low
As
Reasonably
Achievable
(THE ALARA PRINCIPLE)
Optimization of protection can be achieved by optimizing the procedure to
administer the dose of radiation which is
So as to derive maximum diagnostic information with minimum discomfort to
the patient

53. DOSE LIMITATION
There is no absolute evidence of a threshold below which no damage
occurs.
“The totaldoseto any individual should not exceed the appropriatelimits”

54. •Limits oneffective dose, combined with optimization of protection, are designed to avoid a risk
ofstochastic effects.
•Limits onequivalent doseto an organ, combined with optimization of protection, are designed
to prevent the occurrence ofdeterministic effects.

55. MAXIMUM PERMISSIBLE DOSE
Maximum dose of ionizing radiation which an individual may accumulate over
a long period of time with a negligible risk of significant body or genetic
damage
The newer recommendation is MPD = Age in years ×1 rem,
i.e. the individual effective dose for a lifetime should not exceed the value of
his/her age.

56. APPLICATIONS OF PRINCIPLES

57. CARDINAL PRINCIPLES OF RADIATION PROTECTION
TIME DISTANCE SHIELDING

58. MINIMIZE TIME
•During radiography and fluoroscopy , the time of exposure is kept to a
minimum.
•The use of pulse-progressive fluoroscopy can reduce patient dose
considerably.

59. Maximise distance
•Distance between the source of radiation and the exposed individual
•The exposure to the individual decreases inversely as the square of the
distance (inverse square law) which is stated mathematically as:
I = intensity of radiation
d = distance between the radiation source and the exposed individual.
•In radiography, the radiologic technologist is positioned behind a
protective barrier.

60. USE OF SHIELDING
•Positioning shielding between the radiation source and exposed persons
greatly reduces the level of radiation exposure.
•Shielding used in diagnostic radiology usually consists of lead.
X-RAY TUBE
HOUSING
ROOM
SHIELDING
PERSONNEL
SHIELDING
PATIENT
SHIELDING
SHIELDING

61. XRAY TUBE SHIELDING
Every x-ray tube must be contained within protective
housing made up of thin sheets of lead that reduces
leakage radiation during use.
AERB recommends maximum allowable leakage
radiation from tube housing of not more then
10mSv/hr/100cm sq.

62. ROOM SHIELDING (STRUCTURAL SHIELDING)
Lead lined walls are referred to as protective barriers.
PROTECTIVE BARRIERS
a)A. Primary barrier:
One which is directly struck by the
primary or the useful beam
B. Secondary barrier:
One which is exposed to secondary
radiation either by leakage from x-
ray tube or by scattered radiation
from the patient.

63. A. PRIMARY BARRIERS
•First task: evaluate the exposure to the
area
•Exposure calculations depend on 5 factors:
Workload, E’(R/mA.minat a distance of 1
m), Use Factor, Occupancy factor, Distance
•Once the exposure is known,
TO CALCULATE BARRIER THICKNESS-we can use
HVL or precalculated tables to determine the
barrier requirements

64. HVL : Half value layer
•Thickness of a specific substance that when introduced into the path of the beam of
irradiation reduces the exposure rate by one half
•Barrier thickness: repetitively halving the exposure until it reaches a permissible level, and then
multiplying the number of halves times the HVL of the beam.
Precalculated Shielding Requirements Tables
•Inverse square effect and barrier
thicknesses are precalculated
•Effective workload (mA.min/week)
can be calculated by multiplying
the actual workload (W) by the use
factor (U) and occupancy factor (T)
•Knowing the kVpand distance, the
table indicates the primary and
secondary barrier requirements

65. B. SECONDARY BARRIERS
PROTECTION FROM SCATTER RADIATION
•Secondary barrier calculations are less precise
•Two assumptions are made:
1. Energy of scatter radiation is assumed equal to the
primary radiation
2. Intensity of the 90 degree scatter radiation is
reduced by a factor of 1000 at a distance of 1 m for a
field size of 400 cm
2
•Exposures are reduced to permissible levels by
one of the two previously described methods
(HVLs or Precalculated tables)

67. PROTECTION FROM LEAKAGE RADIATION
•Leakage radiation is the radiation that passes through the lead shielding in the tube
housing when the beam is turned on.
•Maximum permissible leakage exposure 1 m from the diagnostic x ray tube is 0.1 R/hour
with the tube operating at its maximum kVpand mA without overheating.
•The customary method for reducing the leakage exposures to permissible levels is HVLs of
barrier
•Leakage radiation is already heavily filtered by lead in the tube housing, so half value
method is quite accurate

68. PERSONNEL SHIELDING
Personnel should remain in the radiation environment only when
necessary
Shielding apparels:
1.lead aprons
2.Lead gloves
3.Thyroid shields
4.Eye glasses with side shield
It is recommended that thickness of lead in the protective apparel
should be 0.5 mm which attenuates >90% of the radiations

69. LEAD APRONS
Lead aprons protect an individual only from secondary (scattered) radiation, not the primary beam .

70. Other protective apparel

71. CARE OF THE LEAD APRON
It is imperative that lead aprons are not abused, such as by –dropping them on the
floor –piling them in a heap –improperly draping them over the back of a chair.
Because all of these actions can cause internal fracturing of the lead, they may
compromise the apron’s protective ability.
When not in use –all protective apparel should be hung on properly designed racks.
Protective apparel also should be radiographed for defects such as internal cracks
and tears at least once a year

72. PATIENT SHIELDING
Most radiology departments shield the worker and the attendant,
paying little attention to the radiation protection of the patient.
It has been recommended that the thyroid and gonads be shielded,
to protect these organs especially in children and young adults

73. Gonad shielding:
Gonad shielding should be considered for all patients, especially children and
those who are potentially reproductive.
As an administrative procedure, this would include all patients younger than 40
years of age and perhaps even older men.
Gonad shielding should be used when the gonads lie in or near the useful beam.

74. RADIATION & PREGNANCY

75. •It is important for radiology facilities to have procedures to determine the pregnancy status of
female patients of reproductive age before any radiological procedure that could result in a
significant dose to the embryo or fetus
10 DAY RULE states
•Whenever possible, one should confine the radiological examination of the lower abdomen
and pelvis to the 10-day interval following the onset of menstruation
•Since organogenesis starts 3 to 5 weeks post-conception, it was felt that radiation exposure in
early pregnancy couldn't result in malformation.

76. RADIATION & PREGNANCY
•Based on this, it was suggested to replace10-day rule with a 28-day rule
28 DAY RULE
•Radiological examination, if justified, can be carried throughout the cycle until a period is
missed
•If there is a missed period, a female should be considered pregnant unless proved otherwise

77. RADIATION & PREGNANCY
EFFECT OF RADIATION ON PREGNANCY
•Factors affecting foetal risk:
Dose
Stage of gestation
Pre implantation-Day 1-10
Organogenesis-Week 3-7
Foetal growth-Week 8-Birth

78. RADIATION & PREGNANCY
Pre implantation-All or Nothing response; Radiation induced abortion/Pregnancy is
carried with no ill effects
Organogenesis-Maximum risk in this period
Dose >100 mGy leads to significant malformations or death
Foetal period-Most sensitive is CNS (between 8-25 weeks)
Foetal doses-> 100 mGy low IQ
> 1000 mGysevere mental retardation (8-17 weeks > 18-25 weeks)

79. RADIATION & PREGNANCY
RADIATION INDUCED LEUKEMIA AND CANCER
•Throughout most of pregnancy, the embryo/foetus is assumed to be at about
the same risk for carcinogenic effects as children
•The relative risk may be as high as 1.4 (40% increase over normal incidence)
due to a foetal dose of 10 mGy

80. RADIATION & PREGNANCY
RADIO-DIAGNOSIS FOR PREGNANT PATIENTS
•If possible, procedure should be performed after 12 weeks (major organogenesis
completed)
•If absolutely necessary to perform an examination, dose optimisation to be carried
by:
Use of lead barriers
TLDs placed on mother’s abdomen will estimate abdomen surface dose -> fetaldose is
assumed to be 50% of that

81. RADIATION & PREGNANCY
WHAT IF PREGNANT FEMALE ESCAPES DETECTION AND IS IRRADIATED?
•STEP 1-estimate the foetal dose using preliminary review of examination technique
used
•The dose to foetus is assumed to be the effective dose to the uterus which can be calculated
using tissue weighting factor of 0.5
If the dose irradiated is >10 mGy, more complete dosimetric evaluation is conducted
•STEP 2-Determine the stage of gestation at which exposure occurred

82. RADIATION & PREGNANCY
RECOMMENDATIONS:
<100 mGy-Therapeutic abortion is not indicated
> 500 mGy-there can be significant foetal damage, the magnitude and type of
which is a function of dose and stage of pregnancy
100-500 mGy-decisions should be based upon individual circumstances

83. RADIATION & PREGNANCY
DOSE
EXAMINATION
Mean (mGy)Maximum (mGy)
Abdomen 1.4 4.2
Chest <0.01 <0.01
Intravenous uro-
gram; lumbar spine
1.7 10
Pelvis 1.1 4
Skull;
thoracic spine
<0.01 <0.01
APPROXIMATE FETAL DOSES FROM CONVENTIONAL X -RAY EXAMINATIONS

84. RADIATION & PREGNANCY
DOSE
EXAMINATION
Mean (mGy)Maximum (mGy)
Barium meal (UGI) 1.1 5.8
Barium enema 6.8 24
Head CT <0.005 <0.005
Chest CT 0.06 1.0
Abdomen CT 8.0 49
Pelvis CT 25 80
APPROXIMATE FETAL DOSES FROM FLUOROSCOPIC AND COMPUTED TOMOGRAPHY
PROCEDURES

85. ICRP STATES
Foetal doses of 100 mGy are not reached even with 3 pelvic CT scans or 20
conventional diagnostic x-ray examinations
THUS RADIATION DOSES FROM MOST OF RADIODIAGNOSIS PRESENTS WITH NO
SUBSTANTIAL RISK TO FETUS

86. REFERENCES
Radiologic Science for technologists (10
th
edition) by Stewart Bushong.
Farr’s physics for medical imaging
Christensen’s physics of diagnostic radiology-4
th
edition.
Annals of the ICRP PUBLICATION 103

87. THANK YOU