Radiation monitoring devices are used to measure radiation exposure. Common devices include film badges, thermoluminescent dosimeters (TLD), and pocket dosimeters. Film badges use photographic film and filters to detect different types of radiation. TLDs use materials like lithium fluoride that store radiation energy and emit light when heated, allowing past exposure to be measured. Pocket dosimeters provide immediate readings of exposure levels. Together these devices help monitor radiation doses received by workers and patients to ensure safe radiation levels are not exceeded.

1. RADIATION MONITORING DEVICES

2. CONTENT
• Introduction
• Electromagnetic spectrum
• Radiation effects
• Principle of radiation protection
• Dosimetry
• Radiation monitoring devices

3. INTRODUCTION
Radiation
• The emission and propagation of energy through space or a substances in the form of
waves or particles.
Radioactivity
• The process by which certain unstable atoms or elements undergo spontaneous
disintegration or decay, in an effort to attain a more balanced nuclear state.
Ionizing radiation
• Radiation that is capable of producing ions by removing or adding an electron to an atom.

4. TYPES OF RADIATION
RADIATION
Particulate radiation
These are tiny particles of matter
that possess mass and travel in
straight lines and at high speeds.
Electromagnetic radiation
Propagation of wave like energy
through space or matter.

5. ELECTROMAGNETIC SPECTRUM
Kinetic energy: It is that
energy produced by virtue of
movement.
Potential energy: It is that
energy that a body has by
virtue of its position, e.g. a
coiled spring
Heat energy: It is the
movement of atoms and
molecules of any material.
The level of heat is indicated
by temperature.
Electrical energy: It is that
energy that is measured by
multiplying the electric
charge being moved by the
electrical force (voltage or
potential difference) against
which it has been moved

6. RADIATION
PROTECTION
• The principle of radiation
protection is to do those things
that will minimize exposure of
patient and dental personnel and
still provide benefits for the
patient from use of diagnostic
radiography.

7. PRINCIPLE OF RADIATION PROTECTION
Justification
Optimization
Dose limits
Justification: Any decision that alters the radiation
exposure situation should do more good than
harm.
Optimization of protection: the likelihood of
incurring exposures, the number of people
exposed, and the magnitude of their individual
doses should all be kept as low as reasonably
achievable(ALARA), taking into account
economic and societal factors
Application of dose limits: The total dose to any
individual from regulated sources in planned
exposure situations other than medical exposure
of patients should not exceed the appropriate
limits recommended by the Commission.
International Commission on Radiological Protection Radiological protection in medicine. ICRP Publication
105. Ann ICRP. 2007;37:1–63.

8. ALARA OR ALADA
The ALARA Principle should be followed;
I. Radiation Workers:
i. Occupationally exposed person—50 mSv (5 rem)
in any one year.
ii. Women of reproductive age and pregnancy shall
not exceed — 10 mSv (1 rem)
II. Members of the Public:
i. Annual effective dose for the public should not
exceed— 1 mSv (0.1 rem)
ii. In any one year, members of public shall not
receive an effective dose equivalent in excess of —
5 mSv (0.5 rem)

9. DOSIMETRY
• Dosimetry is the determination of the quantity of radiation exposure or dose.
• Radiation dosimetry: Deals with the measurement of the absorbed dose or dose rate resulting
from the interaction of ionizing radiation with matter and particularly in different tissues of the
body.

10. Absorbed dose Exposure
KERMA
It is the measure of the energy
absorbed by any type of ionizing
radiation per unit mass of any
type of matter.
SI unit is the Gray (Gy), was
introduced which replaced the
traditional unit Rad (radiation
absorbed dose), where 1 Gy
equals 1 joule/kg
It is a measure of radiation
quantity, the capacity of the
radiation to ionize air.
The SI unit of exposure in the
air is kerma (Kinetic Energy
Released in Matter).
Kerma–measures the kinetic
energy transferred from
photons to electrons and is
expressed in units of dose gray
(Gy), where 1 Gy equals 1
joule/kg.
Replaced the Roentgen (R), the
traditional unit of radiation
exposure measured in air

11. EQUIVALENT DOSE
• Equivalent dose (H): It is used to compare the biologic effects of
different types of radiation on a tissue or organ.
• It is the sum of the products of the absorbed dose (DT) averaged
over a tissue or organ and the radiation weighting factor (WR);
• HT = Σ WR × DT
• SI Unit is Sievert

12. EFFECTIVE DOSE
(E):
• It is used to estimate the risk
in humans.
• It is the sum of the products
of the equivalent dose to
each organ or tissue (HT)
and the tissue weighing
factor (WT)
• E = ΣΗT × WT
• The unit of effective dose is
Sievert (Sv).

13. MAXIMUM PERMISSIBLE DOSE
• Maximum Permissible Dose (MPD) is equal to 0.05 Sv/year.
• This is the equivalent that a person or specified parts of the person shall
be allowed to receive in a stated period.
• i. Average weekly exposure for either patient or operator, is 0.001 Sv.
• ii. A maximum of 13-week exposure is 0.05 Sv. Should an operator
receive more than 0.05 Sv in any 13 week period, he should avoid any
further X-ray exposure until his total for the year falls below what he
would have received at a rate of 0.05 Sv/year.
• iii. For the general public the maximum permissible dose is limited to
1/10th or 0.005 Sv/year.

15. RADIATION MONITORING DEVICES
Radiation monitoring is measuring of
the X-ray exposure of operators or
associated personnel as a protective
measure
I. Electrical -Ionization Chamber •
Thimble Chamber • Proportional
Counter • Geiger Counter
II. Chemical - Film • Chemical
Dosimeter
III. Light - Scintillation Counter •
Gerenkov Counter
IV. Thermoluminescence -
Thermoluminescent Dosimeter
V. Heat - Calorimeter

16. Ionization
chamber
Geiger-Muller counter
thimble ionization
chamber
Photomultiplier tube

17. PERSONAL MONITORING DEVICES
• A dosimeter is a very rugged form of a device called an electrometer
• Personal Monitoring devices:
• a. Pocket dosimeter
• b. Digital electronic dosimeter
• c. Film badge
• d. Thermoluminescent dosimeter

18. AIM OF
PERSONAL
MONITORING
• Monitor and control the individual dose.
• Report and investigate over exposure and
recommend necessary remedial measure, if
needed
• Maintain life time cumulative dose record

19. IDEAL MONITORING DEVICE
Instantaneous response
Distinguish between
different types of radiation
Accurately measure the dose
equivalent from all forms of
ionizing radiation with
energy from KeV-MeV
Independent of angle of
incidence
Small, light weight, rugged,
inexpensive, easy to use
Unaffected by
environmental condition
Unaffected by non ionizing
radiation

20. Personal
monitoring
device
Film badge
TLD
OSL
RPL
POCKET DOSIMETER

21. FILM BADGE
• Used to measure the individual dose from
• X rays
• Beta particle
• Gamma radiation
• Thermal neutrons
Ernest O wollan

22. CONSTRUCTION
FILM BADGE
Photographic
film
Filters
Badge holder

23. FILM BADGE
• The housing of dosimeter is of plastic or
metal.
• 50 mm square (2 in.) by 12 mm (0.5 in.) thick
and equipped with a clip for attaching to
clothing.
• It contains one or more film packets, usually
standard dental X-ray film packets.
• Filters modify the response of different areas
of the film and thereby provide more
information to correct the response to
approximate that of tissue.
• The phenomenon that X-rays blacken
photographic films is applied here

24. PHOTOGRAPHY FILM
• Photographic film is transparent plastic film base
coated one/both side with a gelatin emulsion
containing small light sensitive silver halide crystals
• Film is 4x 3 cm wrapped inside by a light tight
polythene paper cover
• There are two films in the badge one is slow and
another is fast
• Supply of film is for a period of one calendar month

25. FIRST WINDOW
Without any filter
It detects alpha particles
Due to minimum penetration power of alpha
particles no metallic filter is used

26. SECOND WINDOW
Filter made of plastic
Light white colour
It detects beta particles
Thickness of filter 1mm

27. THIRD WINDOW & FOURTH WINDOW
• Filter is made of
cadmium
• Yellow in colour
• It detects thermal
neutrons
• Thickness of filter: 1
mm
Filter is made of thin
copper
Green in colour
It detects low energy X
rays
Thickness of filter
0.15mm

28. FIFTH & SIXTH WINDOW
Fifth window
Filter is made of
thick copper
Pink in colour
Detects high
energy X-rays
Thickness of filter:
1mm
SIXTH window
Filter is made of Lead
Black in colour
It detects gamma rays
Thickness of filter: 1mm

29. WORKING
Radiation exposes the film
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

30. ADVANTAGE DISADVANTAGE
• Accuracy is only 10 to 50%, as many low energy photons
may not penetrate the film.
• Range of exposure is less.
• No immediate indication of exposure- all information is
retrospective.
• The badge is usually monitored every 2 weeks, or
sometimes in 4 weeks, in cases where it is certain that the
radiation hazard is very small.
• Badges are normally worn at the chest or waist level on
the outside of the normal working clothes, to give an
indication of the whole body exposure to which the work
is subjected
Good for measuring any type and energy of
radiation. For example, X-rays, gamma radiations.
Continuous assessment is possible.
Accumulated dose can be calculated.
Provides a permanent record of dose received.
Simple, robust and relatively inexpensive.

31. DOSIMETER
• This is used for measurements of the actual dose
received by the operator /patient as a result of
radiography or radiotherapy exposures and are
the most common type of personnel monitoring
devices used.
• Size is small and it also causes nearly the same
attenuation of the X-ray beam as does soft tissue,
the TLD can very easily be placed on the skin or in
the body cavity during exposure.
• Range 0.2mSv to 10Sv
• TLD badge can cover a wide range of dose from
10mR to 10000R with the accuracy of 10%
THERMOLUMINISCENT

32. TLD badge in India, consists of a TLD card holder cassette of
high impact plastic.
The TLD card consists of a Nickel plated aluminum plate having
3 symmetrical holes, each of diameter 12 mm, over which 3
identical CaSO4 embedded Teflon disks are dipped (13.2 mm
diameter, 0.8 mm thickness, 280 mg weight).

34. PRINCIPLE OF TLD BADGE
When the phosphor is irradiated, the X-ray energy is absorbed and secondary
electrons are produced
The secondary electrons causes holes in the filled zone by lifting the electrons to
the conduction band.
These fall back into traps in metastable states, where they are held.
When the phosphor is heated, to 200°-300°C, the trapped electron acquire
energy to escape back to the valence band
From the conduction band they fall back to fill holes in the filled zone, and when
they recombine, visible light is produced called "Thermoluminescence".

35. TLD READER
• The equipment used to heat the exposed material and
measure the emitted light is called the TLD reader.
• The reading given by this equipment is used as a measure
of the absorbed dose to which the material was subjected.
• The reader comprises of 3 main parts:
• 1. Heater.
• 2. Photomultiplier tube.
• 3. Electronic system

36. APPLICATION
Radiotherapy– for measuring doses
received by patients while actually
undergoing the treatment exposures.
Radio diagnosis– with the increasing
importance being placed on minimum
dose received during radiography. TLD is
assuming an important role.
Personnel monitoring– The ability of the
TLD material to store dose over long
periods of times makes it very suitable for
use as an alternative to photographic film
for personnel measurement.

37. Small in size and light in weight.
Chemically inert.
Almost tissue equivalent, i.e. response
similar to human tissue, as LiF has a low
atomic weight.
Usable over a wide range of radiation
qualities.
Usable over a wide range of dose values.
Read out simple and quick. Apart from
initial fading, can store dose over long
period of time.
Sensitivity independent of dose rate.
Accurate and reproducible readings.
Read out is destructive, giving no
permanant record, results cannot be
checked or reassessed.
Only limited information provided on
the type of energy of the radiation.
Dose gradients are not detectable.
Relatively expensive
ADVANTAGE
DISADVANTAGE

38. OPTICALLY STIMULATED LUMINESCENCE
DOSIMETER
• New technology that uses a LASER to trap energy from radiation fields in a tiny
crystal
• Stored energy from the radiation released from dosimeter material by optical
stimulation
• Energy release in form of luminescence.
• It is more sensitive than TLD
• Capable to detecting dose as low as 10 microSv
• Working mechanism similar to TLD except the light emission is stimulated by
LASER light
• Crystalline Aluminium oxide activated with carbon is commonly used.

39. OSL READING PROCESS

40. Advantage over the TLD, it gives instant reading
that can be repeated
Other advantages
More accurate than TLD
Large exposure range
Re-read to confirm exposure
Most expensive.
Advantage
Disadvantage

41. RPL GLASS DOSIMETER
Radiophotoluminescent glass dosimeters are accumulation type solid state dosimeters
It is based on the radiophotoluminescence phenomenon to measure the radiation dose
They are available in the shape of small glass rods
Material used is silver activated phosphate glass
When silver activated phosphate glass is exposed to radiation stable luminescence
centers are created in silver ions
Read out techniques uses pulsed ultraviolet LASER excitation
A PMT registers the orange fluorescence emitted by glass
RPL signal is not erased during the readout, thus the dosimeter can be re-analyzed
several times.

43. POCKET DOSIMETER
Pocket dosimeters are used to provide the wearer with an
immediate reading of his or her exposure to X-rays and
gamma rays. As the name implies, they are commonly
worn in the pocket

44. WORKING
• It has two electrodes which are charged through an external connection. Since they are the same
charge, they repel each other.
• As ionizing radiation passes between the electrodes and the electrically conductive case, the charge on
the electrodes is neutralized.
• When the charge reduces, an electrode moves away from the zero calibration. The magnifier displays
this motion against a scale.

45. DIGITAL ELECTRONIC DOSIMETER
• These dosimeters record dose information and dose rate.
• These dosimeters most often use Geiger-Müller counters.
• The output of the radiation detector is collected and, when a
predetermined exposure has been reached, the collected charge is
discharged to trigger an electronic counter.
• The counter then displays the accumulated exposure and dose rate in
digital form.

46. DIGITAL ELECTRONIC DOSIMETER
• Some Digital Electronic Dosimeters include an audible alarm
feature that emits an audible signal or chirp with each
recorded increment of exposure.
• Some models can also be set to provide a continuous audible
signal when a preset exposure has been reached.
• This format helps to minimize the reading errors associated
with direct reading pocket ionization chamber dosimeters and
allows the instrument to achieve a higher maximum readout
before resetting is necessary

47. DIGITAL ELECTRONIC DOSIMETER
• The electronic dosimeter is five to two hundred times more sensitive
than a TLD.
• Arrow-Tech dosimeters are rugged, precision instruments about the
size of a pocket fountain pen, which are used to measure
accumulative doses or quantities of gamma and X-ray radiation.
• A metal clip is used to attach the dosimeter to an individual's pocket
or to any available object in an area to be monitored for total
radiation exposure.
• It is pocket-size, conductive-fiber electroscope with an ion chamber
for detecting and indication integrated exposure to gamma and X-
radiation. It has a thin wall which permits the penetration and
detection of radiation.

48. REFERENCES
• Eric whites, Essentials of Dental Radiography and Radiology,5th edition;-57 pg
• Freny Karjodhkar, Essentials of oral and maxillofacial radiology, 2nd edition; 75-79.
• Allan B. Reskin. Advances in Oral Radiology. PSG Publishing Co. 1980.
• Barr JH, Stephens RG. Radiological Health. In Dental radiology. Pertinent Basic Concepts and their
Applications in Clinical Practise. Philadelphia, WB Saunders 1980;66- 80.
• Baumann M, Saunders M, Joiner MC. Modified Fractionation in Basic Clinical Radiobiology. Ed. Steel GG
2002;147.
• Bushong SC. Radiologic Science for Technologist, Physics, Biology and Protection, 7th ed, St. Louis, Mosby
2001.
• Dowd SB, Tilson ER. Practical Radiation Protection and Applied Radiology, 2nd ed, Philadelphia, WB
Saunder 1999.
• Frommer HH. Biological effects of radiation, In Radiology for dental auxiliaries, 6th edition St. Louis, Mosby-
year book, 1996;49-67.