Dosimetry is the measurement of radiation absorbed by the body. It has developed historically since the 1920s with definitions of units like the rad and gray. Various dosimeters exist like film badges, TLDs, and pocket ionization chambers to measure exposure, absorbed dose, or equivalent dose. Properties of dosimeters include accuracy and precision. Dosimetry is important for radiation protection of occupational workers.

2. 
SUBMITTED BY :
Patel Nilesh J.
M.sc Agri.
3rd Sem.
Dept. Of Genetics and
Plant Breeding
C.P COLLEGE OF
AGRICULTURE
SUBMITTED TO :
Dr. M.P.Patel
Professor & Head
Dept. Of Genetics and
Plant Breeding
C.P COLLEGE OF
AGRICULTURE

3. 
 Dosimetry in its original sense is the measurement of
the absorbed dose delivered by ionizing radiation,
the term is better known as scientific radiation.
 The term is better known as scientific sub-speciality
in the fields of health physics and medical physics,
where it is the calculation and assessment of the
radiation dose received by the human body.
Dosimetry

4.  1925:- First International congress for Radiology in
london . Foundation on ICRU “ International
commission on Radiation units and measurement”
 1928:- Second International congress for Radiology in
stock holm. Defination of the unit Roentgen to identify
the intensity of radiation by the number of ion pairs
formed in air.
 1950:- Defination of the dosimetric quantity absorbed
dose as absorbed energy per mass.
 The rad is the special unit of absorbed dose.
1 rad = 0.01 J/kg
Historical Development of
Dosimetry

5. 
 1975:- Defination of the new SI unit of dose the Gray
(Gy) for the quantity absorbed dose
1Gy = 1 J/kg = 100 rad

6.  Dosimeters is a device that measures directly or indirectly
 Exposure
 Kerma
 Absorbed dose
 Equivalent dose
The dosimeter along with its reader is referred to as a
dosimetry systems
Object of Dosimeters

7. 
 Immediate Read
 Pocket Ionization Chambers, Solid state detectors, handheld
GM/Ionization detectors with dose accumulation function
 Delayed read / Personnel monitors
 Film Badges, TLD (Thermo Luminescent Dosimeters), OSL
(Optically Stimulated Light-emitting Dosimeters)
Types of Dosimeters

8.  Most common type of radiation
dosimeter used.
 Works by darkening of x-ray film in
proportion to radiation absorbed.
 Cheap
 Not durable
 Short monitoring period per badge
(6 months or less)
Film Badges

9.  “Captures” radiation dose information
in a crystal matrix
 Releases light when heated, light
intensity proportional to radiation
dose absorbed
 Durable
 Can be expensive (reusable chips)
 Information destroyed when processed
TLD (thermoluminescent dosimeter)

10. 
OSL(Optically stimulated luminescence)
“Captures” information in an
Aluminum Oxide matrix
Releases information by laser
stimulation
Can be reread after processing
Durable
Landauer Only

11.  Electro-statically charged “leaf”
discharges as it is exposed to ionizing
radiation
 Not considered a “legal” record
 Low accuracy (+/- 20%)
 Physical impacts can affect radiation
dose readings
Pocket Ionization

12. 
 Provides instantaneous information
regarding dose accumulation
 Simple to use
 Not a “legal” record
 Dose range device dependent
Solid State

13. 
 Ability to perform both dose rate
and dose accumulation
 Good for spot checks
 Direction dependent
 Not considered a “legal” personnel
dose record
Handheld Radiation Detectors

14. 
 Accuracy:- Specifies the proximity of the mean value
of a measurement to the true value
 Precision :- Specifies the degree of reproducibility of
a measurement.
Note:- High Precision is equivalent to small standard
deviation.
Properties of Dosimeters

15. 
 Dosimetry is used extensively for radiation
protection and applied to occupational radiation
workers, where a radiation dose is expected but
regulatory levels must not be exceeded.

16. 
 The mutation rate is the frequency with which a gene
changes from the wild type to a mutant. It is
commonly expressed as the number of mutations per
biological unit,
 which may mean per cell division per gamete, or per
round of replication.
Factor influencing mutation dose
rate

17. 
 The mutation rate depends on the frequency of
primary changes in DNA. These primary changes
may arise from spontaneous molecular changes in
the DNA, or be induced by chemical or physical
agents in the environment.
Factor 1: Frequency of Primary Changes in
DNA

18. 
 The second influential factor is the probability that, when
a change in DNA takes place, it will be repaired.
 Most cells posses a number of mechanisms to repair
changes in DNA, so most alterations are repaired before
they are replicated.
 If these repair systems are effective, mutation rates will be
low. If they are faulty, mutation rates will be increased.
There are even mutation that increase the overall
mutation rate for other genes. Such mutations usually
occur in genes that encode components of the repair
mechanisms or repair enzymes.
Factor 2: Probability of Repair

19. 
Factor 3: Probability of Recognition
 The third factor is one that influences the ability to
calculate mutation rates. It is the probability that a
mutation is recognized and recorded. When DNA is
sequenced, all mutations are potentially detectable.
 In practice, however, sequencing is still quite
expensive, so most mutations are detected by their
phenotypic effects. Some mutations may appear more
likely to take place simply because they are easier to
detect.

20.  In many studies, frequencies of two-break
chromosomal aberrations were found to be
proportional to square of the dose of radiation.
Chromosome breakage and resulting structural
aberrations are generally regarded as associated with
gene mutations. Effects of irradiation are cumulative.
Therefore prolonged irradiation at low intensities is
known as chronic irradiation. It take long time.
 Produce the same amount of mutations as that
produced by the same dose of irradiation delivered in a
short period at a high intensity is known as acute
irradiation.
Acute and chronic irradiation

21. 
 0-25 : No observable effect.
 25-5 : Minor temporary blood changes.
 50-100 : Possible nausea and vomiting and reduced
WBC.
 150-300 : Increased severity of above and diarrhea,
malaise, loss of appetite.
 300-500 : Increased severity of above and
hemorrhaging, depilation. Death may occur
 > 500 : Symptoms appear immediately, then death
has to occur.
ACUTE DOSE(RAD) EFFECT

22.  These are densely ionizing and highly penetrating
particles.
 Since they are electrically neutral particles, their
action is not slowed down by charged (negative or
positive) particles of tissues.
 They are generated from radioactive decay of
heavier elements in atomic reactors or cyclotrons.
Because of high velocity , these particles also called
fast neutrons.
 Their velocity can be reduced by the use of graphite
or heavy water to produce thermal neutrons.
Thermal Neutrons

23. 
 Thermal neutron result in both chromosomal
breakage and gene mutation.
 Since they are heavy particles, they move in straight
line.
 Effectively used for induction of mutations especially
in asexually reproducing crop species.

24. 
 Neutron radiation is often called indirectly ionizing radiation.
 It does not ionize atoms in the same way that charged particles
such as protons and electrons do (exciting an electron), because
neutrons have no charge. However, neutron interactions are
largely ionizing, for example when neutron absorption results
in gamma emission and the gamma ray (photon) subsequently
removes an electron from an atom, or a nucleus recoiling from a
neutron interaction is ionized and causes more traditional
subsequent ionization in other atoms. Because neutrons are
uncharged, they are more penetrating than alpha
radiation or beta radiation.

25. 
 In some cases they are more penetrating
than gamma radiation, which is depended in
materials of high atomic number. In materials of
low atomic number such as hydrogen, a low energy
gamma ray may be more penetrating than a high
energy neutron