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General requirements for dosimeters
#Dosimeter is a device that measures directly
• Absorbed dose
• Equivalent dose
• Or other related quantities.
#The dosimeter along with its reader is
referred to as a
A useful dosimeter exhibits the following
• High accuracy and precision
• Linearity of signal with dose over a wide
• Small dose and dose rate dependence
• Flat Energy response
• Small directional dependence
• High spatial resolution
• Large dynamic range
Accuracy specifies the proximity of the mean
value of a measurement to the true value.
Precision specifies the degree of
reproducibility of a measurement.
is equivalent to small standard deviation.
Examples for use of precision and accuracy:
High precision High precision Low precision Low precision
and and and and
High accuracy Low accuracy High accuracy Low accuracy
Note: The accuracy and precision associated
with a measurement is often expressed in
terms of its uncertainty.
New Concept by the International Organization
for Standardization (ISO) "Guide to the
expression of uncertainty in measurement“
This new guide serves as a clear procedure
for characterizing the quality of a
It is easily understood and generally
It defines uncertainty as a quantifiable
Standard uncertainty: is the uncertainty of a
result expressed as standard deviation.
Type A standard uncertainty is evaluated by
statistical analysis of a series of observations.
Type B standard uncertainty is evaluated by
means other than statistical analysis. This
classification is for convenience of discussion
It is not meant to indicate that there is a
difference in the nature of
the uncertainty such as random or systematic.
The determination of the final result is normally
based on several components.
The dosimeter reading should be linearly
proportional to the dosimetric quantity.
Beyond a certain range, usually a non-linearity sets
This effect depends on the type of dosimeter.
Two possible cases
Dose rate dependence :
M/D may be called the response of a dosimeter
When an integrated response is measured, the
dosimetric quantity should be independent of the
dose rate dD/dt of the quantity.
The response M/D should be constant for different
dose rates (dD/dt)1 and (dD/dt)
2. M = (M / D)(dD / dt)dt
M = (M / D) (dD / dt)dt
Energy: The response of a dosimetric system
generally a function of the radiation energy.
The term "radiation quality" is often used to
express a specific distribution of the energy
Therefore, a dependence on energy can also
be called a dependence on radiation quality.
Since calibration is done at a specified beam
quality, a reading should generally be
corrected if the user's beam quality is not
identical to the calibration beam quality.
A small radiation monitoring device worn by persons
entering environments that may contain radiation .
# Desirable characteristics
Should be lightweight, durable, and reliable
Should be inexpensive
Healthcare or laboratory workers in non-
emergency environments that may contain
Examples: radiology, nuclear medicine, and
radiation oncology department staff
Workers in emergency environments that
may contain radiation
Examples: first responders and first receivers
Workers in industrial environments where
radiation is used
Examples: nuclear power plant workers or
employees at radiation sterilizing facilities
Flat badges are usually worn on the torso, at the
collar or chest level, but can be worn on the
belt, or forearm
Ring shaped badges can be worn on the finger
when dose to the finger may exceed dose to the
badge worn elsewhere on the body
First responders and first receivers
Wear water-resistant personal dosimeters on the
outer layer of personal protective equipment (PPE).
Should be able to easily see and hear a dosimeter
alarm while wearing PPE
May wear a personal dosimeter underneath
Most widely used and most economical
Consists of three parts:
Plastic film holder
Can read x, gamma, and beta radiation
Accurate from 10mrem - 500rem
Developed and read by densitometer
A certain density value equals a certain level of radiation
Read with a control badge
Results generally sent as a printout
Permanent legal record
Can differentiate between
scatter and primary beam
Can discriminate between
x, gamma, and beta
Can indicate direction from
where radiation came from
Control badge can indicate
if exposed in transit
Only records exposure
where it’s worn
Not effective if not worn
Can be affected by heat
Sensitivity is decreased
above and below 50 keV
Exposure cannot be
determined on day of
Accuracy limited to + or -
The most sensitive personnel dosimeter
Can only be read once
Detects gamma or x-radiation
easy to use
Readings can be
Must be read each
false readout if
dropped or jarred
Looks like a film badge
Contains a lithium fluoride crystal
Responds to radiation similarly to skin
Measured by a TLD analyzer
Crystal will luminescence if exposed to
radiation, then heated
More accurate than a film badge
in TLD interact
radiation as tissue
The initial cost is
greater than that
of a film badge
Can only be read
only where worn
• “Captures” information in an Aluminum
• Releases information by laser stimulation
• Can be reread after processing
• Landauer Only
Provides instantaneous information
regarding dose accumulation
Simple to use
Not a “legal” record
Dose range device dependent