AN EXTREMITY WRIST DOSEMETER BASED ON THE LANDAUER INLIGHTTM WHOLE BODY DOSEMETER
Christopher A Perks*a and Stephane Faugoina
a
LANDAUER EUROPE, 33 Avenue du General Leclerc, F-92266, Fontenay-aux-Roses CEDEX, France.
To perform extremity personal dosimetry around the wrist, LANDAUER EUROPE previously supplied customers in France with standard InLight
dosemeters enclosed within a soft plastic pouch and a band to secure the dosemeter. Clients requested a smaller and more comfortable
design.
This poster gives an overview of the new design and reports on type testing of the proposed wrist badge on an ICRU pillar (wrist) phantom,
in terms of the energy and angular response. Modifications were made to our dose calculation algorithm and the results of the type testing
compared with the international standards.
LANDAUER EUROPE EXTREMITY WRIST BADGE DESIGN
The LANDAUER EUROPE extremity
dosemeter is based on the standard
InLight dosemeter which is used for
whole body monitoring. The processing
and read out of this dosemeter is the
same as for the standard dosemeter.
The dosemeter consists of :
s A CASE THAT CONTAINS METAL AND
plastic filters,
s APLASTICSLIDETHATCONTAINSDETECTOR
elements.
> Case and slide of the InLight
The detector element is a layer of dosemeter
Al2O3:C sandwiched between two
layers of polyester for a total thickness
of 0.3mm.
For the extremity wrist dosemeter the
case and slide are enclosed in a heat
sealed polythene pouch, together with
a paper label. The pouch is designed
to allow a wrist strap to be attached.
This design is substantially smaller
than the previous wrist badge and
gives the client greater comfort while
allowing the badges themselves to be
read out using the same readers and
procedures as our standard whole body
dosemeters. A neutron dosemeter can
> Extremity wrist dosemeter
also be included in this badge.
THE ANALYSIS OF THE EXTREMITY WRIST BADGE
The InLight dosemeters are readout
in readers based on the widely used
conventional Panasonic readers.
Those have been modified for OSL
readout, principally by employing
light emitting diodes as a light source.
Dosemeters can be read automatically
at a speed approaching 10 seconds
per dosemeter, with very little need
for operator intervention.
An algorithm is used to determine the
quantities of interest, including Hp(10)
and Hp(0.07), from the individual
responses of the four OSL detectors.
In addition, the algorithm indicates > Automatic reader for 500 dosemeters
the radiation quality (photon energy
or beta particle) of the exposure.
TYPE TESTING
Irradiation
Irradiations were performed at the
Health Protection Agency’s Laboratory
in the UK.
Eighty badges were irradatied
in accordance with international > The irradiation configuration
standard procedures for photons and
beta particles on an ISO standard pillar
wrist phantom. A secondary standard
ion chamber was used to determine
the doses.
Dosemeters were irradiated with a
nominal 3 mSv dose.
Analysis
Dosemeters were read out and analysed
using the standard algorithm during
normal operations for whole body
dosemeters at our facilities.
Results for Hp(0.07) were compared
to the exposed doses reported by
the Health Protection Agency in
their certificate for the irradiations
performed. Further analysis was
performed using a modification of the
standard algorithm.
RESULTS
Energy response (Hp(0.07)) for photon energy
Energy response for beta radiation
Beta source
90
Sr/90Y
85
Kr
Measured/reported dose
(Standard algorithm)
0.67 ± 0.14
0.25 ± 0.04
Measured/reported dose
(Modified algorithm)
0.97 ± 0.22
0.99 ± 0.16
Angular response for 65 keV photons
MODIFICATIONS TO ALGORITHM
In view of the under-response for beta particles, particularly for the lower
energy 85Kr particles, changes to the algorithm were considered to improve it.
A simple change to the algorithm was tested in which the results for the
assessment of low energy beta particles was multiplied by a factor of four
and those for the higher energy photons multiplied by a factor of 1.5.
The doses assessed in this way are those given in the column for the modified
algorithm. These changes have now been incorporated into the operational
version of the algorithm which has been tested by comparison with these
results.
DISCUSSION
Most of the international standard requirements in terms of type testing are
common to the wrist badge and whole body. The principal differences regard
the energy and angular response.
International standards
requirements (ISO 12794)
LANDAUER EUROPE extremity
dosemeter responses
Energy response for photons (15 keV to 3 MeV)
The response (Hp(0.07)) shall not vary Response is within ISO standard.
by more than ± 50%.
Energy response for beta radiation (0.5 MeV to 3 MeV (Emax))
The response (Hp(0.07)) shall not vary Under-response has been corrected
by more than ± 50%.
by modifications to the algorithm.
Angular response (65 keV photons)
The mean value of the response The response is within the
Hp(0.07) at angles of incidence of 0°, requirements of the standard with
20°, 40° and 60° from normal shall the exception of the response at -60°
not vary for normal incidence by more for horizontal rotation.
than ± 15%.
CONCLUDING REMARKS
A development of the InLight dosemeter has been adopted as
LANDAUER EUROPE’s extremity wrist dosemeter. Type testing revealed
that doses Hp(0.07) assessed using this dosemeter were significantly low.
Nevertheless, simple changes to the dose calculation algorithm have been
adopted which correct this under-response.The dosemeter, with results assessed
using the modified algorithm, meets the requirements of the international
standard with the exceptions of angular response at -60° vertical. The tendency
in this condition is for over-estimation of the dose and the dosemeter has been
adopted for use for our clients requiring this service.
* Presenting author, E-mail: cperks@landauer-fr.com