Landauer Luxel+ dosimeters are equipped with an imaging filter
to aid the client in their dose investigation. The filter pack provides
a unique filter pattern on the Al2O3:C detector that is analyzed
using Pulsed Optically Stimulated Luminesce and interpreted
using Discrete Fourier Transform to decide if the dosimeter (or the
source) was in motion at the time of exposure. Luxel+ dosimeter
with doses of 500 mrem(5mSv) or higher is automatically
imaged. Dosimeters reading lower than 500 mrem(5mSv) could
also be imaged by customer request. Imaging results are
recommended for photon energies below 70keV. The most
common imaging notes listed on the Dosimetry Reports are detailed below.
During a static exposure, the absorbed radiation pattern is sharp and
clear. A static image could be due to intentional irradiation, could
indicate that the dosimeter was not worn by the participant at the time of
exposure, or could originate from a dosimeter that was forgotten in the
exposure room or lost for a period of time during the wear period.
During a dynamic exposure, either the source or the dosimeter is in
motion at the time of exposure and the image pattern is diffuse. Most of
the time, a dynamic note on the Dosimetry Report implies that the
dosimeter was worn during the time the exposure took place. Sometimes
the image appears dynamic due to the irradiation source moving, which
is very common when using Computed Tomography devices (CT).
Image Results are Inconclusive
In the case of a Luxel+ dosimeter being exposed to photon energies above
70keV, we are unable to determine if the image is static or dynamic since
the image behind the image filter looks diffused. This is communicated
to the client by applying a note to the Dosimetry Report.
An irregular exposure note on the Dosimetry Report indicates that the exposure is not typical
and it does not follow the basic rules of radiation absorption. These situations could occur due
to a dosimeter being partially shielded, exposed at extreme angles, and/or exposed from the
back using low-energy photon sources. Depending on the radiation field and the degree of the
irregularity, the dose might be reported as “best evaluation possible” meaning that with the
information Landauer had available, this is the best evaluation that could be offered.