Development of a Multichannel Dosimeter Based on Scintillating Fibers for Medical Applications
Dosimetry with plastic scintillators is an interesting
alternative for the measurement of the absorbed dose. A scintillator does
barely disturb the radiation field due to its mass absorption coefficients
which is water-equivalent in a wide range of energies. Furthermore, plastic
scintillation dosimeters provide a fast and direct reading of the measured
value combined with a high spatial resolution. In the set-up described
so far, the light produced by the scintillators was transported via light-guides
to single-channel or multi-channel photomultipliers to be transformed
into an electric current read out by pico-amperemeters. The use of photomultipliers
becomes expensive and complicated for a dosimeter system with many parallel
channels. For such applications, an image intensifier coupled to a CCD
is a simpler approach which can read out some 80 fibers in parallel.
The described dosimeter will consist altogether of 72
channels, 36 of these channels with a scintillator 1mm³ and an optical
fiber. The remaining 36 channels are without scintillator. They will be
used for the suppression of the Cerenkov background produced in the light
guiding fibers. The read-out system is set up in such a way that
the incoming light guides are kept at fixed positions by a mask to ensure
a good optical contact between fibers and the image intensifier. The image
intensifier transforms the light from all 72 fibers into electrons, amplifies
them in parallel, transforms them back into photons and re-emits an amplified
image of the incoming light signals.
First measurements were made at the Clinic for Radiation Therapy and Radio-Oncology in the Klinikum Wuppertal GmbH.