Purpose: A high resolution, water equivalent, optical and passive x-ray dosimeter has been constructed
using plastic scintillator and optical fiber. This dosimeter has a peak edge-on spatial resolution
of 100 lm in one dimension, with a 10 lm resolution dosimeter under investigation. The
dosimeter design has a potential application in synchrotron x-ray microbeam radiation therapy where
a high resolution is vital for accurate dose measurements and quality assurance.
Methods: BC-400 plastic scintillator, of thickness 100 lm, was optically coupled to an optical fiber
with core diameter 1 mm. The end was coated in optical paint to improve sensitivity. An identical
fiber was made without the scintillator to measure the background Cherenkov radiation induced in
the fiber, to allow background signal subtraction. The light captured by the fibers was measured by
PMTs. The probe system was exposed to a 6 MV, 10 9 10 cm2 LINAC x-ray field and the beam profile
was measured at 100 cm, as well as the depth dose profile.
Results: The measured profiles matched well with ionisation chamber data. Important beam parameters
such as penumbra width and percent depth dose at various depths matched the ionisation chamber
data, within uncertainty.
Conclusions: This work demonstrates that high resolutions can be achieved with a scintillation and
optical fiber system. The probe is water-equivalent, passive, energy independent, radiation hard and
inexpensive, making it ideal for further improvements for use with microbeam radiation therapy.