  Plastic scintillation detectors are increasingly used to measure dose
distributions in the context of radiotherapy treatments. Their
water-equivalence, real-time response and high spatial resolution distinguish
them from traditional detectors, especially in complex irradiation geometries.
Their range of applications could be further extended by embedding
scintillators in a deformable matrix mimicking anatomical changes. In this
work, we characterized signal variations arising from the translation and
rotation of scintillating fibers with respect to a camera. Corrections are
proposed using stereo vision techniques and two sCMOS complementing a CCD
camera. The study was extended to the case of a prototype real-time deformable
dosimeter comprising an array of 19 scintillating. The signal to angle
relationship follows a gaussian distribution (FWHM = 52{\deg}) whereas the
intensity variation from radial displacement follows the inverse square law.
Tracking the position and angle of the fibers enabled the correction of these
spatial dependencies. The detecting system provides an accuracy and precision
of respectively 0.008 cm and 0.03 cm on the position detection. This resulted
in an uncertainty of 2{\deg} on the angle measurement. Displacing the dosimeter
by $\pm$3 cm in depth resulted in relative intensities of 100$\pm$10% (mean
$\pm$ standard deviation) to the reference position. Applying corrections
reduced the variations thus resulting in relative intensities of 100$\pm$1%.
Similarly, for lateral displacements of $\pm$3 cm, intensities went from
98$\pm$3% to 100$\pm$1% after the correction. Therefore, accurate correction of
the signal collected by a camera imaging the output of scintillating elements
in a 3D volume is possible. This work paves the way to the development of
real-time scintillator-based deformable dosimeters.

Medical Physics