Six-probe scintillator dosimeter for treatment verification in HDR-brachytherapy
Résumé
Background In vivo dosimetry (IVD) is gaining interest for
treatment delivery verification in HDR-brachytherapy. Time resolved
methods, including source tracking, have the ability both to detect
treatment errors in real time and to minimize experimental
uncertainties. Multiprobe IVD architectures holds promise for
simultaneous dose determinations at the targeted tumor and
surrounding healthy tissues while enhancing measurement accuracy.
However, most of the multiprobe dosimeters developed so far either
suffer from compactness issues or rely on complex data
post-treatment. Purpose We introduce a novel concept of a compact
multiprobe scintillator detector and demonstrate its applicability
in HDR-brachytherapy. Our fabricated seven-fiber probing system is
sufficiently narrow to be inserted in a brachytherapy needle or in
a catheter. Methods Our multiprobe detection system results from
the parallel implementation of six miniaturized inorganic Gd2O2S:Tb
scintillator detectors at the end of a bundle of seven fibers, one
fiber is kept bare to assess the stem effect. The resulting system,
which is narrower than 320 microns, is tested with a MicroSelectron
9.14 Ci Ir-192 HDR afterloader, in a water phantom. The detection
signals from all six probes are simultaneously read with a sCMOS
camera (at a rate of 0.06 s). The camera is coupled to a chromatic
filter to cancel Cerenkov signal induced within the fibers upon
exposure. By implementing an aperiodic array of six scintillating
cells along the bundle axis, we first determine the range of
inter-probe spacings leading to optimal source tracking accuracy
(first tracking method). Then, three different source tracking
algorithms involving all the scintillating probes are tested and
compared. In each of these four methods, dwell positions are
assessed from dose measurements and compared to the treatment plan.
Dwell time is also determined and compared to the treatment plan.
Results The optimum inter-probe spacing for an accurate source
tracking ranges from 15 to 35 mm. The optimum detection algorithm
consists of adding the readout signals from all detector probes. In
that case, the error to the planned dwell positions is of 0.01
{$\pm$} 0.14 mm and 0.02 {$\pm$} 0.29 mm at spacings between the
source and detector axes of 5.5 and 40 mm, respectively. Using this
approach, the average deviations to the expected dwell time are
of {-}0.006{$\pm$}0.009 s and {-}0.008{$\pm$}0.058 s,
at spacings between source and probe axes of 5.5 and 20 mm,
respectively. Conclusions Our six-probe Gd2O2S:Tb dosimeter coupled
to a sCMOS camera can perform time-resolved treatment verification
in HDR brachytherapy. This detection system of high spatial and
temporal resolutions (0.25 mm and 0.06 s, respectively) provides a
precise information on the treatment delivery via a dwell time and
position verification of unmatched accuracy
Domaines
Optique [physics.optics]Origine | Fichiers produits par l'(les) auteur(s) |
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