Purpose: A miniaturized inorganic scintillator detector (MSD) is demonstrated in the analysis of the small static photon fields used in external radiotherapy
Methods: The detector is constituted by a 0.25 millimeter diameter and 0.48 millimeter long inorganic scintillating cell efficiently coupled to a narrow 125 micron diameter silica optical fiber using a photonic interface. Response of our MSD is tested under a 6MV photon beam of a linac for various field sizes (from 1×1cm2 to 4×4cm2). The MSD measurements are compared to those obtained with two high-resolution reference detectors commonly used in small field dosimetry: a micro-diamond detector and a silicon diode. The spurious Cerenkov signal is rejected with a spectral filtering
Results: The MSD shows a linear response regarding the dose, repeatability within 0.1% and radial directional dependence of 0.36% (standard deviations). Beam profile 5cm depth with the MSD and the micro-diamond detector shows a mismatch in the measurement of the full widths at 80% and 50% of the maximum which does not exceed 0.25mm. The deviation of the percentage depth dose between the MSD and micro-diamond detector remains below 2.3% within the first fifteen centimeters of the decay region for field sizes of 1×1cm2, 2×2cm2 and 3×3cm2 (0.76% between the silicon diode and the micro-diamond in the same field range). The 2D dose mapping of a 0.6×0.6cm2 photon field evidences the strong 3D character of the radiation-matter interaction in small photon field regime. Our detector is a right compromise between high resolution, compactness, flexibility and ease of use. The MSD overcomes problem of volume averaging, stem effects, and despite its water non-equivalence it is expected to minimize electron fluence perturbation due to its extreme compactness.
Conclusion: MSD has the potential to become a valuable dose verification tool in small-field radiation therapy, in Brachytherapy, FLASH-radiotherapy and microbeam radiation therapy.
Scintillators, Optical Dosimetry
Not Applicable / None Entered.