• ultra-high dose rate
• proton therapy
• radiotherapy
• dosimetry

Preclinical in vivo studies in radiation therapy face many challenges: chief among them the efficient characterization and optimization of the 3D dose distribution at the irradiation site to ensure a successful in-vivo sample irradiation. The prescribed dose must be applied in the target volume within a percent-level margin.
In the case of small animal irradiation the target volume dimension shrinks down to a ∼ mm3-scale.
For this reason dosimeters providing sub-mm resolved 3D information about the dose in the target volume are required. Additionally, fast optimization and daily quality assurance of the dose at the irradiation site demands dosimeters with the capability of performing on-line measurements. Established reference dosimeters like ionization chambers are able to perform on-line dose measurements, but do not reach the a sub-mm 3D resolution. Stacks of radiochromic films instead can be used to characterize ∼ mm^3-scale 3D dose distribution, but are not reusable and require a time consuming evaluation process including a manually scanning process multiple days after the irradiation to reach %-level precision.
The miniSCIDOM detector, described in this work, provides the possibility for on-line 3D dose measurements with a sub-mm3 resolution. The detection principle is based on emission tomography. Four parallel projections of the 3D light distribution emitted by the plastic scintillator are collected by a CCD camera and fed to an iterative reconstruction algorithm. The algorithm reconstructs the 3D light distribution which is proportional to the 3D dose distribution deposited in the scintillator. The miniSCIDOM detector allows the reconstruction of ∼1 cm^3 large dose distributions.
The lower detection limit lies below 500 mGy and the upper dose limit can be modified using filters, currently tested up to a 20 Gy level. With a high spatial resolution of 400 μm tested with proton mini beams for the reconstructed dose distributions, control of dose homogeneity is possible.
The miniSCIDOM detector is tested, under small animal irradiation like conditions, at a conventional tungsten X-ray tube (Isovolt 320), a medical cyclotron (ONCORAY, Cylclone 230) and at a laser proton accelerator (DRACO, ALBUS-2S). The linear energy transfer dependent quenching of the scintillator light out-put occurring for proton beams is corrected using Birks’ law and simulated fluence weighted LET values for the measured dose distribution. At ultra high proton dose rate of 10^8 Gy/s applied in a ns-pulse at a laser proton beam-line a deviation from Birks’ law is observed. This opens the question for reduced quenching behaviors of scintillators for ultra high dose rate applications in the time scale of the scintillator response function.