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High Sensitivity and High Resolution Fiber Based Micro-Detector for Sub-Millimeter Preclinical Dosimetry

E Izaguirre

E Izaguirre1,2*, S Pokhrel1,2 , S Hedrick3 , T Knewtson1,2 , (1) University of Tennessee Medical Science Center, Memphis, TN, (2) University of Missouri, Columbia, MO, (3) Provision Center for Proton Therapy, Knoxville, TN.


TU-H-CAMPUS-TeP2-3 (Tuesday, August 2, 2016) 5:00 PM - 5:30 PM Room: ePoster Theater

Purpose:Current precision of small animal and cell micro-irradiators has continuously increased during the past years. Currently, preclinical irradiators can deliver sub-millimeter fields with micrometric precision but there are no water equivalent dosimeters to determine small field profiles and dose in the orthovoltage range of energies with micrometric resolution and precision. We have developed a fiber based micro-dosimeter with the resolution and dosimetric accuracy required for radiobiological research.
Methods:We constructed two prototypes of micro-dosimeters based on different compositions of fiber scintillators to study the spatial resolution and dosimetric precision of small animal and cell micro-irradiators. The first has green output and the second has blue output. The blue output dosimeter has the highest sensitivity because it matches the spectral sensitivity of silicon photomultipliers. A blue detector with 500um cross section was built and tested respect to a CC01 ion chamber, film, and the 1500um green output detector. Orthovoltage fields from 1x1mm2 to 5x5mm2 were used for detector characteristics comparison.
Results:The blue fiber dosimeter shows great agreement with films and matches dose measurements with the gold-standard ion chamber for 5x5mm2 fields. The detector has the appropriate sensitivity to measure fields from 1x1mm2 to larger sizes with a 1% dosimetric accuracy. The spatial resolution is in the sub-millimeter range and the spectral matching with the photomultiplier allows reducing the sensor cross section even further than the presented prototype. These results suggest that scintillating fibers combined with silicon photomultipliers is the appropriate technology to pursue micro-dosimetry for small animals and disperse cell samples.
Conclusion:The constructed detectors establish a new landmark for the resolution and sensitivity of fiber based micro-detectors. The validation of the detector in our small animal and cell irradiator shows that they are appropriate for preclinical and micro single cell irradiation quality assurance and dosimetry.

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