Program Information
A New Approach for Cherenkov Emission Detection Using Silicon Photomultipliers
I Oraiqat1*, C Taylor1 , C Como1 , J Way1 , M Suarez1 , R Pearce1 , S Debruin2 , N Cucinelli2 , R Clarke1,2 , I El Naqa1 (1) University of Michigan, Ann Arbor, MI, (2) Endectra, LLC, Ann Arbor, MI,
Presentations
WE-RAM2-GePD-J(A)-2 (Wednesday, August 2, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Lounge - A
Purpose: Cerenkov emission (CE) during radiation is inefficient using off shelf detector for clinical applications. Therefore, we investigate the feasibility of new Silicon Photomultiplier (SiPM) devices to detect CE during external beam radiotherapy.
Methods: CE is generated using a 1x1cm field of both 6MV and 16MV photons in a water tank phantom. The SiPM (1x1mm sensor size) is placed outside the tank at a position 10cm below the water surface. The distance between the SiPM and radiation field is varied (6.4 to 43.4cm in steps of 0.2cm) to measure the SiPM response as a function of distance. Data from the SiPM is acquired using an oscilloscope that is triggered to the target output of the Linac. A comparison is made between a commercial photodiode (1x1mm sensor size) and the SiPM device using the same tank, sensor position, acquisition technique, and field size.
Results: During irradiation, the output signal of the SiPM from CE showed a pulse width of 3.2μs, corresponding to the target output from the Linac. In addition to the pulse duration, the target output shape also agreed well, including the small ramp up during the first μs. The signal from the 16MV photon beam was approximately five times larger than that from the 6MV beam due to expected increase in CE. As the radiation field is moved away, the SiPM signal droped off following the inverse-squared law. In comparison, the photodiode was not able to detect CE using the same conditions as the SiPMs, only by increasing the field size from 1x1cm to 36x36cm, a faint signal can be detected. The SiPMs have approximately three times higher signal to noise ratio (SNR) compared to standard photodiodes.
Conclusion: This work shows the potential of using SiPM devices gated to individual Linac pulses for improved CE detection during radiotherapy.
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