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Image Guided Radiation Therapy: Design Optimization of High Quantum Efficiency Imaging Detectors

Add Event to your Calendar Fri., Apr. 7, 2017 3:30 p.m. - Fri., Apr. 7, 2017 4:30 p.m.

Location: CL 125

Abstract: Radiotherapy is the use of ionizing radiation to kill or control the growth of cancer cells. The most common form of radiotherapy uses X-rays with energies up to 24MeV delivered by a medical linear accelerator (LINAC). In order to accurately target tumours and spare healthy tissues, some form of image guidance is required. Typical LINACs use an electronic portal imaging device (EPID) for verification procedures including patient positioning and dose deliverance. However, most EPIDS developed to date have a low absorption efficiency for megavoltage (MV) X-rays and are susceptible to noise from low-energy X-rays such as those generated by patient scatter. A new approach for increasing the efficiency, using a scintillation electronic portal imaging device (SPID), employs scintillating fibers for use in MV X-ray imaging in order to increase efficiency and decrease sensitivity to scattered X-rays.

The proposed SPID consists of a matrix of square polystyrene fibers clad with acrylic. The fibers are coupled to an active matrix flat panel imager (AMFPI) for image readout and are surrounded by lead in order to attenuate scattered photons reaching the detector. The light signal that reaches the AMFPI is dependent on the energy and incidence angle of the X-rays that interact with the detector. Monte Carlo simulations have been conducted using the Geant4 toolkit in order to evaluate the response of the proposed SPID to primary incident X-rays as well as scattered X-rays in comparison with that of convential EPIDS. Preliminary results indicate a SPID efficiency upwards of ~50% compared to that of ~2-4% of common EPIDs. The lead in the structure of the SPID acts as a collimator reducing the signal contribution of low energy scattered radiation. 

Speaker: Mr. Matthew Strugari, Department of Physics, University of Regina

Note: This is an Honours Seminar.