Raanan Marants and Laurel Sinclair

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Thursday, January 29, 2015

Time:   3:30 - 5:00 pm

Location:   Room RPB 205 (boardroom), Health Canada, 775 Brookfield Road

1. "Dose and Position Quality Assurance using the RADPOS System for 4D Radiotherapy with CyberKnife"
Raanan Marants - Carleton University
Abstract: Radiotherapy treatment becomes more difficult in cases where patient motion, such as breathing, causes movement of the treatment target or organs-at-risk. The CyberKnife radiosurgery system offers an excellent solution in the form of real-time tumor motion tracking through its Synchrony respiratory motion tracking system. Such a complex dose delivery system needs independent performance verification to assure safe patient treatments, which can potentially be accomplished with the RADPOS 4D dosimetry system. RADPOS consists of a microMOSFET dosimeter combined with an electromagnetic positioning sensor, enabling it to perform real-time dose and position measurements simultaneously. RADPOS is used as an independent QA tool to verify the CyberKnife system's motion tracking and delivered dose. RADPOS motion measurements are compared with internal metal fiducials and external LED optical markers log files. Dose measurements are compared with GAFCHROMIC film and treatment planning calculations

2. "Surface contamination concentration measurements from aerial radiometric survey"
Laurel Sinclair - Natural Resources Canada
Abstract: Natural Resources Canada has responsibility for emergency response mobile radiometric mapping in the event of a radiological or nuclear incident, whether accidental or malicious in nature.  We fly aerial gamma-ray surveys, and extrapolate to isotope-specific concentrations on the surface of the ground, using an assumption that the radiation is infinite in extent and uniform.  This approach can accurately determine the total amount of radioactivity, and specify the locations of high and low concentration.  However, it suffers from the problem that it produces a result which is averaged over a large area.  This is an issue which is particularly acute for emergency response where a highly localized hot spot could be misrepresented as a broad deposit which is relatively weak.  We have developed a method to deconvolve the aerial radiometric map for spatial smearing.  In this way we can recover some of the sharpness of the features on the ground, and get a more accurate measure of the strength of localized hot spots.  In this talk, recent measurements of surface concentrations will be presented, using both synthetic and real-world data.