BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Absolute Dosimetry using a Graphite Calorimeter on the Imaging and Medical Beamline at the Australian Synchrotron DTSTART;VALUE=DATE-TIME:20141120T045000Z DTEND;VALUE=DATE-TIME:20141120T051000Z DTSTAMP;VALUE=DATE-TIME:20260519T094546Z UID:indico-contribution-197-773@events01.synchrotron.org.au DESCRIPTION:Speakers: Peter Harty (ARPANSA)\nIn 2012-13\, the Australian S ynchrotron installed a superconducting multi-pole wiggler (SCMPW) on the i maging and medical beamline (IMBL) with the intention of future preclinica l radiotherapy trials. Before moving to such trials\, accurate knowledge of the dose delivered is required to calibrate the secondary dosimeters in regular use. When this is resolved\, clinical use of the Australian Sync hrotron will be closer to reality. \nThe dose rate achievable on the IMBL is in the range 10 Gy/s to 10 kGy/s\, depending on the SCMPW magnetic fiel d\, the filtration set and the distance of the measurement rooms (or hutch es) from the photon source. High-dose-rate dosimetry is challenging with detectors such as free-air ionization chambers (FAC)\, due to the high ion -recombination corrections required. An absolute method of dose determina tion is required and one such method is graphite calorimetry\, which is ba sed on the temperature rise in graphite when irradiated. In this meth-od\ , the temperature is measured by a calibrated thermistor embedded in the c alorimeter graphite core. The ab-sorbed dose from the irradiation is dete rmined from the product of the temperature rise and the specific heat capa city of graphite\, corrected for the ratio of graphite core area to beam a rea.\nResults will be presented for measurements in hutches 1B\, 2B and 3B \, where the dose rates presently vary from 20 Gy/s to 3000 Gy/s. Compari sons with a free-air chamber and calculated dose rates will be presented.\ n\nhttps://events01.synchrotron.org.au/event/3/contributions/773/ LOCATION: Conference Room AS URL:https://events01.synchrotron.org.au/event/3/contributions/773/ END:VEVENT BEGIN:VEVENT SUMMARY:Characterisation of the PTW microDiamond detector for high spatial resolution dosimetry in microbeam radiation therapy at IMBL DTSTART;VALUE=DATE-TIME:20141120T051000Z DTEND;VALUE=DATE-TIME:20141120T053000Z DTSTAMP;VALUE=DATE-TIME:20260519T094546Z UID:indico-contribution-197-742@events01.synchrotron.org.au DESCRIPTION:Speakers: Jayde Livingstone (Australian Synchrotron)\nMicrobea m radiation therapy (MRT) at IMBL is based on arrays of 50&mu m wide x-ray beams with a pitch of 400&mu m. The peak-to-valley dose ratio (PVDR) is t he ratio of the peak dose to the dose between the microbeams and is an imp ortant radiobiological quantity. Accurate measurements of the PVDR require a dosimeter with high spatial resolution\, dose rate independence and wat er equivalence for the MRT spectrum. The PTW microDiamond detector is a sy nthetic single crystal diamond detector. The 1.1mm radius and 1&mu m thick ness make it a promising candidate MRT dosimetry. Studies have been perfor med at IMBL to characterise the energy\, dose rate and directional depende nce of microDiamond. The ratio of mass energy absorption coefficients in d iamond and water predict that the detector will under-respond at low energ ies\, however\, this was not observed in the experimental ratio of the mic roDiamond response to absorbed dose in water for energies 30-90keV. The do se rate dependence was found to be linear for storage ring currents &ge 50 mA but deviated from linearity by up to 4% for lower currents (2-50mA). Th e reponse of the detector oriented at 0o and 90o relative to normal beam i ncidence agreed to within 3%. This is an important result since the requir ed spatial resolution for PVDR measurements exists in the 90o geometry. Th e detector will be calibrated against reference detectors and the kV prima ry standard for absorbed dose.\n\nhttps://events01.synchrotron.org.au/even t/3/contributions/742/ LOCATION: Conference Room AS URL:https://events01.synchrotron.org.au/event/3/contributions/742/ END:VEVENT BEGIN:VEVENT SUMMARY:X-ray Imaging at IMBL: Detailed Considerations of Contrast and Res olution DTSTART;VALUE=DATE-TIME:20141120T043000Z DTEND;VALUE=DATE-TIME:20141120T045000Z DTSTAMP;VALUE=DATE-TIME:20260519T094546Z UID:indico-contribution-197-675@events01.synchrotron.org.au DESCRIPTION:Speakers: Andrew Stevenson (Australian Synchrotron/ CSIRO)\nTh e Imaging and Medical Beamline (IMBL) at the Australian Synchrotron has th ree hutches\, centred at 22\, 36 and 140m from the source\, in which user experiments are performed. Radiotherapy experiments are currently perform ed in the first of these hutches\, and imaging (including tomography) in t he second and third hutches. The X-ray source is provided by a superconduc ting multipole wiggler (SCMPW) insertion device. A double-crystal Laue mon ochromator (DCLM) can be used to select the desired X-ray energy within th e range 20 - 120keV at present. Alternatively\, a white (pink) beam can be employed\, using appropriate in-vacuo filters.\n\nWe will provide a detai led description and analysis of the key factors which influence the qualit y of X-ray images which can be recorded. In addition to the nature of the sample itself\, the factors considered include the SCMPW field\, X-ray ene rgy or spectrum used\, source size\, detector resolution\, source-to-sampl e and sample-to-detector distances. The key parameters used in describing the “quality” of an X-ray image are contrast (both absorption and phas e) and resolution. An objective assessment of the point-spread function wi ll be central and some discussion of signal-to-noise ratio will also be in cluded. Other factors such as the presence of a small harmonic-contaminati on contribution for certain operation of the DCLM will be considered.\n\nh ttps://events01.synchrotron.org.au/event/3/contributions/675/ LOCATION: Conference Room AS URL:https://events01.synchrotron.org.au/event/3/contributions/675/ END:VEVENT BEGIN:VEVENT SUMMARY:Spatial dosimetric response of an ionisation chamber to kilovoltag e synchrotron radiation by 2D scanning in a sub-millimetre beam DTSTART;VALUE=DATE-TIME:20141120T053000Z DTEND;VALUE=DATE-TIME:20141120T055000Z DTSTAMP;VALUE=DATE-TIME:20260519T094546Z UID:indico-contribution-197-661@events01.synchrotron.org.au DESCRIPTION:Speakers: Duncan Butler (ARPANSA)\nThe IMBL at the Australian Synchrotron is able to provide high-brightness kilovoltage radiation in th e energy range 20 – 200 keV. A PTW 30013 Farmer-type ionisation chamber was scanned through a point-like (sub-millimetre) beam and the ionisation signal from the chamber was recorded as a function of position. In this wa y an image was constructed from the spatial dosimetric response of the cha mber. Such information can be used to determine\, for example\, the fracti on of response from the chamber stem to the overall response of the chambe r. Other interesting features include the contribution from the aluminium central electrode\, and increased response where the walls are side-on to the beam (and therefore contribute a greater number of secondary electrons to the air cavity). The results are compared to a Monte Carlo model. Dosi metric response maps should be useful for investigating the design of ioni sation chambers for radiotherapy.\n\nhttps://events01.synchrotron.org.au/e vent/3/contributions/661/ LOCATION: Conference Room AS URL:https://events01.synchrotron.org.au/event/3/contributions/661/ END:VEVENT END:VCALENDAR