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- Adolfsson, Emelie, 1985-, et al.
(författare)
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Response of Lithium Formate EPR Dosimeters at Photon Energies Relelvant to Brachytherapy
- 2009
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Ingår i: IFMBE Proceedings. - Heidelberg : Springer Berlin Heidelberg. - 9783642034725 - 9783642034749 ; , s. 236-239
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- After development of sensitive dosimeter materials Electron Paramagnetic Resonance EPR dosimetry has been successfully used also in radiation therapy. The intensity of the EPR-signal is a measure of the amount of free radicals created by ionizing radiation which is proportional to the absorbed dose in the dosimeter. Lithium formate monohydrate is a dosimeter material with 2-6 times higher sensitivity than alanine, a linear dose response over a wide dose range and mass-energy absorption properties similar to water. These properties make lithium formate promising for verification of absorbed doses around high dose rate brachytherapy sources where the dose gradient is steep and the photon energy distribution changing with distance from the source. Calibration of the dosimeters is performed in 60Co or MV photon beams where high dosimetric accuracy is feasible. The use in brachytherapy field relies on the assumption that the production of free radicals per mean absorbed dose in the dosimeter is similar at the lower photon energies present there. The aim of this work was to test that assumption. The response of the dosimeters as a function of photon energy was determined by irradiations with four x-ray qualities in the range 100-250 kV and 137Cs, relative to the response when irradiated with 60Co, all photon beams with well-known air kerma rates at the Swedish Secondary Standards Dosimetry Laboratory. Monte Carlo simulations were used to convert air kerma free in air to mean absorbed dose to the dosimeter. The measured response relative 60Co as a function of photon energy was below unity for all qualities. The maximum deviation from unity was 2.5% (100 kV, 135 kV) with a relative standard deviation of 1.5% (k = 1).
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| 2. |
- Patten, Christopher J.D. 1968-
(författare)
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Cognitive Workload and the Driver : Understanding the Effects of Cognitive Workload on Driving from a Human Information Processing Perspective
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral dissertation in psychology focuses on present day transport research issues. Society is affected by the way that our transport system works. In one way or another, the use of the transport system involves different levels of human involvement and control.The main focus of this dissertation is to understand some important effects of cognitive workload on driving. The driver’s cognitive workload is related to human information processing capacity and the use and allocation of the driver’s attention. In-vehicle technologies are of particular interest in the context of driver workload and human information processing.The rationale of this thesis starts with the need to explore and develop a sensitive and objective measure of cognitive workload using the peripheral detection task (PDT) method. The next step continues to study the effects of cognitive workload on the human information processing stages (HIPS) framework and the way in which human information processing can be affected by performance shaping factors (PSFs). One of the PSFs had a beneficial effect on performance (experience) and one had a detrimental effect on performance (distraction).In summary, it is clear that the human driver is limited in the number and the complexity of the tasks he or she can perform at any given time. Moreover, making mistakes, to err, is part of being human; we are fallible. It is impossible to eliminate all driver error so it is therefore important to create an environment for the driver so that his or her slips, lapses and mistakes can be detected and recovered.
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