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EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities

EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities

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HÖFEL, Sebastian, Michael K. FIX, Felix ZWICKER, Edmond STERPIN, Malte DRESCHER, 2019. EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities. In: Physics in Medicine & Biology. 64(17), 175013. ISSN 0031-9155. eISSN 1361-6560. Available under: doi: 10.1088/1361-6560/ab325b

@article{Hofel2019-09-04imagi-47016, title={EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities}, year={2019}, doi={10.1088/1361-6560/ab325b}, number={17}, volume={64}, issn={0031-9155}, journal={Physics in Medicine & Biology}, author={Höfel, Sebastian and Fix, Michael K. and Zwicker, Felix and Sterpin, Edmond and Drescher, Malte}, note={Article Number: 175013} }

Fix, Michael K. Drescher, Malte Zwicker, Felix 2019-09-24T09:49:03Z Fix, Michael K. New hybrid radiotherapy treatment systems combining an MRI scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging.<br /><br />In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying electron paramagnetic resonance imaging (EPRI).<br /><br />Air-filled fused quartz tubes (inner diameter 3 or 4 mm) mimic small air cavities and serve as model systems. The tubes were irradiated inside a PMMA phantom by a 6 MV photon beam. The irradiations were performed in the presence or absence of a transverse, magnetic field providing a magnetic field strength of 1.0 Tesla. The spatial distributions of radiation induced paramagnetic defects in the quartz tubes were subsequently determined by applying field-swept echo-detected EPRI and were then converted to relative dose distributions.<br /><br />The transverse magnetic field leads to considerable local dose enhancements and reductions (up to 35%) with respect to the mean dose within the quartz tubes. The experimentally determined dose distributions are in good quantitative agreement with Monte Carlo radiation transport simulations.<br /><br />The results of this work demonstrate the feasibility of field-swept echo-detected EPRI to measure magnetic field induced perturbations of dose distributions within a sub-millimeter thick surface layer at the dosimeter-air interface. Höfel, Sebastian Sterpin, Edmond Sterpin, Edmond EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities eng Höfel, Sebastian 2019-09-04 2019-09-24T09:49:03Z Drescher, Malte Zwicker, Felix

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