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Sci—Wed PM: Delivery—12: The Radiofrequency Noise from MLCs for a Linac‐MR System
Author(s) -
Lamey M,
Yun J,
Burke B,
Rathee S,
Fallone BG
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3244104
Subject(s) - noise (video) , imaging phantom , linear particle accelerator , radiofrequency coil , physics , electromagnetic coil , nuclear magnetic resonance , acoustics , computer science , optics , artificial intelligence , beam (structure) , quantum mechanics , image (mathematics)
Introduction : This work reports on the feasibility of using an MLC for a linac‐MR system. The radiofrequency)RF(noise produced by a functioning MLC is a possible interference to an MR imaging system. The RF noise spectral density produced by two brushed motors used to drive MLC leaves and one brushless fan motor has been investigated as a function of applied magnetic field. Materials/methods : An electromagnet was used to subject two brushed motors from two MLC assemblies)a Varian 52‐leaf and a Millennium 120 leaf assembly(and one brushless fan motor to a variable magnetic field. The RF noise was measured while the motors moved. The RF noise was measured with a set of commercially available near field electromagnetic probes. In a separate investigation the 0.22 T MR of our linac‐MR system was used to image a phantom. Images were taken with the MLC not present and then again with the MLC present and thirteen leaves moving. Results/Discussion : When viewing the RF noise in the time domain we could see small spikes of measured noise when the two brushed MLC motors were running; no noise could be seen from the brushless fan motor. In the frequency domain, the Millennium MLC motor showed some noise above background. Images with a phantom showed no degradation from possible RF noise interference when 13 MLC leaves from a Varian 52‐leaf MLC assembly were brought close to the MR coil and were moved.