An MRI-compatible hyperthermia applicator for small animals

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Abstract

Introduction to design novel treatment combinations involving mild hyperthermia, pre-clinical trials are essential. These studies into treatment effectiveness require close monitoring of the temperature during testing . Invasive thermometry restricts testing of the link between hyperthermia and immune responses, so MRI-compatibility is a necessity. Next to that, the applicator must heat locally, and secondary hot spots especially in vulnerable regions like the spinal cord must be prevented. Lastly, the system must be non-invasive, for disturbances in the tissues studied interfere with the accuracy of the research.With these goals in mind, we designed and built an applicator based on a novel water-embedded antenna design. In this study, we report the mode of operation for the head&neck region, but it can also be used for other tissues up to about 2 cm deep.MethodsA simulation-based approach was used to design the antenna element, and the surrounding system including the load. Simulation programs SEMCAD and CST were used, both of which use a Finite Difference Time Difference (FDTD) calculation methods. SEMCAD was also used for Penne’s Bioheat equation temperature predictions. The single antenna and array performance were assessed by simulating the power absorption distributions, i.e. the Specific Absorption Rate (SAR), and the temperature distribution. The antenna was designed to achieve at least a -15 dB match to 50 Ω at 2.45 GHz. Furthermore, it was stabilized for various water temperatures and for disturbances in the air-water bolus boundary. The metal plates were designed to be thin enough to ensure MRI compatibility. The latter property was tested by inspecting MRI images for disturbances when the antenna plus related cables were scanned.ResultsAccording to our simulations, a single antenna operating at 5W power is able to heat tongue tissue to 42º C without creating hot spots in other areas. Next to that, experiments showed that the antenna stability required was achieved and a match of -19 dB was reached in all cases. Lastly, the MRI scan showed excellent compatibility in the area of interest.ConclusionsOur novel setup provides operation within the specifications defined. Based on these promising results, we will now elucidate on the experimental validation of the heating performance of the single antenna setup and develop a phased array for deep heating.
Original languageEnglish
Number of pages1
Publication statusPublished - 15 Apr 2016
Event12th International Congress of Hyperthermic Oncology (2016 ICHO), April 11-15, 2016, New Orleans, LA, USA - InterContinental Hotel, New Orleans, LA, United States
Duration: 11 Apr 201615 Apr 2016
http://www.thermaltherapy.org/ebusSFTM/ICHO2016.aspx

Conference

Conference12th International Congress of Hyperthermic Oncology (2016 ICHO), April 11-15, 2016, New Orleans, LA, USA
Abbreviated title2016 ICHO
CountryUnited States
CityNew Orleans, LA
Period11/04/1615/04/16
Internet address

Keywords

  • oncology
  • hyperthermia
  • MR-compatibility
  • antenna design
  • engineering

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