Experimental Validation of the MRcollar: An MR Compatible Applicator for Deep Heating in the Head and Neck Region

Abstract

Clinical effectiveness of hyperthermia treatments, in which tumor tissue is artificially heated to 40–44 °C for 60–90 min, can be hampered by a lack of accurate temperature monitoring. The need for noninvasive temperature monitoring in the head and neck region (H&N) and the potential of MR thermometry prompt us to design an MR compatible hyperthermia applicator: the MRcollar. In this work, we validate the design, numerical model, and MR performance of the MRcollar. The MRcollar antennas have low reflection coefficients (<−15 dB) and the intended low interaction between the individual antenna modules (<−32 dB). A 10 °C increase in 3 min was reached in a muscle-equivalent phantom, such that the specifications from the European Society for Hyperthermic Oncology were easily reached. The MRcollar had a minimal effect on MR image quality and a five-fold improvement in SNR was achieved using the integrated coils of the MRcollar, compared to the body coil. The feasibility of using the MRcollar in an MR environment was shown by a synchronous heating experiment. The match between the predicted SAR and measured SAR using MR thermometry satisfied the gamma criteria [distance-to-agreement = 5 mm, dose-difference = 7%]. All experiments combined show that the MRcollar delivers on the needs for MR—hyperthermia in the H&N and is ready for in vivo investigation.

Application of photogrammetry reconstruction for hyperthermia quality control measurements

“…However this technique in which applicator and phantom are embedded in single object is suitable only for the applicators in the development. For quality assurance of pre-clinical and clinical systems it is feasible to create accurate 3D water bolus based on CT or MRI images [38].…”

Simultaneous ThermoBrachytherapy: Electromagnetic Simulation Methods for Fast and Accurate Adaptive Treatment Planning

“…As an evaluation metric, we used γ-index analysis [ 26 ]. This method has been extensively used in radiotherapy [ 27 , 28 ] and HT [ 29 , 30 ] for field comparisons, mainly between calculation and measurement, but also between two different calculation methods. We applied the 3D evaluation algorithm as applied by de Bruijne et al [ 29 ].…”

Hyperthermia: A Potential Game-Changer in the Management of Cancers in Low-Middle-Income Group Countries

“…In addition, model-based and other new MR-thermometry temperature reconstruction methods are emerging which are quite promising [ 35 , 36 , 37 ]. The unit is currently being validated in clinics for HT delivery in head and neck regions [ 38 ].…”