Electromagnetic redesign of the HYPERcollar applicator: toward improved deep local head-and-neck hyperthermia

Abstract

Accumulating evidence shows that hyperthermia improves head-and-neck cancer treatment. Over the last decade, we introduced a radiofrequency applicator, named HYPERcollar, which enables local heating also of deep locations in this region. Based on clinical experience, we redesigned the HYPERcollar for improved comfort, reproducibility and operator handling. In the current study, we analyze the redesign from an electromagnetic point of view. We show that a higher number of antennas and their repositioning allow for a substantially improved treatment quality. Combined with the much better reproducibility of the water bolus, this will substantially minimize the risk of underexposure. All improvements combined enable a reduction of hot-spot prominence (hot-spot to target SAR quotient) by 32% at an average of 981 W, which drastically reduces the probability for system power to become a treatment limiting source. Moreover, the power deposited in the target selectively can be increased by more than twofold. Hence, we expect that the HYPERcollar redesign currently under construction allows us to double the clinically applied power to the target while reducing the hot-spots, resulting in higher temperatures and, consequently, better clinical outcome.

A Computational Study Using Time Reversal Focusing for Hyperthermia Treatment Planning

“…They utilize the constructive wave interference from a set of antennas at the tumor site [5][6][7][8]. The parameters that determine the system's ability to focus are the phases and amplitudes of the excitation of antennas in the phased array.…”

Focusing microwave hyperthermia in realistic environment for breast cancer treatment

“…For example, the potential of using microwave hyperthermia for the treatment of malignancies in head, neck and chest regions [19], [36][37][38][39][40][41][42] has been clinically tested [43,44]. For microwave hyperthermia to be successful in treating cancer, tumours are heated to a moderate temperature while keeping healthy tissue at normal body temperature.…”

“…According to [43], the hot spot to target specific absorption ratio (SAR) quotient (HTQ) can be used to avoid undesired heating in healthy tissue. It was concluded that if HTQ is less than 1, the resulted temperature induced in the tumour is always higher than other areas.…”

“…This work presents interesting results for a preclinical hyperthermia system for breast cancer treatment using image-based time-reversal focusing technique. In another approach [43], a horse-shoe antenna array arrangement was proposed for microwave hyperthermia treatment of the neck.…”

“…The previously used configurations [73][74][75]77] ignored the radiation properties of realistic antenna arrays, which define the true direction and wave-front shape of travelling waves inside the phantom. Moreover, some of the previously presented systems suffer from a low power efficiency [80], while others, such as [43], are based on optimizing the specific absorption rate without thermal prediction or guarantee that no hot spots are generated.…”