Electrical and Electronic Engineering, National University of Ireland Galway, Galway, Ireland.
Translational Medical Device Lab, National University of Ireland Galway, Galway, Ireland.
Int J Hyperthermia. 2022;39(1):1179-1194. doi: 10.1080/02656736.2022.2114611.
Adrenocortical neoplasms are the main causes of secondary hypertension and related comorbidities including hypokalemia and cardiovascular diseases. Conventional techniques for the management of this condition are often invasive and not resolutive. Recent studies proposed microwave thermal ablation (MWA) to eradicate adrenocortical adenomas arising in proximity to sensitive structures. This study explores a new MWA approach to selectively direct the electromagnetic energy into the target and shield the surrounding tissues. The new solution relies on the anatomical and dielectric characteristics of the adrenal gland and the surrounding fat capsule.
A 3 D model of the adrenal gland is developed, and a cooled microwave applicator is placed parallel to the interface between the fat and adrenal tissue. Numerical simulations are conducted at 2.45 GHz accounting for two energy delivery settings, two orientations of the applicator and blood perfusion of the tissues and ablation procedures are conducted on ovine adrenal glands. Histology analysis completes the experimental studies.
Numerical results show asymmetric ablation profiles in and conditions. The asymmetry ratio is influenced by the procedure settings and orientation of the applicator. Ablation zones obtained experimentally agree with those predicted by the numerical simulations. Histology analysis confirms irreversible cellular changes only in the adrenal tissue close to the applicator.
The outcomes show that the dielectric contrast between the fat layer and tissue target can be a tool in MWA to shape ablation zones to protect the surrounding structures from excessive temperature increases.
肾上腺肿瘤是导致继发性高血压及相关并发症（如低钾血症和心血管疾病）的主要原因。传统的治疗方法往往具有侵入性，且无法完全解决问题。最近的研究提出了微波热消融（MWA）技术来消除紧邻敏感结构的肾上腺腺瘤。本研究探索了一种新的 MWA 方法，旨在选择性地将电磁能量引导至目标组织，并屏蔽周围组织。该新方法基于肾上腺和周围脂肪囊的解剖和介电特性。
建立了肾上腺的 3D 模型，并将冷却式微波天线平行放置于脂肪和肾上腺组织的界面处。在 2.45GHz 下进行了数值模拟，考虑了两种能量传递设置、两种天线方向以及组织的血液灌注情况，并在绵羊的肾上腺上进行了消融实验。组织学分析完成了实验研究。
数值结果显示，在 和 两种情况下，消融剖面呈现不对称性。不对称比受程序设置和天线方向的影响。实验获得的消融区域与数值模拟预测的结果一致。组织学分析证实，仅在靠近天线的肾上腺组织中观察到不可逆的细胞变化。
研究结果表明，脂肪层和组织靶之间的介电对比度可以成为 MWA 中的一种工具，用于塑造消融区域，以防止周围结构因温度过度升高而受到损伤。
