基于仿真的设计和小型动物磁共振引导下的热疗实验研究用微波加热装置的特性描述。
Simulation-based design and characterization of a microwave applicator for MR-guided hyperthermia experimental studies in small animals.
机构信息
Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA.
Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA.
出版信息
Biomed Phys Eng Express. 2020 Jan;6(1). doi: 10.1088/2057-1976/ab36dd. Epub 2019 Nov 27.
PURPOSE
The objective of this study was to design and characterize a 2.45 GHz microwave hyperthermia applicator for delivering hyperthermia in experimental small animals to 2 - 4 mm diameter targets located 1 - 3 mm from the skin surface, with minimal heating of the surrounding tissue, under 14.1 T MRI real-time monitoring and feedback control.
MATERIALS AND METHODS
An experimentally validated 3D computational model was employed to design and characterize a non-invasive directional water-cooled microwave hyperthermia applicator. We assessed the effects of: reflector geometry, monopole shape, cooling water temperature, and flow rate on spatial-temperature profiles. The system was integrated with real-time MR thermometry and feedback control to monitor and maintain temperature elevations in the range of 4 - 5 °C at 1 - 3 mm from the applicator surface. The quality of heating was quantified by determining the fraction of the target volume heated to the desired temperature, and the extent of heating in non-targeted regions.
RESULTS
Model-predicted hyperthermic profiles were in good agreement with experimental measurements (Dice Similarity Coefficient of 0.95 - 0.99). Among the four considered criteria, a reflector aperture angle of 120 °, S-shaped monopole antenna with 0.6 mm displacement, and coolant flow rate of 150 ml/min were selected as the end result of the applicator design. The temperature of circulating water and input power were identified as free variables, allowing considerable flexibility in heating target sizes within varying distances from the applicator surface. 2 - 4 mm diameter targets positioned 1 - 3 mm from the applicator surface were heated to hyperthermic temperatures, with target coverage ratio ranging between 76 - 93 % and 11 - 26 % of non-targeted tissue heated.
CONCLUSION
We have designed an experimental platform for MR-guided hyperthermia, incorporating a microwave applicator integrated with temperature-based feedback control to heat deep-seated targets for experimental studies in small animals.
目的
本研究旨在设计并表征一种 2.45GHz 微波热疗适形器，以便在 14.1T MRI 实时监测和反馈控制下，将深部目标（位于距皮肤表面 1-3mm 处，直径 2-4mm）加热至 4-5°C，同时最小化周围组织的升温。
材料与方法
采用经实验验证的三维计算模型来设计和表征一种非侵入性定向水冷微波热疗适形器。我们评估了以下因素对空间-温度分布的影响：反射器几何形状、单极子形状、冷却水温度和流速。该系统与实时磁共振测温及反馈控制相结合，以监测和维持距适形器表面 1-3mm 处的升温在 4-5°C 的范围内。通过确定加热至目标温度的目标体积分数以及非目标区域的加热程度，量化加热质量。
结果
模型预测的热疗分布与实验测量结果吻合良好（Dice 相似系数为 0.95-0.99）。在考虑的四个标准中，选择反射器孔径角为 120°、具有 0.6mm 位移的 S 形单极子天线以及 150ml/min 的冷却水流速作为适形器设计的最终结果。循环水温度和输入功率被确定为自由变量，这使得在距适形器表面不同距离范围内加热目标尺寸具有相当大的灵活性。将直径为 2-4mm、位于距适形器表面 1-3mm 处的目标加热至热疗温度，目标覆盖比为 76%-93%，11%-26%的非目标组织被加热。
结论
我们设计了一个用于磁共振引导热疗的实验平台，将微波适形器与基于温度的反馈控制相结合，以加热小动物实验中的深部目标。
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