College of Electronics Engineering, Ninevah University, Mosul 41002, Iraq.
School of EECS, The University of Queensland, St Lucia, QLD 4072, Australia.
Biosensors (Basel). 2024 Oct 12;14(10):498. doi: 10.3390/bios14100498.
Synthetic microwave focusing methods have been widely adopted in qualitative medical imaging to detect and localize anomalies based on their electromagnetic scattering signatures. This paper discusses the principles, challenges, and limitations of synthetic microwave-focusing techniques in medical applications. It is shown that the various focusing techniques, including time reversal, confocal imaging, and delay-and-sum, are all based on the scalar solution of the electromagnetic scattering problem, assuming the imaged object, i.e., the tissue or object, is linear, reciprocal, and time-invariant. They all aim to generate a qualitative image, revealing any strong scatterer within the imaged domain. The differences among these techniques lie only in the assumptions made to derive the solution and create an image of the relevant tissue or object. To get a fast solution using limited computational resources, those methods assume the tissue is homogeneous and non-dispersive, and thus, a simplified far-field Green's function is used. Some focusing methods compensate for dispersive effects and attenuation in lossy tissues. Other approaches replace the simplified Green's function with more representative functions. While these focusing techniques offer benefits like speed and low computational requirements, they face significant ongoing challenges in real-life applications due to their oversimplified linear solutions to the complex problem of non-linear medical microwave imaging. This paper discusses these challenges and potential solutions.
合成微波聚焦方法已广泛应用于定性医学成像，基于电磁散射特征来检测和定位异常。本文讨论了合成微波聚焦技术在医学应用中的原理、挑战和局限性。结果表明，各种聚焦技术，包括时间反转、共焦成像和延迟求和，都是基于电磁散射问题的标量解，假设成像对象，即组织或物体，是线性的、互易的和时不变的。它们的目的都是生成一个定性图像，揭示出成像域内任何强散射体。这些技术之间的区别仅在于为推导出解和创建相关组织或物体的图像而做出的假设。为了使用有限的计算资源获得快速的解决方案，这些方法假设组织是均匀的和非色散的，因此使用简化的远场格林函数。一些聚焦方法补偿了耗散介质中的色散和衰减。其他方法则用更具代表性的函数替代简化的格林函数。虽然这些聚焦技术具有速度快、计算要求低等优点，但由于其对复杂的非线性医学微波成像问题的线性简化解，在实际应用中仍面临重大挑战。本文讨论了这些挑战和潜在的解决方案。
