Exploiting Microwave Imaging Methods for Real-Time Monitoring of Thermal Ablation

Abstract

Microwave thermal ablation is a cancer treatment that exploits local heating caused by a microwave electromagnetic field to induce coagulative necrosis of tumor cells. Recently, such a technique has significantly progressed in the clinical practice. However, its effectiveness would dramatically improve if paired with a noninvasive system for the real-time monitoring of the evolving dimension and shape of the thermally ablated area. In this respect, microwave imaging can be a potential candidate to monitor the overall treatment evolution in a noninvasive way, as it takes direct advantage from the dependence of the electromagnetic properties of biological tissues from temperature. This paper explores such a possibility by presenting a proof of concept validation based on accurate simulated imaging experiments, run with respect to a scenario that mimics an ex vivo experimental setup. In particular, two model-based inversion algorithms are exploited to tackle the imaging task. These methods provide independent results in realtime and their integration improves the quality of the overall tracking of the variations occurring in the target and surrounding regions.

Differential Ultra-Wideband Microwave Imaging: Principle Application Challenges

“…However, there is an exception if the weak scattering target of interest is subjected to some variations, which may be caused by the following: temporal fluctuations inherently connected with the test scenario (e.g., the vital motion of inner organs of humans and animals, the breathing motion of buried survivors after an earthquake, and the motion of wood-destroying insects, as well as slowly running events, such as the putrefaction of biological substances, the healing process after a medical surgery [ 6 ], post-event monitoring of stroke [ 7 ], and many more); a targeted influence of the hidden object of interest via modification of its position in space, its volume, and its permittivity or permeability (e.g., the targeting of malignant tissue by nanoparticles, permittivity variation by local heating or cooling [ 8 , 9 ], water accumulation in hygroscopic substances, etc. ); and small deviations between two largely identical SUTs (cancer in one of the two female breasts [ 10 ], foreign objects in chocolate, other identical food pieces, etc.).…”

“…a targeted influence of the hidden object of interest via modification of its position in space, its volume, and its permittivity or permeability (e.g., the targeting of malignant tissue by nanoparticles, permittivity variation by local heating or cooling [ 8 , 9 ], water accumulation in hygroscopic substances, etc. ); and…”

“…In all of these examples, we are only interested in the imaging and localization, respectively, of small differences—hence, we call it differential imaging—in the scattering scenario in its different states. Basically, the imaging may be based on a tomographic approach (see e.g., [ 9 ]) or on radar image processing. Tomographic methods usually work with narrowband signals and require a dense antenna array, while radar-based techniques need wideband sounding signals but do not require a dense antenna array [ 5 ].…”

Monitoring Microwave Thermal Ablation using Electrical Impedance Tomography: an experimental feasibility study

“…Following the above, MTA procedures lack of a reliable, non-invasive, and cost-effective method for real time monitoring of the evolving thermal ablation area [11]. Recent studies investigated applicability of microwave imaging to derive, from the changes in the dielectric properties of tissues induced by the temperature increase [12], the map of the temperature in the treated area [13], [14].…”

Monitoring Thermal Ablation via Microwave Tomography: An Ex Vivo Experimental Assessment

“…Microwave tomography (MWT) has been recently proposed as an alternative imaging modality for non-invasive real-time monitoring of thermal ablation procedures [25,26,27]. MWT images the variation of the electromagnetic properties with respect to an unperturbed situation, by recording (and properly processing) the electromagnetic field backscattered by the region of interest when probed by a known incident wave.…”