Microwave Tomography: Clinical Success and Why So Many Efforts Fail

Authors: Paul Meaney

Source: FERMAT, Volume 18, Communication 6, Sep , 2016

Abstract: There has been a wide range of hype surrounding microwave imaging for a number of decades. Much of the interest has centered in academia and especially in the numerical modeling realm. The major motivations are that tissue dielectric properties can be remarkably specific and that microwave radiation is nonionizing. For instance, breast tumors generally have higher dielectric properties than normal breast tissue - a possible mechanism for cancer detection. In addition, recent studies show that bone dielectric properties change with bone density – a possible alternate to x-ray densitometry for monitoring bone loss. Blood properties are different than those for brain tissue – possible applications in stroke diagnosis. These are only a few potential medical applications. The Dartmouth Microwave Imaging Group is the only group in the world to have an actual working tomography system in the clinic. A large part of this success is related to the unconventional and counterintuitive antenna array we use. Our development has been a unique synergism of hardware and software expertise which has allowed us to perform over 500 patient breast exams along with a small pilot study looking at bone screening. I will briefly discuss some of the more daunting implementation challenges and how we’ve addressed them. This will include our unique algorithmic approach, which now allows us to reconstruct images from exams in only a few minutes compared to hours to days for other modeling groups. In addition, this approach has allowed us to apply a fairly simple hardware configuration that keeps the number of antennas and transmit/receive pairs to a minimum and dramatically impacts the overall system cost. Complementing this design, we’ve also directly addressed multi-path signal interference problems which plague most system implementations. More importantly, we have developed a strategy for recovering images that is not subject to convergence to local minima or unwanted solutions which plagues most current approaches.

I will show a broad array of images from our clinical system including a variety of breast cancer detection and therapy monitoring examples. In addition, I will also show some of the more recent bone results as an example of where this technology can have important healthcare impact.

Index Terms: microwave tomography, breast cancer imaging, multi-path signals, unique solution log transform

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Microwave Tomography: Clinical Success and Why So Many Efforts Fail