What is the Future of Microwave Technology in Diagnostic Imaging?

Researchers at the Cancer Imaging and Radiobiology Research Program (CIR) at Dartmouth-Hitchcock's Norris Cotton Cancer Center study and test new ways to get good images using techniques that exploit different properties of tissue. This research program includes a collaborative team of engineers, family physicians, oncologists, and radiologists.

Focus article photo

A semi-transparent CT view of one a study participant's heel and ankle. The horizontal line overlays indicate where scientists will set the microwave imaging planes.

Microwave imaging has been shown reliable in detecting breast tumors

One area we are exploring is microwave technology: the same basic technology used in microwave ovens can be used to create an image of breast tissue. By sending very low levels (1,000 times less than a cell phone) of microwave energy through tissue, researchers can form a three-dimensional image. These images capture the dielectric properties -- electrical conductivity and permittivity (electrical resistance) -- of the tissue, which translates into detecting anomalies, such as tumors or other aberrations.

Paul Meaney, a professor at Dartmouth's Thayer School of Engineering, has been working on microwave engineering for more than 15 years, primarily with Keith Paulsen, the co-director of the CIR, and also the Robert A. Pritzker Professor of Biomedical Engineering at Dartmouth's Thayer School of Engineering; professor of radiology at the Geisel School of Medicine at Dartmouth; and director of the Dartmouth Advanced Imaging Center at Dartmouth-Hitchcock Medical Center.

Their work together has revealed that microwave imaging is not just for soft tissue, and it's not just for detecting tumors. They have determined that microwave technology can produce images of bones that correlate to other more commonly used techniques that measure bone density, like X-ray, ultrasound, or CT. Their work was published in the journal IEEE Transactions on Biomedical Engineering, and it's the first study to use microwave technology to get images of the calcaneus bone, or heel, in humans.

The heel region is comparable to the allotted breast size. With some minor modifications to the microwave image system Dartmouth scientists constructed to study breasts, they were able to move from investigating soft tissue to looking at heel bones.

Participant's leg being imaged

A study participant's leg being imaging in Dartmouth's microwave tomography system. Engineers constructed the fixture to allow the heel to protrude into the imaging tank below.

Semi-transparent images of the heel bone

Semi-transparent images of the heel bone 2

These semi-transparent images of the heel bone are believed to be the first 3D tomographic images of any anatomical site in a living human being made using microwave imaging technology.

Can Microwave technology work for hips or spine?  They start with the heel.

Meaney, the lead author on the research paper, explains that the calcaneus is comprised primarily of trabecular bone, "which means it has a honeycomb-like structure with a thin outer coating of cortical bone. Its structure and weight-bearing characteristics are similar to the hip and spine, but it's easier to get a picture of as it's small and not near any vital organs."

Could this be used to predict or detect hip fractures?

"This is a pilot study," says Meaney. "It helps us understand if microwave technology works in this way, and it did."  This could help doctors gauge whether an elderly patient, for example, is susceptible to similar broken bones, like the hip bone.

Meaney says, "The microwave properties seemed to track well with the X-ray properties. But since this study only included two people, it's difficult to make strong conclusions. We think they are encouraging findings, though, and enough evidence to keep looking into it."

Meaney and Paulsen worked on this study with Douglas Goodwin, a radiologist at Dartmouth-Hitchcock Medical Center; fellow engineers Amir Golnabi, Tian Zhou, and Matthew Pallone at the Thayer School of Engineering, and Gregory Burke, formerly with the radiology department at Dartmouth's Geisel School of Medicine, now with  the US ARMY ARDEC in Picatinny, NJ.

Learn about how you can help advance medicine by participating in clinical research at Norris Cotton Cancer Center: or call 1 (800) 639-6918 to speak with a cancer research nurse.

Watch this short video interview with Keith Paulsen to learn more about Dartmouth's research into advanced imaging, like microwave technology, for breast cancer.

This work was supported by NIH/NCI grant # P01-CA080139.

December 10, 2012