3D multi-frequency antenna arrays for clinical validation of microwave breast imaging.

摘要

Microwave breast imaging has been identified as a promising low-cost, non-ionizing, and 3D imaging modality for improving breast cancer screening and diagnosis. An array of antennas transmits low-power microwave signals into the breast. The measured scattered signals are used to reconstruct the spatial distribution of the dielectric properties throughout the breast volume via a solution of the inverse scattering problem. Interpreting results from initial clinical studies of microwave tomographic imaging has been hindered by the lack of precise co-registration between microwave and benchmark images. At this stage, rigorous validation of microwave breast imaging against a 3D clinical benchmark such as magnetic resonance imaging (MRI) is needed and requires image co-registration, which is most reliably achieved with the breast in the same position during both the MRI and microwave scans.;We address two key factors that would enable straightforward co-registration and an objective and unambiguous comparison with MRI. First, we investigate the use of a polycaprolactone (PCL)-based thermoplastic mesh to serve as a tissue immobilization interface in a microwave imaging system designed for MRI-based validation. We characterize the wideband dielectric properties of thermoplastic meshes in the frequency range of 0.5-3.5 GHz. We also characterize the dielectric properties of a vegetable oil – a candidate biocompatible immersion medium for the microwave imaging system. We show that the PCL-based thermoplastic material and the vegetable oil are well matched, essentially rendering the mesh invisible during the microwave scan.;Second, we investigate the performance characteristics of a class of slot-loaded patch antennas that compose a 3D microwave breast imaging array configured to occupy the space vacated by removable breast coils in the patient support platform of a breast MRI system. This configuration imposes a constraint on the overall size and layout of the antenna array system and necessitates the use of miniaturized antennas. Additionally, the antennas are designed to operate in the biocompatible immersion medium at multiple frequencies within the frequency range of 0.5-3.5 GHz. Investigations on the radiation characteristics of the slot-loaded patch antenna elements and the multi-static channel characteristics of the array indicate that these sensors are suitable candidates for microwave breast imaging.