Integrating prior information into microwave tomography Part 1: Impact of detail on image quality

Abstract

Including knowledge of the breast surface and skin layer leads to a substantial improvement in image quality compared to the blind case, but the images have limited diagnostic utility for applications such as tumor response tracking. The diagnostic utility of the reconstruction technique is improved considerably when patient-specific structural information is used. This qualitative observation is supported quantitatively with image metrics.

Surface Estimation for Microwave Imaging

“…In the context of microwave tomography, we have collaborated with the Electromagnetic Imaging Laboratory at the University of Manitoba to investigate the impact of incorporating surface estimates in the reconstruction algorithm. The results of the study are reported in [ 14 ] (e.g., Figure 17 page 12). Without the breast surface incorporated into the image domain, internal structures are not clearly resolved.…”

“…Notably, these data are absent from the original set of measurements. The tessellation algorithm [ 21 ] is applied to the point cloud to produce a surface mesh shown in Figure 15 c that may be incorporated into an image reconstruction algorithm to form backscatter energy images [ 3 ], or dielectric property maps [ 14 ].…”

“…Microwave images are improved by providing information on the location of the tissues in the scanner. For microwave tomography, limiting the reconstruction to the breast reduces the number of unknowns and results in images with increased accuracy [ 14 , 37 , 38 , 39 ]. Radar-based approaches benefit from accurate estimates of the path lengths between the sensors and breast [ 3 , 11 , 12 , 13 ].…”

“…For radar-imaging (e.g., [ 3 ]), a coarsely tessellated surface is required to facilitate the calculation of path lengths in the various materials during image formation. Conversely, a finely tessellated surface is more appealing for microwave tomography (e.g., [ 14 ]), or for assessing variables associated with EM data acquisition such as penetration depth and object coverage [ 16 ]. An example showing the steps used to construct a surface model of a patient is shown in Figure 3 .…”

“…These path lengths and estimates of the velocities over the paths are used to evaluate time delays associated with points in the image domain that are used for image formation ([ 3 , 11 , 12 , 13 ], for example). For MW tomography, constraining the imaging domain to within the breast surface substantially improves image quality and also serves to encourage convergence to the actual solution (e.g., [ 14 , 15 ]).…”