Intracranial hemorrhage imaging-based follow-up: experimental assessment using a microwave imaging scanner

This work presents the experimental assessment of a microwave imaging device for the monitoring of intracranial hemorrhages. The considered low-complexity scanner prototype is made of an array of twenty-two antennas, conformally placed on top the head, a 2-port compact vector network analyzer and an ad-hoc electromechanical switching matrix. The device exploits a non-iterative linearized differential algorithm together with additional robustizing stages of pre and post data processing that allow performance in real-life conditions. The pre-processing acts directly on measured S-parameters, limiting the effect of noise on the data. Instead, the post-processing compensates the lack of symmetry of the measured scattering matrix to mitigate the artifacts propagated through the imaging kernel. As a whole, the imaging algorithm performs in almost real-time, retrieving instantaneous 3-D qualitative maps of the head indicating the physical temporal variation of the hemorrhage affected area. The proof-of concept experiment consists in monitoring an evolving hemorrhage condition either worsening (increasing) or recovering (decreasing). To this end the hemorrhage is simulated with a balloon gradually filled with blood-mimicked liquid, positioned in an anthropomorphic single-cavity plastic head phantom filled with an alcohol-water-salt mixture resembling the average dielectric properties of the brain. The outcomes show that the system and algorithm are able to indicate and track variations with a centimetric spatial resolution.