(Sunday, 7/12/2020) 2:00 PM - 3:00 PM [Eastern Time (GMT-4)]
Room: Track 1
Purpose: To develop a microwave imaging system to acquire 4D computed tomographic microwave images reconstructed using holographic back-projection algorithm.
Methods: Microwave images were acquired using an opposed 10.25GHz transmitter-receiver microwave system. The transmitted and scattered microwave signals were measured by scanning the microwave system around a mobile phantom that included inserts of bone, muscle, breast and lung equivalent tissues. A holographic back-projection image reconstruction algorithm was used to reconstruct computed tomographic microwave images. Microwave interference and polarization artifacts in the line projections were corrected prior to image reconstruction. A Motion classification algorithm was developed that correlated variation in the microwave intensity with variations in position, volume and density of the phantom in the field of view to extract motion trajectory.
Results: 4D microwave images of a mobile phantom that included inserts with different densities were acquired using a one transmitter–receiver microwave system and reconstructed using a holographic back-projection algorithm. The microwave images obtained from this system were sensitive to density, size and position of the phantom inserts in the imaging field of view. The measured microwave intensity varied non-linearly with the insert densities and phantom thickness. However, the variations in the microwave intensity changed almost linearly with changes of the water volume in the microwave field of view. Microwave images with high contrast (>5%) and spatial resolutions (3mm) were obtained for the different phantom objects. The use a multiple-array detector system with many transmitters and receivers will improve data acquisition and the microwave image quality and allow real time motion tracking of mobile phantoms.
Conclusions: This system demonstrates the ability to acquire 4D-microwave images for mobile phantoms with different tissue equivalent materials with different densities. Microwave imaging and respiratory motion tracking has potential clinical application in diagnostic imaging and treatment of cancer patients with radiation therapy.
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