Tomographic Imaging of Moving Objects

A classical X-ray computerized tomographic (CT) scanner provides cross-sectional images of objects in a nondestructive manner. This approach gives erroneous results when the object under consideration has certain time-dependent properties. These results can be improved by certain corrections that can be applied in the reconstruction process. An experiment is performed (at IIT Kanpur) on a mini-CT scanner (Procon X-ray GmbH) for dynamic imaging of a circular 20 mm dia object made of Perspex. This CT set-up has a 7 micron focal spot X-ray unit and a flat panel detector of 1024 x 1024 photo-diodes. It gives 3D projection data in cone-beam geometry configuration. Five specimens (made of Perspex) were scanned for 400 projections. These specimens represent the state of a time-dependent object at five different measurement times. They have several holes which represent voids. The positions of hollow cylinders (holes) are changed in all five specimens assuming that voids appear at different positions (on the cross-section) at different times due to the moving boundaries of the object (e.g. the human heart). Convolution back-projection algorithm is used for reconstruction purposes. Dynamic bias correction is applied and corrected cross-sections are characterized with “KT-2” signature. This approach is based on Sobolev space framework and it is “global” in nature. It is useful for predicting the type of flow pattern and the size of bubbles.

References
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