Computer Science
Scanning in the fourth dimension
A novel imaging method makes it possible to capture object deformation in three dimensions over time with unprecedented accuracy.
![A 360-degree scan is completed using each round offset to enhance information capture.](https://discovery.kaust.edu.sa/wp-content/uploads/sites/2/2023/02/5b1e61db62af01e71d7de663.jpg)
A 360-degree scan is completed using each round offset to enhance information capture.
Three-dimensional (3D) computed tomography is a widely used technology that visualizes an object’s external and internal structure by assembling a series of two-dimensional images taken sequentially across or around it. However, as anyone who has had a medical magnetic resonance imaging scan will recall, this type of 3D reconstruction requires the subject to be motionless throughout the capture process, which can take minutes. Capturing a 3D structure that changes or deforms over time is much more difficult, and existing approaches often yield reconstructions marred by image artifacts and partial surfaces.
![Conventional capture methods result in artifacts and partial surfaces (b). This is much improved with the new capture method (c). Then, by propagating information forward and backward in time using a flow field to encode the deformation, a vastly improved reconstruction can be obtained for a given time point (d).](https://discovery.kaust.edu.sa/wp-content/uploads/sites/2/2023/02/5b1e663362af01ea4d5a8d62.jpg)
Conventional capture methods result in artifacts and partial surfaces (b). This is much improved with the new capture method (c). Then, by propagating information forward and backward in time using a flow field to encode the deformation, a vastly improved reconstruction can be obtained for a given time point (d).
Guangming Zang, Ramzi Idoughi and their colleagues, under the leadership of Wolfgang Heidrich at KAUST, have developed a novel four-dimensional imaging method that vastly improves the quality of such space-time tomography for rapidly deforming objects.
“The primary challenge is when the deformation is so fast that the scanner can only capture a few images before the deformation becomes significant,” explains Zang. “The problem is then to reconstruct highly detailed 3D objects given only a few projections with a lot less information than would be available when reconstructing static objects.”
The team tackled the challenge in two parts. First, they modified the capture sequence to have a better distribution of scans over time. Then, they created an algorithm that allows the reconstruction at a given time point by using information from previous and subsequent acquisition steps.
“This is a major step toward making 3D tomography useful for probing internal structures of objects when changes during scanning cannot be avoided,” says Zang.
![The deformation of the object over time can then be reconstructed with high fidelity. This method was used to capture a wide range of dynamic phenomena, such as dehydration and rehydration of organic objects, rising dough and fluid flows.](https://discovery.kaust.edu.sa/wp-content/uploads/sites/2/2023/02/5b1e654a62af01e71d7de669.jpg)
The deformation of the object over time can then be reconstructed with high fidelity. This method was used to capture a wide range of dynamic phenomena, such as dehydration and rehydration of organic objects, rising dough and fluid flows.
All figures were reproduced from reference 1 © 2018 KAUST
Space-time tomography for continuously deforming objects.
© KAUST
References
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