| Research Abstract |
X-ray CT is widely used as non-destructive measuring means for visualizing the interior of an objective e.g. diagnoses of ill focuses. Studies on 3D image reconstruction from 2D observations of penetrating photons with the form of cone-beam from have been recently done in accordance with development of plane photon detectors. However the algorithm of 3D reconstruction under the scenario requires huge amount of computations. Therefore for real-time observation of moving internal organs such as heart, ultra-high speed computer, such as massive array processor, is required. The objective of this project was to drastically shorten the processing time for 3D image reconstruction by using the subband analysis/synthesis technology that receives attention in the field of signal processing to the backprojection computations in the 3D reconstruction algorithm. The main results of the project are as follows
・ Parallel Implementation for 2D reconstruction algorithm
We proved that real-time image reconstruction (approximately 30 msec) of 2D slice picture of the size 256x256 pixels by use of our proposed algorithm is possible on the Pentium 3 personal computer (1GHz) with parallel architecture, while the existing method does not have such a parallel structure. The speed ratio of our method to the existing one is approximately 30 : 1.
・ Development of 3D reconstruction algorithm
In the next, we developed 3D reconstruction algorithm. The simple extension of the above 2D algorithm to 3D that is considered 3D inverse Radon transform was performed approximately 700 times faster than the existing method. In the 3D algorithm, the processing called reprojection is necessary, which also time consuming likely as 3D backprojection. We also showed for that processing we can use subband technique.
If we make use of the SIMD commands prepared in the Pentium 3, we will be able to construct 3D object of the size of 256x256x256 pixels in real time by use of the 16 processors in parallel.
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