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CT RECONSTRUCTION

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CT RECONSTRUCTION

1. In a modern scanner, during acquisition, X-rays are produced continuously.
2. A series of projections through the patient are collected at discrete angles (e.g. every 0.5°).
3. If there are 900 detectors, that’s 900 * (360 * 2) = 648,000 measurements per rotation.
4. Think of the fan beam as composed of many narrow pencil beams, one to each detector.
5. Each detector, therefore, samples a point on the projection that represents the total attenuation along the pencil beam path from source to detector.
6. For every 360° rotation, an individual voxel is traversed by one or more pencil beams for every measurement taken.
7. The attenuation of each voxel, therefore, contributes to the measured transmission for a large number of the ray sums.
8. An algorithm is then used to reconstruct the images using the CT attenuation data for each voxel.


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REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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