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Proceedings Paper

Region of interest (ROI) computed tomography (CT): comparison with full field of view (FFOV) and truncated CT for a human head phantom
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Paper Abstract

Cone-beam CT reconstruction can be performed at lower integral dose, by using a non-uniform beam filter between the x-ray source and the patient to obtain good image quality within an ROI with minimal artifacts. To evaluate the method, a human head phantom was placed on a rotary stage. Cone-beam projection images of the phantom were obtained with and without an ROI filter (dose reduction factor ~7). A mapping function was established to equalize the intensity outside the ROI (to compensate for the attenuation by the filter) to the intensity inside by assuming that those features lying both inside and outside very close to the edge of the ROI are the same. Reconstructed images were obtained using equalized projection images for 2 cases: one in which the outside region was smoothed using an averaging filter and the other with no smoothing outside. In addition, a third case was simulated by calculating the average pixel value inside the ROI for each image and assigning this value to all pixels outside the ROI for that image. The images were then back projected using a Feldkamp algorithm. We found that the three cases yield results inside the ROI comparable to those obtained using FFOV projections. In addition, the ROI filter reconstruction with smoothing provides image information outside the ROI comparable to the FFOV reconstruction. CT using an ROI filter provides a means to reconstruct reliable 3D for a volume of interest with greatly reduced integral dose compared to FFOV projections and with minimal artifacts.

Paper Details

Date Published: 20 April 2005
PDF: 8 pages
Proc. SPIE 5745, Medical Imaging 2005: Physics of Medical Imaging, (20 April 2005); doi: 10.1117/12.595430
Show Author Affiliations
R. Chityala, Toshiba Stroke Research Ctr/State Univ of New York at Buffalo (United States)
Erie County Medical Ctr. (United States)
K. R. Hoffmann, State Univ of New York at Buffalo (United States)
Toshiba Stroke Research Ctr/State Univ of New York at Buffalo (United States)
S. Rudin, State Univ. of New York at Buffalo (United States)
Toshiba Stroke Research Ctr/State Univ of New York at Buffalo (United States)
Erie County Medical Ctr. (United States)
D. R. Bednarek, State Univ. of New York at Buffalo (United States)
Toshiba Stroke Research Ctr/State Univ of New York at Buffalo (United States)
Erie County Medical Ctr. (United States)


Published in SPIE Proceedings Vol. 5745:
Medical Imaging 2005: Physics of Medical Imaging
Michael J. Flynn, Editor(s)

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