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Proceedings Paper

Spatio-temporal filtration of dynamic CT data using diffusion filters
Author(s): H. Bruder; R. Raupach; E. Klotz; K. Stierstorfer; T. Flohr
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Paper Abstract

We present a method for spatio-temporal filtration of dynamic CT data, to increase the signal-to-noise ratio (SNR) of image data at the same time maintaining image quality, in particular spatial and temporal sharpness of the images. Alternatively, the radiation dose applied to the patient can be reduced at the same time maintaining the noise level and the image sharpness. In contrast to classical methods, which generally operate on the three spatial dimensions of image data, noise statistics is improved by extending the filtration to the temporal dimension. Our approach is based on nonlinear and anisotropic diffusion filters, which are based on a model of heat diffusion adapted to medical CT data. Bilateral filters are a special class of diffusion filters, which do not need iteration to reach a convergence image, but represent the fixed point of a dedicated diffusion filter. Spatio-temporal, anisotropic bilateral filters are developed and applied to dynamic CT image data. The potential was evaluated using data from perfusion CT and cardiac dual source CT (DSCT) data, respectively. It was shown, that in perfusion CT, SNR can be improved by a factor of 4 at the same radiation dose. On basis of clinical data it was shown, that alternatively the radiation dose to the patient can be reduced by a factor of at least 2. A more accurate evaluation of the perfusion parameters blood flow, blood volume and time-to-peak is supported. In DSCT noise statistics can be improved using more projection data than needed for image reconstruction, however, as a consequence the temporal resolution is significantly impaired. Due to the anisotropy of the spatio-temporal bilateral filter temporal contrast edges between adjacent time samples are preserved, at the same time substantially smoothing image data in homogeneous regions. Also temporal contrast edges are preserved, maintaining the very high temporal resolution of DSCT acquisitions (~ 80 ms). CT examinations of the heart require careful dose management to reduce the radiation dose burden to the patient. The use of spatio-temporal diffusion filters allows for dose reduction at the same noise level, at the same time preserving spatial and temporal image resolution. Our approach can be extended to any imaging method, that is based on dynamic data, as an efficient tool for edge-preserving noise reduction.

Paper Details

Date Published: 13 March 2009
PDF: 10 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 725857 (13 March 2009); doi: 10.1117/12.811085
Show Author Affiliations
H. Bruder, Siemens, HealthCare (Germany)
R. Raupach, Siemens, HealthCare (Germany)
E. Klotz, Siemens, HealthCare (Germany)
K. Stierstorfer, Siemens, HealthCare (Germany)
T. Flohr, Siemens, HealthCare (Germany)

Published in SPIE Proceedings Vol. 7258:
Medical Imaging 2009: Physics of Medical Imaging
Ehsan Samei; Jiang Hsieh, Editor(s)

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