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IMAGE RECONSTRUCTION METHOD FOR CT SCANNER IN MEDICAL IMAGING

IP.com Disclosure Number: IPCOM000124162D
Publication Date: 2005-Apr-11
Document File: 8 page(s) / 251K

Publishing Venue

The IP.com Prior Art Database

Abstract

In an embodiment, an image reconstruction method based on distance of pixel from centre of a detector in a CT scanner, especially in medical imaging. The method includes maintaining the image noise (resolution) near the center e.g. for the heart, while reducing the image noise gradually towards the edge of the scanning field of view. The method includes pre-generating and storing a family of Smoothing_Gain_Factor (SGF) curves. The SGF curve is a function of the distance of the pixels from the center of the detector. The curve controls the contribution of the smoothing process to the final projections depending on how far the projection is from the center of the detector

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IMAGE RECONSTRUCTION METHOD FOR CT SCANNER IN MEDICAL IMAGING

FIELD OF THE INVENTION
[0001] This invention relates generally, to image reconstruction and more particularly to, image reconstruction method based on distance of pixel from centre of a detector in a CT scanner, especially in medical imaging.

BACKGROUND OF THE INVENTION
[0002] CT scanners offer different X-ray filters (bowties) for scanning different sizes of patients to provide more uniform X-ray flux at the detector. The small bowtie which has narrower opening (longer path length of the bowtie towards the outside of the filter) compared with the large bowtie is used for head and small body scanning, while the large bowtie is mainly used for scanning adult bodies. Therefore traditionally the large bowtie is used for cardiac scanning of an adult.
[0003] Recently, however, reducing the dose to the patients has become a more and more important issue. Since the heart is located near the center of the scan field of view, the use of small bowtie instead of a large bowtie for the cardiac scans can save patient surface by 15% to 20% dependent on the patient size, compared to the use of the large bowtie. Because of the similarity of the small and large bowties near the center, image quality for the heart should not be affected switching from the large bowtie to the small bowtie. However, because of the longer path length of the small bowtie near the edge of the body (where dose saving occurs), image noise increases from the center to the edge.

BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 shows an example of an SGF curve according to this invention.
[0005] FIG. 2 shows an example of mean noise measurement in images obtained by the method according to one embodiment of this invention.

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[0006] FIG. 3 shows an example of edge-mean noise measurement in images obtained by the method according to one embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION
[0007] Various embodiments of this invention provide an image reconstruction method based on distance of pixel from centre of a detector in a CT scanner, especially in medical imaging. However, the embodiments are not limited and may be implemented in connection with other systems including but not limited to cardiac imaging.
[0008] In an embodiment of this invention, an image reconstruction method for CT systems includes filtering the projections based on their distance to the center on the detector. This method maintains the image noise (resolution) near the center e.g. for the heart, while reducing the images noise gradually towards the edge of the scanning field of view.
[0009] A detailed description of this algorithm is as follows: 1. Pre-generate and store in the system, a family of Smoothing_Gain_Factor (SGF) curves. The SGF curve is a function of the distance of the pixels from the center of the detector. The curve controls the contribution of the smoothing process to the final projections depe...