동적 시준을 이용한 CT 촬영과 볼록한 관심영역의 영상재구성
Dynamically Collimated CT Scan and Image Reconstruction of Convex Region-of-Interest
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Computed tomography (CT) is one of the most widely used medical imaging modality. However, substantialx-ray dose exposed to the human subject during the CT scan is a great concern. Region-of-interest (ROI)CT is considered to be a possible solution for its potential to reduce the x-ray dose to the human subject. In mostof ROI-CT scans, the ROI is set to a circular shape whose diameter is often considerably smaller than the full fieldof-view (FOV). However, an arbitrarily shaped ROI is very desirable to reduce the x-ray dose more than the circularlyshaped ROI can do. We propose a new method to make a non-circular convex-shaped ROI along with the image reconstructionmethod. To make a ROI with an arbitrary convex shape, dynamic collimations are necessary to minimizethe x-ray dose at each angle of view. In addition to the dynamic collimation, we get the ROI projection data withslightly lower sampling rate in the view direction to further reduce the x-ray dose. We reconstruct images from theROI projection data in the compressed sensing (CS) framework assisted by the exterior projection data acquired fromthe pilot scan to set the ROI. To validate the proposed method, we used the experimental micro-CT projection dataafter truncating them to simulate the dynamic collimation. The reconstructed ROI images showed little errors ascompared to the images reconstructed from the full-FOV scan data as well as little artifacts inside the ROI. We expectthe proposed method can significantly reduce the x-ray dose in CT scans if the dynamic collimation is realized inreal CT machines.
Abstract
Computed tomography (CT) is one of the most widely used medical imaging modality. However, substantialx-ray dose exposed to the human subject during the CT scan is a great concern. Region-of-interest (ROI)CT is considered to be a possible solution for its potential to reduce the x-ray dose to the human subject. In mostof ROI-CT scans, the ROI is set to a circular shape whose diameter is often considerably smaller than the full fieldof-view (FOV). However, an arbitrarily shaped ROI is very desirable to reduce the x-ray dose more than the circularlyshaped ROI can do. We propose a new method to make a non-circular convex-shaped ROI along with the image reconstructionmethod. To make a ROI with an arbitrary convex shape, dynamic collimations are necessary to minimizethe x-ray dose at each angle of view. In addition to the dynamic collimation, we get the ROI projection data withslightly lower sampling rate in the view direction to further reduce the x-ray dose. We reconstruct images from theROI projection data in the compressed sensing (CS) framework assisted by the exterior projection data acquired fromthe pilot scan to set the ROI. To validate the proposed method, we used the experimental micro-CT projection dataafter truncating them to simulate the dynamic collimation. The reconstructed ROI images showed little errors ascompared to the images reconstructed from the full-FOV scan data as well as little artifacts inside the ROI. We expectthe proposed method can significantly reduce the x-ray dose in CT scans if the dynamic collimation is realized inreal CT machines.
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