Apparatus and method for image reconstruction and CT system

An apparatus for image reconstruction used for image reconstruction according to projection data obtained by an asymmetric detector, said apparatus comprises:

• a region dividing unit configured to divide the projection data into Region 1, Region 2, Region 3, Region 4 and Region 5, Region 1 being an asymmetric region where there are detecting channels but no detecting channels symmetrical about a central channel, Region 2 being a transition region where there are detecting channels and there are also detecting channels symmetrical about the central channel, Region 3 being a symmetric region where there are detecting channels and there are also detecting channels symmetrical about the central channel, Region 4 being a transition region where there are detecting channels and there are also detecting channels symmetrical about the central channel, and Region 5 being a truncated region where there is no detecting channel;
• a view angle weighting unit configured to perform view angle weighting on the projection data in each of Region 1, Region 2, Region 3, Region 4, and Region 5, wherein for an axial scan, weights of the projection data in the Regions are such that weights of the Projection data in Region 1 are 1, weights of the projection data in Region 3 are ½, weights of the projection data in Region 5 are 0, weights of the projection data in Region 2 are 1˜½, and weights of the projection data in Region 4 are ½˜0;
• and
• a reconstructing unit configured to reconstruct a tomographic image of an irradiated subject from the weighted projection data.

A CT system for image reconstruction comprising:

• a tube configured to emit X-rays toward an object;
• a detector system configured to convert X-rays received from said tube into projection data, said detector system comprising at least one symmetric detector and at least one asymmetric detector;
• and
• an apparatus used for image reconstruction according to the projection data obtained by the asymmetric detector, said apparatus comprises:
• a region dividing unit configured to divide the projection data into Region 1, Region 2, Region 3, Region 4 and Region 5, Region 1 being an asymmetric region where there are detecting channels but no detecting channels symmetrical about a central channel, Region 2 being a transition region where there are detecting channels and there are also detecting channels symmetrical about the central channel, Region 3 being a symmetric region where there are detecting channels and there are also detecting channels symmetrical about the central channel, Region 4 being a transition region where there are detecting channels and there are also detecting channels symmetrical about the central channel, and Region 5 being a truncated region where there is no detecting channel;
• a view angle weighting unit configured to perform view angle weighting on the projection data in each of Region 1, Region 2, Region 3, Region 4, and Region 5, wherein for an axial scan, weights of the projection data in the Regions are such that weights of the projection data in Region 1 are 1, weights of the Projection data in Region 3 are ½, weights of the projection data in Region 5 are 0, weights of the projection data in Region 2 are 1˜½, and weights of the projection data in Region 4 are ½˜0;
• and
• a reconstructing unit configured to reconstruct a tomographic image of an irradiated subject from the weighted projection data.