A new technique for region of interest tomographic image reconstruction and a comparison of the related algorithms

It is known that the convolution back-projection (CBP) operator used for reconstruction of images from its 1D projections has a non-local filter that requires global projection data. The exposure time of the object to harmful radiation is thereby increased. It has been proved that the filtering operation done on a chosen wavelet function instead of the projections leads to a localised filter and minimises the number of projections needed to reconstruct the region of interest (ROI) in the image. This concept was extended using two dimensional and one dimensional multiresolution analysis filter banks, in which the filters are combined with the non-local CBP filter to get short length filters. In this paper it is proved that the presence of unwanted information in all previous algorithms is due to aliasing and a new algorithm is proposed for reconstruction without any aliasing. The proposed scheme is implemented using Shepp-Logon phantom head and the performance is compared.