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Exploitation of geometric a priori knowledge for limited data reconstruction in nondestructive testing

: Schorr, Christian; Maisl, Michael

Leahy, R.:
Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine. Proceedings : June 16-21, 2013, Granlibakken Resort, Lake Tahoe, California
Lake Tahoe/Calif., 2013
International Meeting on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine (Fully3D) <12, 2013, Lake Tahoe/Calif.>
Fraunhofer IZFP ()
limited data; computed laminography; computed tomography; iterative reconstruction; a priori knowledge

Computed tomography (CT) is a very powerful tool in medicine and non-destructive testing but is unsuitable for planar objects. A solution can be found in the use of computed laminography (CL), a technique where the object is irradiated by an oblique angle thereby circumventing the problems arising in CT. Due to the limited amount of angular coverage and the special geometric set-up, filtered backprojection methods [4] cannot be employed for the reconstruction in this case. More flexible iterative algorithms like SART (simultaneous reconstruction technique) [1,2] provide an answer to this challenge. One of their important advantages when compared to filtered backprojection methods is their ability to incorporate a priori information about the object into the reconstruction process [6]. Often the object's geometry is known from CAD files or other technical specifications. Especially in the case of limitedangle data, where only a part of the object can be measured, and laminographic geometries, additional information is of great importance. This geometrical a priori knowledge can be exploited to restrict the reconstruction volume to areas where material is definitely present, resulting in correct object contours even in the limited-angle case. This reduces artifacts and increases contrast thereby allowing for a better defect detectability and thus an easier and more reliable inspection of the object.