Efficient projection and backprojection scheme for spherically symmetric basis functions in divergent beam geometry

Journal Article · Fri Dec 15 04:00:00 EST 2006 · Medical Physics

DOI:https://doi.org/10.1118/1.2388570· OSTI ID:20853833

Ziegler, Andy; Koehler, Thomas; Nielsen, Tim; Proksa, Roland ^[1]

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1. Philips Research Europe, Roentgenstrasse 24-26, 22315 Hamburg (Germany)

In cone-beam transmission tomography the measurements are performed with a divergent beam of x-rays. The reconstruction with iterative methods is an approach that offers the possibility to reconstruct the corresponding images directly from these measurements. Another approach based on spherically symmetric basis functions (blobs) has been reported with results demonstrating a better image quality for iterative reconstruction algorithms. When combining the two approaches (i.e., using blobs in iterative cone-beam reconstruction of divergent rays) the problem of blob sampling without introducing aliasing must be addressed. One solution to this problem is to select a blob size large enough to ensure a sufficient sampling, but this prevents a high resolution reconstruction, which is not desired. Another solution is a heuristic low-pass filtering, which removes this aliasing, but neglects the different contributions of blobs to the absorption depending on the spatial position in the volume and, therefore, cannot achieve the best image quality. This article presents a model of sampling the blobs which is motivated by the beam geometry. It can be used for high resolution reconstruction and can be implemented efficiently.

• OSTI ID: 20853833
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 12 Vol. 33; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ABSORPTION
ALGORITHMS
BEAMS
COMPUTERIZED TOMOGRAPHY
IMAGE PROCESSING
IMAGES
ITERATIVE METHODS
SAMPLING
SPATIAL RESOLUTION
X RADIATION