G. Gullberg

Publications481
h-index53
Citations9,875
Highly Influential Citations242
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Unmatched projector/backprojector pairs in an iterative reconstruction algorithm
TLDR
This paper points out that valid backprojectors should satisfy a condition that the projector/backprojector matrix must not contain negative eigenvalues, and investigates the effects when unmatched projector/ backprojector pairs are used.
View on IEEE
Reconstruction and Visualization of Fiber and Laminar Structure in the Normal Human Heart from Ex Vivo Diffusion Tensor Magnetic Resonance Imaging (DTMRI) Data
TLDR
The fibers are shown to lie in sheets that have transmural structure, which correspond to histologic studies published in the literature, and Quantitative measurements show that the sheets as appose to the fibers are organized into laminar orientations without dominant populations.
View on Wolters Kluwer
Assessment of the sources of error affecting the quantitative accuracy of SPECT imaging in small animals.
TLDR
It is found that photon attenuation can reduce the measured concentration of radioactivity in a volume of interest in the center of a rat-sized cylinder of water by up to 50% when imaging with iodine-125, and up to 25% when Imaging with technetium-99m.
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Three-dimensional reconstruction in nuclear medicine emission imaging
The study presents application of methods of ascertaining the three-dimensional distribution of isotope concentration or density in nuclear medicine, and differs from previous three-dimensional…
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An attenuated projector-backprojector for iterative SPECT reconstruction.
TLDR
A new ray-driven projector-backprojector which can easily be adapted for hardware implementation is described and simulated in software and discretely models the attenuated Radon transform of a source distributed within an attenuating medium as line integrals of discrete pixels.
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Frequency domain implementation of the three-dimensional geometric point response correction in SPECT imaging
  • G. Zeng, G. Gullberg
  • Physics
    Conference Record of the IEEE Nuclear Science…
  • 2 November 1991
A 3-D iterative reconstruction algorithm which incorporates models of the geometric point response in the projector-backprojector is presented for parallel, fan, and cone beam geometries. It is shown…
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Total variation regulated EM algorithm
TLDR
Reconstructions of computer simulations and patient data show that the proposed iterative Bayesian reconstruction algorithm has the capacity to smooth the noise and maintain sharp edges without introducing over/under shoots and ripples around the edges.
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Direct least-squares estimation of spatiotemporal distributions from dynamic SPECT projections using a spatial segmentation and temporal B-splines
TLDR
A preliminary study of spatial segmentation errors showed that spatial model mismatch adversely affected quantitative accuracy, but also resulted in structured errors that were easily detected in the authors' simulations, suggesting iterative refinement of the spatial model to reduce structured errors as an area of future research.
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The reconstruction of fan-beam data by filtering the back-projection
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Correction of nonuniform attenuation in cardiac SPECT imaging.
TLDR
Results from a heart-lung phantom study and a 201Tl patient study demonstrated that the iterative EM algorithm with attenuation correction provided improved image quality in terms of reduced streak artifacts and noise, and more accurate quantitative information in Terms of improved radioactivity distribution uniformity where uniformity existed, and better anatomic object definition.
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