PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 3840265

An attenuated projector-backprojector for iterative SPECT reconstruction.

G T Gullberg·R H Huesman·J A Malko·N J Pelc·T F Budinger
View original source ↗Export metadata ↓

Abstract

A new ray-driven projector-backprojector which can easily be adapted for hardware implementation is described and simulated in software. The projector-backprojector discretely models the attenuated Radon transform of a source distributed within an attenuating medium as line integrals of discrete pixels, obtained using the standard sampling technique of averaging the emission source or attenuation distribution over small square regions. Attenuation factors are calculated for each pixel during the projection and backprojection operations instead of using precalculated values. The calculation of the factors requires a specification of the attenuation distribution, estimated either from an assumed constant distribution and an approximate body outline or from transmission measurements. The distribution of attenuation coefficients is stored in memory for efficient access during the projection and backprojection operations. The reconstruction of the source distribution is obtained by using a conjugate gradient or SIRT type iterative algorithm which requires one projection and one backprojection operation for each iteration.

Explore related subjects

HeartHumansLiverLungModels, AnatomicSoftwareSpleenTomography, X-Ray ComputedJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.Research Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

G T Gullberg, R H Huesman, J A Malko, N J Pelc, T F Budinger. 1985. An attenuated projector-backprojector for iterative SPECT reconstruction.. https://doi.org/10.1088/0031-9155%2F30%2F8%2F004

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Cardiac stem cells: isolation, expansion and experimental use for myocardial regeneration.

Cellular cardiomyoplasty (myogenic cell grafting) is actively being explored as a novel method to regenerate damaged myocardium. The adult human heart contains small populations of indigenous committed cardiac stem cells or multipotent cardiac progenitor cells, identified by their cell-surface expression of c-kit (the receptor for stem cell factor), P-glycoprotein (a member of the multidrug resistance protein family), and Sca-1 (stem cell antigen 1, a mouse hematopoietic stem cell marker) or a Sca-1-like protein. Cardiac stem cells represent a logical source to exploit in cardiac regeneration therapy because, unlike other adult stem cells, they are likely to be intrinsically programmed to generate cardiac tissue in vitro and to increase cardiac tissue viability in vitro. Cardiac stem cell therapy could, therefore, change the fundamental approach to the treatment of heart disease.

Heart↗
PubMed2007

Growth-factor-mediated cardiac stem cell activation in myocardial regeneration.

The concept of an intrinsic regenerative capacity of the adult mammalian myocardium owing to the presence of cardiac stem cells (CSCs) in the atria and ventricles is starting to be accepted by the cardiovascular research community. The identification of this cell population has improved the prospects for developing successful clinical protocols for human myocardial regeneration. In the normal adult myocardium, only a small fraction of CSCs undergo amplification and differentiation to replace the parenchymal cells lost by normal wear and tear. Physiological or pathological stimuli cause substantial activation of CSCs, which is mediated by a paracrine feedback loop between myocytes and CSCs. In response to stress, the myocytes produce growth factors and cytokines, for which CSCs have receptors, and autocrine, self-sustaining activation of growth-factor production is simultaneously triggered in the CSCs. These findings from human and animal studies led us to test whether in situ activation of CSCs by growth factors would be as effective as transplantation of CSCs into the regenerating myocardium after ischemia in an animal model that has relevance to humans. In a porcine model, we produced extensive and functionally relevant myocardial regeneration. Here, we discuss the properties of endogenous myocardial stem cells that might be exploited to produce clinical myocardial regeneration without the need for cell transplantation.

Heart↗
PubMed2006

Myocardial strain and torsion quantified by cardiovascular magnetic resonance tissue tagging: studies in normal and impaired left ventricular function.

Accurate quantification and timing of regional myocardial function allows early identification of dysfunction, and therefore becomes increasingly important for clinical risk assessment, patient management, and evaluation of therapeutic efficacy. For this purpose, the application of tissue Doppler echocardiography has rapidly increased. However, echocardiography has some major inherent limitations. Cardiovascular magnetic resonance imaging with tissue tagging provides highly reproducible data on myocardial function, not only in longitudinal and radial directions, but also in the circumferential direction. Because of the development of faster imaging protocols, improved temporal resolution, less time-consuming postprocessing procedures, and the potential of quantifying myocardial deformation in 3 dimensions at any point in the heart, this technique may serve as an alternative for tissue Doppler echocardiography and is now ready for more widespread clinical use. This review discusses the clinical use of cardiovascular magnetic resonance tissue tagging for quantitative assessment of regional myocardial function, thereby underlining the specific features and emerging role of this technique.

Heart↗