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In functional MRI (fMRI), the changes in cerebral haemodynamics related to stimulated neural brain activity are measured using standard clinical MR equipment. Small intensity variations in fMRI data have to be detected and distinguished from non-neural effects by careful image analysis. Based on multivariate statistics we describe an algorithm involving(More)
Commonly used methods for determining split renal function (SRF) from dynamic scintigraphic data require extrarenal background subtraction and additional correction for intrarenal vascular activity. The use of these additional regions of interest (ROIs) can produce inaccurate results and be challenging, e.g. if the heart is out of the camera field of view.(More)
An inter-laboratory comparison study was conducted to assess the image quality of PET scanners in Austria. The survey included both dedicated PET scanners (D-PET, n = 8) and coincidence cameras (GC-PET, n = 7). Measurement of image quality was based on the NEMA (National Electrical Manufacturers Association) NU 2-2001 protocol and the IEC (International(More)
AIM Corrective image reconstruction methods which produce reconstructed images with improved spatial resolution and decreased noise level became recently commercially available. In this work, we tested the performance of three new software packages with reconstruction schemes recommended by the manufacturers using physical phantoms simulating realistic(More)
The physiological interpretation of factors in the factor analysis of dynamic radionuclide studies is dependent on the proper solution of the problem of factor rotation. A new solution suitable for scintigraphic data is suggested using a generalised concept of simple structure in data configurations. The method is described in detail, its efficiency is(More)
Achievement of an unambiguous solution in factor analysis of dynamic radionuclide studies depends on constraints reflecting the known properties of factors. The constraints should be tight enough to prevent ambiguity but sufficiently general in order to ensure the data-based derivation of factors. In dynamic scintigraphy, the non-negativity of factors is(More)
A hybrid phantom is a synthetic dynamic scintigraphic study reconstructed from dynamic components of real clinical data. The aim of a hybrid simulation is to provide realistic reference studies with systematically varying quantitative diagnostic parameters for testing the quality of measurement of regional dynamics. The components of the phantom are(More)
Factor analysis of dynamic radionuclide studies provides their decomposition into the images and time-activity curves corresponding to the underlying dynamic structures. The method is based on the analysis of study variance and on the subsequent differential imaging of its principal components into a simplified factor space. By changing the amount and the(More)
The aim of the study was to examine the physiological relevance of factors produced by a modified procedure for factor analysis of dynamic renal studies. Factor analysis has been applied locally to subsets of dynamic renal data which were well defined in both space and time domains. Optimised factor images resulting from different subsets were used as fuzzy(More)
The aim of the study was a quantitative comparison of relative renal uptake and both the whole-kidney and the parenchymal transit time derived from factor analysis of image sequences and provided by standard clinical procedues. In order to extract the stable, well-interpretable factors, factor analysis was performed locally in the problem-specific time and(More)