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M Sámal

Publications and source records attributed to M Sámal.

12 recordsLinked to original sources
PubMed1989

On the existence of an unambiguous solution in factor analysis of dynamic studies.

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 their essential property which is implied by the physical nature of measured quantities. Considering factors as the images of compartments in the distribution space of a radiopharmaceutical (i.e. performing the factor analysis in the spatial domain), a powerful additional constraint can be applied. This constraint is based on the presence of segments in the image matrix where the subtotal number of compartments is projected. Using this constraint, the existence of physiologically related unique solution in factor analysis can be proved providing the number of factors is chosen properly.

Factor Analysis, Statistical↗
PubMed1989

[Clinical applications of factor analysis in nuclear medicine].

Factor analysis allows to break up dynamic radionuclide studies into constituent parts corresponding to individual compartments of the distribution space of the radiopharmaceutical in the body. Compartment structure is reflected by factor image and its dynamics is shown by factor time activity curves. The method overcomes the drawbacks of other data processing methods in dynamic scintigraphy by its objectiveness and by distinguishing the projection overlap of tissues with different dynamics. The demands on both the patient and personnel are the same as in standard procedures, yet this method extracts more information from the results of the examination. Higher diagnostic accuracy was reported especially in nuclear cardiology and nephrology. A short survey of clinical applications of factor analysis reported over the years 1982-1988 is presented.

Factor Analysis, Statistical↗
PubMed1987

Rotation to simple structure in factor analysis of dynamic radionuclide studies.

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 demonstrated on a phantom and its relationship to existing methods is discussed.

Factor Analysis, Statistical↗
PubMed1986

Enhancement of physiological factors in factor analysis of dynamic studies.

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 composition of the variance processed in the analysis it is possible to enhance the factors that are important for diagnosis while the less important factors can be suppressed. In our report, a short theoretical review of the problem is given and illustrated by the analysis of dynamic cholescintigraphy. It is shown that a suitable choice of region and/or the temporal interval of interest enables the differential evaluation of such intrahepatic compartments, which could not be observed without enhancement.

Calculi↗