Biomedical subjects

Luis M Cruz-Orive

Publications and source records attributed to Luis M Cruz-Orive.

3 recordsLinked to original sources

PubMed2006

New variance expressions for systematic sampling: the filtering approach.

We present a collection of variance models for estimators obtained by geometric systematic sampling with test points, quadrats, and n-boxes in general, on a bounded domain in n-dimensional Euclidean space R(n), n = 1, 2, ... , and for systematic rays and sectors on the circle. The approach adopted - termed the filtering approach - is new and different from the current transitive approach. This report is only preliminary, however, because it includes only variance models in terms of the covariogram of the measurement function. The estimation step is in preparation.

Journal Article↗

PubMed2004

Estimation of particle number by stereology: an update.

Sampling designs dictated by stereology have proven very useful in recent years to estimate in situ the total number of deposited particles, or of macrophages, in different lung compartments at the light microscopical level. The sampling methods are based on parallel slabs which are subsequently subsampled by disectors. The resulting number estimators are unbiased irrespective of tissue shrinkage or swelling, and they are readily applicable in other contexts (notably in neuroscience). Several variants of the design are available, however, and, although they all yield the same number estimates, their precision, and the mathematical prediction of it, vary among the different estimators and are subjected to theoretical improvement. The present paper constitutes a detailed survey of the latest advances, and it illustrates methods and formulae alike by way of a real example stemming from an earlier study on particle retention and clearance.

Animals↗

PubMed2003

Comparison of MR imaging against physical sectioning to estimate the volume of human cerebral compartments.

The purpose of this study was to compare magnetic resonance imaging (MRI) against physical sectioning techniques to estimate the volume of human cerebral hemisphere compartments (cortex, subcortex, and their union, called "total"). The volume of these compartments was estimated postmortem for six human subjects from MRI virtual sections and from physical sections using the Cavalieri design with point counting. Cursory paired t tests revealed no significant differences between the two methods for any of the three compartments considered, although P = 0.06 for the subcortex. A sharper analysis incorporating recent error prediction formulae revealed a significant discrepancy between the two methods in the estimation of subcortex and total volume for three of the specimens. Yet, none of these analyses is adequate to detect possible biases. The incorporation of an explanatory variable, namely hemisphere weight, and the adoption of a specific gravity rho = 1.04 g/cm(3) for the material, enabled us to carry out an allometric analysis for the total compartment which revealed a significant bias of the MRI data. The new error prediction formulae are illustrated by way of example, and their accuracy is checked by a resampling experiment on a data set of 274 MRI sections.

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