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Biomedical subjects

D Ros

Publications and source records attributed to D Ros.

6 recordsLinked to original sources
PubMed1991

Comparative study of the kinetics of the renal tracers 99Tcm-MAG3 and 131I-hippuran.

Serial measurements of plasma activity, plasma protein binding and urine excretion were obtained in order to study 99Tcm-MAG3 (MAG) and 131I-Hippuran (OIH) kinetics after simultaneous injection of both tracers in 21 patients with various renal diseases. Results were compared on the basis of a compartmental model, calculating the rate constants as well as the clearance and volume of distribution. Protein binding was calculated in 10 patients (mean: MAG = 54.7%, OIH = 33.8%). The dependence of time, tracer and patient factors was shown by ANOVA. Time was independent, with tracer and patient factors and their interaction being significant. The mean value of the renal excretion constant was equal for the two tracers (k12 = 0.052 min-1). The clearance values were found to be highly correlated (r = 0.982) with a ratio of 0.57 between them. The volumes of distribution in litres were 4.1 (MAG) and 7.0 (OIH). One-hour urine excretion was nearly the same for both tracers (MAG: 64%, OIH: 63% of the injected dose).

Blood Proteins↗
PubMed1991

Evaluation of thallium myocardial-perfusion imaging by means of washout parametric images: a simulation study.

A method for the evaluation of myocardial perfusion with 201Tl scintigraphic images is presented. The method is based on making a pixel-by-pixel comparison of the stress and the redistribution images aligned by using bidimensional correlation techniques between the nonpathologic regions of the myocardium. The comparison is made by means of parametric images of the washout, which are evaluated by calculating separately the mean values in the normal and the abnormal regions. The study is carried out on controlled models that contain myocardium, an artifact, and noise. The results show the suitability of the method and confirm the validity of its application to individualized studies of clinical interest.

Computer Simulation↗
PubMed1989

Thallium-201 myocardial planar scintigrams. Alignment of stress and rest images by correlation.

The utility of the correlation for alignment of myocardial perfusion imaging with 201TI was studied. The tests were made by numerical simulation of a heart model with an artefact and a theoretical background superimposed in normal and pathological situations. The methods used were bidimensional and unidimensional correlation techniques and were applied either with or without previous background subtraction. Our results show the suitability of this alignment technique, useful in finding the displacement between images with an average error inferior to one pixel in different situations of myocardial damage.

Computer Simulation↗
PubMed1989

Methods of background subtraction in myocardial perfusion imaging with thallium-201: a comparative study in the presence of an artefact.

For thallium imaging quantitation, a simulation study has been made using different methods of interpolation for background subtraction and studying their behaviour in the presence of an artefact. Two artefacts were used, one simulating hepatic or splenic uptake and the other diaphragmatic activity. The interpolative methods used were three classic techniques using standard masks. Their algorithms were modified so that they could also be used with arbitrarily shaped masks enclosing myocardium, and a comparison between the original and modified methods was made. Our results show an improvement when using the modified algorithms adapted to the arbitrarily outlined mask.

Computer Simulation↗
PubMed1988

Optimal filtering values in renogram deconvolution.

The evaluation of the isotopic renogram by means of the renal retention function (RRF) is a technique that supplies valuable information about renal function. It is not unusual to perform a smoothing of the data because of the sensitivity of the deconvolution algorithms with respect to noise. The purpose of this work is to confirm the existence of an optimal smoothing which minimises the error between the calculated RRF and the theoretical value for two filters (linear and non-linear). In order to test the effectiveness of these optimal smoothing values, some parameters of the calculated RRF were considered using this optimal smoothing. The comparison of these parameters with the theoretical ones revealed a better result in the case of the linear filter than in the non-linear case. The study was carried out simulating the input and output curves which would be obtained when using hippuran and DTPA as tracers.

Humans↗