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Biomedical subjects

J Pavía

Publications and source records attributed to J Pavía.

9 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↗
PubMed1989

Indium-111-labeled platelets in monitoring human pancreatic transplants.

We have performed 59 111In-labeled platelet scintigraphies in 12 patients with pancreas transplant, and we have compared retrospectively the 111In platelet uptake with the graft immunological situation. A diffuse uptake in the graft was seen in five of six patients with pancreatic rejection. The scans became positive before changes in biochemical tests were detected. No 111In platelet uptake was seen in five of seven normally functioning grafts. Two cases of venous thrombosis and two perigraft hematomas appeared like a focal 111In platelet accumulation. Indium-111-labeled platelet scintigraphy can be a useful method for monitoring pancreas transplants. It may be helpful in the early detection of pancreatic allograft rejection and in the differential diagnosis between this and other complications such as thrombosis or hematomas.

Adult↗
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↗
PubMed1986

Nasal mucociliary transport in laryngectomees.

A study has been carried out to assess the mucociliary function of nasal mucosa in 30 patients: 16 had undergone surgery due to larynx malignancy and the remaining 14 were divided in two groups. The first group was composed of seven patients suffering from larynx cancer but not operated, and the second group of seven had pathology not related to the airways (control group). The method used a 99mtechnetium sulphur colloid drop deposited on the nasal mucosa of one nostril. To calculate the rate of transport, a new method of quantification has been introduced, based on the formation of a parametric image. The mean velocity in laryngectomees was 3.6 mm/min (range 1.1-6.4). It was compared with the group of 14 patients without tracheostomy (mean 5.3, range 3.3-8.2). An impaired Student's-t-test gave a significant difference between both groups (P less than 0.005). The comparison between patients with nonoperated larynx cancer and normals gave a nonsignificant difference. The 16 operated patients were arbitrarily divided into two groups as per the time elapsed from laryngectomy; seven were studied within the first 3 years of operation and seven other patients after this term. The comparison between them was not significant.

Adolescent↗
PubMed1986

Measurement of nasal mucociliary transport rate in normal man.

After reviewing the main methods existing to calculate the rate of the mucociliary transport, the authors describe their personal technique. A 99mTechnetium Sulphur Colloid drop is deposited in the nasal fossa, which is carried away by the cilia down to the rhinopharynx and followed by a gamma camera. To calculate the transport rate, a new method of quantification has been introduced, based on the formation of a parametric image. A study was carried out in 14 males without any pathology of the upper airways, obtaining a mean velocity of 5.3 mm per min (range 3.3.-8.2).

Adult↗