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Biomedical subjects

J P Esquerré

Publications and source records attributed to J P Esquerré.

9 recordsLinked to original sources
PubMed1996

Technetium labeling of bi, tri and tetradentate ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid: characterization and biodistribution of their oxo and nitrido 99mtechnetium complexes.

We have synthesized and characterized seven ligands derived from 2-aminocyclopentene-1-dithiocarboxylic acid with different donor sets (SN2-, SNO2-, SNN2-, SNNO3- and SNNN3-) and different substituents on the sulfur moieties-SR (with R = H, CH3 or C2H5O(CH3)CH). With five of these ligands technetium nitrido complexes have been obtained with high yields (over 95%) using rather harsh conditions (pH = 1, temperature > or = 80 degrees C), whereas for technetium oxo complexes similar high yields were only obtained with two ligands but with mild conditions (pH = 7-8, temperature approximately equal to 50 degrees C). Changing an OH group for an NH2 has a drastic effect upon labeling yields. The possibility of complexing ligands as either oxo (TcO)3+ or nitrido (TcN)2+ derivatives increases the number of available labeled agents with different overall change and consequently with different biological behavior.

Animals↗
PubMed1996

[Characterization of the response of hexagonal parallel-hole collimators of scintillation cameras].

This paper presents a formulation of the frequency response of hexagonal parallel-hole collimator scintillation cameras. To describe this response, we propose an equation determined semi-empirically from a great number of simulations. The utility of the equation is that it enables the simple calculation of the response from collimator characteristics by taking into account the collimator's hexagonal structure. Because the equation does not assume translation invariance, the results can be directly compared with experimental measurements obtained with a point source. It is particularly interesting for collimators with large holes, like the medium-resolution ones used for high-energy radiation. Quality control and physical performance measurements are thus facilitated for this kind of collimator. Also, we present a new parameter that gives a quantitative assessment of the importance of partition penetration. This parameter is measured directly from the collimator frequency response. It has been studied by simulation, taking into account gamma photon attenuation in collimator partitions. The experimental measurements that have been made are in accord with the proposed equations.

Biophysical Phenomena↗
PubMed1995

Feasibility of first-pass radionuclide angiocardiography with a 10-mCi technetium bolus using a single-crystal digital gamma camera: implications for technetium-sestamibi single-day protocols.

To test the feasibility of rest first-pass radionuclide angiocardiography (FPRNA) using a 370-MBq (10-mCi) bolus and a single-crystal gamma camera, 40 patients underwent both FPRNA and equilibrium radionuclide angiocardiography (ERNA). Ejection fraction (EF) and regional wall motion (RWM) were assessed by three observers. The interobserver reproducibility was good: the intraclass correlation coefficient was 0.97 for both techniques. The correlation coefficient between FPRNA and ERNA EFs ranged between 0.90 and 0.92. FPRN EFs were significantly higher (P < 0.003) by less than 5 percentage points, this difference having no clinical implications for patient classification. The study provides arguments as to why this difference may be explained self-attenuation rather than counts statistics problems. Both techniques were concordant for RWM analysis. We conclude that FPRNA with 10 mCi is a reliable tool to assess rest left ventricular function, which makes it possible to perform simultaneously myocardial perfusion and function assessment in a single-day protocol using a single-crystal gamma camera.

Feasibility Studies↗
PubMed1991

Normalization of stress and delayed thallium-201 myocardial SPECT: where is the normal reference area?

We describe an unusual uptake pattern in a thallium SPECT study performed after dipyridamole infusion in a patient with a documented history of prior inferior infarction and recent typical chest pain. The stress study exhibited maximum uptake in the inferior wall. The delayed study showed an inferior defect more consistent with the notion of inferior necrosis, with a maximum uptake in the anterior wall. The authors propose a pathophysiologic interpretation consistent with coronary angiography findings, based on the assumption of coronary steal suggested by the occurrence of chest pain at the end of the dipyridamole infusion. The problem of selecting myocardial normal reference area(s) necessary to normalization prior to quantitative comparison stress and delayed studies is discussed.

Aged↗
PubMed1990

[A simulation method for studying scintillation camera collimators].

This paper presents a computer simulation of photon interaction with collimator septa, which allows the point spread function of scintillation camera collimators to be calculated. The method simulates photon attenuation along their propagation direction in a determinist way. Using this simulation, the spatial resolution, geometric efficiency and penetration index of collimators may be easily assessed. Results obtained with this method are presented and compared with those obtained from standard formulae. We show the usefulness of the simulation which precisely accounts for effects of septum penetration. Measurements performed on two collimators with 131I and 99Tcm point sources provide results consistent with those obtained from the simulation method. In conclusion we show that this method is an accurate tool to assist conception of collimators for nuclear medicine.

Computer Simulation↗
PubMed1989

Prone decubitus: a solution to inferior wall attenuation in thallium-201 myocardial tomography.

We propose an efficient method to suppress inferior wall attenuation in 201TI 180 degrees myocardial tomography. We systematically performed redistribution studies in both supine and prone decubitus, assuming that the latter should result in shifting with respect to each other's cardiac structures and diaphragm as well as subphrenic organs possibly responsible for attenuation. The comparison of both studies in 25 normal subjects by visual interpretation and circumferential profiles analysis showed a complete suppression of significant attenuation in the inferior wall in prone studies. In addition and consequently, the standard deviation of activity in this area was markedly reduced and became close to its value in anterior and lateral walls. This simple technique now routinely performed in over 400 patients drastically improves specificity in the evaluation of inferior wall abnormalities by suppressing attenuation artifacts and, incidently, the effect of high individual variability in left phrenic and subphrenic anatomic configuration.

Coronary Disease↗