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Biomedical subjects

E Laffon

Publications and source records attributed to E Laffon.

14 recordsLinked to original sources
PubMed2006

Measurement of cardiac ventricular volumes using multidetector row computed tomography: comparison of two- and three-dimensional methods.

This study compared a three-dimensional volumetric threshold-based method to a two-dimensional Simpson's rule based short-axis multiplanar method for measuring right (RV) and left ventricular (LV) volumes, stroke volumes, and ejection fraction using electrocardiography-gated multidetector computed tomography (MDCT) data sets. End-diastolic volume (EDV) and end-systolic volume (ESV) of RV and LV were measured independently and blindly by two observers from contrast-enhanced MDCT images using commercial software in 18 patients. For RV and LV the three-dimensionally calculated EDV and ESV values were smaller than those provided by two-dimensional short axis (10%, 5%, 15% and 26% differences respectively). Agreement between the two methods was found for LV (EDV/ESV: r=0.974/0.910, ICC=0.905/0.890) but not for RV (r=0.882/0.930, ICC=0.663/0.544). Measurement errors were significant only for EDV of LV using the two-dimensional method. Similar reproducibility was found for LV measurements, but the three-dimensional method provided greater reproducibility for RV measurements than the two-dimensional. The threshold value supported three-dimensional method provides reproducible cardiac ventricular volume measurements, comparable to those obtained using the short-axis Simpson based method.

Adult↗
PubMed2006

[Pleural mesothelioma: imaging contribution].

Imaging plays an essential role in management of patients of with pleural mesothelioma. In this article, we discuss the respective roles for ultrasonography, computed tomography, magnetic resonance imaging, and positon emission tomography for the diagnosis, staging, and postherapeutic evaluation of pleural mesothelioma.

Diagnostic Imaging↗
PubMed2001

Feasibility of endocardial edge detection by using an inversion recovery artifact.

An inversion recovery (IR) artifact was used to delineate the blood/wall boundary in left ventricles. The artifact consisted of a hypointensity signal in pixels located at the boundary of two contiguous tissues with different T(1) relaxation times. The feasibility of measuring the ejection fraction using the artifact was tested in ten healthy volunteers, with two IR snapshot-FLASH sequences possessing different times of repetition (TR = 11msec and TR = 3.5msec) and appropriate times of inversion. The comparison with a cine-MRI sequence showed that ejection fraction measurements are feasible when performed with a snapshot-FLASH sequence that has a sufficiently short TR (3.5msec).

Adult↗
PubMed2001

Tuning of pulmonary arterial circulation evidenced by MR phase mapping in healthy volunteers.

Magnetic resonance (MR) phase mapping was used to noninvasively assess both blood flow and cross-sectional area (CSA) in the main pulmonary artery (MPA) of 12 healthy volunteers. Flow and CSA patterns exhibited two positive peaks: high systolic and small diastolic. This finding can be explained using a simple "distributed" theoretical model that takes into account the role of a reflected pressure wave from pulmonary vascular impedance in generating a diastolic flow. The mean reflection coefficient of pressure wave, MPA input impedance, and pulmonary vascular impedance were assessed. We verified, in this series, that pressure wave velocity appears to be age-dependent. MR phase mapping has been used to observe the tuning (resonance) of the right cardiovascular system at rest under physiological conditions. MR phase mapping could be used to assess pathological modifications of the tuning that occurs in cases of pulmonary arterial hypertension.

Adult↗
PubMed2001

Noninvasive assessment of pulmonary arterial hypertension by MR phase-mapping method.

We describe a magnetic resonance (MR) imaging method that emphasizes pressure wave velocity to noninvasively assess pulmonary arterial hypertension. Both the blood flow and the corresponding vessel cross-sectional area (CSA) were measured by MR phase mapping in the main pulmonary artery (MPA) in 15 patients. MPA pressures were also measured, in the same patients, by right-side heart catheterization. Two significant relationships were established: 1) between the pressure wave velocity in the MPA and the mean pressure in the MPA (Ppa) writing pressure wave velocity = 9.25 Ppa - 202.51 (r = 0.82) and 2) between the ratio of pressure wave velocity to the systolic blood velocity peak in the MPA (R) and the mean pressure in the MPA writing R = 0.68 Ppa - 4.33 (r = 0.89). Using these relationships, we estimated two pressure values to frame the actual Ppa value in each patient from the present series with a reasonable reliability percentage (87%).

Adult↗
PubMed1999

Segmented 5 versus nonsegmented flow quantitation: comparison of portal vein flow measurements.

RATIONALE AND OBJECTIVES: Times of acquisition, mean velocities, mean flows, and their respective standard deviations provided by segmented and nonsegmented flow quantifications (FQ) were compared in the main portal veins of ten healthy adults. METHODS: The segmented FQ performed five phase-encoding lines per segment. The authors successively applied the two electrocardiogram-triggered techniques in the same slice perpendicular to the portal flow direction. Their measurements were compared in particular by means of the statistical analysis proposed by Bland and Altman. RESULTS: The segmented 5 FQ reduced the acquisition time by two compared with the nonsegmented FQ. The mean velocity and mean flow values of the two techniques were not significantly different. The standard deviations were similar. CONCLUSIONS: The segmented 5 FQ showed its major advantage in the portal vein: the acquisition time was reduced without any loss of accuracy or any uncertainty enhancement.

Adult↗
PubMed1998

A validation of a flow quantification by MR phase mapping software.

AIM: We evaluated a Siemens software of flow quantification (FQ) by MR phase mapping, in the framework of a common practical use. METHODS: Experiments with a laminar flow phantom and in vivo pulsatile flow were performed. In particular, FQ in ascending aorta was investigated in healthy volunteers. RESULTS AND CONCLUSION: Flow phantom experiments reveal that the FQ slightly underestimates (8% on the average) actual velocities (mean velocities over a vessel area), and also that velocity uncertainties are related to the encoding velocity value, whatever the measured velocity. Furthermore, using well characterized working criteria, we found low intraobserver variability and negligible interobserver variability in ascending aorta FQs. The role played by the choice of reference area in FQ accuracy is emphasized. When recording several cardiac cycles during the same acquisition, it is shown that the FQ software may provide erroneous results. Several comments for FQ software use in the ascending aorta are added.

Adult↗
PubMed1996

On the Deiters cell contribution to the micromechanics of the organ of Corti.

We give the first estimate of Young's modulus of the proteinaceous beam that makes the stiffness of the Deiters cell phalangeal processes. We show that the fundamental mode of vibration of an isolated phalanx is overdamped due to the damping imposed by the surrounding fluid. Then we consider the mechanical couplings that have so far been neglected in the micromechanics of the organ of Corti. Conclusions are drawn concerning the lack of significance of some expected resonant behaviour of isolated outer hair cells.

Animals↗
PubMed1995

Organic material concentration in auditory outer hair cells measured by laser interferometry.

Outer hair cells (OHC) of the mammalian cochlea are quasicylindrical cells of different length, which play a major role in hearing at threshold. Their particular shape allows the use of a noninvasive laser interferometric technique of isolated cells in vitro in order to measure the organic material concentration (OMC), hence the density of each cell body. In most (95%) of the OHCs isolated from the same guinea pig, when the cell diameter is normalized, the results show that the cell body OMC does not vary with cell length. In different animals, the respective normalized OMC mean values can vary between 70 kg/m3 and 103 kg/m3. A few OHCs with morphological particularities often possess cell body OMCs > 103 kg/m3. The results of the interferometric measurements in isolated OHCs confirm that density variations in the cell bodies are not involved in a sound frequency coding. The in vitro OMC variations of the OHCs could be related to the isolation procedure; however, they could also correlate with actual in vivo OMC variations.

Animals↗
PubMed1994

Photo-released intracellular Ca2+ evokes reversible mechanical responses in supporting cells of the guinea-pig organ of Corti.

Loaded under whole cell patch-clamp configuration, the caged Ca2+ molecule DM-nitrophen was used to increase [Ca2+]i rapidly and reversibly in isolated Deiters cells of the organ of Corti. Photolysis of DM-nitrophen increased [Ca2+]i from resting concentrations of 20-50 nM to values above microM, as measured with the fluorescent indicator Fluo-3. Immediately after the photoliberation of Ca2+, a movement of the head of the phalangeal process could be observed in 75% of cells (n = 28). This mechanical movement, with an amplitude ranging between 0.5 to 1 micron within few hundred of ms, consisted of an extension of the phalanges away from the cell body. Measurement of phalangeal stiffness in transversal flexion toward the cell body ranged between 15-440 pN/micron. Stiffness can increase by 28 to 51% after rising [Ca2+]i. The results suggest Ca2+ as a potential intracellular messenger for active mechanical responses in Deiters cells.

Acetates↗
PubMed1993

Mammalian cochlear outer hair cells density evaluated by means of an optical tweezer.

We report on the first individual measurements of guinea pig's cochlear outer hair cells densities. Cells were isolated in vitro and manipulated with an optical tweezer. They were levitated in an upward laser beam coaxially trapping the cells. Then they were released by switching off the laser and let fall down in upright position. Measuring their speed and using the Stokes' law, we calculated their mean density. In our experimental frame, the results suggest that the density of the cellular body (between the basal nucleus and the apical cuticular plate) remains quasi constant whatever the cells' length. This implies that density variation of the cellular body does not participate in an intrinsic tuning mechanism.

Animals↗