Biomedical subjects

Marcelo Trivi

Publications and source records attributed to Marcelo Trivi.

5 recordsLinked to original sources

PubMed2006

Speckle activity images based on the spatial variance of the phase.

We propose the display of the local spatial variance of the temporal variations of the phase as an activity descriptor in dynamic speckle images. The spatial autocorrelation of the speckle intensity is calculated in sliding windows, and an estimation of the variance of the phase variations in each region of the sample is determined. The activity images obtained in this way depict some interesting features and in some cases they could be related to physical magnitudes in the samples. A simulation is presented, and examples corresponding to usual study cases are also shown, namely, fruit bruising and paint drying.

Journal Article↗

PubMed2006

Comparison of the amplitude of the P-wave from intracardiac electrocardiogram obtained by means of a central venous catheter filled with saline solution to that obtained via esophageal electrocardiogram.

Recognition of the P wave is important for the correct characterization of atrial and ventricular arrhythmias. When the P wave is difficult to identify on standard electrocardiography (SECG), either esophageal electrocardiography (EECG) or intracardiac electrocardiography (IC-ECG), central venous catheter may be used. The feasibility of these methods has already been demonstrated, but there is no published study comparing them. This study compared the amplitude of the P wave obtained by IC-ECG with those of the P waves obtained by EECG and SECG. SECG, EECG, and IC-ECG were performed on each patient. IC-ECG and EECG made it possible to register P waves larger than registered by SECG (p <0.00001). The difference between the largest P waves obtained with IC-ECG (5.93 +/- 3.56 mm) and EECG (4.67 +/- 2.16 mm) was not statistically significant (p = 0.1953). In conclusion, IC-ECG is easy to perform and magnifies the P wave at least as effectively as EECG.

Arrhythmias, Cardiac↗

PubMed2006

Distal protection during primary angioplasty: a feasibility and safety study utilizing a novel filter technology.

BACKGROUND: The degree of myocardial reperfusion after primary percutaneous coronary intervention (PCI) may be reduced by distal embolization. We tested the safety, feasibility and efficacy of a novel filter device, the Spider Distal Embolic Protection System, as an adjunct to primary PCI. METHODS AND RESULTS: Twenty consecutive patients undergoing primary PCI with the Spider Embolic Protection Device were included in the analysis. Successful Spider device positioning was obtained in all cases, with predilatation of the lesions in 1 of these cases (5%). There were no procedural complications attributable to the use of a filter. Histological analysis of the content of 5 filters showed multiple embolic debris in all cases, from 8 to 48 particles per filter, from 101-1,299 mm in diameter and from 212-1,487 mm2 in area. The use of the Spider filter was associated with a profound ST-segment resolution (STR: 85.6 +/- 16.5%) and the occurrence of complete (50%) STR of 90%. CONCLUSIONS: The Spider Embolic Protection Device as an adjunctive therapy during primary PCI is feasible and safe, preventing distal embolization and improving myocardial reperfusion. Currently, an international, multicenter, randomized clinical trial is prospectively testing this challenging hypothesis.

Aged↗

PubMed2003

Phase-object detection by use of double-exposure fringe-modulated speckle patterns.

We study the properties of a double-exposure image specklegram of a diffuse object obtained by use of a double-aperture pupil. A phase object is placed in front of one aperture during the first or the second exposure. Also, it is assumed that a uniform displacement of the diffuser between exposures is produced. The recorded specklegram is coherently illuminated and analyzed by Fourier transform operations. The average intensity distribution and the interference fringe visibility in the Fourier plane are investigated. On this basis, an alternative interference technique to detect phase objects is proposed.

Journal Article↗

PubMed2002

Wavelet transform analysis of dynamic speckle patterns texture.

We propose the use of the wavelet transform to characterize the time evolution of dynamic speckle patterns. We describe it by using as an example a method used for the assessment of the drying of paint. Optimal texture features are determined and the time evolution is described in terms of the Mahalanobis distance to the final (dry) state. From the behavior of this distance function, two parameters are defined that characterize the evolution. Because detailed knowledge of the involved dynamics is not required, the methodology could be implemented for other complex or poorly understood dynamic phenomena.

Journal Article↗