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Publicações

Publicações por CTM

2015

Correlation Study Between Blood Pressure And Pulse Transit Time

Autores
Pereira, T; Sanches, R; Reis, P; Pego, J; Simoes, R;

Publicação
2015 IEEE 4TH PORTUGUESE MEETING ON BIOENGINEERING (ENBENG)

Abstract
Blood pressure (BP) determination is a fundamental parameter in cardiovascular assessment. The gold standard method to measure BP is based on the inflatable arm cuff, however has several disadvantages for continuous monitoring. New techniques were developed to overcome these limitations using correlations between the pulse transit time (PTT) and BP. This work draws attention to the PTT rationale using several methods. In order to determine the PTT, an electrocardiogram (ECG) was used combined with multiple photoplethysmography (PPG) sensors applied to different arm locations, these signals were acquired with a bioPLUX device. The Ultrassound system (SonoSite Edge) was used to measure the artery diameter. As reference, BP was measured using a cuff- based sphygmomanometric device. Measurements were performed in a study population of 36 volunteers. The correlation coefficient for DBP determined and DBP measured was r = 0,689. The results suggest PTT deduced from different locations can be used to measure BP.

2015

Novel Methods for Pulse Wave Velocity Measurement

Autores
Pereira, T; Correia, C; Cardoso, J;

Publicação
JOURNAL OF MEDICAL AND BIOLOGICAL ENGINEERING

Abstract
The great incidence of cardiovascular (CV) diseases in the world spurs the search for new solutions to enable an early detection of pathological processes and provides more precise diagnosis based in multi-parameters assessment. The pulse wave velocity (PWV) is considered one of the most important clinical parameters for evaluate the CV risk, vascular adaptation, and therapeutic efficacy. Several studies were dedicated to find the relationship between PWV measurement and pathological status in different diseases, and proved the relevance of this parameter. The commercial devices dedicate to PWV estimation make a regional assessment (measured between two vessels), however a local measurement is more precise evaluation of artery condition, taking into account the differences in the structure of arteries. Moreover, the current devices present some limitations due to the contact nature. Emerging trends in CV monitoring are moving away from more invasive technologies to non-invasive and non-contact solutions. The great challenge is to explore the new instrumental solutions that allow the PWV assessment with fewer approximations for an accurately evaluation and relatively inexpensive techniques in order to be used in the clinical routine.

2015

Arterial pulse pressure waveform monitoring by novel optical probe

Autores
Pereira, T; Pereira, TS; Santos, H; Correia, C; Cardoso, J;

Publicação
INTERNATIONAL JOURNAL OF CARDIOLOGY

Abstract

2015

PEPITO, atmospheric optical turbulence profiling from long-exposure aniokinetism-affected images of star fields

Autores
Bharmal N.A.; Beltramo-Martin O.; Correia C.M.;

Publicação
Optics InfoBase Conference Papers

Abstract
A novel technique to measure C2n and L0 in the atmosphere from anisokinetism in tip/tilt corrected images of star fields by fitting parameter-based PSF models, enabling a low-complexity 24×7 capability.

2015

Anti-aliasing wave-front reconstruction with Shack-Hartmann sensors

Autores
Bond C.Z.; Correia C.; Teixeira J.; Sauvage J.F.; Véran J.P.; Fusco T.;

Publicação
Adaptive Optics for Extremely Large Telescopes 4 - Conference Proceedings

Abstract
The discrete sampling of a wave-front using a Shack-Hartmann sensor limits the maximum spatial frequency we can measure and impacts sensitivity to frequencies at the high end of the correction band due to aliasing. Here we present Wiener filters for wave-front reconstruction in the spatial-frequency domain, ideally suited for systems with a high number of degrees of freedom. We develop a theoretical anti-aliasing (AA) Wiener filter that optimally takes into account high-order wave-front terms folded in-band during the sensing (i.e., discrete sampling) process. We present Monte-Carlo simulation results for residual wave-fronts and propagated noise and compare to standard reconstruction techniques (in the spatial domain). To cope with finite telescope aperture we've developed and optimised a Gerchberg-Saxton like iterative-algorithm that provides superior performance.

2015

Experimental implementation of a Pyramid WFS: Towards the first SCAO systems for E-ELT

Autores
Bond C.Z.; El Hadi K.; Sauvage J.F.; Correia C.; Fauvarque O.; Rabaud D.; Neichel B.; Fusco T.;

Publicação
Adaptive Optics for Extremely Large Telescopes 4 - Conference Proceedings

Abstract
Investigations into the Pyramid wavefront sensor (P-WFS) have experimentally demonstrated the ability to achieve a better performance than with a standard Shack-Hartmann sensor (SH-WFS). Implementation on the Large Binocular Telescope (LBT) provided the first operational demonstration on a facility-class instrument of a P-WFS on sky. The desire to implement a Pyramid on an Extremely Large Telescope (ELT) requires further characterisation in order to optimise the performance and match our knowledge and understanding of other wave-front sensors (WFSs). Within the framework of the European Extremely Large Telescope (E-ELT), the Laboratoire d'Astrophysique de Marseille (LAM) is involved in the preparation of the Single Conjugate Adaptive Optics (SCAO) system of HARMONI, E-ELT's 1st light integral field spectrograph (IFU). The current baseline WFS for this adaptive optics system is a Pyramid WFS using a high speed and sensitive OCAM2 camera. At LAM we are currently carrying out laboratory demonstrations of a Pyramid-WFS, with the aim to fully characterise the behaviour of the Pyramid in terms of sensitivity and linear range. This will lead to a full operational procedure for the use of the Pyramid on-sky, assisting with current designs and future implementations. The final goal is to provide an on sky comparison between the Pyramid and Shack-Hartmann at Observatoire de la Côte d'Azur (OCA). Here we present our experimental setup and preliminary results.

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