Search results for "Biomedical engineering"

Nevus Oligemicus on the Breasts: A Report of 2 Cases

2012

Effect of the Alterations in Contractility and Morphology Produced by Atrial Fibrillation on the Thrombosis Potential of the Left Atrial Appendage

2021

Atrial fibrillation (AF) is a common arrhythmia mainly affecting the elderly population, which can lead to serious complications such as stroke, ischaemic attack and vascular dementia. These problems are caused by thrombi which mostly originate in the left atrial appendage (LAA), a small muscular sac protruding from left atrium. The abnormal heart rhythm associated with AF results in alterations in the heart muscle contractions and in some reshaping of the cardiac chambers. This study aims to verify if and how these physiological changes can establish hemodynamic conditions in the LAA promoting thrombus formation, by means of computational fluid dynamic (CFD) analyses. In particular, sinus …

Hyperhomocysteinemia in hemodialysis patients: Is it a risk factor for cardiovascular disease?

2005

Information transfer and information modification to identify the structure of cardiovascular and cardiorespiratory networks

2017

To fully elucidate the complex physiological mechanisms underlying the short-term autonomic regulation of heart period (H), systolic and diastolic arterial pressure (S, D) and respiratory (R) variability, the joint dynamics of these variables need to be explored using multivariate time series analysis. This study proposes the utilization of information-theoretic measures to measure causal interactions between nodes of the cardiovascular/cardiorespiratory network and to assess the nature (synergistic or redundant) of these directed interactions. Indexes of information transfer and information modification are extracted from the H, S, D and R series measured from healthy subjects in a resting…

Canal transportation caused by a new instrumentation technique and three standard techniques

1996

The ability of three different enlarging techniques (balanced force concept, step-back, and recapitulation) and a prototype system to maintain the original canal path during root canal preparation were compared, in vitro, with a theoretical ideally prepared root canal. Measurements were made at the concave and convex sides of the canal at four different levels (1, 4, 5, and 7 mm from apical, respectively). Simulated root canals embedded in clear casting resin and an enlarging computer-supported device were used for this study. The results showed that none of the enlarging techniques used in this study was able to prepare a canal ideally. The prototype system, at level 1, showed an ideal amo…

Resonance frequency analysis-reliability in third generation instruments : Osstell mentor ®

2012

Few studies assess repeatability and reproducibility in registers of resonance frequency analysis (a value of dental implant stability). Objective: Few studies assess repeatability and reproducibility in resonance frequency analyses (implant stability evaluation). This study is aimed at assessing reliability (repeatabilty and reproducibility) in the Osstell Mentor® system using the intraclass correlation coefficient (ICC) as the statistical method. Study Design: ISQ measurements of RFA were carried out by means of the Osstell Mentor ® instrument in 58 implants in 19 patients. Six measurements were performed on each implant by means of two different Smart-Pegs (I and II). Three consecutive m…

A nonlinear biomechanical model for evaluation of cerebrospinal fluid shunt systems.

1994

In view of complications arising from physical properties of cerebrospinal fluid shunts, a biomechanical model of hydrocephalus was set up to study in vivo parameters that may influence their function. These include: intracranial pressure, compliance and pulses, intrathoracic, intra-abdominal, and subcutaneous pressures, and the effects of siphonage and repeated valve flushing. Each of these factors was studied separately upon shunt implantation in the model. Results of testing of a sample low-pressure valve with antisiphon device conformed with consumer information in regard to valve opening pressure and pressure flow measurements. No customer information, however, was supplied concerning …

<title>Ultrasound detection of cavitation as a phenomenon common to intervention devices causing tissue ablation</title>

1992

Cavitation previously has been observed in association with ultrasonic angioplasty and high- frequency rotational atherectomy. This study evaluates the production of cavitation accompanying the use of several catheter-based devices under development or in current use in the practice of interventional cardiology. Catheters were examined in an in vitro model, and cavitation was evaluated using standard ultrasound imaging equipment. Cavitation was detected with each of the devices that effects tissue ablation, but not tissue resection. Devices produced characteristic patterns of cavitation dependent on the mode of energy release of the device. The size, but not the intensity, of the cavitation…

Hybrid segmentation and exploration of the human lungs

2004

Segmentation of the tracheo-bronchial tree of the lungs is notoriously difficult. This is due to the fact that the small size of some of the anatomical structures is subject to partial volume effects. Furthermore, the limited intensity contrast between the participating materials (air, blood, and tissue) increases the segmentation of difficulties. In this paper, we propose a hybrid segmentation method which is based on a pipeline of three segmentation stages to extract the lower airways down to the seventh generation of the bronchi. User interaction is limited to the specification of a seed point inside the easily detectable trachea at the upper end of the lower airways. Similarly, the comp…

Histologic evaluation of thermal damage produced on soft tissues by CO2, Er,Cr:YSGG and diode lasers

2010

Objective: The aim of this in vitro experimental study was to perform histological evaluation of the thermal effect produced on soft tissue irradiated with CO2 , Er,Cr:YSGG or diode lasers. Study design: Porcine oral mucosa samples were irradiated with Er,Cr:YSGG laser at 1 W with and without water / air spray, at 2 W with and without water / air spray, and at 4 W with water / air spray, with CO2 laser at 1 W, 2 W, 10 W, 20 W continuous mode and 20 W pulsed mode and diode laser at 2W, 5W, and 10W pulsed mode. The thermal effect was evaluated measuring the width of damaged tissue adjacent to the incision, stained positively for hyalinized tissue with Hematoxylin-Eosin and Masson Trichrome st…