Search results for "Biomedical engineering"

Realignment of myocardial first-pass MR perfusion images using an automatic detection of the heart-lung interface

2004

International audience; Abstract: Magnetic resonance first-pass imaging of a bolus of contrast agent is well adapted to distinguish normal and hypoperfused areas of the myocardium. In most cases, the signal intensity-time curves in user defined regions of interest (ROI) are studied. As image acquisition is ECG-gated, the images are acquired at the same moment in the cardiac cycle, and the basic shape of the heart is similar from one view to the next. However, superficial respiratory motion can displace the heart in the short-axis plane. The aim of this study is to correct for the respiratory motion of the heart by performing an automatic realignment of the myocardial ROI based on a method t…

Magnetically labeled water perfusion imaging of the uterine arteries and of normal and malignant cervical tissue: initial experiences.

1998

Purpose: The aim of this pilot study was to evaluate a magnetically labeled water perfusion imaging technique as a non-contrast-enhanced approach to demonstrate the uterine artery, its branches, and to assess the cervical uterine blood flow in healthy volunteers and in patients with advanced uterine cervical carcinoma (FIGO IIB-IVA). Methods and Materials: Seven healthy volunteers (mean age, 29 years) and twenty-two patients (mean age, 52 years) with advanced cancer of the uterine cervix (FIGO IIB-IVA) were prospectively examined by magnetically labeled water perfusion imaging at different inversion delay times (300–900 ms). The magnetic resonance imaging (MRI) findings of all patients were…

Neuromuscular function and mechanical efficiency of human leg extensor muscles during jumping exercises

1982

The influence of prestretch amplitude on the mechanical efficiency was examined with 5 subjects, who performed 5 different series of vertical jumps, each of which differed with respect to the mechanics of the knee joint action during the prestretch (eccentric) phase of the contact on the floor. Electromyographic activity was recorded from the major extensor muscles during the entire work period of 1 min per series. In addition, expired air was collected during the test and recovery for determination of energy expenditure. Mechanical work was calculated from the vertical displacement of the body during the jumps. The results indicated that high net efficiency of 38.7% was observed in conditi…

Neuromuscular responses to explosive and heavy resistance loading

2000

The EMG power spectrum may shift towards higher frequencies with higher movement velocities. Fatigue, on the other hand, can cause a decrease in the frequency components. The purpose of this study was to examine acute effects of explosive (EE) and heavy resistance (HRE) concentric leg press exercise on muscle force, EMG and blood lactate. The EE included five sets of ten repetitions with 40+/-6% of the isometric maximum at a 100 degrees knee angle performed as explosively as possible. The same number of repetitions was performed in HRE but with a heavier load (67+/-7% of the isometric maximum at a 100 degrees knee angle). Maximal isometric and single concentric actions of different loads, a…

Functional characterization of hepatocytes for cell transplantation: customized cell preparation for each receptor.

2009

The first indication of hepatocyte transplantation is inborn liver-based metabolic disorders. Among these, urea cycle disorders leading to the impairment to detoxify ammonia and Crigler-Najjar Syndrome type I, a deficiency in the hepatic UDP-glucuronosyltransferase 1A1 present the highest incidence. Metabolically qualified human hepatocytes are required for clinical infusion. We proposed fast and sensitive procedures to determine their suitability for transplantation. For this purpose, viability, attachment efficiency, and metabolic functionality (ureogenic capability, cytochrome P450, and phase II activities) are assayed prior to clinical cell infusion to determine the quality of hepatocyt…

On-line measurements of body fat content by the caliper method

1986

Optical noninvasive monitoring of skin blood pulsations

2005

Time-resolved detection and analysis of skin backscattered optical signals (remission photoplethysmography or PPG) provide rich information on skin blood volume pulsations and can serve for reliable cardiovascular assessment. Single- and multiple-channel PPG concepts are discussed. Simultaneous data flow from several locations on the human body allows us to study heartbeat pulse-wave propagation in real time and to evaluate vascular resistance. Portable single-, dual-, and four-channel PPG monitoring devices with special software have been designed for real-time data acquisition and processing. The prototype devices have been clinically studied, and their potential for monitoring heart arrh…

Probabilistic liver atlas construction

2017

Background Anatomical atlases are 3D volumes or shapes representing an organ or structure of the human body. They contain either the prototypical shape of the object of interest together with other shapes representing its statistical variations (statistical atlas) or a probability map of belonging to the object (probabilistic atlas). Probabilistic atlases are mostly built with simple estimations only involving the data at each spatial location. Results A new method for probabilistic atlas construction that uses a generalized linear model is proposed. This method aims to improve the estimation of the probability to be covered by the liver. Furthermore, all methods to build an atlas involve p…

Bone marrow after autologous blood stem cell transplantation and total body irradiation: magnetic resonance and chemical shift imaging.

1993

Magnetic resonance studies of the lumbar, pelvic, and femoral bone marrow were performed in 10 patients after autologous blood stem cell transplantation, including total body irradiation and myeloablative chemotherapy. The posttreatment interval varied between 2 and 6 yr. The appearance on T1-weighted images and the quantitative data obtained from chemical shift imaging (relative fat signal) were compared to 10 age-matched healthy volunteers. The classification of the T1-weighted images yielded no significant differences between the two groups. Chemical shift imaging by determination of the relative fat signal was able to detect a significant fatty replacement of the patients' lumbar (p < .…

Validation of a mechanical method for measuring skin thickness: relation to age, body mass index, skin thickness determined by ultrasound, and bone m…

2009

In a number of endocrine disorders, typical changes in skin thickness can be observed which make measurement of skin thickness interesting in this field. A newly developed mechanical method for measuring skin thickness is presented. Using a digital measuring screw on the dorsum of the hand with a defined measuring force of 10 newton and a resulting tissue compression of 1500 mm Hg, highly reproducible results were obtained (mean coefficient of variation 2.56%). In 129 women, 37 to 78 years old, body mass index < 30 kg/m2, there was no significant relation between body mass index and skin fold thickness. A negative correlation between skin fold thickness and age (r = 0.37, p < 0.001) was det…