Near-infrared (NIR) fluorescence has the potential to provide surgeons with real-time intraoperative image-guidance.
Increasing the signal-to-background ratio of fluorescent agents involves delivering a controllable excitation
fluence rate of proper wavelength and/or using complementary imaging techniques such as FLIM. In this study we
describe a low-cost linear driver circuit capable of driving Light Emitting Diodes (LEDs) from DC to 35 MHz, at high
power, and which permit fluorescence CW and lifetime measurements. The electronic circuit Gerber files described in
this article and the list of components are available online at www.frangionilab.org.
A three dimensional numerical model for elastic wave propagation in multilayered structures is the subject of this paper. The model is based on the Transmission Line Matrix method (TLM) and has a three dimensional acoustic node as a key element. A full description of the numerical method implementation is provided. The numerical analysis was applied to structures with a relatively complicated geometry, similar to the geometries used in non-destructive testing and in medical imaging. The comparison between the experimental and numerical frequency response for a multi-layered cylindrical piece validates the proposed numerical model. An acoustic impedance profile similar to biological tissue was numerically modeled. The comparison between real and numerically generated signals shows good agreement between experiment and numerical analysis.
A method for early failure detection for elastic diaphragms during their operation is described in this paper. The method is based on frequency analysis of the acoustic signal obtained from an air-driven pump. A fully digital system for frequency analysis based on a personal computer was developed for practical implementation of this method. The system was tested in the laboratory and in plant conditions. In laboratory, diaphragms with different artificial flaws were mounted in the pump and the corresponding spectra recorded. The results helped to set the parameters for in-plant experiments. These experiments were between three and fourteen days. During this time the system performed acquisition and data processing at 10 second apart. Three in-plant experiments have shown that a failure initiation event can be detected from frequency behavior analysis for each test and that a subsequent failure occurs. All failures indicated by the system have been confirmed by visual inspection.
A transmission-line matrix (TLM) model was developed to simulate the ultrasound propagation in the multi-layer structures. The spatial resolution of the proposed model is better than tenth wavelength. The numerical modeling is carried-out for frequencies that are usually used in ultrasound imagery (3.5 - 25MHz). The acoustic impedance profile of multi-layer structures considered are similar to those found in nondestructive evaluation and in medical imaging. The structures modeled are: brazed joints, stomach and colon walls. Structures with artificial flaws are also modeled. A comparison between real images and numerical generated ones is provided for each considered structure. Both frequency and time domain responses are obtained from the structures under investigation. Both single and array transducer techniques are modeled and their performances are evaluated for the proposed structures. Different shapes for the incident pulse are considered in numerically generated images.