Near-infrared spectroscopy study of tourniquet-induced forearm ischaemia in patients with coronary artery disease

Near-Infrared Spectroscopy (NIRS) can be employed to monitor local changes in haemodynamics and oxygenation of human tissues. A preliminary study has been performed in order to evaluate the NIRS transmittance response to induced forearm ischaemia in patients with coronary artery disease (CAD). The population consists in 40 patients with cardiovascular risk factors and angiographically documented CAD, compared to a group of 13 normal subjects. By inflating and subsequently deflating a cuff placed around the patient arm, an ischaemia has been induced and released, and the patients have been observed until recovery of the basal conditions. A custom NIRS spectrometer (IRIS) has been used to collect the backscattered light intensities from the patient forearm throughout the ischaemic and the recovery phase. The time dependence of the near-infrared transmittance on the control group is consistent with the available literature. On the contrary, the magnitude and dynamics of the NIRS signal on the CAD patients show deviations from the documented normal behavior, which can be tentatively attributed to abnormal vessel stiffness. These preliminary results, while validating the performance of the IRIS spectrometer, are strongly conducive towards the applicability of the NIRS technique to ischaemia analysis and to endothelial dysfunction characterization in CAD patients with cardiovascular risk factors

Microcontroller-based digital front-end for near-infrared spectroscopy

Near Infrared Spectroscopy (NIRS) can be employed to noninvasively and continuously measure in-vivo local changes in haemodynamics and oxygenation of human tissues. Monitoring of these parameters is particularly useful both for basic research and during surgery, when a continuous and real-time measurement can help to avoid permanent damage to the tissues. We present a modular acquisition system in which each subsystem, from the case to the single acquisition front-end is designed to meet all the requirements of a research-grade instrument, dedicated to intraoperatory measurements. Part of the modules of the acquisition system has been dedicated to multipoint NIRS. A module prototype has been developed, which is able to control four LED sources and two detectors. On each front-end a RISC microcontroller performs source and detector multiplexing with a digital correlation technique. A number of such modules can be independently addressed through a bus by a PC-based workstation (integrated on the instrument) for data collection, processing and visualization. Preliminary tests of the prototype on tourniquet-induced forearm ischaemia show adequate detectivity and time response. The operating parameters derived from the prototype will be employed in the design of a high channel count module, which will exploit the capabilities of a digital signal processor (DSP), for spatially mapped brain oxygenation monitoring

An intelligent acquisition system for near infrared spectroscopy

This chapter looks at an intelligent acquisition system for near infrared spectroscop

Investigation of GaInAs/InP superlattices by electron microscopy, x-ray diffraction and spectroscopic ellipsometry

Two sets of GaInAs/InP lattice-matched superlattices containing 30 periods, with a wide range of barrier and well thicknesses, were grown on (100) InP substrates by metal organic vapour phase epitaxy, using growth interruptions for interface optimization. Structural, compositional and optical characterization was performed by transmission electron microscopy, high-resolution x-ray diffraction and spectroscopic ellipsometry. The results from these complementary techniques agree quantitatively and show the good crystal quality of the samples. The interfaces in the long-period structures appear flat and sharp, while in the short-period ones they show undulations and graded-composition transition layers. A possible explanation for these effects is proposed