Fiberoptic technique

Bechi P., Pucciani F., Baldini F., Cosi F., Falciai R., Mazzanti R., Castagnoli A., Passed A., Boscherini S., Long-term ambulatory enterogastric reflux monitoring. Validation of a new fiberoptic technique, Digestive Diseases and Sciences 1993 38 1297. 

An improved knowledge about photoinduced biological processes in man is of great interest as a basis for the medical therapy with light and photosensitizing drugs. Photomedical therapy is, of course, especially concerned with the skin, but via fiberoptic techniques and endoscopes internal treatment is also accessible. 

An increasing number of physicians are using integrated laser-fiberoptic systems, such as laser catheters or laser endoscopes, in a clinical setting. A few examples illustrate the use of laser catheters and endoscopes for clinical applications. The sections on cardiology and on cancer diagnosis and therapy illustrate the enormous potential of laser-fiberoptic techniques. 

No doubt fiberoptic techniques will replace more traditional procedures in the coming years. 

In recent years no truly new basic principles have been introduced for the detection of luminescence. However, the technical evolution in the field of microelectronics and optoelectronics, charge coupled device (CCD) detectors, fiberoptics, assembly techniques, and robotics resulted in the introduction on the market of new generations of instruments with increased performance, speed, and ease of handling. In this chapter, some of their typical features will be reviewed. To keep this presentation at a concrete level and to illustrate some specific item, instruments of different makes will be referred to. However, this does not imply they are better than those not cited. It is more a matter of availability of recent documentation at the time of writing. Note that numerical values cited typically relate what can be done today and may vary from one instrument to another from the same company. 

Figure 9.6. Stability of a lifetime-based fiberoptic oxygen sensor over a period of 100 h of continuous operation. Lifetime techniques are insensitive to the process of photobleaching only in the absence of excited state reactions. Excited state reactions of the sensor-carrier system cause drifts in the observed lifetime with photobleaching. They are avoided by limiting the concentration of the sensor in the carrier. (From Ref. 21 with permission.)...

In the preceding two examples, Raman spectra were obtained from tissues and cell samples ex vivo. Recently, Buschman et al. (46) were able to measure Raman spectra of sheep arterial walls in vivo using a miniature fiberoptic probe. They have demonstrated that the in vivo intravascular Raman signal obtained directly from a blood vessel is a simple summation of signals from the blood vessel wall and blood itself. This technique may be useful in predicting the risk of arterial plaque rapture and determining plaque composition in human arteries. 

The communications revolution also relies on a diverse set of CVD technologies. Some components are similar to those used in silicon microelectronics, but many are unique, involving complex epitaxial heterostructures of SiGe or compound semiconductor (e.g., AlGaAs) alloys that are required to yield high frequency (1-100 GHz) device operation. The communication revolution also relies on optoelectronic components, such as solid state diode lasers (another complex heterostructure device), and these devices are often grown by CVD. - Even the fiberoptic cables that transmit the optical component of the communications network are manufactured using a CVD technique to achieve the desired refractive index profile. ... 

The chapter thus far has addressed fiber-optic sampling techniques and hardware, illustrated with a few applications. As noted earlier, there has been a wide range of fiber-optic Raman applications presented in the literature, and new reports continue to appear at an accelerating rate. Table 12.4 lists some examples of applications to illustrate the wide variety and breadth of fiberoptic samples. The list is by no means comprehensive, but it should provide the reader with a starting point to explore applications in particular areas. 

The second focus of this chapter will be on high-throughput techniques for the assessment of product quality. These techniques—NIR analysis, fiberoptic dissolution, robotics, and flow injection analysis (FIA)—promise to allow the analyst more time for problem solving, invention, and interaction with the analytical department s multiple customers. 

A number of recent analytical techniques have been used to improve the reliability of chemical analysis from a qualitative and quantitative point of view. The work of Tubino et al.13 should be mentioned as an example of using fiberoptic devices for spot tests of diffuse reflectance measurements. 

The techniques that are able to perform the on-line evaluation of PSDs include fiberoptic dynamic light scattering (FODLS), turbidimetry, size fractionation techniques (such as capillary hydrodynamic fractionation chromatography, CHDF and field-flow fractionation. 

Fluorescent sensors in solution (chemosensors) and fiberoptic sensors. Fluorescence is a particularly important technique in this field because of its high sensitivity of detection down to a single molecule, subnanometer spatial resolution with submicrometer visualization and submillisecond temporal resolution. 

The history of real endoscopy of the middle ear was started in 1967 by Zini when he tried to visualize the middle ear using a system of micromirrors, which allowed the exploration of the retrotympanum. This method, called indirect microtympanoscopy, is still used in clinical practice. Mer et al. (1967) introduced the fiberoptic endoscope into the tympanic cavity through a perforation of the tympanic membrane. Marquet and Boedts D (1975) described an endoscopic technique based on the use of a 1.7-mm... 

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