Laser Doppler Flowmeter (LDF) is a new, reliable and simple method to monitor regional Cerebral Blood Flow (rCBF). Our group began to perform intraoperative LD recordings in 1986. Recently, the advent of new special probes and the use of computer techniques, allowed two important improvements: an easy and safe postoperative LDF monitoring in Intensive Care Unit; and the simultaneous (intra- and postoperatively) acquisition of other signals on a computer: i.e., ICP, SAP, CVP, and end-Tidal CO₂.

The present study attempts to assess the in-vivo effects of Nd:YAG laser irradiation on the brain in different gaseous environments. Such an investigation is critical for determining the extent of injury under such conditions to further improve clinical applications. The authors define the influence on laser-tissue interaction of room air, 30% oxygen, helium, and nitrogen

Receptor inactivation by means of chromophore-conjugated receptor ligands and laser is discussed. The results of preliminary experiments aimed at inactivation of FMRFamide receptors in snail neurons using a He-Ne laser and FMRFamide analogs conjugated with Azure B are presented. Because the conjugates synthesized apparently bound to another class of binding sites on the neuronal membrane, the FMRFamide receptor inactivation was not achieved. However, laser inactivation was demonstrated for the conjugate binding sites.

A unit is presented that provides the neurosurgeon with CT, MRI, x-ray, DA, and DSA compatible headholder and multimodality image localization as well as freedom of choice for surgical approach on patient's intraoperative positioning. The unit consists of a carbon fiber ring-shaped headholder which allows free selection for location of three or four fixation pins, avoiding interference with the flap sites or craniotomy. The base ring is mounted intraoperatively on a special adapter that allows any patient positioning including supine, lateral, prone, 3/4 prone, sitting, etc. Surgical draping can be performed given a completely sterile field. An arc/quadrant localizing device can be mounted on any four alternative positions according to the neurosurgeon's preference. A PC compatible software gives the setting for any possible mounting. Intraoperative the localizing unit can be used in a 'fixed' permanent setting or as a 'non-fixed' system to provide intraoperative three-dimensional orientation. Different are adapted instruments which give the unit further capabilities, especially 'bayonet' type brain retractors (cylinders and speculum) that allows the neurosurgeon to keep the surgical corridor unobstructed from the arc. As an alternative, in the 'non-fixed' setting, self-retaining arms are fixed to the base ring and brain retractors and conventional microsurgical technique can be used without any mechanical obstruction. This article presents the unit details, methodology and the clinical experience in 103 consecutive cases of 'open stereotaxis' for resection or internal decompression of deep seated or near eloquent area lesions.

Based on previous experimental investigations which indicated that low-power laser irradiation has a significant therapeutic effect and treatment potential on the injured nerve tissue, the authors began using this method in clinical practice. This data represents the first clinical results in the treatment of four patients with tethered spinal cord resulting from fibrous adhesions at the site of previous myelomeningocele and lypomyelomeningocele repair, thickened filum terminale and spinal lipoma. After surgical release of the tethered spinal cord, stable evoked responses were recorded and the conus medullaris was subjected to direct laser irradiation (CW He-Ne laser, 632.8nm, 7Jcm²). The findings show intraoperative laser treatment increases evoked responses from 15-52% (mean 26.7%). In a previous work, it was shown that direct laser irradiation promotes restoration of the electrophysiological activity of the severely injured peripheral nerve, prevents degenerative changes in neurons of the spinal cord and induces proliferation of astrocytes and oligodendrocytes. This suggested a higher metabolism in neurons and improved ability for myelin production under the influence of laser treatment. It is well known that tethering of the spinal cord causes mechanical damage to neuronal cell membranes leading to metabolic disturbances in the neurons. For this reason, the authors believe that using low-power laser irradiation may improve neuronal metabolism, prevent neuronal degeneration and promote improved spinal cord function and repair.

This paper describes a 'real time' surgical treatment planning interactive workstation, utilizing multimodality imaging (computer tomography, magnetic resonance imaging, digital angiography) that has been developed to provide the neurosurgeon with two-dimensional multiplanar and three-dimensional 'display' of a patient's lesion.

No abstract available.

Low-light fluorescence video microscopy has established itself as an excellent method for investigations of cell dynamics. There is a growing interest in resolving multiple images of 'ratio' fluorophores like indo or BCECF or the emission from multiple dyes placed in the same cell system. For rapid kinetic studies, the problems of photodynamic damage and photobleaching on one hand and the need for good spatial and temporal resolution on the other, press the resolution of the instrumentation. Rapid resolution of multiple probes at multiple wavelengths presents a third set of problems of exciting the probes and appropriately imaging the emitted light. The authors have designed a new real-time low-light fluorescence video microscope for capturing intensified images of up to four dyes contained in the same cell system. These can be two dual-emission wavelength 'ratio' dyes or multiple dyes. The optics allow simultaneous excitation of up to four fluorophores and the real-time (30 frames/second) capture of four separate fluorescence emission images. Each emission wavelength is imaged simultaneously by one of four cameras, then digitized and appropriately combined at standard video frame rates to be stored at high resolution on tape or video disk for further off-line correction and analysis. The design has no moving parts in its optical train, which overcomes a number of technical difficulties encountered in filter wheel or mechanical shutter designs for multiple imaging. The instrument can be assembled form off-the-shelf components. Coupled to compatible image processing software utilizing PC-AT computers, it can be realized for relatively low cost. Two examples of simultaneous multi-parameter imaging are presented. Synchronous observations of calcium and pH distribution in kidney epithelial cells, loaded with both indo-1 and SNARF-1^TM, show that both are altered in response to ionomycin treatment; however, the kinetics for the two changes are quite different. Intracellular calcium increases rapidly when the bath Ca²⁺ is raised. The pH remains stable for several seconds, then suddenly collapses. The second example concerns fusion of human red blood cells (RBC) to fibroblasts expressing influenza hemagglutinin. Movement of soluble and membrane-bound dyes follow different kinetics, depending upon the molecular weight of the soluble dye. Furthermore, the swelling of the RBC occurs after the onset of fusion, and therefore cannot provide the driving force.

The rapid motion of microscopic features such as the cross-striations of contracting cardiac muscle cells are difficult to capture with conventional RS-170 video systems and image processing approaches. In this report, efforts to extract, enhance and analyze striation data from widefield optical sections of single contracting cells recorded with a charge-coupled device (CCD) video camera modified for high-speed RS-170 compatible operation are described. Each video field from the camera provides four 1/4 height images separated by 4 ms in time for a 240 Hz image acquisition rate. Data are continuously recorded on S-VHS video tape during each experiment. Selected image sequences are digitized field by field and stored in a computer system under automated software control. The four individual images in each video field are separated, geometrically corrected for time base error, and reassembled as a single sequence of images for interpretable visualization. The images are then processed with digital filters and gray scale expansion to preferentially enhance the cross-striations and minimize out of focus features. Regions within each image containing striations are identified and their positions determined and followed during the contraction cycle to obtain individual, regional and cellular sarcomere dynamics. This approach permits the critical evaluation of the magnitude, time course and uniformity of contractile function throughout the volume of a single cell with higher temporal and spatial resolutions than previously possible.

Charge coupled devices (CCD) have several advantages over tube camera imaging devices. These advantages include: geometric stability, high dynamic range (12, 14, or 16 bits) and photometric linearity. In order to achieve low-readout noise the readout is usually limited to 50 kpixels per second. The readout time is several times longer than video rates; the slow readout at less than video rates is the major disadvantage. A new CCD imager has been coupled to a Nipkow disk, confocal light microscope and its performance is evaluated using both reflected light and low-light-level fluorescence imaging. The CCD imager is a TK515, silicon CCD which is sensitiveequalsve from the UV to the near-IR. The sensor is a full frame area imager, with CCDs fabricated using a buried channel, three-level polysilicon gate process with very high charge-transfer efficiency (>0.9999) and low dark current. Low noise on-chip amplifiers provide and interface to external preamplifiers with readout noise typically <10 electrons at -90 degree(s) C, and 50 kpixels/second data rate. The chip is a thinned, back-illuminated device with anti-reflection coatings. The quantum efficiency is >80% at 400 nm and >90% at 600 nm. To determine its performance the Tektronix CCD was mounted in a Photometrics liquid cooled camera, attached to a Technical Instruments K2Bio confocal microscope.

Most low-light-level 3D bio-imaging systems use sensors with high spatial resolution but relatively low temporal resolution. The authors aim to measure events in skeletal muscle cells that include (1) changes in cross-sectional area during contraction and (2) regions of contracting cells illuminated by Ca²⁺-activated photoproteins compared with those that are dark or partly lit. This paper outlines some limits of the system's ability to detect these events.

The image reconstruction method of maximum likelihood estimation (MLE) has been used in the authors' previous work for fluorescence microscopy. By computer simulations, it was previously found that this method worked very well for addressing two dimensional superresolution and three dimensional optical sectioning problems. In this paper, the results of 3D reconstructions with real data will be presented.

The new methodology of chromosome analysis based on eigenanalysis and iterative Fourier synthesis has been developed. The approach is inspired by the analysis developed in electron microscopy of particles, and has been modified to address particular problems of chromosome analysis. Preliminary results on data sets containing 40-80 images for each of the human chromosomes indicate that this methodology provides an improvement of chromosome band resolution and potentially can provide cytogeneticist with some new insights. The proposed procedure is a novel approach in chromosome analysis and represents a significant contribution to quantitative cytogenetics. It opens the possibility of identifying defects in chromosome banding pattern automatically.

Previous studies from this laboratory demonstrated degradation of cholesterol crystals ingested by macrophages in a cell culture system. Those studies also indicated that intracellular phospholipids could play an important role in mobilization of crystalline cholesterol. The purpose of this study was to further explore the role of each of the three major intracellular phospholipid species in degradation of crystals. Fluorescently labeled cholesterol crystals were incubated with phospholipids over a period of 5 days. Morphological changes in crystals were monitored by the use of digital imaging fluorescence microscopy, fluorescence redistribution after photobleaching, confocal microscopy, as well as epifluorescent and phase contrast microscopy. Results clearly demonstrated that all three phospholipids were able to mobilize crystalline cholesterol; however, mechanisms by which they exerted mobilization were different. Sphingomyelin and phosphatidylcholine were found to cause gradual and uniform dissolution of crystals, more or less preserving their original shape. Phosphatidylethanolamine appeared to penetrate into the crystal, causing its fragmentation and solubilization. In the mixture of all three phospholipids representing the composition found in macrophages, both of the described mechanisms were working simultaneously.

Elucidation of the pathogenesis of AIDS is confounded by the finding that few actively infected CD4⁺ cells (1 in 10⁴-10⁵) can be detected in the peripheral blood, even though there is dramatic depletion (often >90%) of CD4⁺ cells as the disease progresses. A sensitive, ³⁵S-based human immunodeficiency virus (HIV) mRNA in situ hybridization technique was coupled with a new detection method, confocal laser scanning microscopy, to examine transcriptionally active HIV-infected cells from individuals at different disease stages. An algorithm for image segmentation and analysis has been developed to determine the proportion of HIV-positive cells. Data obtained using this improved detection method suggest that there are more HIV mRNA-producing cells in HIV-infected individuals than previously thought, based on other detection methods.

Digital Imaging Light Microscopy technology has made major advancements over the past years. Changes have included significant improvements in sensitivity and image quality, but also the advent of innovative methods that have greatly increased the versatility of instruments. Methods to yield contrast in the specimen have made leaps in specificity and signal-to-noise ratio. The combination of these advanced technologies now permits the acquisition of 2 and 3 dimensional image data, of up to five independently labeled parameters, in fixed specimens, or - in time lapse series - of living cells. Given the vast amount of data that can be generated with these instruments, there is a growing need for image analysis software that can yield quantitative measurements from these complex images. The authors are developing a knowledge driven image analysis system that is capable of handling the described image data. The proposed architecture tries to optimize robustness by taking advantage of knowledge that is available both from the expert user as well as from the multiple image sources. It therefore offers significant potential for improvements in performance over linear and mathematical morphology based systems. The authors applied this system to trace actin-based fiber bundles using knowledge constraints, and analyzed their distribution, shape, sizes and orientation in fixed cells by immunofluorescence with good results.

A novel imaging spectroscope with an optical recombination scheme is reported. Image quality. bandwidth and some other characteristics have been discussed. Some preliminary experimental results are also presented.

The Laser sits near the top of any list of greatest inventions of the last half of the twentieth century. Together with the computer, fiber optics and robots, it is a symbol of "high-tech". Nowadays, laser technology is both fascinating in itself and an important tool in fields from telecommunications to medicine. Since 1960, the advancement of Laser technology has granted a significant contribution to a number of medical fields, particularly ophthalmology. Laser in this specialty stands in a ripe phase and has been given evidence of its indispensability during daily procedures. In Neurosurgery, Lasers were incorporated for more than a decade as a precise tool to remove lesions from eloquent areas of the brain, spinal cord and brain stem (3). In Neurovascular surgery, Laser technology stays in a cut edge, although further studies need to be done, in order to ensure that a fine technique can take place as an efficient therapeutic modalities. In this concern, more emphasis will be placed on finding new ways to use Lasers in less invasive procedures. So far we intend to review some preliminary studies and discuss how Lasers will become an effective addition to the neurosurgeon's armamentarium in treating vascular problems.

This paper shows that the contents of liposomes with encapsulated or membrane-bound dye can be released by localized heating induced by pulsed nanosecond laser excitation. With 50 mM sulforhodamine encapsulated in 4 micron diameter vesicles of diphosphatidyl choline (DPPC), nearly 100% of liposome contents are released with a single 8 ns pulse of 532 nm at 0.5 J/cm². Dependence on laser pulse energy density, pulse sequence, dye concentration, vesicle size and ambient temperature was also demonstrated. These results may be useful for the application of selective modification techniques in neuroscience and the understanding of laser-tissue effects in neurosurgery at the cellular level.

The research has focused on understanding the effects of irradiating liposomes containing organic dyes with nanosecond and picosecond pulses at 532 nm from Nd:YAG lasers. Time-correlated photon counting and phase-resolved fluorescence spectroscopy techniques have been employed to obtain multicomponent fluorescence lifetimes for the dye-liposome system. A quantitative model based on the experimental data supports a photo-induced thermal mechanism for release of liposome contents.

In recent years, the C02 laser has proved to be a valuable instrument in neurosurgery. Its primary role has been in the ablation of tumors, although it may also be used in intricate dissection of other tissues. The C02 laser beam can be focused and used with a microscope and micromanipulator. This, coupled with the principle that 90% of the radiation is absorbed in the first 0.03 mm. of water makes the instrument exquisitely precise in Lumor removal while sparing tissues which must be preserved. This precision makes for an instrument which usually has a high degree of safety. However, while it usually is quite innocuous, this powerful tool carries the potential for injury.(2) The otolaryngologists report serious injury by inadvertent ignition of endotracheal tubes by laser.(1) This can result in extensive injury to the airway and lungs due to heat and smoke. In the neurosurgical operating room, injury can occur either by the beam striking structures directly or indirectly. Other instruments are usually present in the surgical field during laser use. Hand-held or self-retaining retractors, suction devices, or probes are used to retract or manipulate structures or to evacuate smoke or fluids. These may be inadvertently passed into the path of the beam or may be struck by a moving beam. The injury can be divided into that in which tissues in contact with the instruments are burned by the instrument which absorbs the energy and heats up, and injuries which occur by energy which is reflected off of an instrument. Both the patient and the surgical personnel are at risk from this reflected energy. Reflected power can even ignite surgical drapes. Measures are routinely taken to help reduce the risks of injury. These include the requirement that safety glasses are used by all operating room personnel. Delicate structures within the surgical field are covered with moist cottonoids. Instrument design should incorporate features which reduce the risk of injury due to reflection and absorption of energy. Many companies offer the service of "ebonizing" instruments with the claim that they will improve the safety of laser surgery. Unfortunately, there have been few studies performed which ascertain the ideal characteristics of instrument design. This study was performed to determine whether varying certain characteristics of the surface of an instrument can reduce surgical risks. Flat brain retractors were used to control for variation in the beam striking a curved surface. Identical retractors were prepared 128 / SPIE Vol. 1428 Three-Dimensional Bioimaging Systems and Lasers in the Neurosciences (1991) O-8194-0518-3/91/$4.OO with surfaces with various grades of roughness and with different surface materials. Each retractor was tested for absorption and for reflection of energy.

This is a series of sixty consecutive sitting position suboccipital extirpations of acoustic neuromas operated between January 1986 and March 1990 where a CO₂ laser was used in an attempt to preserve patients' facial and cochlear nerve function. Following surgery, four patients had normal and one had near-normal hearing (PTA<30 dB, SD>70%). These patients had tumors of 4, 3.2, 3, 1.5 and 1.2 cm in the greatest dimension. Two other patients (tumor size, 1.9 and 1.2 cm) have useful hearing (PTA<50dB, SD>50%) and four patients have sufficient hearing for the successful use of a hearing aid (4.6, 2.8, and 2 cm). One of thirty-two patients with the perception of useless hearing improved to useful hearing following surgery.

Up to the present 5 patients with cerebral gliomas (WHO II-III) were treated by stereotactic, laser-induced, interstitial thermal therapy (SLIITT). Parameters used in SLIITT were 3 watts as continuous wave over 5-10 minutes in single or multiple foci depending on the size of the tumor.