Brain electro- (EEG) or magnetoencephalogram (MEG) can be analyzed by using methods of the nonlinear system theory. We show that even for very short and nonstationary time series it is possible to functionally differentiate various brain activities. Usually the analysis assumes that the analyzed signals are both long and stationary, so that the classic spectral methods can be used. Even more convincing results can be obtained under these circumstances when the dimensional analysis or estimation of the Kolmogorov entropy or the Lyapunov exponent are performed. When measuring the spontaneous activity of a human brain the assumption of stationarity is questionable and `static' methods (correlation dimension, entropy, etc.) are then not adequate. In this case `dynamic' methods like pointwise-D2 dimension or chaoticity measures should be applied. Predictability measures in the form of local Lyapunov exponents are capable of revealing directly the chaoticity of a given process, and can practically be applied for functional differentiation of brain activity. We exemplify these in cases of apallic syndrome, tinnitus and schizophrenia. We show that: the average chaoticity in apallic syndrome differentiates brain states both in space and time, chaoticity changes temporally in case of schizophrenia (critical jumps of chaoticity), chaoticity changes locally in space, i.e., in the cortex plane in case of tinnitus.

Medical optical imaging (MOI) uses light emitted into opaque tissues in order to determine the interior structure and chemical content. These optical techniques have been developed in an attempt to prospectively identify impending brain injuries before they become irreversible, thus allowing injury to be avoided or minimized. Optical imaging and spectroscopy center around the simple idea that light passes through the body in small amounts, and emerges bearing clues about tissues through which it passed. Images can be reconstructed from such data, and this is the basis of optical tomography. Over the past few years, techniques have been developed to allow construction of images from such optical data at the bedside. We have used a time-of-flight system reported earlier to monitor oxygenation and image hemorrhage in neonatal brain. This article summarizes the problems that we believe can be addressed by such techniques, and reports on some of our early results.

Laser-Doppler-vibrometry is used successfully to detect the motions of the tympanic membrane under normal hearing conditions. For more detailed information about the dynamical behavior of the middle ear, it is necessary to improve the experimental signal-to- noise-ratio, which is mainly determined by the amount of light coupled back into the interferometer. The paper focuses onto two possibilities to yield of this amount light by increasing the solid angle of the optics and increasing the reflectivity of the tympanic membrane.

By the introduction of the laser Doppler perfusion imager (LDPI) the microvascular blood flow in a tissue area can be mapped by sequentially moving a laser beam over the tissue. The measurement is performed without touching the tissue and the captured perfusion values in the peripheral circulation are presented as a color-coded image. In the ordinary LDPI-set-up, 64 X 64 measurement sites cover an area in the range of about 10 - 150 cm² depending on system settings. With a high resolution modification, recordings can be done on tissue areas as small as 1 cm². This high resolution option has been assessed in animal models for the mapping of small vessels. To be able to record not only spatial but also temporal perfusion components of tissue blood flow, different local area scans (LAS) have been developed. These include single point recording as well as integration of either 2 X 2, 3 X 3, or 4 X 4 measurement sites. The laser beam is repeatedly moved in a quadratic pattern over the small tissue area of interest and the output value constitutes the average perfusion of all captured values within the actual region. For the evaluation, recordings were performed on healthy volunteers before and after application of a vasodilatating cream on the dorsal side of the hand.

Liquid crystal televisions (LCTVs) have recently become popular spatial light modulators. This paper describes in detail the design of a joint transform correlator (JTC) system that uses two inexpensive LCTVs obtained from a video projector. A prototype JTC system was used to measure blood flow and tissue motion in ultrasound speckle images. The design of spatial filters that allow real-time image processing of the ultrasound images are presented along with experimental results that characterize the improved performance. A novel spatial multiplexing technique that allows many flow vectors to be computed simultaneously is described. This spatial multiplexing technique can enhance the overall system vector throughput of a conventional JTC system by over a factor of 100. The prototype JTC system has the same tracking accuracy as the digital methods that are currently being used. In addition to speed, the JTC system offers advantages in cost, size, and power consumption.

The analysis of laser treated surfaces has relied heavily on traditional methods of microscopy. For the analysis of fine detail, scanning electron microscopy (SEM) remains the method of choice. Though the resolution of SEM is superb, the cost and time required to prepare tissue for analysis is often prohibitive. This is particularly true with respect to the analysis of laser treated tissues. In this study, scanning white light interferometry is compared with conventional SEM for analysis of ablation craters in bone. Porcine calvarial bone (cortical and otic) is machined into thin sections and treated with argon (514 nm) and KTP (Nd:YAG) (532 nm). SEM is performed on selected ablation specimens. Similar specimens are scanned using a white light interferometer, and the images are compared. While the interferometric methods lack the spatial resolution of SEM, it provides useful information on the surface contour. Detailed topographic information on the bone surface and ablation crater is obtained. This information can be used for analysis of surface texture. The interferometric methods are particularly useful for characterizing subtle surface changes. Interferometric methods of microscopy have their greatest utility in that no special preparation of tissue beyond dehydration is necessary, in contrast to SEM where gold-coating of tissue is required. Scanning white light interferometry is a simple and cost-effective alternative to SEM when quantitative structural and morphologic information is required.

A special electronic circuit for phase-resolved imaging of scattering media like tissues has been developed. Two contrarily arranged acousto-optic modulators provide a frequency shift of about 1 MHz between an object beam, which crosses the medium, and a reference beam. These two beams have been derived from one laser diode source (670 nm). After passing the medium an interferometric heterodyning of the two beams is provided. That gives a periodic signal determined by the shift frequency. This signal has been optical-electrically transformed by a photomultiplier and adjacent photon-counting and compared to the electrically provided shift frequency, generated by the two oscillation frequencies of the acousto-optic modulators and an electronic circuit. So it is possible to select the photons with the undisturbed phase (in- phase-photons). That amount consists of the number of unscattered, directly forward scattered, and random phased background. The single and multiple scattered photons with various randomly distributed pathways together with the background noise should contribute a constant (dc) value. Therefore by phase-gated imaging a decrease of background noise is achieved. The electronic circuit performs an rf-mixer, analog phase-shifting unit, high-speed digital gate, photon-detecting unit including preamplifier and discriminator, dual-channel high-speed counter and a control logic. The counter readout is provided by an external PC via I/O-card. This instrumentation allows a high-resolution cw coherence imaging and performs in combination with conventional tomographic arrangements (object rotation and translation) or confocal scanning a new approach to optical tomography for biological specimen in the range up to 5 mm thickness.

We are studying the use of the laser-induced fluorescence (LIF) endoscopic images of colonic mucosa for detection of pre-malignant lesions. LIF images were collected through a fiber optic colonoscope, and adenomatous polyps were used as a model of dysplasia. A total of 12 tissue samples containing 29 adenomas, obtained from colectomy specimens from 3 familial adenomatous polyposis patients, were studied. Regions of colonic mucosa were illuminated by a quartz optical fiber with near-UV light from an argon-ion laser. Autofluorescence between 400 and 700 nm was detected by means of an intensified CID camera. In the LIF images, adenomatous polyps appeared lower in intensity than normal mucosa by about a factor of 2. The LIF images were processed by dividing the raw image by a spatially averaged one to correct for differences in the distance to the tissue and in the light collection efficiency of the optics. Relative intensity thresholds were set at values varying between 55% and 90% compared to the spatial average to determine likely areas of disease. The results were compared to histology taken at 2 mm intervals along several transverse cross-sections of the specimens. At a threshold of 75%, 26 true positives, 256 true negatives, 22 false positives, and 3 false negatives were identified, resulting in a sensitivity, specificity, positive predictive value and percentage of correct determinations of 90%, 92%, 54%, and 92%, respectively. These values are comparable to results of independent diagnoses by two pathologists, demonstrating the potential of LIF to guide biopsy.

Dual-laser photothermal (PT) techniques are applied for a live blood cell studies. The measurement of the action of a pump pulse (400-600 nm, 10 ns, 1-500 pJ) on a single cell provides the imaging of cell's absorbing structure/thermal field, spectroscopy and control of cell's state. The imaging technique includes acquisition of three types of images: optical image, pulsed laser image with 5 ns temporal resolution and PT-image with the same temporal and 0.5 jim spatial resolution. In PT-images of WBC the details of a cell structure have been found that can not be obtained from optical images of these cells. Quantitative analysis of PT-images enables abnormal cell differentiation in a case of anaemia (RBC) and pulinanaiy diseases (neutrophyls). Analysis of cell population according to the cell ability to survive a pump pulse is considered as the viability test. This technique was used for RBC comparative studie. Significant differences in RBC populations have been found. Also the viability test was applied for monitoiing of action of the drugs upon RBC membrane. Fully automated experimental system was built for PT-studies of the cell populations. All set up is technically compatible to optical microscope. Operation rate is 1 cell/s. The required capacity of cell suspension is about 1 j.d. Keywords: image cytometry, photothermal microscopy.

Detailed investigations of the projection moire and grid projection methods used for the computer aided studies of the shape of the muscle-osseous system and postural deformities are presented. The shape determination process is readily automated using the phase methods for analyzing the fringe patterns. The issue of subtracting the reference surface inherent to the measurement-by-comparison methods is discussed. Specialized medical software for studying the deformity of the back and front of the human body illustrated by clinical examples is presented.

The diagnosis of osteoporosis has traditionally been made by observing bone radiographs and analyzing the optical density. More advanced methods measure the mineral content or the quantity of bone tissue, but do not determine bone quality, which depends on the bone tissue architecture. The structure and organization of bone tissue is a vital factor for assessing bone strength, as minute changes in the structure strongly affect bone strength. This study describes a novel method, based on optical and digital image processing of conventional radiographs for a quantitative evaluation of bone tissue architecture. The trabecular pattern appearing on the femoral neck radiograph was analyzed based on the power spectrum of this pattern, which was obtained by optical Fourier transform. The two-dimensional optical power spectrum was captured to the computer by a CCD device and after filtering and noise reduction, it was characterized using spatial frequencies in different directions. Software was developed for the analysis of the power spectrum of the trabecular pattern to yield a bone index. The effect of the image optical density on the calculated bone index was not significant. On the other hand, the bone index, based on the trabecular structure, was found to differ significantly between normal and osteoporotic bones. Thus, the power spectrum analysis could differentiate normal from osteoporotic bones much better than the amount of radiation absorbed by the bone.

This paper reports the results of our preliminary investigation into developing imaging techniques for full-size digital x-ray mammography. We have explored a novel `radiation shielding, CCD scanning' concept. Two system configurations were studied: one uses a lens coupled CCD module with a mirror scanning mechanism; the other uses a lens coupled CCD which is mounted on a scanning carrier platform. Using this technique, small CCD imagers can be used effectively to cover a large field without losing spatial resolution.

A new reconstruction algorithm is introduced to obtain a high quality computerized tomography image from limited information. There are many practical cases in which only limited projection data can be collected due to the physical constraints of the hardware system and the object structure. In these cases, conventional reconstruction algorithms which require complete projections are often unacceptable because it causes severe streak artifacts and distortions. So image reconstruction from limited information is very important and many authors have contributed to it. But the methods presented are often time consuming, less efficient and some algorithm's convergency cannot be guaranteed. For iterative algorithms, it is more important to guarantee the convergency and accelerate the convergency speed. In this paper, a CT image reconstruction method which exploits the Helgason-Ludwig consistency condition is designed to consider obtainable information content about object and reconstruction error in the situation of a finite number of projections. Based on the consideration, we developed a new iterative algorithm which can reconstruct high quality artifactless CT image from limited information, and we design a new histogram constraint obtained from a priori knowledge to guarantee the convergency and to acquire high convergency speed. The results of simulated tests show the great advantages of this new method.

Recent developments in optical, optoelectronic, and digital electronic imaging and metrology are creating opportunities for a new type of diagnostics methods and systems. Some of these techniques, established already in the field of technical and industrial non-destructive testing, have increasingly gained importance in biomedical research and may enter the clinical scene, as well. Even the laboratory investigations can have strong impact for further developments in this field. However, in experimental medicine the quantitative analysis of experimental data is sometimes required. When applying different interferometric methods, the obtained results are in the form of fringe pattern images. In this paper some of these methods, including holographic interferometry, laser interferometry and moire techniques are described and illustrated by experimental results. For acquisition and evaluation of the fringe pattern images, the Bioscan Optimas package from Bioscan, Incorporated of Edmonds, Wash., running under Microsoft Windows was used.

The deformation of a vein due to heart beats is measured by sticking a small mirror to the skin and recording the deviation of a laser beam incident upon the mirror as a function of time. As an example of possible clinical applications of this method the curves (vein deformation vs. time) corresponding to an individual executing a physical effort of increasing intensity are presented. In another experiment the skin is directly illuminated without interposition of a mirror. The reflected speckle pattern is deformed when the pulse is passing through. It is shown that the contrast of the recorded speckle pattern is a minimum at the instants of time when the vein deformation speed is a maximum. This allows remote measuring of heart beats frequency by a fully non-invasive technique.

Local statistical properties of the far-zone speckles intensity fluctuations are examined in application to the biotissues scattering structure imaging. The exponential factor of the intensity structure function is proposed as the informative parameter. Two-dimensional- mapping of the human epidermis strippings and blood cells specimens is carried out using the developed technique. The influence of the sample illumination conditions on the spatial distributions of the visualization parameter is discussed.

In general, when laser light is incident on biotissue, four interactions can happen: some light is reflected; some of the remaining transmitted light is scattered inside the tissue; some of the light is absorbed; finally, some may be transmitted all the way through the tissue. In the field of speckle metrology for biomedical science, speckle pattern forming by biotissues, such as human skin, sclera, etc., consists of the above first part as well as the second part. The multiple reflection and scattering (multi-effect) occurs, which may cause the polarization state of laser speckles to have some changes. Therefore, it is necessary to pay attention to the properties of polarized laser speckles in biomedical application. Unfortunately, relatively few experimental results are available in the literature since the `speckle' as a key word appeared in 1975. For basic work, we simply make several pieces of ground glasses coated with different thicknesses of white paint as simulated biotissues, i.e., diffusers having multi-effects. Based on the study of speckles polarization for multi-effects, we provided an experimental study of speckle-moire phenomenon previously. In this paper, we present a new concept of paired correlation speckle patterns, and explain the mechanism of moire-specklegram theoretically. Also, speckle-moire phenomenon are further investigated.

A new coherent method for measuring the topography of curved surfaces is presented. The sensitivity of the method is adjustable and thus the proposed technique closes the gap between the white light and interferometric measuring methods. The method yields the deflection angles in x- and y-direction obtained from deflectograms. These angles are used for calculating the topography of the object under study. A brief description of the theory is given. The first experimental results for a simulated corneal surface are demonstrated. This technique can be suitable for measurement of contact lenses or corneal surface.

The setup for reconstruction of 2D quasi periodical structures from the measurements of its ultrasonic diffractive field is presented. Construction of the ultrasonic head is based on the prototype of our ultrasonic sensor for fingerprint pattern recognition. An example of the measured and reconstructed acoustic image of a fingerprint is compared with an optical picture.