Search

This paper presents a digital signal processor (DSP)-based new multichannel electrocardiogram (ECG) system for 12-lead synchronization ECG automatic analysis in real-time with high sampling rate at 1000 Hz and 12-bits precision. Using the hardware structure of double-CPU based on Microprocessor (MPU) 89C55 and DSP TMS320F206 combines the powerful control ability of MPU with DSPs fast computation ability. Fully utilizing the double-CPUs resource, the system can distribute the reasonable CPU-time for the real-time tasks of multichannel synchronization ECG sampling, digital filter, data storing, waveform automatic analysis and print at high sampling rate. The digital ECG system has the advantages of simple structure, sampling with high speed and precision, powerful real-time processing ability and good quality. The paper discusses the system's principle and the skilful hardware design, also gives the ECG processing using the fast simple integer-coefficient filter method and the automatic calculation algorithms of the ECG parameters such as heart rate, P-R interval, Q-T interval and deflexion angle of ECG-axis etc. The system had been successfully tested and used in the ECG automatic analysis instrument.

Radio frequency modulation spectroscopy is a capable method to determine tissue optical parameters in-vivo. For the eventual purpose of clinical measurements we have developed and tested an rf laser spectroscopy device which enables a measurement of the spatial amplitude and phase shift profiles of backscattered modulated laser light. Spectral absorption and scattering coefficients are computed by inverse formulas derived from analytical solutions of the diffusion model of light transport in a semi-infinite geometry.

Im folgenden wird ein Verfahren zur Segmentierung von medizinischen Volumendaten vorgestellt. Ausgehend von einem Punkt innerhalb eines zu segmentierenden Objektes wird radial nach Kanten gesucht, welche das Objekt begrenzen. Durch eine Oberflachenfilterung werden Punkte die nicht auf eine Objektkante treffen (Ausreiser) eliminiert. Die so gefundenen Begrenzungspunkte werden anschliesend verbunden und reprasentieren die Objektoberflache.

Die hier vorgestellte Software erlaubt die Generierung dreidimensionaler medizinischer Datensatze. Dabei kann der Benutzer durch die Zuweisung zahlreicher geometrischer und physikalischer Parameter die Eigenschaften der berechneten Bilddaten genau und reproduzierbar festlegen. Ausgehend von einer idealen Ausgangsgeometrie physiologischer oder auch technischer Strukturen konnen gezielt parametrisierte Serien von simulierten Volumendaten erzeugt werden. Damit steht ein leistungsfahiges Werkzeug fur die objektive quantitative Untersuchung verschiedenster Bildverarbeitungsalgorithmen zur Verfugung.

Diabetic foot syndrome (DFS) is a common sequel of long-term diabetes mellitus. There is a urgent need of noninvasive, objective and quantitative diagnostic tools to assess tissue viability and perfusion for a successful therapy. NIR spectroscopy seems to be qualified to measure local capillary hemoglobin saturation of the outer extremities in patients with progressive diabetic disorders. We investigate how NIR spectroscopy can be applied to the assessment of diabetic foot problems such as neuropathy and angiopathy. Thereby we use spatially resolved spectroscopy in conjunction with a specially developed continuous-wave laser spectrometer. Comparison of intra- and interindividual measurements is expected to yield quantitative measures of local tissue viability which is a prerequisite for a successful therapy.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Optical tomography and NIR spectroscopy are potential methods to improve the diagnosis of testicular pathologies. Toevaluate the methods clinically we developed a special measurement device with the capability of spatially resolvedlaser spectroscopy and optical tomography of the testis. Simple spectroscopy is primarily used to obtain global tissueoptical properties of the testis and to find correlations of optical parameters with type and stage of certain pathologies.Optical tomography is applied to visualize spectral contrasts in limited tissue volumes, such as tumors. In the course ofthe study we will determine whether NIR techniques posses the required specifity and sensitivity to give additionalquantitative information about tissue perfusion parameters and to serve for a tumor differentiation.Keywords: Medical and biological imaging, diffuse spectroscopy, optical tomography 1. INTRODUCTION 1.1. NIR techniquesNIR spectroscopy and tomography are noninvasive and risk-free diagnostic techniques which until today have beenapplied to different medical fields with varying success. Our investigations aim at an evaluation of these methods forthe improvement of the diagnosis of testicular pathologies. This application field is of some interest, since NIRtechniques may be helpful to differentiate between pathologies with similar or no structural tissue changes byevaluating perfusion parameters or tissue consistency. Furthermore, the outer male reproductive organs are easilyaccessible for optical measurements and should not be exposed to ionizing radiation as in Xray imaging or PET.NIR spectroscopy is a method to obtain local functional tissue parameters such as oxygen saturation and blood volumeand more generally information on the presence of certain tissue chromophores (absorption) and on tissue structure(scattering). Common application fields of NIR spectroscopy are the measurement of blood oxygenation in brain andmuscle [1]-[3]. Thereby, modulation and time-resolved spectroscopy are principle methods to absolutely quantifyabsorption and scattering coefficients of the tissue. In our study, however, we use continuous-wave spatially resolvedspectroscopy [4]-[6] which is able to quantify the total attenuation coefficient =[3

Diffuse optical imaging and tomography is of some interest in the diagnosis of testicular pathologies. For a clinical evaluation of 3D optical tomography a special laser scanning device as well as dedicated tomography algorithms have been developed. With the device we are able to obtain continuous- wave tomographic scans from an object under investigation using different laser wavelengths. Tomographic image reconstruction is based on the solution of the linearized inverse problem of optical absorption imaging for a three- dimensional volume. Priority is given to a spatial resolution adapted volume discretization and an efficient matrix solution algorithm based on singular value decomposition.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

NIR spectroscopy is a method principally capable of measuring tissue perfusion and oxygen saturation in subsurface and deeper tissue layers. In urology such perfusion related parameters are of some importance for the differentiation and evaluation of certain types of testicular pathologies. Among them are in the first place the differentiation between inflammations and torsion of the testis, both with similar symptoms, and the assessment of tissue viability in cases of torsion and necrosis, which is sometimes not sufficiently covered by sonography. Although NIR spectroscopy is the method of choice to measure blood oxygen saturation in tissue non- invasively the strong light scattering complicates spectroscopy quantification methods. Spatially-resolved spectroscopy (SRS) is one method to quantify absolute oxygen saturation and relative blood volume. To evaluate this method for in-vivo measurements we have developed a laser scanning device and evaluated quantification algorithms by help of numerical and experimental investigations. As first results suggest the method can in principle quantify absorption differences in tissue, oxygen saturation measurements, however, not work on the testis under the simplified assumptions made for other parts of the body.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fuer die Qualitaetssicherung der Praezisionsbestrahlung mit schweren Ionen wurde der Positronen-Emissions-Tomograph BASTEI in die Therapieanlage der GSI Darmstadt integriert.Die Messung der durch Fragmentierung waehrend einer Bestrahlung erzeugten b+-Aktivitaet erlaubt eine Kontrolle der raeumlichen Dosisverteilung nach jeder Therapiefraktion. Als besondere Probleme dieser PET-Anwendung sind die Erfassung von Annihilationsereignissen in einem eingeschreankten Winkelbereich und eine durch die Dosis limitierte Aktivitaet zu benennen, woraus eine geringe Zaehlstatistik folgt. Unter Beruecksichtigung dieser Messbedingungen wurde der MLE-Rekonstruktionsalgorithmus implementiert. Die Leistungsfaehigkeit des Verfahrens wird anhand von Phantomexperimenten und ersten Patientendaten dargestellt. SCHLUESSELWOERTER:Positronen-Emissions-Tomographie, Bildrekonstruktion, MLE-Algorithmus, dreidimensional

The determination of objective numerical criteria from nuclear medicine image data renders it possible to plan and control therapies, to compare inter- and intra-individual studies as well as time course studies and to facilitate the dominating visual interpretation of scintigrams. SPECT performs real 3D functional imaging of radionuclide distributions. The basic numerical value is the functional volume of a certain region. The volume is one prerequisite for activity measurement, but the value itself is of diagnostic importance, too. For determining the region boundaries several segmentation approaches are commonly used which are generally based on interactive ROI drawing, thresholding or edge detection methods. The image quality properties of SPECT render the segmentation process more difficult in any case. We propose an alternative segmentation approach where the crisp decision `object: yes or not' is substituted by a fuzzy boundary model `object: more or less'.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this paper we present a reconstruction algorithm to invert the linearized problem in optical absorption tomography for objects with radially symmetric boundaries. This is a relevant geometry for functional volume imaging of body regions that are sensitive to ionizing radiation, e.g., breast and testis. From the principles of diffuse light propagation in scattering media we derive the governing integral equations describing the effects of absorption variations on changes in the measurement data. Expansion of these equations into a Neumann series and truncation of higher-order terms yields the linearized forward imaging operator. For the proposed geometry we utilize an invariance property of this operator, which greatly reduces the problem dimensionality. This allows us to compute the inverse by singular value decomposition and consequently to apply regularization techniques based on the knowledge of the singular value spectrum. The inversion algorithm is highly efficient computing slice images as fast as convolution-backprojection algorithms in computed tomography (CT). To demonstrate the capacity of the inversion scheme we present reconstruction results for synthetic and phantom measurement data.

Seit Dezember 1997 werden an der experimentellen Therapieeinrichtung der Gesellschaft für Schwerionenforschung Darmstadt Tumorpatienten mit hochenergetischen Kohlenstoffionen behandelt. Diese Strahlen werden beim Eindringen in Gewebe kaum abgelenkt und geben ihre Energie am Ende ihrer Reichweite konzentriert und mit erhöhter biologischer Wirksamkeit ab. Mit einer speziell für diese Anwendung gebauten Positronenkamera werden während der Bestrahlung die Beta+-Zerfälle von Kernen gemessen, die als Nebenprodukt bei Fragmentierungsreaktionen der Ionen des stabilen Therapiestrahles mit den Atomen des Körpergewebes entstehen. Durch Vergleich der gemessenen mit der durch Simulationsrechnungen aus den Daten der Bestrahlungsplanung zu erwartenden Positronenemitterverteilung wird die Genauigkeit der Dosisapplikation jeder einzelnen Therapiefraktion beurteilt.

We present a reconstruction scheme which solves the inverse linear problem in optical absorption tomography for radially symmetric objects. This is a relevant geometry for optical diagnosis in soft tissues, e.g. breast, testis and even head. The algorithm utilizes an invariance property of the linear imaging operator in homogeneously scattering media. The inverse problem is solved in the Fourier space of the angular component leading to a considerable dimension reduction which allows to compute the inverse in a direct way using singular value decomposition. There are two major advantages of this approach. First the inverse operator can be stored in computer memory and the computation of the inverse problem comprises only a few matrix multiplications. This makes the algorithm very fast and suitable for parallel execution. On the other hand we obtain the spectrum of the imaging operator that allows conclusions about reconstruction limits in the presence of noise and gives a termination criterion for image synthesis. To demonstrate the capabilities of this scheme reconstruction results from synthetic and phantom data are presented.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

ofNuclear Medicine, University Hospital,Dresden University of Technology, Dresden, GermanyABSTRACTSingle photon emission computed tomography (SPECT) performs real three-dimensional functional imaging in nuclearmedicine. Even though the visual interpretation of nuclear medicine images by experienced physicians predominates indiagnostics the quantitative image analysis can reduce the subjective observer influences and offers the possibility for theuse of objective numerical criteria. An essential problem of the quantitative evaluation of SPECT images is the determina-tion of functional volumes from reconstructed SPECT data. This is the prerequisite for the estimation of the absolute radionuclide concentration as a high level quantitation.In this paper we present a combined technique for the determination of functional volumes in SPECT data including ele-ments of voxel based clustering methods and edge based fuzzy segmentation.Keywords: nuclear medicine, SPECT, volume quantitation, three-dimensional image segmentation, fuzzy segmentation1. INTRODUCTIONQuantitative evaluation of nuclear medicine images offers the possibility to use objective numerical criteria for the investi-gation and the comparison of normal and abnormal studies, planning and monitoring therapies as well as supporting thevisual interpretation by reduced subjective observer influences.From 3D SPECT data the functional volume of a region (organ, anatomical structure,lesion) characterized by a higher orlower activity concentration relative to the background can be obtained. To determine the volume of a region its bounda-ries have to be defmed by means of 3D image segmentation. To obtain the volume the voxels inside the region boundaryare counted, and the voxel sum is multiplied by a factor representing the elementary voxel volume. The poor spatial resolu-tion, low contrast and the high noise characteristics of SPECT images render the segmentation process more difficult. Forthe segmentation of 3D medical image data several 2D and 3D approaches are known. These are generally based either onclustering methods or on edge detection methods.The first group includes thresholding techniques with fixed thresholds (mostly implemented in nuclear medicine computersystems) or adaptive thresholds and region growing approaches. These methods are capable of detecting the existance ofobjects correctly, but the geometric accuracy at the object boundaries is poor.The second group of methods is based on the explicit determination of object contours which is mostly performed with agray value gradient calculation. Typical for these techniques is their noise sensitiveness producing incomplete contours inthe case of noise corrupted images with destroyed coherence of the structures. Long et al.' have investigated several proce-dures ofboth groups. They pointed out that the 3D gradient based method is most appropriate for 3D image segmentation inSPECT but they remarked the high computational expense ofthis approach.In this paper we descibe the structure and first results of a hybrid method including elements of both voxel based clusteringand surface segmentation. Our method has the advantage of a decreased computational expense and a better modelling ofthe object boundary regions with fuzzy sets resulting in more accurate volume calculation.2. MATERIALS AND METHODSFirst let us assume that the image data is available in volumetric representation where the image is approximated by a three-dimensional array. The elements of this array are called volume elements (voxels). Each voxel is descibed by its coordina

Photons irradiated into biological materials show interactions with cells, molecules and molecule structures, the amount of interaction being dependent on wavelength, energy density, radiation duration and properties of biological materials. Soft tissue is known to have photons strongly forward scattered, because of the inhomogeneity of its cellular and subcellular structures. The geometric dimensions of the scattering centers are in the order of wavelengths (Mie-scattering). Investigations described in this paper will show the influence of photons on single, live standard cells and how the light transmission through a monolayer cell will change within a measuring time of up to one hour and in dependence on cell intensity. Experiments were carried out in vivo with monolayers of standard bovine kidney cells by means of optical spectroscopy in a range of wavelengths from 200 nm to 1.500 nm. Cell cultures as mono cell layers in chambers of glasses were developed by a nutrient solution within 3 days. The growth of the cell layers was microscopically controlled. Details are described in the paper. Spectrophotometric measurements in visual- and near infrared range were carried out with cells on chambers of glasses (in nutrient solutions). Various effects, such as color of the nutrient solution or dying of cell regions will influence the measuring results. The measurements allow conclusions as to the determination of optimal wavelengths for an optical inspection of tissue. A photon scattering is possible preferably at the boundaries (cell faces, nuclear membrane, alteration of refractive index).

An experimental set-up for the optical tomography using photon density waves is described. The intensity of a NIR laser diode (825 nm) is modulated with a frequency of 110 MHz (modulating degree equal to 80%). The line scan of a rat brain at 64 linear steps and 64 angular steps contains the ac attenuation and the phase shift separately. Due to the impact of scattering in the medium these data are not the basis for a backprojection and deconvolution for the tomographic reconstruction itself. The first approach for a preprocessing consists in the determination of the geometry dependent modulation transfer function (MTF). The line scan is then corrected by the filter which varies with the position. An optical tomogram of a rat brain is presented. This procedure is suitable for biological objects up to a diameter of 30 mm approximately, for example small finger joints.

The determination of scattering phase function as a microscopic basic tissue-optic parameter is very important for the theoretical description and practical realization of optical tomography in biomedical engineering. Right now there are only a few publications containing experimental data, measuring arrangements or even theoretical explanations for the realistic scattering phase functions of biological tissue. This is probably due to the very complex structure of biological specimen and some difficulties with the experimental setup. For the important field of radiation propagation simulations the analytical Henyey-Greenstein phase function has been assumed generally. But for the often used numerical modeling by the Monte-Carlo method an analytical representation of the angular scattering behavior is not required; sufficient are individual sample points. The determination of scattering phase functions of biological specimen is pretty difficult because of the several shapes, sizes, and concentrations of scatterers. But their distinguished consideration is necessary for the comparison with different theories of scattering, e.g. Mie theory. In particular the angular distribution of the scattered light intensity for a single scattering event has to be measured. Therefore the angular scattering distribution of tissues has to be evaluated as superpositioned individual scattering phase functions. The main problem with the instrumentation for investigating scattering phase functions is the need for generating and detecting the angular intensity distribution caused by single scattering events and its high dynamics. Because of the multiple scattering properties of tissues almost the entire object is illuminated often. But an intensity distribution caused by multiple scattering events could not represent the scattering phase function. Thus its contribution to the scattering distribution has to be suppressed. Therefore the detector's view field (i.e. the viewable solid angle with regard to the illuminated area) has to be limited to obtain a high angular resolution. This could be done for instance by controlling the detector's aperture, by introducing angular light wave guides or different techniques like polarization evaluation. Eventually the scattering location can be monitored by a built-in microscope.

Investigations in performing an optical tomography of biological specimen have been carried out by using the phase-correlated single photon counting method. This method is capable of selecting non-interacted, on-beam-axis forward scattered and snake-line photons, i.e. the straight-forward propagating photons. The phase correlated single photon counting unit performs the mutual monitoring of a high-speed photomultiplier tube and adjacent gain by a broadband preamplifier. The detection occurs in phase correlation to the difference frequency of the optical modulation of the two arms of a Mach-Zehender interferometer arrangement. The object arm is crossing the scattering test medium. To prevent strong intensity ratios between the two interferometer arms the reference arm crosses an optically equivalent phantom medium, but without introduction of inhomogeneities. The correlation between the phase of the optical modulation and the electrically derived phase can be varied by 2(pi) phase shifting of the electrical signal. This allows the user to set a phase range comparable to the time window in time-resolved detection. Two different principle methods can be used for generating tomographic images: the confocal scanning and conventional (object rotation and translation) tomographic setups.

Investigations on photon migration in strongly scattering media have shown that due to the practical bandlimitation of the media's transfer characteristic a complete reconstruction of size, shape, and optical parameters of embedded inhomogeneities is generally impossible. However, using a priori information can considerably reduce the solution space. In this article we present a method to determine the position of an inhomogeneity in a cylindrical scattering object by backprojecting the changes in measurement value. For the backprojection a set of trajectories is used approximating the maximum probability photon path. Reconstruction methods as known from computed tomography (CT) are used to obtain a visually improved slice image giving the opportunity to estimate size and shape of the inhomogeneities. Although in this article the procedure is described for time-integrated measurements it should be applicable to any other measurement technique. Above all the method is computationally very efficient.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The results of several measurements of optical tissue properties often show a wide range of variety. This could be a reason for neglecting time-dependent alterations after the preparation or during the measurement procedure itself. To combine the opportunities optical tomography offers (i.e. structural and functional imaging) with two- or even three-dimensional spectroscopy without using any contrast means of fluorescence dyes, we measured several transmission spectra of various tissues of biological specimen. To prove reproducibility three consecutive measurements were carried out. Generally, a variation in the transmission or extinction could be seen. Their value and direction usually depends on the type of biological specimen. Living cells, freshly taken from the nutritive medium, showed a significant decrease in transmission in contrast to various types of originally frozen animal tissue, which revealed an increase in transmission. But here the value of increase was found to be dependent on the tissue, too. Furthermore, we have made investigations on the dependence of transmission alterations by changing the tissue preparation, e.g. the cutting area in regard to tissue properties. In general, the relative spectral response remained the same, thus resulting in a shift to higher or lower transmissions. The investigations were made with tissue of a thicknesses between 300 micrometers and 1 mm. Details will be explained in this paper. These measurements allow the conclusion, that thin biological specimen are subject to changes of optical properties at the time after having taken them out of a stable in vitro state. These changes are probably due to varying anisotropy. Finally, this leads to the conclusion, that for thin biological specimen the rules of geometrical optics have to be preferred rather than making radiation transport calculations. Optical rules should be part of common methods to determine optical properties of tissue.

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.

By the interpretation of the segmentation process as an assignment of labels to objects dependent on spatial constraints, image segmentation can be described as a constraint satisfaction problem (CSP). Starting from this model, a new technique for the segmentation of medical images is presented: the constraint satisfaction synergetic potential network (CSSPN). In CSSPN the actually possible labels of an object are represented by singular points of synergetic potential systems. The fuzzy-algorithmic initialization model of the CSSPN allows a label-number-independent dimensioning of the network with n2 nodes. The parallel relaxation dynamics of the CSSPN controlled by interactions of the potential systems will bring selection or evolution of the input image by complete deterministic or stochastically perturbed equations of motion in the potential systems. Constraint functions are significant to the relaxation dynamics and to the result of segmentation within an object adjacency, information of the image model like the image semantics or the optimization strategy of network parameters are mapped onto the CSP with them. Experimental comparative analyses of the segmentation results demonstrate the efficiency of the technique and confirm that the CSSPN is a very promising method for image segmentation.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The discrepancy between diagnostic importance of nuclear medicine images and their quality and the predominating visual interpretation of the images demand quality improvements. Digital image restoration procedures are known for being capable to solve this problem considering both noise and blurring. In this paper we propose the application of a modified 2D Kalman filter for nuclear medicine images (SPECT). In addition to the special capability of processing instationary signals the Kalman filter offers a possibility for controlling the filtering effect in a convenient way. The Kalman filter is based on a state space approach subdividing the imaging process into image generation and image degradation processes. The tested filter operates adaptively by permanent identification of the image generation model. For adaptation to the human visual system the filtering effect is modified depending on image quality represented by the mean information density and the local image contents represented by a structure information. The appropriate filtering effect is determined by modifying filter parameters with a predefined piecewise linear characteristic curve. The both smoothing and structure enhancing effect of our Kalman filtering approach is demonstrated in numerous tests performed with SPECT phantom images and brain SPECT studies.

The evaluation of HMPAO brain SPECT studies is often difficult because of insufficient resolution and anatomical complexity. The object of this research work is to improve the image quality with respect to better visual detectability of lesions by a restoration approach based on a Kalman filter.