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At least 235 records · Page 13Linked to original sources
PubMed1998

A neural network for the optimization of fed-batch glutamic acid production.

A neural network system, which is composed of a simulation subnetwork and an optimization subnetwork, was constructed to predict and optimize the industrial fed-batch fermentation of glutamic acid. A data-compression and filtration network structure was incorporated into the simulation subnetwork to extract "noise-free" patterns from the input signals. The sole-variant optimization and the multiple-variant optimization can be easily carried out by the neural network developed. A satisfactory result has been achieved.

Computer Simulation↗
PubMed1991

[Thyroid carcinoma as cystic nodule. The diagnostic role of cytology by needle aspiration].

195 patients affected by a cystic thyroid lesion were studied by a Fine Needle Aspiration biopsy (FNAb). 42 patients were operated on account of clinical data, compressive phenomena or cytologic results suggesting a neoplasia. Out of the operated patients, 3 were affected by a carcinoma in the cystic lesion (one "pure" cystic nodule and two "mixed" ones), while three more patients with multinodular goiters showed a carcinomatous lesion in a nodule different from the cystic one. Macroscopic characteristics of the aspirated fluid (quantity and quality) didn't affect the cytologic diagnosis. Cytology was useful in the preoperative diagnosis of benign thyroid nodules (only two false positives out of 42 patients) and was diagnostic in all the three patients affected by a carcinoma in the cystic nodule.

Adolescent↗
PubMed1991

Digital imaging and picture archiving and communication systems.

Great progress has been made in digital imaging of the chest. Most studies are dealing with computed radiography. Chest radiography in the intensive care unit may, in most cases, be performed using computed radiography. However, subtle pulmonary interstitial disease can be demonstrated less confidently using computed radiography. Significantly better detection of calcified lung nodules can be obtained by using simplified single-exposure dual-energy technique that uses storage phosphor. The wide latitude of computed radiography permits images of high quality in areas other than chest radiography. Encouraging results are presented especially in the diagnostic evaluation of scoliosis and other musculoskeletal abnormalities. An important technical innovation in digital radiography is an improved method for single-exposure dual-energy digital imaging using prefiltration with gadolinium, a cassette consisting of four photostimulable phosphor plates, spatially dependent scatter and beam hardening corrections, and noise reduction algorithm. Other groups tested algorithms for enhancement of digital images that allowed significant data compression. The implementation of picture archiving and communication systems (PACS) is inevitable; the question concerning PACS implementation is not why, but when. A comparison of the cost-effectiveness of PACS with conventional film archiving and communication systems shows that PACS should provide indirect savings when regarding the hidden costs of conventional systems. Much more experience will be needed before there is general agreement on the best design for the radiologist's workstation. Teleradiology should contribute to radiologic consultation for remote locations, because it improves the efficacy of management of patients in such locations.

Child↗
PubMed1989

Shape description in osteology using automatic Fourier analysis. Example of the human atlas.

An image analysing procedure for the shape characterisation in osteology is described. We used expansion in Fourier series of an equiangular polar representation of the contour. Fourier analysis is an information preserving technique, and it is therefore possible to reconstruct the original contour from the shape descriptors (Fourier coefficients and descriptors). The properties of the truncated expansion of the Fourier series can be used for smoothing effect and noise reduction, for interpolated reconstruction, and for data compression. Fourier analysis also allows a quantitative description of the shape. The first components describe the gross feature, the following ones the fine details.

Cervical Atlas↗
PubMed1989

[Diagnostic limitations of isolated axiography interpretation].

Axiographic images of eccentric condylar paths can be more reliably interpreted by considering the clinical function data, compression test results and the MPI. In the case presented the abnormal position of the right condyle would have gone unnoticed without such a combined approach to the problem.

Cephalometry↗
PubMed1988

Towards a digital model for an electron-microscope image.

An image model is defined based on the boundaries between image regions with different textures and series of descriptions of those textures. Six models of texture are studied under the categories of pixel-based and region-based models. Several techniques for the determination of the unit-cell of textures are presented. The model is applied to the consideration of (a) image correction, (b) the classification of image texture, (c) image enhancement including averaging of detail in periodic specimens, and (d) image data compression. A floating point format, which provides a significant simplification for the Huffman code, is also introduced.

Algorithms↗
PubMedDate not supplied

Adaptive predictive coding with applications to radiographs.

Picture archiving and communications systems (PACS) require storage and transmission of vast amounts of data. For design/cost considerations, it is desirable to reduce the size of these data without sacrificing the integrity of the stored information. The major considerations in designing a data-compression scheme for a PACS system are discussed: fidelity of the reconstructed image, bit rate, hardware complexity, and processing time. The basic principles of conventional nonadaptive differential pulse-code modulation (DPCM) are reviewed and compared with adaptive techniques. The effect of adaptive quantization on radiographic images is examined. Special consideration is given to block-adaptive DPCM or the "switched quantizer," which greatly enhances the system performance as compared with nonadaptive techniques, and conservatively has a 5:1 compression ratio. Sample radiographs substantiate the results.

Bone and Bones↗
PubMed1985

Analysis of biomedical signals by means of linear modeling.

The recording and subsequent analysis of electrical signals of physiological origin constitutes an important aspect of current biomedical research. A versatile method for the analysis of such signals is based on linear, i.e., autoregressive (moving average) modeling. These techniques are based on fitting a hypothetical model to the signal under observation. These models are capable of generating the original signal by a linear combination of past observations and past and present noise samples. High resolution spectral estimates can be obtained in this way. Also, the often small number of model coefficients offer a concise description of the signal and may be used for classification purposes. Other applications entail the detection of nonstationarities, data-compression, and signal enhancement. In this review, linear modeling methods for the analysis of electroencephalograms, electro- and phono-cardiograms, electromyograms, and gastrointestinal signals are surveyed.

Digestive System Physiological Phenomena↗
PubMed1983

A computer-based system for the study of ECG/VCG variability.

A description is given of a computer-based system for electrocardiogram and vectorcardiogram analysis. Its main purpose is to provide a basic research and study tool of the variability occurring in electrocardiographic activity when the observation time is of the order of 30 min. System/operator interaction is designed to allow the user to validate or correct the identifications executed by the program. Special attention is given to graphic representation techniques suitable for synthesizing a great many numerical results. Data acquisition and analysis are performed by two different PDP 11 systems. The acquisition programs are written in ASSEMBLER, the analysis programs are in FORTRAN. Intermediate files are structured by a data compression technique. At present the program is oriented to study normal subjects. A new version to study bundle-branch blocks is now available.

Computers↗
PubMed1983

[Generation of response functions of a NaI detector by using an interpolation technic].

A computer method is developed for generating response functions of a NaI detector to monoenergetic gamma-rays. The method is based on an interpolation between measured response curves by a detector. The computer programs are constructed for Heath's response spectral library. The principle of the basic mathematics used for interpolation, which was reported previously by the author, et al., is that response curves can be decomposed into a linear combination of intrinsic-component patterns, and thereby the interpolation of curves is reduced to a simple interpolation of weighting coefficients needed to combine the component patterns. This technique has some advantages of data compression, reduction in computation time, and stability of the solution, in comparison with the usual functional fitting method. The processing method of segmentation of a spectrum is devised to generate useful and precise response curves. A spectral curve, obtained for each gamma-ray source, is divided into some regions defined by the physical processes, such as the photopeak area, the Compton continuum area, the backscatter peak area, and so on. Each segment curve then is processed separately for interpolation. Lastly the estimated curves to the respective areas are connected on one channel scale. The generation programs are explained briefly. It is shown that the generated curve represents the overall shape of a response spectrum including not only its photopeak but also the corresponding Compton area, with a sufficient accuracy.

Gamma Rays↗
PubMed1995

SD filtering for enhancement of a nuclear medicine image sequence.

This paper explores the use of an image sequence processing algorithm, called the simultaneous diagonalization (SD) filter, which can be effectively applied to long noisy image sequences. This filter was developed to filter a spatially invariant image sequence to form one new image in which a desired feature is enhanced and one or more undesired features (and noise) are suppressed in the filtered image. This filtering technique, applied to a long noisy image sequence, can be used to achieve significant data compression for image storage and provide surprisingly good enhanced image reconstructions. For this investigation, SD filtering is applied to a temporal image sequence, a renogram, with compression of a very noisy 180-image sequence to a 4-image set. The renogram, a nuclear medicine technique, was chosen due to its low signal-to-noise ratio over a long image sequence. Before the application of the SD filter, classical image processing techniques, median and averaging filtering, are used as a preliminary method to reduce the image sequence noise content. Compared to any of the images in the original image sequence, the reconstructed images are remarkably good. The SD filter with prefiltering, thus, can collect information distributed over a 180-image temporal sequence with low signal-to-noise ratio.

Algorithms↗
PubMed1994

Femoral nerve palsy. An unusual complication of anterior lumbar interbody fusion.

SUMMARY OF BACKGROUND DATA: Compression neuropathy of the femoral nerve has been reported as an uncommon complication of bleeding into the iliopsoas muscle. OBJECTIVE: The authors detected anatomic reasons of direct injury to the femoral nerve at the lower lumbar level. METHODS: Keeping the hip in extension during the course of carrying out anterior fusion on a previously failed posterior fusion was considered another causative factor of femoral nerve injury. Anatomical dissection confirmed the likelihood of this injury being produced in this situation. RESULTS: Femoral nerve traction and compression can occur after prolonged compression of the nerve within the psoas muscle stretched between an immobile lower lumbar spine and the lesser trochanter when the hip is kept in extension. In the patients described no other reasons for direct or indirect injury were identified. CONCLUSION: Although uncommon, the complication should be kept in mind. It can be avoided by intraoperative hip flexion.

Cadaver↗
PubMed1975

Computer signal processing of long duration biotelemetric brain data.

The EEG represents brain processing under diverse physiological conditions. A complete system involving acquisition and quantitation of this important information about brain function is described. The time-domain EEG and other biological signals are obtained using a multichannel PAM/FM biotelemeter mounted on the head of the experimental animal. This data is transmitted, demodulated and recorded by electronic recording techniques. A computer-based EEG analysis system is described for acquiring the primary data and transforming it into the frequency domain using Fourier methods. The computing system is developed to semi-automatically signal process about 4 h of eight channel EEG records. Data compression by plotting in a quasi-three-dimensional spectral profile allows visual correlations of pattern features to drug manipulations, etc. The software programs are briefly described for each step in signal processing. The feasibility of the complete system approach is demonstrated using biotelemetry to acquire low voltage EEG signals without behavioral distortions or introduction of artifacts by cables.

Animals↗
PubMed1996

Teleradiology and telemedicine.

This article provides a historical perspective as well as an update on the current state of teleradiology and telemedicine in the United States. Technical implementation issues are discussed and enabling technologies are described. Considerations that impact network design are outlined including data transmission, data compression, applicable standards, and band-width requirements. Reimbursement, medicolegal, licensure, and regulatory issues related to the delivery of teleradiology and other telemedicine services are reviewed. Insight is provided into the role of teleradiology and telemedicine in a changing health care environment.

Computer Communication Networks↗
PubMed1996

Source localization and bioelectric imaging as it relates to continuous waveform analysis.

One of the goals of the mathematical analysis of scalp-recorded continuous EEG waveforms is to elucidate non-invasively the neural generators of these voltages. One way of accomplishing this is to simulate these generators by equivalent current sources and follow the apparent motion of these theoretical generators during the temporal evolution of the EEG. Another way of accomplishing this is to follow the changes in scalp or simulated cortical surface potential or Laplacian maps during the temporal evolution of the EEG. We first discuss the possible theoretical pitfalls of using linear techniques on an essentially nonlinear problem (the localization of the sources of the EEG), as well as possible computational pitfalls associated with realistic, but complex, conductive medium models simulating the head. Various mathematical source localization methods and bioelectric imaging techniques are then outlined. Later in this paper a collaborative project involving mathematicians, computer scientists, and clinical neuroscientists is described. In this project EEG waveform data will be analyzed, millisecond-to-millisecond, using the various mathematical techniques for localizing equivalent current sources and simulating cortical surface potential and Laplacian topographical maps mentioned above. One of the clinical aims of this research project is to localize epileptic foci without employing invasive recording procedures. Since the EEG datasets that will be analyzed are large (22 Mb, in some cases), data compression and parallel processing strategies will be important parts of this research project. Such strategies, as they may apply to continuous waveform analysis, are discussed in the two appendices at the end of this paper. Many of the presentations at the Symposium and the corresponding papers in this Supplement are related to the ideas and goals of this research project and the implementation of the mathematical/computational techniques for realizing these goals.

Brain↗
PubMed1996

Wavelets, adapted waveforms and de-noising.

This is a short summary of a talk given at the Frontier Science in EEG Symposium, Continuous Waveform Analysis, held on 9 October 1993 in New Orleans. We describe some new libraries of waveforms well-adapted to various numerical analysis and signal processing tasks. The main point is that by expanding a signal in a library of waveforms which are well-localized in both time and frequency, one can achieve both understanding of structure and efficiency in computation. We briefly cover the properties of the new "wavelet packet" and "localized trigonometric" libraries. The main focus will be applications of such libraries to the analysis of complicated transient signals: a feature extraction and data compression algorithm for speech signals which uses best-adapted time and frequency decompositions, and an adapted waveform analysis algorithm for removing fish noises from hydrophone recordings. These signals share many of the same properties as EEG traces, but with distinct features that are easier to characterize and detect.

Electricity↗
PubMed1997

Update on new technologies in pediatric echocardiography.

Advances in ultrasound technology will continue to expand the utility of echocardiography in the assessment of structural and functional cardiac disease in children. Tissue Doppler imaging and dobutamine stress echocardiography are 2 promising clinical applications that are expected to become increasingly used with time. Advances in data compression technology, including JPEG and MPEG techniques, will significantly affect digital archival and transmission of echocardiograms, which also have clinical implications, particularly in the expanding use of telemedicine. Continued research and clinical experience will further define the ultimate roles of these technologies in the future.

Cardiotonic Agents↗
PubMed1998

[The Monte Carlo method and parallel estimation in the drawing up of radiosurgery treatment plans].

PURPOSE: We investigated the practical application of a calculation algorithm based on the Monte Carlo method to stereotactic radiosurgery treatment planning. In radiosurgery, high dose gradients and the lack of electronic disequilibrium make high resolution matrices and high computing power and speed necessary to obtain accurate dose distribution. To date, the main obstacle to the wider-spread use of the Monte Carlo method has been the huge computing time necessary to obtain a dose distribution on current hardware. MATERIAL AND METHODS: In this project, developed within the ESPRIT program, funded by the European Union, a Parsytec CC (Cognitive Computing) computer was used with 9 processors (Power PC 604, 133 Mhz, RAM 64 Mb) with IBM AIX/EPX OS and availability for Fortran parallel codes compilation, connected to a PC for data input, results rendering, and dose distribution calculation with a conventional algorithm for comparison with the Monte Carlo code (an EGS4 user code). The module named Rapt Region Extractor performs data compression with an octree method without decreasing resolution, for RAM and computing time requirements to remain acceptable. A model of the 6 MV photon beam from Clinac 2100C Varian linear accelerator was devised, based on incident photon energy spectrum and, for each collimator dimension, on bidimensional dose distribution orthogonal to beam direction measured at SSd = SAD = 100 cm. RESULTS: Parallelization was carried out on event numbers, allowing a simulation speed to number of processor ratio close to unity. A new random number generator was used, capable of correctly running on the parallel architecture. The simulation procedure includes: 1) CT acquisition in DICOM 3.0 format, Analyze or with scanner; 2) Target delineation, treatment arc definition. 3) Dose calculation, with both conventional and Monte Carlo methods. 4) Dose distribution rendering on every transverse, sagittal or coronal planes overlapped in color wash on anatomical representation. Comparison between conventional and Monte Carlo algorithms were carried out on an anthropomorphic phantom and 10 real patients, with 2.5 mm anatomical resolution and standard deviation never exceeding 2%. A simulation with 10,000,000 events and 1% maximum variance can be run in 43'. When PTV is an homogeneous areas the differences between the two methods are around 5%, while when PTV is localized in dishomogeneous areas discrepancies reach 20% in the bone. CONCLUSIONS: In conclusion, the feasibility of direct simulation with the Monte Carlo method in radiosurgery has been demonstrated within time and hardware costs compatible with clinical practice.

Algorithms↗