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PubMed1985

Radiological image compression: full-frame bit-allocation technique.

A full-frame bit-allocation technique has been developed for radiological image compression based on encoding the cosine transform of the image. Six different types of diagnostic images were used to examine this technique, and the results have been encouraging. Reconstructed images from compressed-image data with compression ratios of 4:1, 8:1, 12:1, and 16:1 did not have excessive visual degradation. It is concluded that this technique is suitable for diagnostic image compression.

Computers↗

PubMedDate not supplied

Synergetic interpretation of patterned vasomotor activity in microvascular perfusion: discrete effects of myogenic and neurogenic vasoconstriction as well as arterial and venous pressure fluctuations.

Synergetic concepts allow to identify emergent coordination phenomena between interacting physiological systems, for example between the cutaneous microcirculation, the sympathetic nervous system and the cardiac and pulmonary systems. The temporal patterns (oscillations of various frequencies) that are found in the data obtained with laser-Doppler anemometers (LDA; e.g. Periflux 2 used in the study) can be investigated by simultaneous recording of photoplethysmographic data obtained in the identical region of interest, as well as in cutaneous regions treated with vasoparalytic procedures which permit to record the dynamics of the arterial system. These strategies were applied to studies in the cutaneous microcirculation (volar side of the index fingers) as well as to mucosal microcirculation (maxillar gingiva) in healthy subjects and in patients suffering from autonomic dysfunction (cutaneous microcirculation) or gingivitis. By this procedure, it could be corroborated that - contrary to popular notions - the temporal fluctuations in the LDA records do not necessarily reflect myogenic vasomotion, but can have multiple causes. In a confirming recent study [Schmid-Schönbein et al., J Auton Nerv Syst, 57, 136-140, 1996], we have demonstrated that the LDA fluctuations under conditions of normal ambient temperature and hand position most likely reflect neurogenic vasoconstriction. Under exceptional conditions, different patterns emerge. Prolonged exposure to ambient temperature (18 degrees C) leads to marked vasoconstriction, with occasional vasodilator escape ('miniature hunting reaction'). Normal subjects under gravitational load and in warm environment (28 degrees C ambient) silence their neurogenetic vasoconstriction reactions, which allows sinusoidal vasomotion to dominate. A similar phenomenon is seen in neuropathic patients at 21-24 degrees C (presumably due to structural defects). Fluctuations in LDA signal taken from the healthy gingiva are entrained to arterial, those taken from inflamed gingiva to respiratory activity. The theory and practice of nonlinear analysis is discussed, and data compression procedures allowing to portray characteristic temporal patterns for future diagnostic procedures are presented.

Autonomic Nervous System Diseases↗

PubMed2001

ECG data reduction method for medical telemetry systems.

In current medical practice, all transmitters used for monitoring an ECG send data continuously. If transmission could be limited to only the ECG data that requires the attention of a technician, the likelihood of interference and power consumption would be reduced considerably. In this paper, we propose a new ECG telemetry system. The transmitter has a simple ECG analyzer and it only transmits data when abnormal waveforms are detected. As part of this system, we propose a simple algorithm to detect an abnormal ECG. The algorithm is composed of a baseline drift canceller (utilizing a moving average calculation), a waveform detector (using a modified second order derivative) and an ECG analyzer. In order to test the effectiveness and feasibility of the algorithm, computer simulations (with a MIT-BIH ECG database) and experiments (with microprocessor-based hardware) were performed. The results of the simulations show that the detection performance and data compression performance of the algorithm are adequate. The results of the experiment show that the algorithm even performs adequately when used with microprocessor-based hardware that is of limited size or limited power consumption.

Algorithms↗

PubMedDate not supplied

Effect of interlayer potential on mechanical deformation of multiwalled carbon nanotubes.

A study on the modeling and simulation of interlayer interaction in the multiwalled carbon nanotube (MWCNT) system is presented. We use an interlayer Morse potential previously developed from a local density approximation (LDA) treatment of a bilayer of graphite. We have fit this Morse potential to experimental high-pressure compressibility data for graphite and to a more extensive LDA equation of state (EOS) for graphite, and excellent agreement is observed. We employ this potential to treat the interlayer mechanics of MWCNTs, where the MWCNT is so highly deformed that interlayer separation well below approximately 0.34 nm, such as down to approximately 0.26 nm, is occurring. This, to our knowledge, is the first treatment that attempts to account for deformations that have the layers approaching each other at very high local (interlayer) stress levels. Since evaluating the interlayer potential for a large MWCNT system is computationally intensive, a continuum simulation approach is proposed that saves on computational time and thus on cost. Comparisons with experimental results of buckled and highly kinked MWCNTs are presented.

Computer Simulation↗

PubMed2006

What are the etiology and epidemiology of out-of-hospital pediatric cardiopulmonary arrest in Ontario, Canada?

BACKGROUND: Pediatric cardiopulmonary arrest (CPA) outside of the hospital has a very high mortality rate. OBJECTIVES: To evaluate the etiology and initial compromise of pediatric CPA cases in hopes of developing strategies to improve out-of-hospital resuscitation. METHODS: The Ontario Prehospital Advanced Life Support (OPALS) study was a large multicenter initiative to evaluate the impact of emergency medical services (EMS) programs on 17 communities with 40,000 critically ill and injured patients who were older than 11 years. As part of this study, the authors conducted a retrospective observational cohort study that included all children younger than 18 years of age with out-of-hospital CPA, during an 11-year period from 1991-2002. CPA was defined as patient being pulseless, apneic, and requiring chest compressions. Data were collected from ambulance call reports and centralized dispatch data and were reviewed by two independent investigators. RESULTS: There were 503 children with CPA in the sample. Mean age was 5.6 years (range, 0-17 yr); 58.4% of patients were male, and 37.8% were younger than 1 year of age. Cardiopulmonary resuscitation (CPR) first was started by a bystander in 32.4% of cases, whereas 66.0% were unwitnessed arrests. Initial rhythms were asystole 77.2% of the time, pulseless electrical activity 16.4% of the time, and ventricular fibrillation or ventricular tachycardia 4% of the time. Annual incidence was 9.1/100,000 children. CPA was witnessed in 34.0% of cases; 80.7% of these were bystander-witnessed, and 18.1% were EMS-witnessed. Primary pathogenic cause of arrest was medical in 61.2% of cases, trauma in 37.2% of cases, and indeterminate in 1.6% of cases. Initial underlying physiologic compromise of witnessed arrests was judged to be respiratory in 39.8% of cases, sudden collapse (presumed electrical) in 16.4% of cases, progressive shock in 1.2% of cases, and indeterminate in 42.6% of cases. Presumed etiology was trauma, 37.6%; sudden infant death syndrome (SIDS), 20.3%; and respiratory disease, 11.6%, most commonly. Survival to hospital discharge was 2.0%. CONCLUSIONS: This is one of the largest population-based, prospective cohorts of pediatric CPA reported to date, and it reveals that most pediatric arrests are unwitnessed and receive no bystander CPR. Those that are witnessed most often are caused by respiratory arrests or trauma. Trauma, SIDS, and respiratory disease are the most common etiologies overall. These data are vital to planning large resuscitation trials looking at specific interventions (i.e., increasing bystander CPR) and highlight the need for better strategies for prevention and early recognition.

Adolescent↗

PubMed1989

Foot strike and the properties of the human heel pad.

Many force-plate records of human locomotion show an impulse (the foot strike) shortly after ground contact. The authors' hypothesis is that this results from the rapid deceleration of a mass (the 'effective foot') under forces which compress the heel pad. The quantitative implications are investigated through an illustrative calculation. The observations used are (a) the peak force reached in foot strike (b) the vertical velocity of the foot immediately before ground contact and (c) the properties of the heel pad in compression. Data for (a) and (b) are available in the literature; measurements for (c) are presented here. The deductions are: (a) the time taken to reach peak force is about 5.4 ms, which agrees with published measurements; (b) the mass of the effective foot is about 3.6 kg. The effective foot thus includes a substantial portion of the leg: this seems reasonable. The models used for the calculations clarify the relationship between the foot strike and the shock wave, which it generates.

Biomechanical Phenomena↗

PubMed1997

Remote consultation for computerized tomography and magnetic resonance studies by means of teleradiology--experience at the Singapore General Hospital.

A teleradiology link was established between Singapore General Hospital in Singapore and Stanford University in California, USA. Over eight months, a total of 28 cases (involving 27 magnetic resonance investigations and three computerized tomography scans) were transmitted by ISDN to California. Our initial experience with teleradiology for remote consultation was encouraging, although the data transmission cost was higher than we anticipated. however, costs could be reduced by using data compression. Long-distance telecommunication charges continue to fall, so intercontinental teleradiology of this type may be financially viable in future.

Hospitals, General↗

PubMed1997

Teleradiology in rural imaging centres.

An economic analysis of a private commercial magnetic resonance (MR) imaging service was carried out. At an expected case-load of 2000 per year, a mid-field MR unit was predicted to cost $470 per case using teleradiology and $544 per case using film and a courier service. Routine and emergency MR services were provided to two communities in Maryland. In a two-year study period, 8083 teleradiology examinations were performed. Digital images were acquired and transmitted without data compression via ISDN at 128 kbit/s to a central diagnostic workstation for interpretation by a team of radiologists. The average transmission time for a typical case of 50 images was 6-8 min. Preliminary interpretations were normally available within 2 h and the final transcribed reports were usually faxed to the physicians' offices within 24 h. The results of a survey indicated that the system was well received by both referring physicians and patients. Costs per case in practice were similar to those predicted.

Feasibility Studies↗

PubMed2002

Image acquisition and image processing for the intraocular vision aid.

The contribution describes an "intraocular vision aid (IOVA)" system for patients suffering from corneal opacification. In order to gain patients' acceptance the system has to be miniaturized to a magnitude that image acquisition, image processing, and power supply can be integrated into a portable unit. A CMOS camera whose dynamic range covers more than 100 dB takes pictures of the scenery. Its image sensor has a resolution of 380 x 300 pixel. In order to reduce fixed pattern noise correlated double sampling is implemented on-chip. In addition, this sensor stands out for low power consumption, random pixel access, and local brightness adaptation. An analog-digital-converter allows direct coupling to an external signal processor or a monolithically integrated unit for image processing to compress data.

Computer Systems↗

PubMed2004

The influence of short-chain alcohols on interfacial tension, mechanical properties, area/molecule, and permeability of fluid lipid bilayers.

We used micropipette aspiration to directly measure the area compressibility modulus, bending modulus, lysis tension, lysis strain, and area expansion of fluid phase 1-stearoyl, 2-oleoyl phosphatidylcholine (SOPC) lipid bilayers exposed to aqueous solutions of short-chain alcohols at alcohol concentrations ranging from 0.1 to 9.8 M. The order of effectiveness in decreasing mechanical properties and increasing area per molecule was butanol>propanol>ethanol>methanol, although the lysis strain was invariant to alcohol chain-length. Quantitatively, the trend in area compressibility modulus follows Traube's rule of interfacial tension reduction, i.e., for each additional alcohol CH(2) group, the concentration required to reach the same area compressibility modulus was reduced roughly by a factor of 3. We convert our area compressibility data into interfacial tension values to: confirm that Traube's rule is followed for bilayers; show that alcohols decrease the interfacial tension of bilayer-water interfaces less effectively than oil-water interfaces; determine the partition coefficients and standard Gibbs adsorption energy per CH(2) group for adsorption of alcohol into the lipid headgroup region; and predict the increase in area per headgroup as well as the critical radius and line tension of a membrane pore for each concentration and chain-length of alcohol. The area expansion predictions were confirmed by direct measurements of the area expansion of vesicles exposed to flowing alcohol solutions. These measurements were fitted to a membrane kinetic model to find membrane permeability coefficients of short-chain alcohols. Taken together, the evidence presented here supports a view that alcohol partitioning into the bilayer headgroup region, with enhanced partitioning as the chain-length of the alcohol increases, results in chain-length-dependent interfacial tension reduction with concomitant chain-length-dependent reduction in mechanical moduli and membrane thickness.

Adsorption↗

PubMedDate not supplied

Are minidisc recorders adequate for the study of respiratory sounds?

Digital audio tape (DAT) recorders have become the de facto gold standard recording devices for lung sounds. Sound recorded on DAT is compact-disk (CD) quality with adequate sensitivity from below 20 Hz to above 20 KHz. However, DAT recorders have drawbacks. Although small, they are relatively heavy, the recording mechanism is complex and delicate, and finding one desired track out of many is inconvenient. A more recent development in portable recording devices is the minidisc (MD) recorder. These recorders are widely available, inexpensive, small and light, rugged, mechanically simple, and record digital data in tracks that may be named and accessed directly. Minidiscs hold as much recorded sound as a compact disk but in about 1/5 of the recordable area. The data compression is achieved by use of a technique known as adaptive transform acoustic coding for minidisc (ATRAC). This coding technique makes decisions about what components of the sound would not be heard by a human listener and discards the digital information that represents these sounds. Most of this compression takes place on sounds above 5.5 KHz. As the intended use of these recorders is the storage and reproduction of music, it is unknown whether ATRAC will discard or distort significant portions of typical lung sound signals. We determined the suitability of MD recorders for respiratory sound research by comparing a variety of normal and pathologic lung sounds that were digitized directly into a computer and also after recording by a DAT recorder and 2 different MD recorders (Sharp and Sony). We found that the frequency spectra and waveforms of respiratory sounds were not distorted in any important way by recording on the two MD recorders tested.

Algorithms↗

PubMedDate not supplied

Background of the demonstrated IMAGIS activities and future expectations.

In The Netherlands a national PACS development programme has been started, supported by the Dutch Society of Radiology and funded by the Dutch Department of Health because of the national character of the project. Three main partners are cooperating in this development: the Utrecht University Hospital (AZU), BAZIS and Philips International (Product Division Medical Systems), with the Delft University of Technology as the main BAZIS subcontractor. The non-profit foundation BAZIS, developing and supporting the ZIS Hospital Information System (in use in some 30 Dutch hospitals, over 15,000 acute beds), initiated its current IMAGe Information System (IMAGIS) projects in 1984. The activities were later integrated into the Dutch PACS project started in 1986. The final goal of the project is to achieve a PACS which is fully integrated with already existing hospital information systems (HIS). The development and operation of a HIS-PACS include many aspects of technical and clinical. The current efforts of BAZIS are concentrated on three main issues: diagnostic image quality evaluation (e.g. effects of data compression); modelling, software simulation and technology assessment of a prototype PACS (both general and detailed aspects); and coupling and integration of PACS and HIS (e.g. the BAZIS ZIS). Philips, Hamburg, is supplying equipment, particularly prototype components. A systematic clinical evaluation will take place at the Utrecht University Hospital.2+ We outline the background of the intermediate results as demonstrated during the 6th EuroPACS Conference:the psychophysical software package for Feature Evaluation And System Inspection By Logged Experiments (FEASIBLE); the modelling and simulation software package for Medical Image Representation, Archiving and Communication, Learned by Extensive Simulation (MIRACLES); and first results of the coupling experiments.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Communication Networks↗

PubMedDate not supplied

Conoidal fitting of corneal topography height data after excimer laser penetrating keratoplasty.

PURPOSE: To demonstrate a mathematical method for approximation of discrete corneal topography height data with a biconic model surface for better appreciation of the optical performance of the graft after penetrating keratoplasty. METHODS: In this retrospective study we included 50 eyes of 50 patients (30 keratoconus; 20 Fuchs' dystrophy) undergoing nonmechanical excimer laser penetrating keratoplasty. Conventional keratometry, corneal topography (TMS-1), subjective refraction, and best spectacle-corrected visual acuity (BSCVA) were assessed preoperatively, 3 and 6 months postoperatively, and before/after suture removal. A biconic model surface was fitted to the topographic raw data (8.0-mm region of interest) minimizing the root mean square error and a set of parameters (meridional power, axis, conic constant, and approximation error) was determined. The refractive cylinder was correlated with keratometric power readings, the Simulated Keratometry (SimK) of the topography system, and the respective parameters of the model surface. RESULTS: Keratometric/SimK astigmatism increased from preoperatively (3.40/4.30 D) to 3 months (4.30/4.80 D) and decreased to 3.40/3.90 D after suture removal. Refractive cylinder/cylinder of the biconic increased slightly from 2.10/2.60 D preoperatively to 3.20/3.30 D after suture removal. The topographic cylinder SimK yielded the highest and the refractive cylinder the lowest values at each follow-up examination. Central keratometric power readings were stable before suture removal and decreased (about 1 D) due to suture removal. The conic constants in both meridional cross-sections changed from a prolate to a spherical shape in the early time course after penetrating keratoplasty and reconverted to a prolate shape after suture removal. Regarding cylinder axis, there was a significant correlation of the model surface with the refractive cylinder at all examination (P < .05) but only a mild correlation of the keratometric and SimK cylinder axis to the refractive cylinder axis at some examination stages. CONCLUSION: Approximation of corneal topography height data with a biconic model surface renders reconstruction of clinically relevant corneal topography parameters including corneal asphericity with marked data compression. The correlation of amount/axis of refractive cylinder was best represented with the model surface parameters.

Aged↗

PubMed1998

Radiology devices; classifications for five medical image management devices; correction--FDA. Final rule; correction.

The Food and Drug Administration (FDA) is correcting a final rule that appeared in the Federal Register of April 29, 1998 (63 FR 23385). The document classified, along with other devices, the medical image storage device and medical image communications device. These devices were classified into Class I and were exempted from the requirement of premarket notification when they do not use irreversible data compression. The document was published with an incomplete device identification and description of the conditions for exemption from premarket notification. This document corrects those errors.

Information Storage and Retrieval↗

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↗

PubMed2000

Sequence complexity for biological sequence analysis.

A new statistical model for DNA considers a sequence to be a mixture of regions with little structure and regions that are approximate repeats of other subsequences, i.e. instances of repeats do not need to match each other exactly. Both forward- and reverse-complementary repeats are allowed. The model has a small number of parameters which are fitted to the data. In general there are many explanations for a given sequence and how to compute the total probability of the data given the model is shown. Computer algorithms are described for these tasks. The model can be used to compute the information content of a sequence, either in total or base by base. This amounts to looking at sequences from a data-compression point of view and it is argued that this is a good way to tackle intelligent sequence analysis in general.

Algorithms↗

PubMed1999

The impact of teleradiology in clinical practice--a Malaysian perspective.

Teleradiology is the most mature and rapidly evolving specialty in telemedicine. The use of teleradiology has grown tremendously during the past few years. This article describes the role of teleradiology in health care along with a brief history of its development in tandem with advances in telecommunications and computer technologies. Teleradiology standards, image acquisition, data compression, transmission and image interpretation are summarised. The impact of teleradiology in the practice of radiology, traces the evolution of the modality especially in the Malaysian perspective and its current and future role are discussed.

Delivery of Health Care↗

PubMed1999

[Progress in technique of computer for three dimensional reconstruction from biological tissue series slices images].

The development of the technique of computer processing images and biotechnology from late 80's to early 90's has rovided the possibility of displaying three dimensional images of biological tissues truly. Now the technique of computer for three dimensional reconstruction is more and more widely used in the biological territory. This paper introduces the progress in the technique of computer for three dimensional reconstruction from biological tissue series slices images. Emphasis is laid on registration, reconstruction & display, image data compressing and image automatic segmentation.

Algorithms↗