Automatic detection of ultrasonic Doppler signal episodes resulting from fetal breathing movements.

A method for automatic detection of fetal breathing movements has been proposed, based on the time-frequency structure of the corresponding continuous wave ultrasonic Doppler signals. The method uses spectral analysis of the envelope of the directional Doppler signal and cross-correlation analysis of both directional envelopes. Detection rule comprises the following criteria: presence of the peak in the envelope spectrum and of the adequate signal level in the frequency range corresponding to the fetal breathing rhythm, the peak value and the position limits of the peak of the cross-correlation coefficient of the both directional envelopes. The effect of the criteria setting on the rule performance and the tradeoff between the specificity and sensitivity was investigated. The rule is most sensitive to the threshold value of the cross-correlation coefficient of the envelopes. The limits of the position of this peak are crucial for the distinction between the breathing episodes and hiccups. The optimal settings of the criteria, resulting in average sensitivity and specificity exceeding, respectively, 0.70 and 0.80, are proposed.

Measurements of the neutron dose near a 15 Mv medical linear accelerator.

In this work, simplified recombination methods for routine estimation of dose equivalent in mixed (gamma and neutrons) radiation field outside the irradiation field of linear medical accelerators is considered. The author's earlier reported method of H(10) measurements, involving determination of the recombination index of radiation quality, Q(4) by tissue-equivalent recombination chamber was combined with the new method for determination of the photon to neutron dose ratio D(X)/D(n) from the ratio of ion collection efficiencies measured in the investigated radiation field and in two reference fields of gamma and neutron radiations. The method is suitable when the neutron contribution to the total absorbed dose, D(n)/D, is >3%.

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part I. Laser and ultrasonic Doppler flow studies.

Irregular carotid lesion surface is considered as a factor increasing the risk of the cerebral embolism. The objective of the study was to investigate the possibility to distinguish models of stenosed carotid bifurcation with lesion irregularity on the basis of the properties of flow velocity distributions. Two groups of elastic replicas of carotid bifurcations with different stenosis degree were investigated. Each group consisted of three models with different severity of plaque surface irregularity and one with smooth wall. Velocity data were collected using a one-component laser Doppler anemometer (LDA) system and a pulsed Doppler flowmeter. The LDA velocity distributions and Doppler spectral broadening index, turbulence intensity index and coefficient of skewness were analysed. The lesion irregularity resulted in change of the size and/or shape of reversed/reduced flow areas and of the position of the jet with respect to those observed in a smooth wall model. The flow features observed in the ultrasonic Doppler spectra were generally coherent with the axial LDA velocity distributions. Doppler spectral parameters demonstrated different sensitivities to the severity of the wall irregularity, however, the complexity of curves of these indices versus time did not allow to draw decisive conclusions and implied use of a more sensitive tool of analysis.

The discrimination of stenosed carotid bifurcation models with smooth and irregular plaque surface. Part II. The multivariate statistical analysis of ultrasonic Doppler velocity data.

According to the conclusion of the first part of the paper the Doppler spectral indices were analyzed in a detailed manner to provide a means to differentiate bifurcation models with different irregularities. Autoregressive (AR) models using the Akaike FPE criterion were fitted to the curves of the spectral broadening index, turbulence intensity index and coefficient of symmetry. These curves were also submitted to the data reduction significant point extraction algorithm. The multivariate discriminant analysis was performed on parameter vectors containing coefficients of AR models, data reduction rate and data reduction error. The discriminant analysis allowed distinguishing models with the same degree of stenosis and different plaque surface characteristics on the basis of these vectors. The highest discrimination efficiency was observed for parameter vectors obtained from TBI and SKEW curves. The efficiency of discrimination was slightly higher for more severely stenosed models.

Oximetric and capnometric studies--aspects of natural and artificial ventilation.

Methods and instrumentation of own design and their application to the measurement of oxygen and CO2 content in blood and respiration gases are discussed. Spectrophotometry, particularly double wavelength colorimetry using red light and IR light, applied to the measurement of oxygen blood saturation for in vitro examination and through an intravascular catheter for invasive in vivo study and by means of pulse oximetry for non-invasive in vivo examination are presented. The electrochemical methods applied to in vitro and in vivo measurement of oxygen in blood (amperometric method) and in respiration gases (amperometric and fuel cell methods) are discussed. The electrochemical Stow-Severinghaus method of CO2 tension measurement in blood and CO2 partial pressure in respiratory gases as well as the selective IR light (4.26 microm) absorption method and instruments of own design for CO2 measurements in respiratory gases are also discussed. The methods and instrumentation described are very important for monitoring respiratory and circulatory function, particularly during artificial ventilation and circulatory support.

Platform independent implementation of DICOM-based miniPACS.

Platform independence is an important issue for a software designed to run across a hospital environment which is practically always heterogeneous one. This paper presents a simple miniPACS solution designed over an existing Intranet (Internet limited to a local area network). Platform independence is achieved with Java programming language which allows resulting code to be executed on virtually all machines. System consists of a server application providing DICOM (Digital Imaging and Communications in Medicine) services and clients that can use these services over a TCP/IP connection. The server application is capable of an image storage and supports a query mechanism to allow access to stored data, thus the clients may perform two major functions: providing image data for archiving or image retrieval for viewing. Presented client application provides both these functions. It retrieves stored images for further processing and returns calculated results to the archive. The parts of the system are connected through a DICOM interface. Consequently the system architecture is open and any devices like scanners or viewing stations supporting specific DICOM services may be attached.

Detection of fetal breathing and cardiac movements and rhythms in ultrasonic Doppler signal recorded on the surface of the maternal abdomen.

It is proposed to use information on the direction of reflector movement and extensive filtering in the detection of fetal breathing and cardiac movements in the ultrasonic Doppler signal recorded on the surface of the material abdomen. The method appears fairly insensitive to spurious signals and allows those of interest to be distinguished without any reference technique. A decision rule for breathing and cardiac rhythm detection, incorporating movement direction, amplitude, shape and periodicity criteria, is also proposed.

Effect of method and parameters of spectral analysis on selected indices of simulated Doppler spectra.

The sensitivity of Doppler spectral indices (mean frequency, maximum frequency, spectral broadening index and turbulence intensity) to the conditions of spectral analysis (estimation method, data window, smoothing window or model order) increases with decreasing signal bandwidth and growing index complexity. The bias of spectral estimate has a more important effect on these indices than its variance. A too low order, in the case of autoregressive modeling and minimum variance methods, and excessive smoothing, in the case of the FFT method, result in increased errors of Doppler spectral indices. There is a trade-off between the errors resulting from a short data window and those due to insufficient temporal resolution.

[Our experience with using amrinone in circulatory failure]. / Doswiadczenia wlasne nad stosowaniem amrinonu w niewydolnosci krazenia.

A study aimed at evaluating an effect of amrinone of blood circulation dynamics (cardiac output), using impedance ++rheography. The study involved patients with acute, congestive cardiac failure (NYHA III-IV degrees). Cardiac output was measured prior to and 3 and 24 hours following amrinone administration. A favourable effect of a 24-hour i.v. infusion of amrinone on blood circulation dynamics was confirmed. The drug proved to be proarrhythmic.

[Activitrax--a pacemaker with a regulated rhythm rate]. / Activitrax--stymulator z regulowana czestoscia rytmu.

In 10 patients: 7--with the complete atrioventricular block and 3 with the sick sinus syndrome the rate responsive activity sensing pacemaker--Activitrax was implanted. Significant increase of rheographically measured cardiac output in a course of rate responsive pacing in comparison with on demand constant frequency rate stimulation was stated during treadmill exercise tests performed 6 and 12 weeks after a pulse generator implantation.

[Comparative investigation of cardiac output using impedance rheography and invasive methods]. / Badania porównawcze rzutu minutowego serca metoda reografii impedancyjnej i metodami inwazyjnymi.

Authors performed comparative measurements of cardiac output using the impedance rheography and Fick's method in healthy men (6) reaching the value of correlation coefficient 0.88 and in patients with acquired cardiac defects (n = 21; r = 0.68). Authors also compared cardiac output values measured at rest and during exercise by means of thermodilution and rheographic methods in patients with heart failure (n = 9). Correlation coefficient was respectively 0.92 and 0.81.

Augmented chemoreceptor reflex tonic drive in early human hypertension and in normotensive subjects with family background of hypertension.

The study was carried out in 30 subjects with mild primary hypertension and in 82 normotensive age-matched volunteers, 18-20 years of age. Hyperoxia test was used to withdraw the tonic chemoreceptor reflex drive. The following circulatory and respiratory effects of short lasting hyperoxia were observed in the hypertensive group and in most of the normotensive subjects yet with a family background of hypertension: a decrease in the mean arterial pressure, in total peripheral vascular resistance, and in forearm vascular resistance, and a significantly greater reduction of the resting ventilation as compared to the normotensive group. Our results suggest that the augmented arterial chemoreceptor drive is one of the mechanisms responsible for the elevated arterial blood pressure and total peripheral resistance in early human hypertension. The positive response to hyperoxia test in healthy subjects with a family background of hypertension suggests a familial occurrence of the hyperactivity of the arterial chemoreceptors.