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Biomedical subjects

J Krejza

Publications and source records attributed to J Krejza.

At least 19 recordsLinked to original sources
PubMed2005

Detection and monitoring of cerebral hemodynamic disturbances with transcranial color-coded duplex sonography in patients after head injury.

Reduced cerebral blood flow after severe head injury results in an increased risk of ischemic brain damage. Blood flow should therefore be monitored with a simple, reliable method. Transcranial color-coded Doppler sonography (TCCS) is an accepted tool for the diagnosis of cerebral vasospasm; however, its usefulness in evaluating patients with head injury has not been proven. Cerebral blood-flow velocity in the middle, anterior, and posterior cerebral arteries was measured with a 2.5 MHz probe (Aplio SSA 770A, Toshiba, Japan) in 36 subjects with moderate or severe head injury. Serial measurements of resistance index (RI), peak-systolic, end-diastolic, and mean velocity in the middle cerebral arteries were performed 2-24 h after head trauma and in the subsequent days during hospitalization. Immediately after head trauma, increased RI values, and unusually decreased blood-flow velocity (mainly in MCA) were observed. Microcirculation disturbances were suspected because the end-diastolic velocity had substantially diminished. Changes in blood-flow parameters correlated with the clinical state, and in most cases, a poor prognosis. In some patients, blood-flow velocity increased above the normal reference limit and this implied poor prognosis. Transcranial color-coded Doppler sonography is a reliable, repeatable, and accessible tool that provides information about cerebral blood-flow disturbances and may hold diagnostic and prognostic importance.

Blood Flow Velocity↗
PubMed2005

Assessment of variability of renal blood flow Doppler parameters during the menstrual cycle in women.

OBJECTIVE: To estimate variability of renal flow Doppler parameters during the menstrual cycle in young women, and to explore whether the parameters oscillate substantially throughout the cycle. METHODS: The peak systolic, mean, and end-diastolic velocities, pulsatility (PI) and resistance (RI) indices, acceleration time (AT) and index (AI) of the right renal artery were measured nine times during the cycle with duplex sonography in 14 healthy women (age range, 23-25 years), and correlated with plasma concentrations of 17beta-estradiol and progesterone. Coefficient of variation (CV), interclass correlation (rho), and repeatability coefficients (RC) were used to measure the variability. RESULTS: The measures of the variability for AI and AT were: CV = 45.4% and 37.3%; rho = 0.25 and 0.15; RC = 10.1 and 99.5, respectively. The CV for flow velocities varied from 24.1% to 25.5%, rho from 0.49 to 0.50, RC from 22.7 for end-diastolic to 63.3 for peak systolic velocity. The respective figures for PI and RI were: CV = 17% and 8.3%; rho = 0.21 and 0.29; RC = 0.53 and 0.15. Fluctuations of the flow parameters, hematocrit, hemoglobin, heart rate, and systolic blood pressure during the menstrual cycle were insignificant, while the diastolic blood pressure decreased by about 7 mmHg (P < 0.01) in the luteal phase. CONCLUSION: The variability of renal flow Doppler parameters during the menstrual cycle in young healthy women is substantial. However, fluctuations of the values of the parameters throughout the cycle were non-significant.

Adult↗
PubMed2003

Oscillations of cerebrovascular resistance throughout the menstrual cycle in healthy women.

OBJECTIVES: Increased concentration of endogenous estrogen during a typical menstrual cycle has been shown to correlate with augmentation of blood flow through the internal carotid arteries (ICAs), which may be related to changes in vascular resistance within the brain. In this study we investigated the effects of endogenous estrogen and progesterone on cerebrovascular impedance in young healthy women. METHODS: The blood flow in the ICA and the common (CCA) and external (ECA) carotid arteries was studied with duplex Doppler sonography. The resistance index (RI) was determined and correlated with plasma 17beta-estradiol concentration in 14 young healthy women throughout their menstrual cycle. RESULTS: The concentration of 17beta-estradiol increased in the follicular phase of the cycle and reached a peak on day 14, whereas concentration of progesterone remained low. Along with an increase in estrogen concentration, the ICA RI had decreased from its initial level on average by 9.2% on day 13 and by 6.7% on day 14 (P < 0.05). In contrast, the trend of the ECA RI was to increase during the peak of estrogen concentration. There were no significant changes in the CCA RI or in the systolic blood pressure, heart rate, hematocrit and hemoglobin concentration through the menstrual cycle. CONCLUSIONS: Estrogen-related augmentation of blood flow through the ICA is caused mainly by decreased cerebrovascular impedance, as shown by a decrease in the ICA RI. These changes in RI suggest that estrogen influences cerebral impedance mainly by altering the resistance of cerebral microvasculature.

Adult↗
PubMed2001

Human brain temperature in vivo: lack of heating during color transcranial Doppler ultrasonography.

This study was undertaken to assess the effect of ultrasound on human brain temperature in vivo. The investigation consisted of direct recording of intracranial temperature during color transcranial Doppler (TCD) sonography in a neurosurgical patient. The temperature was recorded from 3 thermocouples. One was implanted together with an intracranial pressure sensor into a surgically reduced intraparenchymal hematoma, the second was placed within the subdural space close to the temporal acoustic window, and the third was located extracranially at the outer surface of the temporal bone. Tympanic temperatures were also measured to give an approximation of global brain temperature. A 2.5-MHz transducer was used, and the system settings were as follows: spatial peak temporal average intensity = 234 mW/cm2 in B-mode at a maximum power of 32.3 mW and 2132 mW/cm2 in Doppler mode at a maximum power of 149.3 mW. Neither increase in the intraparenchymal brain temperature nor increase in the temperature at the bone/soft tissue interface was observed during 30 minutes of insonation. The ipsilateral tympanic temperature increased by only 0.06 degree C, and this value may be regarded as a measure of the overall increase in brain temperature. Passive cooling effect produced by the transducer, which was at ambient temperature, was found to reach the brain surface and to surpass any possible heating caused by the ultrasound. The results indicate that no noticeable increases in human brain temperature occur in response to ultrasound emitted by a color TCD device at high transmitter power settings within the diagnostic range.

Body Temperature↗
PubMed2001

Effect of endogenous estrogen on blood flow through carotid arteries.

BACKGROUND AND PURPOSE: Recent evidence suggests that physiological changes in the concentration of endogenous estrogens may influence stroke outcome. The purpose of this study was to determine a menstrual cycle-related profile of blood flow through the carotid arteries and its correlation with estrogen concentration. METHODS: The flow velocity and cross-sectional area of the common carotid artery, internal carotid artery (ICA), and external carotid artery (ECA) were measured with duplex Doppler sonography throughout the menstrual cycle in 14 healthy women. Concentration of plasma 17beta-estradiol, progesterone, hematocrit, hemoglobin, and blood pressure were also determined. RESULTS: In the follicular phase, the concentration of estrogen increased to reach a peak on day 14, whereas concentration of progesterone remained low. The mean and end-diastolic velocities in the ICA increased on average by 15% of their base values, along with increasing concentrations of estrogen (r=0.59 and 0.65, respectively). The profile of flow velocity changes in this artery corresponded to the profile of estrogen concentration. In contrast to the ICA, flow velocities in the ECA decreased from their base value, reaching their minimum in the luteal phase. The mean flow velocity in the common carotid artery increased on day 14 by just 2% of its base value. The lumen of the carotid arteries was stable throughout the cycle. Hematocrit, hemoglobin, and systolic blood pressure also remained unchanged. CONCLUSIONS: Increased concentration of endogenous estrogen correlates with substantial augmentation of flow in the internal carotid artery. This promotion of flow is caused mainly by decreased cerebrovascular resistance with consequent "stealing" of blood from the ECA.

Adult↗
PubMed2001

Importance of angle correction in the measurement of blood flow velocity with transcranial Doppler sonography.

BACKGROUND AND PURPOSE: The angle of insonation cannot be assessed with conventional transcranial Doppler sonography. Findings in healthy control subjects suggest that the angle is relatively small in routine clinical practice. Data regarding the angle in middle cerebral artery (MCA) stenosis are scarce. In this study, the angle and its effect on flow velocity measurements were assessed with transcranial color Doppler sonography in patients with MCA stenosis. METHODS: Eighteen patients (median age, 53 y; age range, 22-72 y) who satisfied qualifying criteria (eg, angiographically revealed unilateral MCA stenosis of > or =50%) were selected from 149 consecutive patients enrolled in a prospective study of transcranial color Doppler sonography and cerebral digital subtraction angiography. All had active neurologic symptoms. The angle of insonation and peak systolic and mean flow velocities in both MCAs were measured from videotapes generated at sonography. RESULTS: The mean angle of insonation was 47 +/- 11 degrees (range, 19-64 degrees ) on the stenotic side and 34 +/- 18 degrees on the contralateral side (P <.05). Angle-corrected velocities were higher than uncorrected ones. Differences between angle-corrected and uncorrected peak systolic and mean flow velocities on the stenotic side were 46.6% and 45.9%, respectively, of uncorrected values. Differences between corrected and uncorrected peak systolic and mean velocities were larger on the stenotic side compared with those on the contralateral side (P <.05). CONCLUSION: In patients with moderate or severe MCA stenosis, the angle of insonation can be substantial and cause large errors when flow velocities are measured without angle correction.

Adult↗
PubMed2001

[Malignant or benign thyroid nodules: a diagnostic dilemma].

The aim of this study was to determine the incidence of cysts and cystoid-solid lesions in thyroid carcinomas basing on preoperative ultrasonographic examinations (USG), fine needle aspiration biopsy (FNAB) and postoperative histopathological examinations. 661 patients with different thyroid disorders were treated surgically. Carcinoma was found in 46 patients (3.9%). Papillary carcinoma was predominant (n = 34). Of the 46 patients with carcinoma, preoperative USG examination revealed cystic or cystoid-solid lesions in 18 patients (39%). FNAB of this 18 patients was positive in 5 cases, negative in 4 and suspect in 9. In 6 cases the neoplastic lesion was strictly connected with cysts (foci in the wall or in solid masses within the cyst) and in the remaining 12 patients lesions were found in the vicinity of the neoplastic focus. We conclude that malignant neoplasms of the thyroid gland are frequently (in approximately 40%) accompanied by cystic and cystoid-solid lesions, FNAB diagnostic material should be obtained even through several USG-controlled punctures and negative FNAB does not exclude thyroid carcinoma, particularly in nodular-cystoid goitre.

Adolescent↗
PubMed2001

[Transcranial color-coded Doppler sonography: getting started].

Transcranial color Doppler sonography, in contrary to conventional transcranial Doppler ultrasound, allows outlining of the parenchymal structures and visualization of the vessel examined. Angle-corrected blood velocities can be obtained which are closer to in-situ values. In this educational assay, we demonstrate cerebral vascular anatomy using 3-D MR angiographic images of the major cerebral arteries to show their relationship to neighboring structures, the acoustic window, and the ultrasound beam. We describe principles of the examination, and discuss the different types of physiological flow velocity spectra. We show how to identify with color Doppler ultrasonography the main intracranial arterial trunks, and how to avoid pitfalls caused by anatomic variability of their course and location. We draw attention on significant age and sex dependency of blood flow parameters which makes standardization of obtained transcranial Doppler results indispensable for clinical valuable concluding.

Blood Flow Velocity↗
PubMed2000

Transcranial colour Doppler sonography in emergency management of intracerebral haemorrhage caused by an arteriovenous malformation: case report.

We present a case which demonstrates the use of transcranial colour Doppler (TCCD) sonography in screening for an underlying arteriovenous malformation (AVM) in a middle-aged hypertensive patient with a spontaneous thalamic haematoma. The AVM was not detected on emergency CT but its presence, site and shape were demonstrated by TCCD, in the presence of a massive cerebral haemorrhage and acute intracranial hypertension.

Arteriovenous Malformations↗
PubMed2000

Intracranial pressure processing with artificial neural networks: prediction of ICP trends.

It is well known that intracranial pressure (ICP) is influenced by an array of predictable and unpredictable factors, which gives rise to a signal heavily loaded with stochastic, i.e. random components. Hence, statistical modelling of this signal has proved to be of limited utility, in spite of the very sophisticated mathematical methods applied. In recent years, neural network algorithms (ANN), which are an alternative to statistical methods, have proved their effectiveness in the prediction of trends, as applied in a variety of medical and non-medical tasks. We therefore attempted to test the efficiency of neural models in the on-line prediction of ICP values, compare their effectiveness to statistically oriented algorithms and combine ANN methods with some newer signal processing algorithms, like wavelet decomposition. Prediction horizons of up to 5 minutes have been tested with various architectures of the neural predictor. For a 3 minute prediction horizon, a satisfactory accuracy of forecasting has been achieved with "plain" ANN, as expressed by the "average relative variance coefficient". This was measured by the ratio of the prediction error obtained, in relation to the error which would occur if a current value were taken as the forecasted one. The prediction quality with statistical autoregressive models has proved unsatisfactory, whilst the result obtained using the ANN model with the wavelet transform incorporated, performed significantly better than the ANN models alone. The prediction quality obtained with the ANN methodology seems to be satisfactory over a short time horizon, though no conclusion can be derived at this stage of the study, as to the clinical utility of this method. In particular, even with this methodology, it is not possible to forecast any sudden dehiscencies of the ICP signal with any practical reliability. From the point of view of modelling theory, such sharp deviations of the signal may be regarded as a "catastrophe". This implies the necessity for a different approach to the ICP signal analysis with the artificial intelligence methodology; one, that is more oriented towards the global properties of the signal.

Cerebral Hemorrhage↗
PubMed2000

Intracranial pressure processing with artificial neural networks: classification of signal properties.

Intracranial pressure (ICP) is commonly used by neurosurgeons as a source of valuable information about the current condition of the neurosurgical patient. Nevertheless, despite years of effort, extracting clinically valuable information from the ICP signal is still problematical. Approaches, using current values of ICP, may fail to disclose imminent risk, because unpredictable factors can rapidly change the properties of the signal. An alternative approach is to determine some global characteristics of the signal within a longer time interval and such statistical analyses have been proposed by several authors. A further, rarely considered, problem is assessment of the results obtained from the point of view of their practical utility and/or such classification of the obtained properties of the signal that they correspond to certain clinical states of the patient. While this might be a typical task for discriminant analysis, we approached the analysis using an alternative methodology, that of computational intelligence, implemented in artificial neural networks (ANN). We tested two variants of the ANN algorithms for classification and discrimination of global properties of the ICP signal. In a "dynamic pattern classification" the network was presented with several sections of ICP records together with information from the expert-neurosurgeon, classifying 4 risk groups. In this mode no data pre-processing was carried out, in contrast to our second approach, in which the signal had been pre-processed using published statistical analyses and only these intermediate coefficients were fed into the ANN classifier. The results obtained with both classification methods at their current stage of training were similar and approximated to a 70% rate of judgements consistent with the expert scoring. Nevertheless, the method based on the assessment of global parameters from the ICP record looks more promising, because it leaves the possibility for modification of the set of parameters analysed. The new parameters may include information extracted not only from the ICP signal, but also from other diagnostic modalities, like colour coded Doppler ultrasonography. The ultimate goal of this work is to build up a pseudo-intelligent computer expert system, which would be able to reason from a reduced set of input information, available from a standard monitoring modality, because it had been taught salient links between these data and higher-order data, upon which expert scoring was based.

Cerebral Hemorrhage↗
PubMed2000

Registration of three-dimensional MR and CT studies of the cervical spine.

A three-dimensional image registration technique for CT and MR studies of the cervical spine was evaluated for feasibility and efficacy. Registration by means of external fiducial markers was slightly more accurate than registration by anatomic landmarks. The interrelationships between bony (eg, neural foramina) and soft tissue structures (eg, nerve roots) in the cervical spine were more conspicuous on registered images than on conventional displays. Registration of CT and MR images may be used to examine more precisely the relationships between bony and soft tissue structures of the cervical spine.

Adult↗
PubMed1999

Transcranial color Doppler sonography of basal cerebral arteries in 182 healthy subjects: age and sex variability and normal reference values for blood flow parameters.

OBJECTIVE: Only a limited number of transcranial color-coded Doppler studies have provided ranges for the normal reference values of cerebral hemodynamic parameters. These reports are not fully convergent in relation to the range of values or to the age and sex dependence of blood flow parameters. The aim of the present study was to provide data regarding normal reference ranges. SUBJECTS AND METHODS: We examined 182 healthy volunteers (79 men and 103 women; age range, 20-86 years old) with color-coded Doppler sonography via a temporal acoustic window with a 2.5-MHz transcranial probe. The subjects were divided into three age groups: 20-40 years old (group 1), 41-60 years old (group 2), and more than 60 years old (group 3). Angle-corrected peak systolic, end-diastolic, and mean velocities as well as impedance indexes were determined in anterior, middle, and posterior cerebral arteries. RESULTS: Mean velocity values for middle, anterior, and posterior cerebral arteries in age group 1 were 81+/-20, 56+/-14, and 52+/-12 cm/sec (mean +/- SD), respectively. In group 2, the values were 73+/-19, 53+/-16, and 51+/-12 cm/sec (mean +/- SD), and in group 3, the values were 59+/-11, 44+/-11, and 40+/-9 cm/sec (mean +/- SD). Decrease in blood flow velocities and a concomitant increase in impedance indexes were found in all vessels with advancing age-findings that were most pronounced in subjects who were more than 40 years old. In the 20- to 40-year-old group, mean velocities for all vessels were higher in women than in men, whereas impedance indexes were not significantly different. CONCLUSION: Flow velocities in basal cerebral arteries range widely and are significantly age dependent. Age and sex matching of Doppler sonographic data is a prerequisite for clinically valuable conclusions.

Adult↗
PubMed1999

[Variations of Doppler blood flow parameters in central retinal artery in relation to position of sample volume].

PURPOSE: To determine variability in measurements of Doppler blood flow parameters in central retinal artery in relation to sample volume location from the optic disc. MATERIAL AND METHOD: Eighty central retinal arteries were examined using color Doppler ultrasonography in 40 healthy volunteers (22 female, 18 male), aged 45 +/- 9 with 7.5 MHz linear-array probe. The measurements of blood velocities and resistance indices in the arteries were obtained at points where distance from optic disc surface ranged from 1.5 mm to 6 mm. RESULTS: Blood velocities increased significantly when sampled closer to the globe (r = -0.61, and r = -0.32 for peak-systolic and end-diastolic velocities, respectively). Mean peak-systolic velocities were 13.0 +/- 2.7 cm/s when distance 2.1 +/- 0.46 mm from optic disc, and 9.3 +/- 2.5 cm/s when distance 4.27 +/- 0.9 mm. Mean end-diastolic velocities were 4.3 +/- 1.2 cm/s and 3.6 +/- 1.1 cm/s, respectively. Resistance indices inclined to increase when the distance between the measurement site and the globe shortened. Resistance indices were 0.67 +/- 0.06 when measured closer to the globe and 0.60 +/- 0.06 when measured farther from it. CONCLUSION: Position of sample volume in relation to optic disc has to be taken into account and defined if measurements of blood flow Doppler parameters of the central retinal artery are to be reproducible.

Blood Flow Velocity↗