Biomedical subjects

J Krejza

Publications and source records attributed to J Krejza.

29 records · Page 2Linked to original sources

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↗

PubMed1999

[Blood flow parameters in ocular vessels of patients with glaucoma].

PURPOSE: To determine Doppler flow parameters in ocular vessels of glaucomatous patients. MATERIAL AND METHODS: 38 glaucomatous patients, aged 64 +/- 16, and 57 healthy volunteers were examined with 7.5 MHz linear-array probe. Consistently identified arterial structures included ophthalmic artery, central retinal artery and short posterior ciliary arteries. The peak systolic, end-diastolic and mean velocities were measured from Doppler spectra. Resistance and pulsatility indices were also determined. RESULTS: End-diastolic and mean velocities in central retinal artery of glaucomatous eyes were: 1.5 +/- 1.9 cm/s, 4.0 +/- 2.0 cm/s, whereas in healthy eyes they were significantly higher: 3.5 +/- 1.0 cm/s, 5.4 +/- 1.5 cm/s, respectively. These velocities in short posterior ciliary arteries in glaucomatous patients were significantly lower: 2.4 +/- 2.3 cm/s, 5.6 +/- 2.2 cm/s, comparing to healthy subjects: 4.8 +/- 1.7 cm/s, 7.3 +/- 2.2 cm/s. Resistance and pulsatility indices in central retinal artery and short posterior ciliary arteries were significantly higher in the group of patients: RI = 0.85 +/- 0.18, PI = 2.11 +/- 0.92--in central retinal artery and RI = 0.81 +/- 0.18, PI = 1.96 +/- 0.91--in short posterior ciliary arteries, comparing to healthy subjects: RI = 0.61 +/- 0.08, PI = 1.20 +/- 0.17--in central retinal artery, RI = 0.61 +/- 0.09, PI = 1.13 +/- 0.18--in short posterior ciliary arteries. Impedance indices were increasing progressively with intraocular pressure elevation. There were no significant differences of Doppler blood flow parameters in ophthalmic artery between patients and control group. CONCLUSIONS: Blood flow velocities in central retinal and short posterior ciliary arteries are lower, and resistance and pulsatility indices are higher in glaucomatous eyes in comparison to healthy subjects, whereas in ophthalmic artery doppler parameters are similar in both groups.

Adult↗

PubMed1997

Ultrasound vascular imaging with subtraction in evaluation of lung tumor vascularity--a case report.

Ultrasound vascular imaging with subtraction is considered as very useful method to evaluation vascularity of tumor and its relationships to great vessels. Lung tumor was evaluated with power color Doppler ultrasound with and without B-mode scanning. Power color Doppler imaging without B-mode scanning is better depicted tumor internal vascular architecture and its relationships to great vessels then with B-mode. This method makes differentiation of tumor character possibly and interventional procedures more safely.

Aged↗

PubMed1997

Evaluation of colour Doppler sonography in lung tumor biopsy.

Between 1986 and 1995, 1800 ultrasound examinations of the chest were done. Addition of colour Doppler imaging improves safety of procedures and allowed to perform ultrasound guided biopsy in 47 patients. On the basis of our experience we state that colour Doppler sonography guided needle aspiration biopsy is useful, sufficient and safety diagnostic method of malignant lung masses, especially peripheral and wall-chest located.

Adult↗

PubMed1996

Focal solitary hypoechoic area in hepatic fatty infiltration: a cause of hepatic pseudomass in ultrasound examination.

A unusual pattern of hepatic fatty infiltration was detected sonographically in 43 patients over a 2-year period. At appropriate gain settings and time gain compensations, the liver parenchyma demonstrated diffuse increased echogenicity except for a solitary hypoechoic area with relatively distinct margins, usually locate in the medial segment of the left hepatic lobe or right lobe in pericholecystic, perivascular or subcapsular locations. This hypoechoic focus varied in size between 15 and 50 mm and was typically ovoid, but was occasionally spherical or irregular in shape. Fourteen patients with such skip area underwent percutaneous needle biopsy because of concern that there was a space-occupying mass. Microscopic examination of specimens from the hypoechoic region revealed normal hepatic parenchymal cells, while tissue samples from the surrounding liver had high fat levels. In the remaining 29 patients, correlative radiologic studies supported the diagnosis of fatty liver and excluded a central-mass lesion. A localized area of normal hepatic tissue should be considered among the possible hypoechoic periportal area demonstrated within a fatty liver.

Adult↗

PubMedDate not supplied

Transcranial color Doppler sonography in the emergency diagnosis of middle cerebral artery occlusion in a patient after head injury.

The purpose of this report is to highlight the utility of transcranial color Doppler sonography (TCCDS) in the emergency diagnosis of an ischemic stroke in a 64-year-old patient after head injury. An emergency CT identified a subdural hematoma, subarachnoid hemorrhage, a brain contusion and edema. The patient's status deteriorated after admission, and a second CT revealed an intracerebral hematoma and marked mass effect. Transcranial color sonography revealed no flow in the ipsilateral middle and anterior cerebral arteries, which was consistent with ischemic stroke. This case demonstrates that transcranial color Doppler sonography performed early after head injury may be useful in detecting associated occlusion of cerebral vessels.

Arterial Occlusive Diseases↗

PubMedDate not supplied

Limitations of color Doppler sonography in the imaging of ocular vessels.

PURPOSE: To describe a case where detection of blood flow in the central retinal artery and the central retinal vein was limited by an artifact evoked by the optic disc drusen. METHODS Case report. RESULTS: During color Doppler sonography, examination of optic disc drusen may generate an artifact--the so-called twinkling artifact--which can simulate blood flow and make evaluation of the central retinal vessels impossible. CONCLUSIONS: Twinkling artifact does not allow evaluation of color Doppler sonography in the imaging of ocular vessels.

Artifacts↗

PubMedDate not supplied

[Transcranial color Doppler estimation of blood flow parameters in respective basal cerebral arteries in healthy subjects].

Transcranial colour-coded Doppler sonography enables estimation of blood flow parameters in the basal cerebral arteries. Reference values as well as age and gender dependence of these parameters are not sufficiently established in transcranial Doppler studies. There are no reports regarding blood flow in the respective arteries of the circle of Willis. Therefore we examined 185 healthy volunteers--82 men (mean age 47, range 20-78 years old) and 103 women (mean age 47, range 22-86 years old). The subjects were divided into three age groups: 20-40 years old (group I), 41-60 years old (group II) and more than 60 years old (group III). The examinations were performed via the temporal acoustic window with a 2.5 MHz probe. Angle-corrected peak systolic, mean and end-diastolic velocities as well as impedance indices were determined in the anterior, middle and posterior cerebral arteries. In the group I mean velocity values (mean +/- SD) for the anterior, middle and posterior arteries amounted to 56 +/- 14 cm/s, 81 +/- 20 cm/s and 52 +/- 12 cm/s, respectively. In group II the values were 53 +/- 16 cm/s, 73 +/- 19 cm/s and 51 +/- 12 cm/s, and in group III the values were 44 +/- 11 cm/s, 59 +/- 11 cm/s and 40 +/- 9 cm/s. Decline in the blood flow velocities and increase in the impedance indices were found in all vessels with advancing age. This was most pronounced in subjects who were more than 40 years old. The decrease with age in blood flow velocities was more substantial in the middle cerebral arteries than in the anterior and posterior cerebral arteries. In contrast, the impedance indices increased more distinctly in the anterior cerebral arteries than in the middle and posterior cerebral arteries. We have demonstrated that the blood flow Doppler parameters are age and, in the group I (20-40 years old), also gender dependent. The range of the normal reference values of these parameters has proved to be wide. Decrease with age in blood flow velocities was found to be varied in the major cerebral arteries.

Adult↗

PubMedDate not supplied

[Analysis of intracranial pressure signals using artificial neural networks].

Intracranial pressure (ICP) is influenced by an array of predictable and unpredictable factors. Statistical modelling of this signal has only limited applicability because of the significant load of stochastic components. We tested the efficiency of an alternative approach, based on the methodology of artificial neural networks (ANNs) in the on-line prediction of future values of ICP and in the classification of signal properties. Satisfactory accuracy of forecasting was achieved with the ANNs for a 3-minute prediction horizon, while the prediction quality with autoregressive models of statistical origin was proved unsatisfactory. The results obtained with the ANNs were further improved when signal pre-processing with wavelet transform was employed. Nevertheless, even with the ANN methodology, no sudden breakdowns in the ICP signal (which in this respect might be compared to a "catastrophe") can be forecast with any practical applicability. We therefore applied two ANN algorithms, oriented at classification and discrimination of the global properties of the ICP signal. The neural network was expected to discriminate those sets of signal properties, which were assumed to correspond to certain clinical conditions of the patient. In a "dynamic pattern classification" the network was presented with several sections of ICP records. This was combined with information about the assignment of a given record to one of four arbitrary classes of danger. In this mode no data pre-processing was carried out, in contrast to our second approach, in which the signal was pre-processed with statistical analyses and only these intermediate coefficients were fed to the ANN classifier. The results obtained with both classification methods at their present stage of training were similar and approximated to a 70% rate of judgements consistent with expert scoring. Nevertheless, the method based on the assessment of global parameters of the ICP record seems more promising, because it leaves the possibility of extending the set of training data by information from other diagnostic modalities. The study aims towards the development of a pseudo-intelligent computer expert system, which has would be taught salient links between data extracted from the ICP signal and higher- order data, which contributed to the expert score. Hence the system would be able to make decisions on the basis of a reduced set of input information, available from a standard monitoring modality.

Algorithms↗

PubMedDate not supplied

Diffusion tensor imaging in amyotrophic lateral sclerosis: volumetric analysis of the corticospinal tract.

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) allows direct visualization and volumetric analysis of the corticospinal tract (CST). The purpose of this study was to determine whether color maps and fiber tracking derived from DTI data are valuable in detecting and quantifying CST degeneration in patients with amyotrophic lateral sclerosis (ALS). METHODS: Sixteen patients with ALS with clinical signs of upper motor neuron (UMN) involvement and 17 healthy subjects were studied with the use of DTI. Disease severity was determined by means of the ALS Functional Rating Scale-Revised (ALSFRS-R) and an UMN involvement score. DTI was acquired with a 12-direction, single-shot, spin-echo echo-planar sequence. The CST from the lower pons to the corona radiata at the level of the corpus callosum on 4 contiguous coronal sections was manually segmented by using color maps generated from the DTI data. The left and right CST volumes were measured separately and normalized to the total intracranial volume. Normalized CST volumes were compared between patients with ALS and healthy subjects. RESULTS: The CST volumes of patients with ALS were significantly reduced (P < .01, unpaired t test) compared with healthy subjects, in both affected and nonaffected hemispheres. No significant correlation was found between CST volumes and any of the clinical parameters, including disease duration, ALSFRS-R, or UMN involvement score. CONCLUSION: This study shows that volumetric analysis by using DTI-based color maps is valuable in detecting and monitoring structural degeneration of the CST. This will lead to objective and quantitative assessment of axonal degeneration in ALS.

Adult↗