PubMed Health⌕ Search

Biomedical subjects

M Kaps

Publications and source records attributed to M Kaps.

At least 73 records · Page 4Linked to original sources
PubMed1999

Harmonic grey scale imaging of the human brain.

Harmonic imaging increases the signal-to-noise ratio in grey-scale imaging. With the use of ultrasound contrast agents (UCA), imaging of brain perfusion seems possible. The authors used an ultrasound system in connection with a 1.8/3.6-MHz harmonic sector transducer and an acoustic densitometry unit for quantification of ultrasound intensity in the thalamus (THAL), the temporoparietal white matter (TPWM), and the lateral fissure (LF). Ten milliliters of BY963, a spherosome-air-based UCA, was injected intravenously in 12 healthy volunteers. Time-intensity curves were calculated. Mean increase of intensity (standard deviation [SD]), mean area under the time-intensity curve (AUC) from baseline (SD), and mean transit time (MTT) (SD) in the region of LF, THAL, and TPWM were 2.2 +/- 1.7, 1.1 +/- 0.6, 0.9 +/- 0.9 dB and 16.7 +/- 22.7, 4.7 +/- 4.7, 3.7 +/- 6.3 as well as 11.1 +/- 3.5, 9.7 +/- 3.1, and 11.9 +/- 8.0, respectively. There was a statistically significant difference for mean AUC (p = 0.02) but none comparing mean intensity increase (p = 0.07) and MTT (p = 0.9). The authors' study indicates that different regions of the human brain show different time-intensity curves. These results suggest that it is possible to measure parameters closely related to perfusion in various regions of the adult human brain.

Adult↗
PubMed1999

Assessment of intracranial venous hemodynamics in normal individuals and patients with cerebral venous thrombosis.

BACKGROUND AND PURPOSE: Despite ongoing improvements in noninvasive imaging techniques, transcranial color-coded duplex sonography (TCCS) has so far been used only on a limited basis in patients with cerebral venous thrombosis. We evaluated the diagnostic value of both noncontrast and contrast-enhanced TCCS by comparing normal volunteers and patients with acute cerebral venous thrombosis. METHODS: In 75 healthy volunteers (aged 45.8+/-17.4 years), normal values for the deep cerebral veins (DCVs) and the posterior fossa sinuses were established by transtemporal insonation. Eight patients with cerebral venous thrombosis were assessed by TCCS, through which the hemodynamics of the DCVs were measured, and the patients were followed-up over a period of between 33 and 387 days after examination. MR angiography served as the "gold standard" technique for confirming the venous status in all 8 patients. RESULTS: No side differences in flow velocities were detected in the paired venous structures in normal volunteers. As indirect signs of (and diagnostic criteria for) cerebral venous thrombosis, pathologically increased flow velocities or significant side differences in the DCVs were registered in 5 of the 8 patients; the other patients showed nonsignificant increases in flow velocity which decreased over time. During follow-up, the status of the posterior fossa sinuses could be diagnosed correctly in seven patients after contrast enhancement when these results were compared with those of venous MR angiography. In 1 patient, a partial recanalization was mistakenly diagnosed as an occlusion. CONCLUSIONS: TCCS allows a reliable evaluation of the major DCVs and posterior fossa sinuses. The anterior and mid portions of the superior sagittal sinus and cortical veins cannot be assessed. Increased venous blood flow velocity can be used as an indirect criterion for indicating a cerebral venous thrombosis. Clinical recovery coincided with decreases in blood flow velocity in the series of patients investigated in this study.

Adult↗
PubMed1999

Frontal bone windows for transcranial color-coded duplex sonography.

BACKGROUND AND PURPOSE: The use of the conventional temporal bone window for transcranial color-coded duplex sonography (TCCS) often results in difficulties in obtaining angle-corrected flow velocity measurements of the A2 segment of the anterior cerebral artery, the posterior communicating artery, and the midline venous vasculature because of the unfavorable insonation angle. The same applies to B-mode imaging of the frontal parenchyma. However, transorbital TCCS raises problems with the insonation of the orbital lens. To overcome these drawbacks, we studied the feasibility of frontal bone windows for TCCS examinations. METHODS: In 75 healthy volunteers (mean age, 45.3+/-17.0 years; age range, 17 to 77 years), the circle of Willis and the venous midline vasculature were insonated through a lateral and paramedian frontal bone window. Insonation quality of parenchymal structures (B-mode) was graded on a 3-point scale depending on the visibility of typical parenchymal landmarks. In a similar manner, the quality of the color-/Doppler-mode imaging of the arteries of the circle of Willis and the internal cerebral veins was assessed. In 15 patients (mean age, 62.7+/-13.7 years; age range, 33 to 83 years), the color-/Doppler-mode imaging quality of the intracranial vessels before and after application of an ultrasound contrast-enhancing agent was compared. RESULTS: B-mode insonation quality was optimal to fair in 73.3% of cases using the lateral and in 52.0% of cases using the paramedian frontal bone window, with defined parenchymal structures used as reference. Insonation quality decreased in those older than 60 years. In those younger than 60 years, angle-corrected flow velocity measurements of the A2 segment of the anterior cerebral artery and the internal cerebral vein were possible in 73.6% and 60.0%, respectively. Contrast enhancement resulted in a highly significant improvement in the imaging quality of the intracranial vessels. CONCLUSIONS: The transfrontal bone windows offer new possibilities for TCCS examinations, although the insonation quality is inferior to the conventional temporal bone window in terms of failure of an acoustic window. This can be compensated for by application of an ultrasound contrast-enhancing agent.

Adolescent↗
PubMed1999

Transcranial color-coded duplex sonography of intracranial veins and sinuses in adults. Reference data from 130 volunteers.

BACKGROUND AND PURPOSE: Transcranial color-coded duplex sonography (TCCS) of intracranial veins and sinuses in adults is a new, emerging application of ultrasonographic imaging. This study reports a standardized examination protocol for venous TCCS and provides reference data for clinical application. METHODS: In 130 healthy volunteers (mean age, 45.9+/-16.9 years; range, 14 to 77 years) the intracranial venous system was examined using frequency-based transtemporal TCCS. Identification rate, blood flow velocity, resistance index, and systolic/diastolic ratio were recorded for each examined venous vessel. RESULTS: Intracranial veins and sinuses show a low pulsatile forward flow with maximal systolic blood flow velocity up to 20 cm/s. Significant side differences of blood flow velocity in the paired venous structures could not be detected. Venous flow velocities decreased with age, whereas resistance indices and systolic/diastolic ratios increased. Women showed higher flow velocities than men. Mean identification rates for all age groups ranged from 70% to 90% for the deep middle cerebral vein, the basal cerebral vein, and the great cerebral vein of Galen. The straight sinus, the transverse sinus, and the rostral part of the superior sagittal sinus could be detected in 55% to 70% of cases. Detection rates were dependent on age and decreased as age increased. CONCLUSIONS: Venous TCCS can reliably image a significant part of the cerebral venous system. This method can provide information on venous hemodynamics in normal subjects and pathological cases.

Adolescent↗
PubMed1999

Genetic and environmental parameters for mature weight in Angus cattle.

Genetic and environmental variances and covariances and associated genetic parameters were estimated for weaning weight, asymptotic mature weight, and repeated mature weights. Data consisted of a set of weight measurements of 3,044 Angus cows born between 1976 and 1990. Mature weight was predicted by individually fitting Brody growth curves (asymptotic weight) and by using weights repeatedly measured after 4 yr of age. Variance and covariance components for mature weight were estimated by REML from a single-trait animal model with asymptotic weight, a two-trait animal model with asymptotic and weaning weight, and a two-trait animal model with repeated weights and weaning weight. Weaning and cow contemporary groups were defined as fixed effects. Random effects for weaning weight included direct genetic, maternal genetic, and permanent environmental effects; and for mature weight, direct genetic and repeated measurements (if in the model). Heritability estimates for weaning weight were similar for both two-trait models (.53 and .59). Estimates of heritability for mature weight were .44, .52, and .53 for the single-trait model with asymptotic weight, two-trait model with asymptotic weight, and two-trait model with repeated measures weights, respectively. The estimate of the genetic correlation between mature and weaning weight was higher for the repeated measures model (.85 vs. .63). A lower heritability estimate for mature weight from the single-trait model was likely due to postweaning culling. Therefore, a genetic evaluation of mature weight from field data should include a trait recorded earlier in life that is less subjected to selective data reporting.

Animal Husbandry↗
PubMed1999

Components of growth in mice hemizygous for a MT/bGH transgene.

The objective of this study was to determine the effects of a metallothionein/bovine GH transgene on duration and rate of growth of lean and fat in mice. Mice were produced by mating hemizygous transgenic males to nontransgenic females. Ten weights and six measurements of total body electrical conductivity to estimate body composition were taken on 147 progeny between birth and 84 d of age. Growth traits for fat-free mass (FFM) and body fat mass (FM) were obtained by fitting FFM and FM to a logistic curve y = A/(1 + exp(k(b - t))), where y is FFM or FM, A is asymptotic mass, k and b are curve parameters, and t is time in days. The function and its first, second, and third derivatives for FFM and FM were used to model growth. A mixed model was used with animal and litter as random effects and trans-genotype, sex, and transgenotype x sex as fixed effects in analyses of growth traits. Estimates of transgeno-type and transgenotype x sex interaction were tested by using their corresponding standard errors. Males had greater response to the transgene than females in final FFM and growth rate during the entire growth period. Transgenic males and females had greater duration of lean growth than nontransgenics. Transgenic males began to accumulate fat later, but they eventually gained more fat than transgenic females.

Adipose Tissue↗
PubMed1999

Comparison of transcranial color-coded duplex sonography and cranial CT measurements for determining third ventricle midline shift in space-occupying stroke.

BACKGROUND AND PURPOSE: Transcranial color-coded duplex sonography (TCCS) allows the noninvasive, easily reproducible measurement of midline dislocation (MLD) of the third ventricle in space-occupying stroke, even in critically ill patients. However, the method has been validated only in a small number of subjects. The aim of this study was to test the method under clinical conditions. METHODS: In 61 prospectively recruited patients (mean age, 62+/-15 years) with supratentorial ischemic infarction or intracranial hemorrhage, the sonographic measurement of MLD was compared with cranial CT data in a 12-hour time window. Subgroup analysis was also undertaken for comparing TCCS and cranial CT measurements within a 3-hour time window. RESULTS: One hundred twenty-two data pairs of TCCS and cranial CT MLD measurements were correlated within the 12-hour time window. TCCS and cranial CT measurements of MLD correlated both in the total patient group and in the different subgroups with coefficients of over 0.9. The 2-SD confidence interval of the difference between the TCCS measurements and the respective means of both methods in the total patient collective was +/-1.78 mm. CONCLUSION: TCCS provides a noninvasive, easily reproducible and reliable method for monitoring MLD of the third ventricle in stroke patients. It is particularly suitable for critically ill patients who are not fit for transportation.

Adult↗
PubMed1998

[Apoptosis and ischemic infarct].

Apoptosis and programmed cell death have attracted major scientific interest during the last few years. Apoptosis can be differentiated from necrosis by means of morphological, biochemical, molecular and pharmacological parameters. Several molecular pathways leading to apoptosis have been elucidated over the last few years. Apoptosis is not only important for physiological cell turnover, but also plays a role in many pathological processes. Recently, a number of laboratories have found evidence of apoptotic cell death in cerebral ischemia in animal models. Quantitatively, apoptosis seems to be important in the border zone of the infarction, the so-called penumbra. Since parts of the apoptotic cascade can be inhibited, pharmacological treatment seems feasible. The so-called caspase inhibitors are promising therapeutic agents for the treatment of acute stroke and may be administered with other neuroprotective medications in humans in the near future.

Animals↗
PubMed1998

Low frequency of clinically silent circulating emboli in patients with mitral valve prolapse or patent foramen ovale detected by bigated transcranial Doppler ultrasound.

Patent foramen ovale (PFO), but not uncomplicated mitral valve prolapse (MVP), is a possible source of cardiac embolism to the brain. There are only a few reports on the frequency of clinically silent circulating microemboli in these two conditions. We performed 1-hour recordings of one middle cerebral artery in 4 patients with MVP and 14 patients with PFO to detect circulating microemboli. For the identification of microembolic signals we used blinded off-line evaluation and bigated transcranial Doppler sonography (sampling from two different depths in the vessel). Microembolic signals were detected conventionally in 3 out of 14 patients with PFO (3, 8, and 14 microemboli/h), and in none out of the 4 patients with MVP. The absence of microembolic signals in patients with MVP and the low frequency of microemboli in patients with PFO reflect the different embolic potential of these two cardiac abnormalities.

Adult↗
PubMed1998

The influence of different gases on acoustic properties of a spherosome-based ultrasound contrast agent (BY963). A transcranial Dopplersonography study.

Ultrasound contrast agents improve the signal-to-noise ratio of reflected ultrasound, enhancing the diagnostic value of transcranial Doppler (TCD). In dog studies, we investigated the time course of TCD signal amplitude after application of a phospholipid-containing ultrasound contrast agent (BY963) filled with different gases. The median time of Doppler amplitude enhancement exceeding 5 dB was determined using isoflurane-, isopentane-, trichlortrifluoroethane-, air-, argon-, and perfluoropentane-filled BY963 (69, 72, 75, 78, 88, and 245 seconds respectively). The decrease of time-intensity curve and the duration of signal enhancement showed significant differences comparing the different gases (p = 0.04 and 0.03, respectively). The time course of in vitro stability of BY963 agitated with the different gases measured by absorbance of light (500 nm) showed a retarded decay for perfluoropentane, a rapid decrease for air, isopentane, trichlortrifluoroethane, and argon, and a very rapid decrease using isoflurane. The time course of the different gases depended on the physiochemical properties (lipophilicity and the solubility in water) of the gas encoated in the phospholipid shell. Perfluoropentane-filled BY963 showed the highest in vitro stability and the longest duration of TCD enhancement compared with the other gases used.

Acoustics↗
PubMed1998

Administration of modified spherosome suspension (BY963) leads to an increase of acoustic impedance in dog brain tissue.

Ultrasound contrast agents change the acoustic properties of brain tissue. This can be quantified with acoustic densitometry. In a dog model, the authors examined changes in acoustic impedance in the thalamic and parietal white-matter regions of the brain after intravenous injection of the spherosome containing an ultrasound contrast agent (BY963) filled with perfluoropentane gas. The authors examined six sedated mongrel dogs with a Hewlett-Packard Sonos 1500 device. BY963 filled with perfluoropentane (0.2 ml/kg body weight) was injected three times with a time interval between injections of 5 minutes. Time-dependent changes in mean acoustic impedance were calculated. The authors found a significant increase in peak acoustic impedance after fractional injection of 0.6 ml/kg body weight (3 x 0.2 ml/kg body weight) in the thalamus region up to 7.0 IU (p = 0.006). In the parietal white matter the increase in peak acoustic impedance was not significant (p = 0.06). Statistical comparison of the increase in peak acoustic impedance between placebo and BY963 injection in the thalamus region showed a significant difference after the first injection (p = 0.01) but showed no significance after the second and third injections. The authors concluded that thalamus and parietal white matter of the brain showed different accumulations of BY963.

Animals↗
PubMed1998

Consensus on microembolus detection by TCD. International Consensus Group on Microembolus Detection.

Transcranial Doppler ultrasound is capable of detecting microembolic material, both gaseous and solid, within the intracranial cerebral arteries. To avoid discrediting this promising and exciting new technique, experts in this field met in January 1997 in Frankfurt, Germany, to discuss the limitations and problems of embolus detection and to determine guidelines for its proper use in clinical practice, as well as in scientific investigations. In particular, the authors suggest that studies report the following parameters: (1) ultrasound device, (2) transducer type and size, (3) insonated artery, (4) insonation depth, (5) algorithms for signal intensity measurement, (6) scale settings, (7) detection threshold, (8) axial extension of sample volume, (9) fast Fourier transform (FFT) size (number of points used), (10) FFT length (time), (11) FFT overlap, (12) transmitted ultrasound frequency, (13) high-pass filter settings, and (14) recording time. There was agreement that no current system of automatic embolus detection has the required sensitivity and specificity for clinical use.

Humans↗
PubMed1998

Transcranial sonographic monitoring during thrombolytic therapy.

Two patients with acute occlusion of the middle cerebral artery (MCA) were treated with intravenous alteplase. Neurovascular monitoring, which was performed simultaneously via transcranial sonography, enabled precise documentation of MCA recanalization. This information was used to tailor the dosage and duration of alteplase treatment. Sonographic information concerning the arterial segments involved in the occlusive process, the actual hemodynamic status, and the collateral blood supply may help to identify those patients most likely to benefit from thrombolysis.

Arterial Occlusive Diseases↗
PubMed1997

Circulating microemboli in patients after aortic valve replacement with pulmonary autografts and mechanical valve prostheses.

BACKGROUND: The pulmonary autograft procedure (Ross) is now considered the gold standard for aortic valve replacement. One of its advantages is the freedom from macroemboli without anticoagulation. Whether this holds true for circulating microemboli, detectable as high-intensity transient Doppler signals (HITS), has not yet been verified. METHODS AND RESULTS: We investigated 8 patients (2 women, 6 men; mean age, 50.6+/-17.9 years) after the Ross procedure, 9 patients (3 women, 6 men; mean age, 67.2+/-9.46 years) after aortic valve replacement with a mechanical valve prosthesis, and 12 young healthy volunteers by unilateral 1-hour recording of the middle cerebral artery on digital audio tape. Patients with extracranial carotid artery disease were excluded by color duplex sonography. During the off-line evaluation, the investigator was not aware of any patient details. No HITS were detected in healthy volunteers (95% confidence interval [CI], 0% to 26.46%). After the Ross procedure, 1 patient had 11 and 1 patient had 1 HITS (95% CI, 3.19% to 65.09%). All recipients of mechanical valves had HITS, ranging from 2 to 84 per hour (95% CI, 66.7% to 100%). Significantly more recipients of mechanical valves exhibited HITS than recipients of pulmonary autografts (P<.05) or control subjects (P<.05). CONCLUSIONS: In contrast to mechanical valves, pulmonary autografts are seldom the source of microemboli, confirming the pulmonary autograft as the superior substitute for aortic valve replacement.

Adult↗
PubMed1997

[Microembolizatoins during heart surgery under extracorporeal circulation].

OBJECTIVE: By means of transcranial Doppler sonography (TCD), microembolic signals (MES) representing embolic events can be registered during cardiac surgery and extracorporeal circulation in a considerable number of patients. We conducted the present study to determine the neuro-psychiatric consequences of MES. METHODS: 25 patients scheduled for elective aorto-coronary bypass grafting (ACBG; n = 10) or aortic valve replacement (AVR; n = 15) were studied pre- and postoperatively with neuropsychiatric testing. Results were related to the number of MES noted intraoperatively. In addition, we registered the intraoperative changes of middle cerebral artery blood flow velocity, mean arterial pressure, arterial blood gases, haemoglobin and haematocrit. Statistics included t-test, two-way analysis of variance, Mann-Whitney-U-test and Spearman correlation with p < 0.05 considered significant. RESULTS: Regarding demographic data and intraoperative parameters, both study groups (ACBG vs. AVR) were comparable except for age. AVR patients showed significantly more MES than those undergoing ACBG (p < 0.012) which was most pronounced in the late state of surgery (aortic clamp off; p < 0.0003). However, MES counts did not correlate with neuropsychiatric test results. CONCLUSIONS: In contrast to recent reports, we were unable to show a deterioration of postoperative neuropsychiatric state related to high intraoperative MES count in our patients. Future TCD studies should focus on the differentiation between gaseous emboli and particles even in the clinical setting, as the latter may well play a major role for the development of cerebral dysfunction following cardiac surgery and extracorporeal circulation.

Analysis of Variance↗
PubMed1997

[CADASIL: 2 case reports of hereditary multi-infarct dementia].

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary stroke disease linked to chromosome 19 q 12. We report on two families affected by this disease, which is characterised by recurrent subcortical ischaemic strokes, progressive pseudobulbar palsy, and presenile dementia. Neuroimaging revealed multiple deep infarcts and diffuse leukoencephalopathy. Diagnosis of CADASIL based on the typical clinical feature without vascular risk factors, the neuroradiological signs of extensive leukoencephalopathy, and the autosomal dominant pattern of inheritance. CADASIL might be an underestimated cause of familial stroke and should be considered in the differential diagnosis of hereditary stroke.

Brain↗
PubMed1997

Comparison of ultrasonic and histopathological features of carotid artery stenosis.

Besides the degree of carotid artery stenosis, the composition of the plaque may help to predict the thromboembolic risk. Low echogenicity on ultrasound and hemorrhage into the atheroma demonstrated histopathologically have been shown to be associated with a higher risk of embolism. Twenty-nine consecutive patients with carotid artery stenosis and scheduled for carotid endarterectomy were investigated preoperatively by B-mode ultrasound. Post-operatively the endarterectomy specimens were examined histopathologically. Neither atheroma with hemorrhage nor atheroma without hemorrhage were significantly associated with echolucent ultrasound presentation. Out of the 10 lesions echolucent and homogeneous on ultrasound, six corresponded to atheroma with hemorrhage, two corresponded to atheroma with hemorrhage plus thrombus, two corresponded to fibrous plaque plus thrombus, and one corresponded to pure thrombus. Out of the 4 lesions heterogeneous and predominantly echolucent, one corresponded to atheroma without hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage, one corresponded to atheroma with hemorrhage plus thrombus, one corresponded to atheroma with hemorrhage plus fibrous plaque. Seven out of the 18 atheromas with hemorrhage did not present as purely or predominantly echolucent lesions, six of them were even homogeneously echogenic. Plaque surface could not reliably be predicted by ultrasound. In our study, there was no significant correlation between ultrasound and histology of the lesion.

Aged↗