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Biomedical subjects

R Loose

Publications and source records attributed to R Loose.

At least 19 recordsLinked to original sources
PubMed2002

[Quality assurance with teleradiology].

Teleradiology offers many applications for quality assurance in medicine. The spectrum reaches from electronic consultations in emergency or special cases and double reading--along with new models of cooperative work and medical networks--to technical quality assurance and integration into interinstitutional and patient controlled health records. Regional teleradiology networks based on server concepts can fulfill the developing technical and organisational requirements. The increasing mobility arising from smaller radiological equipment and improved accessibility to experts with minimized visualisation and reporting systems will change the radiological world of tomorrow, especially in combination with the usage of knowledge based systems in reference data bases and computer assisted diagnosis (CAD). Teleradiology by itself must be liable to quality assurance measurements to prevent unnecessary radiation exposure or danger to the doctor patient relation.

Computer Communication Networks↗
PubMed2002

MELAS: a neuropsychological and radiological follow-up study. Mitochondrial encephalomyopathy, lactic acidosis and stroke.

We report on a patient with long standing, full-blown mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). In contrast to earlier publications, detailed neuropsychological assessment revealed no dementia but a pattern of distinct cognitive deficits with marked impairment of visuo-constructive and executive functions. Focal lesions and progressing atrophy mainly of the basal ganglia and the temporo-parieto-occipital area with preservation of hippocampal and entorhinal structures were present. Furthermore, a 4-year follow-up assessment revealed an increasing deterioration of distinct cognitive functions, including phasic alertness, tactile functions and the discrimination of tone pitch and rhythm. This may be because of chronic regional metabolic disturbances, as there was no further stroke-like episode in that period of time.

Adult↗
PubMed2002

[Ultrasound-guided puncture of the subclavian vein to implant central venous ports].

PURPOSE: To assess the safety and efficacy of ultrasound guided puncture of the subclavian vein instead of blind puncture or surgical procedure. The advantages compared with implantation of brachial ports are demonstrated. PATIENTS AND METHODS: In 41 oncologic patients the subclavian vein was punctured by ultrasound guidance in order to implant a port (34 left side, 7 right side). The study included 21 women and 20 men (range 34 - 79, mean 61 years). Imaging of the subclavian vein was performed with a 7,5 MHz linear ultrasound probe in B-mode and in colour doppler mode. Puncture was performed under ultrasound control (18 G, 45 mm needle when skin-vessel distance was < 3 cm, 19 G, 75 mm needle when skin-vessel distance was > 3 cm). In 27 patients a Bardport was implanted, in 14 patients a Vitalport (Cook). In three patients surgical port implantation failed. One of these patients had a partial thrombosis of the subclavian vein. RESULTS: Technical success was 100 %. In one patient we first punctured the subclavian artery at the beginning of our series without any complication. All port systems could be implanted. There was one haematoma in the port pocket without any effect to the port function. In the three surgical patients subclavian vein puncture and portimplantation was successful. CONCLUSION: Ultrasound guided puncture of the subclavian vein and port implantation by radiologists is a save procedure. A low risk approach to the subclavian vein is possible at any location. The long approach through the cubital vein with brachial port implantation is not necessary.

Adult↗
PubMed2001

Magnetoencephalographic response characteristics associated with tongue movement.

Whole-head magnetoencephalography (MEG) was employed to study the sources of activation evoked by both active tongue movement and swallowing in five healthy subjects. Evoked magnetic fields were adequately explained in both paradigms by a time-varying single-dipole model which localized in the tongue in all subjects. No additional brain sources were detectable. Therefore, MEG detects fields associated with tongue movement that best fit a single-dipole source in the tongue. Future electrophysiological brain activation studies where tongue movement is likely should be aware of this observation since the tongue behaves like a strong current dipole.

Adult↗
PubMed2001

Investigations of the mechanism of membrane activity of selected triterpenoid saponins.

The experiments with different triterpenoid saponins showed a significant difference in the microphysiometric activity between acylated and non-acylated compounds. Only acylated saponins in low concentrations were able to activate the metabolism of endothelial cells after short-time incubation in a transient manner lasting approximately 2 hours. The strongest effect was produced by virgaureasaponin b, an incubation with 4 microg/ml over 6 min induced a stimulation of the metabolic activity of 190% maximum after 30 min. This treatment did not induce non-reversible toxic effects, and could be repeated in the same way after a recovery period. The saponins without acylation in the glycosidic part did not induce metabolic stimulation, even in concentrations higher than observed for the acylated compounds. The current interpretation of the results is connected with the suggestion that especially acylated saponins are able to integrate into the cellular membrane transiently. This integration might induce pore-like structures which change the membrane permeability associated with alterations in the ionic homeostasis between intracellular and extracellular compartments.

Animals↗
PubMed2001

Velocity not acceleration of self-motion mediates vestibular-visual interaction.

We investigated the influence of vestibular stimulation with different angular accelerations and velocities on the perception of visual motion direction. Constant accelerations resulting in different angular velocities and constant angular velocities obtained at different accelerations were combined in twenty healthy subjects. Random-dot kinematograms with coherently moving pixels and randomly moving pixels were used as visual stimuli during whole-body rotations. The smallest percentage of coherently moving pixels leading to a clear perception of motion direction was taken as the perception threshold. Perception thresholds significantly increased with increasing angular velocity. Increased acceleration, however, had no significant effect on the perception thresholds. We conclude that the achieved angular velocity, and not acceleration, is the predominant factor in the processing of vestibular-visual interaction.

Adult↗
PubMed2000

Teleradiology requirements and aims in Germany and Europe: status at the beginning of 2000.

Specific radiological requirements have to be considered for realization of telemedicine. In this article the goals and requirements for an extensive implementation of teleradiology are defined from the radiological user's point of view. Necessary medical, legal and professional prerequisites for teleradiology are presented. Superior requirements, such as data security and privacy or standardization of communication, must be realized. Application specific requirements, e. g. quality and extent of teleradiological functions as well as technological alternatives, are discussed. Each project must be carefully planned in relation to one's own needs, extent of functions and system selection. Topics like legal acceptance of electronic documentation, reimbursement of teleradiology and liability must be clarified in the future.

Europe↗
PubMed2000

Intra-arterial Doppler flowmetry in the superficial femoral artery following angioplasty.

The aim of the study was to assess the diagnostic value of an intravascular Doppler guidewire in patients with peripheral percutaneous angioplasty (PTA). The prognostic value was also evaluated. Measurements were done prior and following angioplasty in 22 patients with peripheral arterial occlusive disease. As additional therapy, stent insertion and peripheral (Aa. poplitea Tll/tibial) angioplasty was performed (4 patients per group). For stress testing, adenosinetriphosphate (ATP) was given intra-arterially. Follow-up was performed by angiography, colour-coded duplex ultrasound or judged by unequivocal clinical stage at follow-up to 13 months. Average (APV) and maximal peak velocity (MPV) increased following PTA, after additional treatment (peripheral PTA or stent), and after intra-arterial application of a vasodilator. Patients with peripheral lesions had markedly lower velocities prior treatment and following PTA after vasodilatation. Following peripheral PTA, the values were similar to the patients with PTA alone. Velocities after stenting were markedly increased in the stress condition. Of the 22 patients, 7 had a recurrent disease. The latter patients had higher velocities at rest prior to and following PTA. In stented lesions higher velocities seem to be linked with a worse outcome. The ratio between velocity prior to and after the application of the vasodilator seems to be of diagnostic importance. A ratio of 1.9 or more was of positive prognostic value. The Doppler guidewire is a practical and valuable tool in assessing technical success after angioplasty of peripheral lesions, critical or morphologically worse lesions. In our study the decision for stent application was made on the morphological image; however, increased velocity and changes in phasicity substantiated our decisions. Increased ratios prior to and after vasodilation (flow reserve) are of prognostic value and therefore suitable as indication for stent placement or tibial angioplasty.

Adult↗
PubMed2000

Cortical activations during paced finger-tapping applying visual and auditory pacing stimuli.

In order to study neural systems which are involved in motor timing we used whole-brain functional resonance imaging while subjects performed a paced finger-tapping task (PFT) with their right index finger. During one condition, subjects were imaged while tapping in synchrony with tones separated by a constant interval (auditory synchronisation, AS), followed by tapping without the pacing stimulus (auditory continuation, AC). In another condition, subjects were imaged while tapping in synchrony with a visual stimulus presented at the same frequency as the tones (visual synchronisation, VS) followed by a tapping sequence without visual pacing (visual continuation, VC). The following main results were obtained: (1) tapping in the context of visual pacing was generally more variable than tapping in the context of auditory stimuli; (2) during all conditions, a fronto-parietal network was active including the dorsal lateral premotor cortex (dPMC), M1, S1, inferior parietal lobule (LPi), supplementary motor cortex (SMA), the right cerebellar hemisphere, and the paravermial region; (3) stronger activation in the bilateral ventral premotor cortex (vPMC), the left LPi, the SMA, the right inferior cerebellum, and the left thalamus during both auditory conditions (AS and AC) compared to the visual conditions (VS and VC); (4) stronger activation in the right superior cerebellum, the vermis, and the right LPi during the visual conditions (VS and VC); (5) similar activations for the AS and AC conditions; but (6) marked differences between the VS and VC conditions especially in the dorsal premotor cortex (dPMC) and LPi areas; and (7) finally, there were no activations in the auditory and visual cortices when the pacing stimuli were absent. These findings were taken as evidence for a general difference between the motor control modes operative during the auditory and visual conditions. Paced finger tapping in the context of auditory pacing stimuli relies more on brain structures subserving internal motor control while paced finger-tapping in the context of visual pacing stimuli relies on brain structures relying on the subserving processing or imagination of visual pacing stimuli.

Acoustic Stimulation↗
PubMed2000

Proximal aortic dissection late after aortic valve surgery: 119 cases of a distinct clinical entity.

BACKGROUND: Besides systemic hypertension and Marfan syndrome, only previous aortic valve replacement (AVR) is independently associated with proximal (type A) aortic dissection. Little, however, is known to date about the characteristic features of this clinical entity. METHODS: Clinical, prognostic and predisposing profiles in 119 cases of dissection and/or aneurysm occuring 1 month to 16 years after routine AVR were analyzed comprising 62 cases from our database and 57 reported cases. RESULTS: Dissection after AVR has been observed in 0.6% of all routine AVR procedures in the past four decades. With clinical signs, symptoms and anatomical features different from classic aortic dissection post-AVR dissection is a distinct clinical entity with a high intraoperative mortality of 44% and a 30-day and 5-year survival of 62% and 43%, respectively. Aortic regurgitation and a thin and/or fragile aortic wall at AVR, however, predict late dissection. Using a prediction model, the risk of late dissection can be stratified based on information obtained during AVR surgery. CONCLUSIONS: Aortic dissection following AVR is likely to represent a distinct clinical entity which can be predicted and possibly prevented at AVR.

Aged↗
PubMed1999

Predictors of proximal aortic dissection at the time of aortic valve replacement.

BACKGROUND: Type I aortic dissection develops in 0.6% of patients late after aortic valve replacement (AVR), and 13% of patients with type I aortic dissections have a history of AVR. Predictors of aortic dissection at AVR, however, have not been characterized. METHODS AND RESULTS: A study group of 33 patients with type I aortic dissection had aortic surgery 49+/-55 months after routine AVR. A group of 101 controls, who did not have morphological progression of aortic diameters >/=6 years after AVR, was used to identify predictors of postsurgical dissection. Multivariate analysis identified aortic regurgitation (P<0.002) and fragility (P<0.001) or thinning of the aortic wall (P<0.007) at AVR as predictors, associated with a 14%, 22%, and 7% probability of late aortic dissection, respectively. Clamping times, types of valve prostheses, concomitant coronary artery bypass grafting, and mean ascending aortic diameters of 43+/-10 mm at AVR did not predict late dissection. A separate analysis of 29 nondissecting aneurysms of the ascending aorta developing 104+/-64 months after routine AVR revealed younger age at AVR (P<0.003) and congenitally bicuspid aortic valves (P<0.03) as predictors of late aneurysm formation. CONCLUSIONS: Aortic regurgitation combined with fragile and thinned aortic walls in patients with moderate aortic dilation may reflect aortic root disease, with a high risk for postsurgical aortic sequelae if it is treated incompletely by isolated valve replacement.

Adult↗
PubMed1999

[Severe pulmonary hypertension in systemic lupus erythematosus. The successful therapy of an unusual manifestation].

UNLABELLED: OBJECTIVE AND CLINICAL FINDINGS: A 48-year-old woman was hospitalized because of haemoptysis. Until shortly before admission she had been on phenprocoumon after pulmonary embolism sustained 18 months previously. Six months before admission systemic lupus erythematodes (SLE) had been diagnosed and treatment with cortisone initiated. Physical examination revealed jugular venous congestion, tachycardia, dyspnoea on even minimal physical activity and pretibial oedema. INVESTIGATIONS: Lung scintigraphy showed a perfusion deficiency in the right lung, unchanged since a test 18 month before. Doppler echocardiography recorded an estimated pulmonary artery systolic pressure of 110 mm Hg. Angiography showed a fully patent superior vena cava and nearly complete occlusion of the main right pulmonary artery by a thrombus. DIAGNOSIS, TREATMENT AND COURSE: The haemoptyses ceased after 5 days of treatment with methylprednisolone, 130 mg daily for 5 days, reduced after 5 days to 80 mg i.v. every other day, plus cyclophosphamide, 50 mg daily by mouth. The pulmonary hypertension remained unchanged so that pulmonary thrombendarterectomy was indicated. Surgery revealed extensive mediastinal fibrosis and almost complete occlusion of the thick-walled right pulmonary artery by thrombus adherent to the wall. Histology showed vasculitis of the pulmonary arterial intima and of the small pulmonary vessels. After thrombectomy the pulmonary arterial systolic pressure fell to an remained at below 40 mm Hg. Phenprocoumon was continued (at an INR of 2.5-3.5) as was immunosuppressive treatment. The patient has remained free of symptoms and is able to be physically active. CONCLUSION: Pulmonary hypertension is a serious complication of SLE. Echocardiography is recommended for both the original diagnosis and serial follow-up, complemented by other imaging methods if indicated.

Acute Disease↗
PubMed1999

Visual motion direction evoked potentials are direction specifically influenced by concurrent vestibular stimulation.

We investigated the influence of vestibular stimulation on visual motion-direction perception using electrophysiological recordings. Visual motion-direction evoked potentials decreased in area during the rotation of subjects about their vertical z-axis, when visual and vestibular motion directions were incongruous (visual and vestibular stimulation in the same directions). Visual pattern onset evoked potentials, however, remained unaffected by vestibular stimulation. For rotations about the interaural y-axis, decreased area of visual-direction evoked potentials was found for both congruous and incongruous combinations of visual and vestibular stimulation. The results are in accordance with previous psychophysically obtained data and discussed in terms of postnatal development and neurophysiological optimization processes. An interaction model focused on reciprocal inhibition of the middle temporal visual (MT) area and the medial superior temporal (MST) area is presented.

Adult↗
PubMed1999

Cortical activation during oesophageal stimulation: a neuromagnetic study.

We investigated the neuromagnetic responses to mechanical stimulation of the oesophagus. In six healthy right-handed volunteers (mean age 31.6 years) the proximal and distal oesophagus were stimulated by electronically controlled pump-inflation of a silicone balloon once every 4.5-5.5 sec (dwell time 145 msec). The balloon volume was adjusted to induce different sensation levels (i) just above threshold of perception, (ii) strong sensation and (iii) painful sensation. Evoked magnetic brain responses were recorded time-locked to stimulus onset with a Neuromag-122TM whole-head neuromagnetometer and modelled as equivalent current diploe (ECD) sources. ECDs were superimposed on individual magnetic resonance imaging (MRI) scans. Magnetic brain responses following distal oesophageal stimulation were adequately explained by a time-varying 2-4 dipole model with unilateral or bilateral sources in second somatosensory cortex and later sources in the frontal cortex. With increasing stimulus intensities, latencies of the sources decreased and amplitudes increased. Proximal oesophageal stimulation led to activation of source areas spatially similar to those of distal oesophageal stimulation but with shorter response latencies. Both painful and nonpainful mechanical stimulation of the oesophagus activate the second somatosensory cortex (SII). Evidence for topographic organization of oesophageal afferents in SII is poor.

Adult↗
PubMed1999

Inhibition of lipopolysaccharide (LPS)-induced endothelial cytotoxicity by diosmin.

The cytotoxic effect of lipopolysaccharide (LPS) on cultivated bovine aortic endothelial cells was determined. This LPS-induced cytotoxicity was attenuated by diosmin. That means, the IC50 value of LPS in the combination with 8 mumol/l diosmin was shifted from 31 to 70 ng/ml in a concentration dependent manner. As a hypothesis it was suggested, that the inhibition of LPS-induced cytotoxicity in bovine aortic endothelial cell cultures by diosmin could be probably mediated via inhibition of tyrosine kinases.

Animals↗