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Biomedical subjects

I Nyáry

Publications and source records attributed to I Nyáry.

At least 19 recordsLinked to original sources
PubMed2001

[Radiosurgery of the brain at the beginning of the 21st century: gamma knife with C-table].

The goal of stereotactic radiosurgery by definition is "the delivery of a single, high dose of radiation allowing the precise and complete destruction of chosen target structures containing healthy and/or pathological cells, without significant concomitant or late radiation damage to adjacent tissues". This effect is obtained by the precise focusing of multiple low energy radiation beams crossing at the target. Three different techniques can be used for radiosurgery: linear accelerator (LINAC) based radiosurgery, Bragg-peak (proton) therapy and Gamma Knife radiosurgery. Leksell Gamma Knife (LGK) is a dedicated neurosurgical device for brain surgery to destroy predetermined intracranial targets through the intact skull. It operates via the radiobiological effect of stereotactically directed, highly focused ionizing gamma-beams of 201 cobalt-60 sources. The LGK offers the best precision of target during irradiation. The mechanical accuracy is about 0.3 mm, which makes it particularly suitable for highly sophisticated neurosurgical interventions. Radiosurgery was originally developed to treat functional neurological disorders, but soon after its introduction cerebral arteriovenous malformations, and brain tumors became the main targets for the technique. Since the first LGK installation at the Sophiahemmet Hospital, Stockholm, Sweden in 1967, over 150,000 patients have already been treated in more than 150 units worldwide. The accumulated clinical experience with the LGK has established this method as the "golden standard" of radiosurgery. In December 1999, a new development, the LGK Model-C was installed at the Centre Gamma Knife, Université Libre de Bruxelles, Hôpital Académique Erasme, Brussels, Belgium. This was followed by completion of two similar units in Krefeld, Germany, and at the Presbyterian University Hospital, Pittsburgh, Pennsylvania, U.S.A. The major innovation in the design of the LGK Model-C is the robotic Automatic Positioning System, which allows computer-controlled automatic and sequential positioning of multiple shots during treatment. Thus all steps of the procedure are performed through an unbroken digital chain, from stereotactic image acquisition to the control of the irradiation sequence. This represents a significant achievement which increases the accuracy and practicality of the treatment. The technical details of the method are described, and the main treatment indications are reviewed.

Brain Neoplasms↗
PubMed2000

[Neuronavigation in pediatric neurosurgery].

The precise orientation in the intracranial space is essential for the minimal invasive neurosurgical interventions. The CT and MR based neuro-navigation permits small, targeted exposures on the skull, and intraoperatively gives exact graphic-interactive guidance to the targeted intracranial lesions. The use of neuro-navigation can shorten the time of surgery and diminish the surgical mortality and morbidity. The favourable experiences of the first 21 neuro-navigation aided operations in pediatric patients performed in the National Institute of Neurosurgery (Budapest, Hungary) with the Vector Vision Neuro-navigation System (BrainLAB Gmbh, Germany) are discussed.

Adolescent↗
PubMed1999

[Speech activation SPECT measurements in the determination of hemispheric dominance].

Cognitive activity leads to an increased regional cerebral blood flow (rCBF) and energy metabolism in both cerebral hemispheres. In order to assess the reliability of rCBF-SPECT measurements in hemispheric dominance (Broca's area) speech activation SPECT studies were performed in nine patients. Patients (men, n = 6; women, n = 3, mean age: 33.8 +/- 13.8 years) with diagnosis of epilepsy (n = 7) and AVM (n = 2) participated in the preoperative study. Two SPECT studies were performed in each case, one in rest, and one during speech activation. 740 MBq of 99mTc-HMPAO/ECD was injected and stereo TCD monitoring was performed during the three minutes of speech activation. The acquisition was performed by a dual-head ADAC Solus Epic Atlas SPECT camera (ADAC Laboratories, Milpitas, USA). RCBF SPECT measurements were analyzed visually and by a special region-of-interest (ROI) program. The hemispheric dominance profiles were established on the basis of the respective blood flow velocity values obtained by fTCD and cortical hyperperfusion measured by SPECT. The neuropsychological test battery, used in the present study, was developed in our institute. The results of rCBF-SPECT studies highly correlated with the lateralization of hemispheric dominance measured by fTCD. There was a significant increase of rCBF in the inferior posterior frontal cortex (Broca's area, p < 0.0003). The non-invasive speech activation rCBF-SPECT measurement is a highly reliable and useful method in the determination of hemispheric dominance. SPECT studies are especially useful in cases where the performance of fTCD measurements are impossible due to the lack of temporal bone window or occlusive cerebral arterial disease.

Dominance, Cerebral↗
PubMed1999

[Positron emission tomography ia an effective tool in modern oncology].

A total of 399 positron emission tomography (PET) examinations were carried out with a GE 4096 Plus PET scanner during the past 5 years on patients referred to the National Institute of Oncology in Budapest. The majority (n = 316) of these investigations were performed with the use of [18F]-fluorodezoxyglucose (FDG) to map the glucose metabolism; [11C]-methionine PET was indicated in 79 cases to detect protein transport and metabolism. The perfusion tracer [15O]-butanol was applied in only 4 cases to answer certain oncology-related, differential diagnostic questions. The oncological examinations were related to primary diagnostics, staging/restaging and therapy monitoring. In the staging/restaging and therapy monitoring of known tumours, conclusive results were achieved in 81-82% of the cases by using either FDG or [11C]-methionine as tracer. The concordant numerical data indicated that the PET investigation provides a definite answer to the question of the presence or absence of viable tumour tissue, with similar effectivity in any of the above indications, no matter whether FDG or [11C]-methionine is used. The search for occult primary tumours was the most frequent indication within the primary diagnostics: 10 (37%) primaries were localized by using FDG PET in the 27 investigated cases. This is a remarkably high value, especially in view of the failure of all the conventional diagnostic procedures carried out prior to the PET investigations. Application of PET may be indicated in all cases when the ultimate question is a non-invasive estimation of viable tumorous tissue.

Fluorodeoxyglucose F18↗
PubMed1999

[Neurosurgery using the Gamma Knife].

Gamma Knife radiosurgery is a neurosurgical technique dedicated to treat a wide spectrum of intracranial pathologies. Radiosurgery is a method employing a single fraction of high dose ionizing radiation beams focused on the stereotactically defined intracranial target volume through the intact skull. This precise irradiation of intracranial volumes can necrotize the targeted cell mass--as in treatments of tumors and functional syndromes--or may induce certain biological effects in the target tissue-as in treatments of AVM's and epilepsy--without imposing a significant risk on the neighboring intact neural tissues. The clinical application of Gamma Knife includes a wide range of neurosurgical indications, such as treatments of arteriovenosus malformations, pituitary adenomas, craniopharyngiomas, meningiomas, vestibular schwannomas, gliomas, metastatic tumors, as well as functional neurosurgical syndromes, such as trigeminal neuralgia, extra-pyramidal dysfunctions, epilepsy, pain- and psychiatric syndromes. The clinical effect of irradiation is not immediate, it becomes detectable on follow up studies after a few months. The application of the technique is determined by the histological type, size and location of the pathology. Gamma Knife has evolved to become an established alternative to opened cranial surgery in certain cases with low morbidity and no mortality, offering a safe neurosurgical treatment for inoperable as well as operable lesions that carry significantly high surgical risk. In our review we present the technical and radiobiological principles, clinical indications, limitations and outcome results of this method. Our data are based on the practice and results of the Lars Leksell Center for Gamma Surgery, Department of Neurosurgery, University of Virginia, Charlottesville, Virginia, USA (Director: Ladislau Steiner dr.).

Arteriovenous Malformations↗
PubMed1998

[The gamma-knife in stereotaxic surgery. A new era in brain surgery].

The gamma knife is a dedicated neurosurgical equipment for brain surgery to treat predetermined intracranial normal or pathological targets through the intact skull without damaging the surrounding normal brain tissue. The operating method is called radiosurgery and it works with the biological effect of stereotactically directed, highly focused ionizing beams of 201 independent cobalt-60 sources. The treatment is a single day procedure with obvious advantages over the invasive conventional craniotomy-related surgery. It has the benefits of increased biological efficacy of the irradiation along with decreased hospital stay and side effects. The device and radiosurgery was originally developed to treat functional neurological diseases, but very soon arteriovenous malformations and tumours became the main objects for the method, and a new dimension opened in the treatment of brain pathologies with difficult access. The first gamma knife was installed in Stockholm, Sweden in 1968. Since then 85 units have been set up, and more than 70,000 patients were treated with the device worldwide. The simple management technique and high mechanical and beam accuracy made the gamma knife a reliable and effective tool for its intended purpose over 30 years now. This review summarizes the history of the device, the basic radiation physics and biology related to stereotactic radiosurgery, the description of the unit and the possibilities and limits of the treatment modality.

Brain↗
PubMed1997

[First Hungarian experiences with positron emission tomography (PET) studies. Members of the PET working group].

Diagnostic investigations commenced on the 28th of June 1994 in Hungary's and Central Europe's first PET Centre at the University Medical School of Debrecen. The Centre is equipped with a GE 4096 Plus whole body PET scanner. A metabolic tracer, 18F-deoxy-D-glucose (FDG), was used in the investigations. During the first 15 months 249 PET investigations were made in the Centre of which 242 were diagnostic and 7 normal subjects served as control for the patient studies with brain scans. The number of oncological indications (intra- and extracranial tumours, Hodgkin's lymphomas) was n = 105 (43.4% of the 242 diagnostic examinations), neurological investigations (without intracranial tumours) formed the dominant group (n = 117; 48.3%), whereas the number of cardiological indications was 20 (8.3%). The oncological studies included those of intracranial tumours (n = 76; 31.4%); thyroid tumours (n = 9; 3.7%); Hodgkin's lymphomas (n = 7; 2.9%) and other extracranial tumours (n = 13; 5.4%). The distribution of different neurological and psychiatric investigations was as follows: localization of focal epileptogen zone (n = 60; 24.8%); differential diagnosis of dementias (n = 30; 12.4%); exploration of cerebrovascular diseases (n = 10; 4.1%); and other neurological diseases (n = 17; 7.0%). The main objective of the cardiological PET investigations was the exploration of viable myocardium. The present paper overviews both the procedures (including administrative issues, as well) and the results of the first 249 FDG-PET investigations.

Aged↗
PubMed1996

Tumors of the cerebellopontine angle. Changing policy in treatment.

One hundred and twenty-six cases of cerebellopontine angle tumors with various histologies are presented. Results of 75 operated vestibular neurinomas, 22 meningiomas, and 16 tumors with other histologies are discussed. The method of irradiation and non-radical surgery may be an alternative for treatment.

Anastomosis, Surgical↗
PubMed1996

Endogenous opioid mechanisms in hypothalamic blood flow autoregulation during haemorrhagic hypotension and angiotensin-induced acute hypertension in cats.

The influence of naloxone-induced general opiate receptor blockade on hypothalamic blood flow autoregulation was investigated in anaesthetized, artificially ventilated, temperature controlled cats. In order to study the changes of the hypothalamic blood flow (H2-gas clearance technique) at the lower limit of autoregulation systemic arterial pressure was reduced in a stepwise manner to 100, 80, 60 and 40 mmHg, by haemorrhage. Autoregulatory mechanisms of the hypothalamic vessels remained effective and hypothalamic blood flow showed no significant reduction until the arterial pressure was reduced to 60 mmHg in the vehicle-treated control cats. General opiate receptor blockade by 1 mg kg-1 mL-1 i.v. injected naloxone resulted in a significant reduction of the autoregulatory capacity of the hypothalamic vessels: the blood flow followed passively the arterial pressure fall already from 100 mmHg mean arterial pressure. The effect of opiate receptor blockade on the upper limit of the autoregulation was studied during acute arterial hypertension, induced by angiotensin-II infusion (25 micrograms 0.1 mL-1 min-1 i.v.). Hypothalamic blood flow remained remarkably steady following angiotensin-II infusion in the saline-treated control animals. Naloxone pretreatment (1 mg kg-1 mL-1 i.v.), however, induced a significant downward shift of the upper limit of the autoregulation, and hypothalamic blood flow started to increase in the 125-145 mmHg arterial pressure range. The narrowing of the autoregulatory range following general opiate receptor blockade suggests an important role of endogenous opioid peptides in hypothalamic blood flow autoregulatory mechanisms both in hypotensive and in hypertensive conditions.

Angiotensin II↗
PubMed1996

Regional heterogeneity and differential vulnerability of cerebral and spinal vascular CO2-responsiveness during graded haemorrhagic hypotension.

Regional inhomogeneity of cerebrovascular CO2-sensitivity as well as its changes at three different levels of standardized haemorrhagic hypotension were studied in ten distinct brain and spinal cord regions of anesthetized, ventilated cats. Regional cerebral blood flow was measured with radiolabelled microspheres in hypocapnic, normocapnic, and hypercapnic conditions, and CO2-responsiveness was determined from the equation of the slopes of the best fit regression lines to the obtained flow values. It was concluded that in normotensive, normoxic cats response of the cerebral and spinal vessels to PaCO2 alterations can be assigned to four major categories. The CO2-responsiveness of a brain region is not solely determined by the rate of its basal steady state blood flow: CO2-reactivity of the hypothalamus was significantly different from that of any other investigated regions with almost identical steady state flow values. Vulnerability of the cerebrovascular CO2-sensitivity during hypotension was different from region to region, with the vessels of the pons-medulla oblongata region being the most sensitive to haemorrhage. Reduced regional cerebral and spinal CO2-responsiveness during haemorrhage is not a consequence of a reduced L-arginine supply for nitric oxide generation since administration of an excess amount of the precursor L-arginine failed to restore the haemorrhage-induced reduction of regional CO2-sensitivity at the 60 mm Hg mean arterial pressure level.

Animals↗
PubMed1990

Stroke rehabilitation: a method and evaluation.

Subjects of this study were 53 patients who presented with cerebrovascular stroke and who took part in a rehabilitation programme that included the basic elements of Bobath's concept and Peto's Conductive Education. The protocol called for a three point assessment: on admission to the rehabilitation ward and at one month and one year after entry. Baseline and follow-up examinations included clinical and laboratory tests, CT scan, cerebral blood flow studies and angiography. Motor functions were evaluated by the Rivermead Motor Assessment and dependence (ADL) was measured by the Barthel index. Neuropsychological evaluations were also made using Benton's test, Bourdon's letter cancellation test and the Wechsler Adult Intelligence Scale. Significant improvement was found in functional conditions both one month and one year after entry. There was a strong correlation between the Rivermead Motor Assessment and the Barthel index. The Rivermead Motor Assessment proved to be the most sensitive indicator of improvement in relation to the size and site of the infarct.

Activities of Daily Living↗
PubMed1988

Contralateral approach to bilateral and ophthalmic aneurysms.

In a previous survey, we found a high incidence of fatal rupture of an unclipped aneurysm in patients with multiple aneurysms. To deal with this problem, we introduced a more vigorous technique that accesses aneurysms previously considered unapproachable during one operating session. Attempts were made to clip middle cerebral and ophthalmic aneurysms contralateral to the operative exposure. We have successfully clipped contralateral aneurysms of the posterior communicating artery when bilateral aneurysms were present. We have also used this contralateral approach successfully with single ophthalmic and proximal carotid aneurysms that pointed medially. We review the cases of 39 patients with 43 intracranial aneurysms operated from the contralateral side and present the surgical technique in relation to the angiographic findings.

Adult↗
PubMed1984

Late reopening of an interposed vein graft for EC/IC bypass.

The authors report a case of EC/IC bypass with venous interposition between the external carotid artery and the middle cerebral artery cortical branch without function in the first eight months after surgery but, after the reopening of the graft, very good revascularization of the brain could be seen. The possible causes are discussed.

Brain Ischemia↗
PubMed1982

Dependency on bypass circulation: a case study.

In a case of consecutive occlusion of both internal carotid arteries bilateral STA-MCA anastomoses were established. Since a series of angiographic examinations were undertaken, dynamics and probable efficacy of both natural and artificial collateral circulations could be followed up in a two-year period. Objectively in the evaluation of anastomoses was enhanced by direct percutaneous STA-angiography (STAG), in order to delineate the vascular territory irrigated exclusively by the anastomosis. By demonstrating exactly the functional capacity of anastomoses in correlation with the clinical course, dependency on bypass circulation could be assessed.

Arterial Occlusive Diseases↗