Biomedical subjects

P Várady

Publications and source records attributed to P Várady.

4 recordsLinked to original sources

PubMed2005

Speech activation SPECT and plasticity of language networks.

Neuronal activity might be measured by regional cerebral blood flow (rCBF) Single Photon Emission Computed Tomography (SPECT) as there is a close relationship between neuronal activity and rCBF changes. In order to study the hemispheric dominance for language and the plasticity of language networks by measuring the rCBF rest and language activation SPECT studies were performed in the presurgical evaluation of ten right-handed and two left handed patients with brain lesions of the dominant hemisphere. A special group of hemisphere-specific neuropsychologic tasks were used for activation, after a proper psychologic conditioning. The rCBF results were calculated by comparing the rest and activation SPECT data using a special regions of interest program and asymmetry index (AI). We compared the results of speech-activation to the results of clinical, morphological (MRI), and postoperative data. In controls, significant activation was found in Brodmann's area 44 and 45, contralateral cerebellum, superior middle and posterior temporal gyrus. In patients, additional regions of activation were seen in contralateral frontal and temporal regions, and in ipsilateral temporal region. AIs of the cerebellum demonstrated a negative correlation with hemispheric dominance for language. In conclusion, significant changes in rCBF in or adjacent to the eloquent areas with various patterns of rCBF changes of the additional regions demonstrate the close relationship between neuronal activity and cerebral blood flow, that can be measured by SPECT.

Adolescent↗

PubMed2001

[Fetal phonocardiography with a novel approach].

The long-term recording of the fetal heart rate (FHR) variability is one of the most frequently used tools of routine fetal diagnostics which is usually carried out by the means of ultrasound cardiography. Frequent measurement of FHR is recommendable, however the cost of high quality ultrasound devices is unfortunately so high that this technology is not viable for low-cost devices used in the home-care sector. An alternative approach of FHR recording can be based on the fully non-invasive, passive acoustic recording, called phonocardiography. The evaluation of fetal phonocardiograms is complicated by various internal and external noise factors. The development of accurate and robust fetal phonocardiographs has been studied by biomedical researchers since long. This paper presents a novel two-channel phonocardiographic device and an advanced signal processing method, which provides a performance comparable to that of ultrasound cardiography. The proposed system offers an optimal trade-off between complexity and feasibility and it is viable in low-cost, stand-alone, battery-powered FHR monitoring devices. The developed system provided 83% accuracy compared to the simultaneously recorded reference ultrasound records.

Artifacts↗

PubMed2000

A hybrid on-line ECG segmenting system for long-term monitoring.

This paper introduces a new hybrid ECG beat segmenting system, which can be applied in the processing unit of single-channel, long-term ECG monitors for the on-line segmentation of the ECG signal. Numerous ECG segmentation techniques are already existing and applied, however sufficiently robust and reliable methods currently require more than one ECG signal channel and quite complex computations, which are practically not feasible in stand-alone, low-cost monitors. Our new system approach presents a time domain segmentation technique based on a priori physiological and morphological information of the ECG beat. The segmentation is carried out after classifying the ECG beat, using the linear approximation of the filtered ECG signal and considering the pathophysiological properties as well. The proposed algorithms require moderate computational power, allowing the practical realization in battery powered stand-alone long-term cardiac monitors or small-sized cardiac defibrillators. The prototype version of the system was implemented in Matlab. The test and evaluation of the system was carried out with the help of reference signal databases.

Algorithms↗

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↗