Vlad Toronov

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The aim of this study was to compare functional cerebral hemodynamic signals obtained simultaneously by near infrared spectroscopy (NIRS) and by functional magnetic resonance imaging (fMRI). The contribution of superficial layers (skin and skull) to the NIRS signal was also assessed. Both methods were used to generate functional maps of the motor cortex(More)
To study the behavior of cerebral physiological parameters and to further the understanding of the functional magnetic resonance imaging (fMRI) blood-oxygen-level-dependent (BOLD) effect, multisource frequency-domain near-infrared and BOLD fMRI signals were recorded simultaneously during motor functional activation in humans. From the near-infrared data(More)
We have noninvasively studied the motor cortex hemodynamics in human subjects under rest and motor stimulation conditions using a multichannel near-infrared tissue spectrometer. Our instrument measures optical maps of the cerebral cortex at two wavelengths (758 and 830 nm), with an acquisition time of 160 ms per map. We obtained optical maps of oxy- and(More)
Neurovascular coupling is the generic term for changes in cerebral metabolic rate of oxygen (CMRO(2)), cerebral blood flow, and cerebral blood volume related to brain activity. The goal of this paper is to better understand the effects of neurovascular coupling in the visual and motor cortices using frequency-domain near-infrared spectroscopy. Maps of(More)
We have developed an instrument for non-invasive optical imaging of the human brain that produces on-line images with a temporal resolution of 160 ms. The imaged quantities are the temporal changes in cerebral oxy-hemoglobin and deoxy-hemoglobin concentrations. We report real-time videos of the arterial pulsation and motor activation recorded on a 4 x 9 cm(More)
The aim of our study was to explore the possibility of detecting hemodynamic changes in the brain using the phase of the intensity modulated optical signal. To obtain optical signals with the highest possible signal-to-noise ratio, we performed a series of simultaneous NIRS-fMRI measurements, with subsequent correlation of the time courses of both(More)
Near-infrared spectroscopy and imaging are powerful tools to detect and continuously monitor the cerebral hemodynamic and oxygenation changes induced by brain activity. However, in addition to the focal neuronal-activation-induced hemodynamic signals, near-infrared methods are also sensitive to the cerebral hemodynamic fluctuations of systemic origin(More)
Frequency-domain near-infrared spectro-imaging offers significant advantages over the continuous-wave method in human brain applications. However, the drawback of existing instruments is a low signal-to-noise ratio for measured phase and modulation depth changes caused by cerebral activation. In this paper we show that in the case of the geometry specific(More)
We introduce a new algorithm for the reconstruction of functional brain activations from near-infrared spectroscopic imaging (NIRSI) data. While NIRSI offers remarkable biochemical specificity, the attainable spatial resolution with this technique is rather limited, mainly due to the highly scattering nature of brain tissue and the low number of measurement(More)
A new method to non-invasively measure the absolute tissue oxygen saturation (SO2) and arterial oxygen saturation (fdSaO2) by frequency-domain spectroscopy is described. This method is based on the quantitative measurement of the tissue absorption spectrum, which is used to determine global SO2. From the amplitude of absorption changes caused by arterial(More)