M Deppe1, S Knecht, H Lohmann, E B Ringelstein. 1. Department of Neurology, University of Münster, Albert-Schweitzer-Str. 33, D-48129, Germany. mail@michael-deppe.de
Abstract
BACKGROUND AND PURPOSE: Transcranial Doppler sonography (TCD) can guide and complement investigations based on functional magnetic resonance and positron emission tomography imaging by providing continuous information on cerebral perfusion changes correlated to cerebral activation. So far, however, the role of functional TCD has been limited by a lack of sensitivity. METHODS: Here, the authors present an outline of a method that increases the potential of TCD to detect perfusion changes within a vascular territory. Sensitivity on the order of 1% can be achieved by transformation of Doppler envelope curves, which accounts for systemic quasi-periodic and irregular spontaneous blood flow modulations and artificial disturbances related to the recording. A statistical technique is introduced that allows the automatic detection of time periods of significant hemispheric lateralization in evoked flow studies. Furthermore, an index of laterality is defined quantifying the extent of hemispheric dominance during stimulus processing. RESULTS AND DISCUSSION: The analysis technique described in this article has been successfully employed in recent examinations on vision, motor activation, language, language recovery, and other cognitive tasks. CONCLUSION: The novel functional TCD technique permits valid and reproducible assessments of the temporal characteristics of functional hemispheric lateralization.
BACKGROUND AND PURPOSE: Transcranial Doppler sonography (TCD) can guide and complement investigations based on functional magnetic resonance and positron emission tomography imaging by providing continuous information on cerebral perfusion changes correlated to cerebral activation. So far, however, the role of functional TCD has been limited by a lack of sensitivity. METHODS: Here, the authors present an outline of a method that increases the potential of TCD to detect perfusion changes within a vascular territory. Sensitivity on the order of 1% can be achieved by transformation of Doppler envelope curves, which accounts for systemic quasi-periodic and irregular spontaneous blood flow modulations and artificial disturbances related to the recording. A statistical technique is introduced that allows the automatic detection of time periods of significant hemispheric lateralization in evoked flow studies. Furthermore, an index of laterality is defined quantifying the extent of hemispheric dominance during stimulus processing. RESULTS AND DISCUSSION: The analysis technique described in this article has been successfully employed in recent examinations on vision, motor activation, language, language recovery, and other cognitive tasks. CONCLUSION: The novel functional TCD technique permits valid and reproducible assessments of the temporal characteristics of functional hemispheric lateralization.