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Cerebral activation using a MR-compatible ... - Purdue University

Cerebral activation using a MR-compatible ... - Purdue University

Cerebral activation using a MR-compatible ... - Purdue

Cerebral activation using a MR-compatible piezoelectric actuator with adjustable vibration frequencies and in vivo wave propagation control Elke R. Gizewski,* Oezlem Koeze, Kai Uffmann, Armin de Greiff, Mark E. Ladd, and Michael Forsting Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University of Duisburg-Essen, Germany Received 19 April 2004; revised 1 August 2004; accepted 14 September 2004 Available online 24 November 2004 www.elsevier.com/locate/ynimg NeuroImage 24 (2005) 723–730 Functional magnetic resonance imaging (fMRI) studies are increasingly used in patients with brain tumors near the sensory motor cortex for planning of therapy. Passive stimuli can be helpful for reproducible results. The purpose of our study was to investigate frequency and amplitude dependencies of cerebral activation patterns using a vibratory stimulus that involves sensory and motor function and allows exact adjustment of vibratory frequencies and direct control of penetration depth into the tissue. Fifteen volunteers were studied with fMRI during vibratory stimulation of the right biceps muscle utilizing a block design (frequencies: 150 and 300 Hz, amplitudes: 400, 600, and 800 Am). In addition, visualization of the wave propagation into the biceps tissue itself was performed with a modified phase contrast sequence. A specially developed MR-compatible mechanical oscillator was used to apply the vibrotactile sensations. fMRI revealed activation of the left primary somatosensory cortex during application of both vibratory frequencies. Additionally, activity of the primary and supplementary motor cortex was revealed using 150-Hz stimuli, while only minimal at 300 Hz. The activity strength correlated with increasing stimulus amplitudes and the visualized penetration depth. Activation of motor areas was more pronounced at the beginning of the rest period. In conclusion, sensory motor areas can be activated using a piezoelectric actuator, with less pronounced motor area activation at higher frequencies. Our setup allowed local control of stimulus penetration through the tissue correlated to central activation, providing objective stimulus control. The pronounced activation of the motor cortex during the rest condition may reflect the subjective feeling of arm movement after the end of the stimulus. D 2004 Elsevier Inc. All rights reserved. Keywords: fMRI; Piezoelectric actuator; Cerebral activation Introduction Functional imaging studies are useful for planning of neurosurgery therapy, for example, in patients with brain tumors near to the sensory motor cortex (Righini et al., 1996). Furthermore, there might be benefit from an analysis of somatosensory activation patterns in recovery after stroke or traumatic brain injuries (Cramer and Bastings, 2000). Especially in these cases, motor function is often impaired. Therefore, a vibrotactile sensory stimulus that involves sensory as well as motor function would be useful. Experimental data on vibrotactile stimulation using H 2 15 O positron emission tomography (PET) revealed increased activation signal intensity in the primary somatosensory area (SI), the secondary somatosensory area (SII), the retroinsular field, the anterior parietal cortex, the primary motor area, and the supplementary motor area (SMA) (Seitz and Roland, 1992). Furthermore, functional magnetic resonance imaging (fMRI) revealed activation of the contralateral perirolandic region, comparable to the activation pattern due to finger-to-thumb-tapping (Golaszewski et al., 2002a; Harrington et al., 2000). The tonic vibratory reflex is best evoked at frequencies between 50 and 150 Hz (Golaszewski et al., 2002a). During stimulation at higher frequencies, the tonic vibratory reflex should be less intense, and the sensory activation should be more pronounced. The aim of our study was to investigate whether these differences in vibrotactile processes could be revealed in distinct cerebral activation patterns using fMRI. For this aim, we used a specifically developed, MRcompatible piezoelectric device that can apply vibratory stimuli, adjustable in both amplitude and frequency, to any body region. Furthermore, direct monitoring of stimulus amplitude and penetration depth into the tissue was assessed utilizing direct MRI visualization. Subjects and methods * Corresponding author. Department of Diagnostic and Interventional Radiology and Neuroradiology, University of Duisburg-Essen, Hufelandstr. 55, D-45127 Essen, Germany. Fax: +49 201 723 5959. E-mail address: elke.gizewski@uni-essen.de (E.R. Gizewski). Available online on ScienceDirect (www.sciencedirect.com). Subjects Eight male and seven female healthy right-handed volunteers (mean age 29 years, range 17 to 55) were examined. No subject 1053-8119/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2004.09.015

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