A ventilator for magnetic resonance imaging. Breathing motion severely degrades the quality of magnetic resonance images (MRI) of the thorax and upper abdomen and interferes with the acquisition of quantitative data. To minimize these motion effects, we built an MRI compatible ventilator for use in animal studies. Solid state circuitry is used for controlling ventilation parameters. The ventilator can be triggered internally at frequencies of 0.1 to 30 Hz or it can be triggered externally such as by the MRI pulse sequence. When triggered by the scanner, ventilation is synchronized to occur between image data acquisitions. Thus, image data are obtained when there is no breathing motion and at a minimum lung volume when hydrogen density is maximum. Since the ventilator can be adjusted to operate at virtually any frequency from conventional to high frequency, ventilation can be synchronized to all commonly used repetition times (100 ms to 2000 ms or more; 600 to 30 breaths/min). Scan synchronous ventilation eliminates breathing motion artifacts from most imaging sequences (single and multiple spin echo and inversion recovery).

In addition, a 2D ultrasound transducer will be swept to obtain image volumes in approximately the same location. Inter-costal and trans-abdominal images will be obtained according to a repeatable protocol. All S-WAVE scans will be performed by two trained and very experienced sonographers, Ms. Vickie Lessoway and Ms. Jan Reid. Magnetic Resonance Elastography will be performed on the 3T Philips Elition MR scanner located at the UBC MRI research centre. The scan will begin with axial T1 and T2 images, followed by Diffusion Weighted imaging. Then MR elastography examination using the eXpresso sequence and concurrent excitation of tissue will be performed next. The eXpresso sequence has been used in phantom, liver, and prostate studies. The excitation system is an electromagnetic actuator that has been built in house and comprises of loops of wire arranged into a coil. Vibrations result when current is passed through the wires in the presence of the magnetic field of the MR scanner. It is synchronized with the MRI imaging sequence. The shaker will be placed over the right rib cage of the subject whilst lying in a supine position.

In the so-called rubber hand illusion, synchronous visuotactile stimulation of a visible rubber hand together with one's own hidden hand elicits ownership experiences for the artificial limb. Recently, advanced virtual reality setups were developed to induce a virtual hand illusion (VHI). Here, we present functional imaging data from a sample of 25 healthy participants using a new device to induce the VHI in the environment of a magnetic resonance imaging (MRI) system. In order to evaluate the neuronal robustness of the illusion, we varied the degree of synchrony between visual and tactile eve Abstract In the so-called rubber hand illusion, synchronous visuotactile stimulation of a visible rubber hand together with one's own hidden hand elicits ownership experiences for the artificial limb. Recently, advanced virtual reality setups were developed to induce a virtual hand illusion (VHI). Here, we present functional imaging data from a sample of 25 healthy participants using a new device to induce the VHI in the environment of a magnetic resonance imaging (MRI) system. Asynchronies between visual and tactile input of ±300 ms did not significantly diminish the vividness of illusion, whereas asynchronies of ±600 ms did. The temporal order of visual and tactile stimulation had no effect on VHI vividness. Conjunction analyses of functional MRI data across all conditions revealed significant activation in bilateral ventral premotor cortex (PMv). Further characteristic activation patterns included bilateral activity in the motion-sensitive medial superior temporal area as well as in the bilateral Rolandic operculum, suggesting their involvement in the processing of bodily awareness through the integration of visual and tactile events. Virtual hand illusion device The VHI was implemented using a VR device based on the simulation software KISMET (Kinematic Simulation, Monitoring and Off-Line Programming Environment for Telerobotics, V6.0.3, Karlsruhe, Germany), which was used to visualize the environment of an MRI (for technical details see [18] , [20] ). In this setting, a life-like model of an arm (i.e., hand, forearm, and parts of the upper arm) and a lower body covered by a blanket were modeled, simulating the egocentric perspective of a participant lying in an MRI scanner ( Figure 1a and 1b ). This device was linked to the computer executing the KISMET software, which delivered signals for triggering the pneumatic stimulation. The pneumatic tubes were led out of the scanner room through underground cable shafts and connected to the relay device in the control room. The pressure of compressed air driving the pneumatic stimulation was set to 3 bar, which caused a clearly perceptible, but non-painful tactile stimulus on the stimulation site. VHI procedure in the fMRI scanner The participant was instructed about the experimental procedure and the duration of the investigation, before he or she was positioned in the MR scanner ( Figure 1e ). In our VHI setup, both the visual stimulation in VR as well as the tactile stimulation through the pneumatic relay device was synchronized with the software running the MRI scanner. Although both the onset of the visual (start of the movement of the virtual rod) and the tactile stimulation (release of the compressed air) were triggered simultaneously, we had to adjust three parameters of the virtual rod (velocity and distance of down-movement as well as the starting point of the rod in virtual space) to account for perceived temporal incongruencies of visuotactile stimulation caused by the transportation of air along the pneumatic tube length of approximately seven meters. Negative signs indicate the temporal delay (in milliseconds, ms), meaning that the tactile stimulation was applied prior to the visual stimulation; positive signs indicate that the tactile stimulation was applied after the visual stimulation. Each condition was implemented in a separate scanning trial with a duration of 4∶34 min. We used a block design with blocks of 6 images ( = 20 s) of visuotactile stimulation (on-blocks), interspersed with 5 blocks of 7 images ( = 23.3 s) of rest (off-blocks). The simulation model of the moving rod was synchronized to the image recordings of the MRI. Each image of the on-block triggered the rod to move downwards and upwards and one single pneumatic stimulus was applied. To account for irregularities in the hemodynamic responses triggered by the visuotactile stimulation, we added a temporal jitter, with a randomized time delay of 0, 100, 200, 300, 400, or 500 ms before stimulation onset. The sequence of conditions was randomized. To account for alpha inflation due to multiple testing of a single hypothesis, we also adjusted these results applying Bonferroni-correction, if necessary. Statistical analyses were performed across the whole sample, VHI perceivers as well as VHI non-perceivers. Analyses of fMRI data fMRI data were evaluated with Statistical Parametric Mapping software (SPM8; Wellcome Institute of Imaging Neuroscience, London, UK) implemented in Matlab 7.1 (Mathworks Inc., Natick, MA, USA). There were no significant differences between the synchronous and slightly asynchronous conditions for any item.Error bars indicate standard error; b) For illustrative purposes, the ratings of participants who responded minimally (participant # 1–5) or maximally (participant # 21–25) to illusion induction are depicted, arranged according to the proneness to perceive the VHI in the 0 condition (VHI Finally, we performed contrasts for the temporal order of sensory events, but there were no significant activity differences, neither for the −600/−300>+600/+300 contrast, nor for the inverse contrast (this holds for the whole brain as well as for PMv and IPC analyses applying small volume correction). Discussion The present study revealed first experimental data on the rubber hand illusion induced by a virtual reality set-up of an MRI compatible device.