Yuichi Tamura

Development of the needle insertion robot for percutaneous vertebroplasty

Percutaneous Vertebroplasty (PVP) is an effective and less invasive medical treatment for vertebral osteoporotic compression fractures. However, this operative procedure is quite difficult because an arcus vertebra, which is narrow, is needled with accuracy, and an operators hand is exposed to X-ray continuously. We have developed a needle insertion robot for Percutaneous Vertebroplasty. Its experimental evaluation on the basic performance of the system and needle insertion accuracy are presented. A needle insertion robot is developed for PVP. This robot can puncture with accuracy and an operator does not need to be exposed to X-ray. The mechanism of the robot is compact in size (350 mm x D 400 mm x H270 mm, weight: 15 kg) so that the robot system can be inserted in the space between C-arm and the patient on the operating table. The robot system is controlled by the surgical navigation system where the appropriate needle trajectory is planned based on pre-operative three-dimensional CT images. The needle holding part of the robot is X-ray lucent so that the needle insertion process can be monitored by fluoroscopy. The position of the needle during insertion process can be continuously monitored. In vitro evaluation of the system showed that average position and orientation errors were less than 1.0 mm and 1.0 degree respectively. Experimental results showed that the safety mechanism called mechanical fuse released the needle holding disk properly when excessive force was applied to the needle. These experimental results demonstrated that the developed system has the satisfactory basic performance as needle insertion robot for PVP.

Surgical Tool Alignment Guidance by Drawing Two Cross-Sectional Laser-Beam Planes

Conventional surgical navigation requires for surgeons to move their sight and conscious off the surgical field when checking surgical tools positions shown on the display panel. Since that takes high risks of surgical exposure possibilities to the patients body, we propose a novel method for guiding surgical tool position and orientation directly in the surgical field by a laser beam. In our navigation procedure, two cross-sectional planar laser beams are emitted from the two laser devices attached onto both sides of an optical localizer, and show surgical tools entry position on the patients body surface and its orientation on the side face of the surgical tool. In the experiments, our method gave the surgeons precise and accurate surgical tool adjusting and showed the feasibility to apply to both of open and percutaneous surgeries.

Preoperative Analysis of Optimal Imaging Orientation in Fluoroscopy for Voxel-Based 2-D/3-D Registration

We have developed a system for the 3-D localization of anatomical structures without the need for surgical exposure by using multiple-view fluoroscopy images. In this paper, we describe the system and evaluate its application to the estimation of optimal imaging orientations in fluoroscopy. For positional measurement, a voxel-based 2-D/3-D registration technique was employed. Since the measurement condition depends on the object shape, spatial distribution of X-ray absorption, and overlap of organs or structures (which differs at each imaging position), determining the optimal combination of fluoroscopy orientations is significant. We propose a system for preoperative determination of the optimal imaging orentation by using the accuracy estimation of stereo localization from single-plane localization results. In an experiment, the computation time needed was 10 hours, which was about 14 times shorter than the time required for a full search of imaging orientation combinations.

Frequency-dependent oscillatory neural profiles during imitation

Imitation is a complex process that includes higher-order cognitive and motor function. This process requires an observation-execution matching system that transforms an observed action into an identical movement. Although the low-gamma band is thought to reflect higher cognitive processes, no studies have focused on it. Here, we used magnetoencephalography (MEG) to examine the neural oscillatory changes including the low-gamma band during imitation. Twelve healthy, right-handed participants performed a finger task consisting of four conditions (imitation, execution, observation, and rest). During the imitation and execution conditions, significant event-related desynchronizations (ERDs) were observed at the left frontal, central, and parietal MEG sensors in the alpha, beta, and low-gamma bands. Functional connectivity analysis at the sensor level revealed an imitation-related connectivity between a group of frontal sensors and a group of parietal sensors in the low-gamma band. Furthermore, source reconstruction with synthetic aperture magnetometry showed significant ERDs in the low-gamma band in the left sensorimotor area and the middle frontal gyrus (MFG) during the imitation condition when compared with the other three conditions. Our results suggest that the oscillatory neural activities of the low-gamma band at the sensorimotor area and MFG play an important role in the observation-execution matching system related to imitation.

Spatiotemporal profiles of neuromagnetic oscillatory changes related to the human mirror neuron system

It has been long postulated that social decision making consists of at least two different levels: rapid intuitive and slow reflective processes. However, behavioral and neuronal evidence of this hypothesis remains poorly identified. Here, we address this issue by conducting behavioral and fMRI experiments of the ultimatum game with cognitive load. Prior to the experiments, subjects were classified into prosocials (n = 39) and individualists (n = 20) by the definition of social value orientation (Van Lange et al., 1989; Haruno and Frith, 2010), which has been proposed as characterizing rapid and intuitive attitudes towards the division of resources. Subjects were asked to respond whether to accept or reject a sequence of divisions of 500 yen offered by proposers. The subjects were also required to memorize a fivedigit number prior to the presentation of the offer, and had to answer the next number to the one displayed on the screen after the response. To control the availability of subject’s cognitive resource for reflective thinking, we compared the loaded (random number) and unloaded (always “01234”) conditions. Behaviorally, prosocials rejected more often than individualists (p < 0.00001; three-way ANOVA). More importantly, prosocials showed more rejections in the loaded condition than in the unloaded condition (p < 0.05; paired t-test), while individualists accepted more often in the loaded condition. In parallel with this behavioral difference, activity in the nucleus accumbens correlated with proposer’s payoff minus subject’s payoff revealed a statistically significant difference between the two groups in the loaded condition (p < 0.05; FWE corrected), but not in the unloaded condition. These results indicate that “social value orientation” indeed represents subject’s rapid intuitive attitude and the nucleus accumbens plays a key role in making behavioral decisions under the influence of the social value orientation. Research fund: This study was supported by PRESTO/JST, KAKENHI (22300139), and SRPBS.

14. Lateralization of cerebral oscillatory changes during memory encoding and retrieval of words

The Wada test has been a golden standard to evaluate the lateralization of language dominance before epilepsy surgery. However, this test has not been applied to going children, especially with mental retardation. Because it is an invasive test with risks of neurologic complications. Although some non-invasive alternatives, such as MEG, fMRI or NIRS are recently applied, there are a few reports of children. We performed three types of non-invasive procedures for language lateralization (NIRS, MEG and Dichotic listening test) as well as the Wada procedure by using very short-acting anesthesia in a child of intractable epilepsy with mild mental retardation before hemispherotomy. Each indicated that the language dominance is lateralized in the same hemisphere. Although there are many risks for Wada test in the introduction of catheter for restless children who can not follow directions, using very short-acting general anesthesia may allow them to diminish risks. In addition, the result that all of three non-invasive tests are in good concordance with Wada test, which suggests these non-invasive tests have a potential to substitute for Wada test even in young children. Further studies in pediatric patients with mental retardation are needed in order to confirm usefulness of these non-invasive methods.

56. Spatiotemporal analysis of the cerebral oscillatory changes induced by imitation of finger movement

lished. Our study aimed to investigate the relationships between pain and the stimulus duration when stimulus intensity is just sufficient to obtain the supramaximal stimulation. Fourteen normal subjects were enrolled for this evaluation. Tibial nerve was stimulated at the ankle with two out of three durations of 0.05, 0.2, and 1.0 ms. Six such combinations were tested in a random order, and subjects were asked to report which duration was more painful at each trial. Following two stimulus patterns were examined: pattern 1 was single supramaximal stimulation, and pattern 2 was a train of five maximal stimulations with 1 Hz, respectively. The stimulus duration with 0.2 ms caused minimum pain for both patterns, followed by 0.05 and 1.0 ms. This result indicate shorter duration is not always less painful. Furthermore, if we use 0.05 ms duration, the intensity necessary for supramaximal stimulation may easily exceed 100 mA for a pathological nerve with increased threshold. It is concluded that 0.2 ms duration, widely employed in Japan, is well appropriate.

P19-18 Spatiotemporal dynamics of neuromagnetic oscillatory changes during observation of actions

fMRI experiment showed that left frontal and middle frontal gyrus near BA 10 and BA 46 were activated. Furthermore, cingulate gyrus (BA 23) and corpus callosum (BA 29, 30), and so on were also activated. The reaction time of Yes response was a fairly shorter than that of No response about 50 ms in the MEG experiment. From the results of these experiments, it was estimated that the activation area of working memory was changing through cigulate gyrus to frontal area. It was also suggested that the difference of the reaction time (50 ms) for the judgment of Yes or No response could be affected by the priming effect.

P33-10 Prediction of motor execution using magnetoencephalography: Relationship between neuromagnetic motor fields and decoding performance

current dipoles at 1 ms steps using individual spherical head models. Sources were then superimposed on the coregistered structural MRIs. Results: Statistically significant CKC was evident in all ten subjects at 1.5 4.5 Hz and 3 9 Hz, corresponding to hand kinematics. Coherence values ranged from 0.164 to 0.788. In the no-touch condition, clusters of sources were mostly located at the contralateral primary motor (M1) cortex, while in the touch condition they were both at contralateral primary somatosensory (SI) and M1 cortices. Conclusions: Voluntary movements can be monitored during MEG recordings with an accelerometer. The coherence between the accelerometer and the MEG signals reveals activations of M1 and S1 cortices. Acknowledgments: Brains Back to Brussels grant (VJ) by the Institut d’Encouragement de la Recherche Scientifique et de l’Innovation de Bruxelles (Brussels, Belgium), ERC Advanced Grant #232946, and FRS-FNRS (Fonds de la Recherche Scientifique, Belgium; Chercheur scientifique logistique (MB)) for the financial support. Helge Kainulainen and Ronny Schreiber at the Brain Research Unit for the technical support.