Isao Muro

Relation of bimanual coordination to activation in the sensorimotor cortex and supplementary motor area: Analysis using functional magnetic resonance imaging

The aim of this study was to analyze how functional activation in the supplementary motor area (SMA) and sensorimotor cortex (SMC) is related to bimanual coordination using functional magnetic resonance imaging. Subjects included 24 healthy volunteers, 15 of whom were right-handed and 9 left-handed. Three kinds of activation tasks, all of which required the repetitive closing and opening of a fist, were performed: unimanual movement of the nonpreferred hand (task A); simultaneous, agonistic movement of both hands (task B); simultaneous, antagonistic movement of both hands (task C). The SMA activation during task C was more pronounced than that during the other two tasks for right and left handers. The results suggested that the activation of the SMA, at least during a simple motion used in the present study, was little influenced by whether the motion was unimanual or bimanual but instead how the bimanual motion was composed of the motion element of a single hand. The SMC activation during task C was significantly larger than that during task B, whereas hemispheric differences in the activation were not found. This indicated that the complexity of the bimanual movement also affected the SMC activation.

Activation of Pre–Supplementary Motor Area (SMA) and SMA Proper During Unimanual and Bimanual Complex Sequences: An Analysis Using Functional Magnetic Resonance Imaging

Several functional imaging studies have shown that the extent of activation and percentage change in cerebral blood flow in the supplementary motor area (SMA) during a bimanual mirror performance of a simple repetitive movement are almost identical to those during a unimanual movement. The aim of this study was to investigate whether this finding was also applicable to a more complex movement. Eight right‐handed, healthy volunteers performed unimanually (with their right and left hands) and bimanually (in a mirror fashion) thumb‐finger opposition in a nonconsecutive order (index‐middle‐index‐ring‐index‐little‐index‐middle… fingers). The SMA proper was more activated during the bimanual movement than the unimanual movement with either hand. This is in accordance with the hypothesis that bimanual movement, even in a mirror fashion, is more difficult than unimanual movement when the task is complex but not when the task is simple. Pre‐SMA was inconsistently activated. The results suggest that the SMA proper plays an active role in executive processing during bimanual mirror performance of complex movements.

Apparent diffusion coefficient measurement in a moving phantom simulating linear respiratory motion.

PurposeThe aim of this study was to examine the effect of simulated linear respiratory motion on apparent diffusion coefficient (ADC) measurements.Materials and methodsSix rectangular test tubes (14 × 92 mm) filled with either water, tomato ketchup, or mayonnaise were positioned in a box containing agarose gel. This box was connected to a double-acting pneumatic cylinder, capable of inducing periodic linear motion in the long-axis direction of the magnetic bore (23-mm stroke). Diffusion-weighted magnetic resonance imaging was performed for both the static and moving phantoms, and ADC measurements were made in the six test tubes in both situations.ResultsIn the three test tubes whose long axes were parallel to the direction of motion, ADCs agreed well between the moving and static phantom situations. However, in two test tubes that were filled with fluids that had a considerably lower diffusion coefficient than the surrounding agarose gel, and whose long axes were perpendicular to the direction of motion, the ADCs agreed poorly between the moving and static phantom situations.ConclusionADC measurements of large homogeneous structures are not affected by linear respiratory motion. However, ADC measurements of inhomogeneous or small structures are affected by linear respiratory motion due to partial volume effects.

Application and validation of three-dimensional data sets from a phase contrast MR angiography for preoperative computer simulation of brain tumors.

We applied a three‐dimensional (3D) phase contrast magnetic resonance angiography as the source for generating integrated 3D images for surgical planning of brain tumors. In the 3D model, we defined the Cingulomarginal sulcus and subsequently the central sulcus in the interhemispheric plane. This method solved the misregistration problem caused by the combination of multi‐sequence data sets and can be feasible for surgical planning.J. Magn. Reson. Imaging 1999;10:102–106.

Optimized 4D time‐of‐flight MR angiography using saturation pulse

To assess arterial visibility on 4D time‐of‐flight (4D‐TOF) by temporal magnetization transfer contrast pulse (t‐MTC) and temporal tilted optimized nonsaturating excitation (t‐TONE). 3D‐TOF magnetic resonance angiography (MRA) is used for the noninvasive assessment of the intracranial arteries. However, it does not provide temporal information for diagnosing hemodynamics. To noninvasively obtain more detailed hemodynamics‐related information, we developed a novel time‐resolved MRA without the arterial spin labeling technique, termed 4D‐TOF MRA using saturation pulse.

Time-spatial Labeling Inversion Pulse (Time-SLIP) with Pencil Beam Pulse: A Selective Labeling Technique for Observing Cerebrospinal Fluid Flow Dynamics

We assessed labeling region selectivity on time-spatial labeling inversion pulse (Time-SLIP) with pencil beam pulse (PB Time-SLIP) for the use of visualizing cerebrospinal fluid (CSF) flow dynamics. We compared the selectivity of labeling to the third and fourth ventricles between PB Time-SLIP and conventional Time-SLIP (cTime-SLIP) in eight volunteers and one patient using a 1.5T MRI. PB Time-SLIP provided more selective labeling in CSF than cTime-SLIP, particularly in complex anatomical regions.