BRMP-05. Intraoperative neural tract positioning method for the maximal safe resection of tumors

Brain mapping is a gold standard for the surgery of tumors in eloquent area. Especially subcortical mapping is an essential method for the preservation of important neural fibers conveying motor, sensory and even higher brain functions such as language control. The efforts to estimate the fiber localizations in brain white matter sometimes result in the unprecise identification that is caused by several factors including electrical heterogeneity of brain tissues. To solve this long-standing problem, NY Tract Finder (Yamaguchi Tract Finder) was invented and has been used for intraoperative brain mappings. Now this electrode and method is used in more than 30 major hospitals in Japan, China, Taiwan and Russia. The novel and unique neural fiber positioning technique and our efforts for the maximal preservation of patients’ QOL will be introduced.

Photons detected in the active nerve by photographic technique

The nervous system is one of the most complex expressions of biological evolution. Its high performance mostly relies on the basic principle of the action potential, a sequential activation of local ionic currents along the neural fiber. The implications of this essentially electrical phenomenon subsequently emerged in a more comprehensive electromagnetic perspective of neurotransmission. Several studies focused on the possible role of photons in neural communication and provided evidence of the transfer of photons through myelinated axons. A hypothesis is that myelin sheath would behave as an optical waveguide, although the source of photons is controversial. In a previous work, we proposed a model describing how photons would arise at the node of Ranvier. In this study we experimentally detected photons in the node of Ranvier by Ag+ photoreduction measurement technique, during electrically induced nerve activity. Our results suggest that in association to the action potential a photonic radiation takes place in the node.

Challenges for Tractogram Filtering

Tractography aims at describing the most likely neural fiber paths in white matter. A general issue of current tractography methods is their large false-positive rate. An approach to deal with this problem is tractogram filtering in which anatomically implausible streamlines are discarded as a post-processing step after tractography. In this chapter, we review the main approaches and methods from literature that are relevant for the application of tractogram filtering. Moreover, we give a perspective on the central challenges for the development of new methods, including modern machine learning techniques, in this field in the next few years.

Stick Stippling for Joint 3D Visualization of Diffusion MRI Fiber Orientations and Density

This paper investigates a stick stippling approach for glyph-based visualization of complex neural fiber architecture derived from diffusion magnetic resonance imaging. The presence of subvoxel crossing fibers in the brain has prompted the development of advanced modeling techniques; however, there remains a need for improved visualization techniques to more clearly convey their rich structure. While tractography can illustrate large scale anatomy, visualization of diffusion models can provide a more complete picture of local anatomy without the known limitations of tracking. We identify challenges and evaluate techniques for visualizing multi-fiber models and identified techniques that improve on existing methods. We conducted experiments to compare these representations and evaluated them with in vivo diffusion MR datasets that vary in voxel resolution and anisotropy. We found that stick rendering as 3D tubes increased legibility of fiber orientation and that encoding fiber density by tube radius reduced clutter and reduced dependence on viewing orientation. Furthermore, we identified techniques to reduce the negative perceptual effects of voxel gridding through a jittering and re-sampling approach to produce a stippling effect. Looking forward, this approach provides a new way to explore diffusion MRI datasets that may aid in the visual analysis of white matter fiber architecture and microstructure. Our software implementation is available in the Quantitative Imaging Toolkit (QIT).

Diffusion Tensor Imaging Studies on Recovery of Injured Optic Radiation: A Minireview

The optic radiation (OR) is a visual neural fiber pathway for the transfer of visual information from the lateral geniculate body of the thalamus to the primary visual cortex. To demonstrate the recovery of an OR injury, quantification and visualization of changes to the injured OR are necessary. Diffusion tensor imaging (DTI) allows determination of the state of an OR by assessing the obtained DTI parameters. In particular, diffusion tensor tractography (DTT), which is derived from DTI data, allows three-dimensional visualization of the OR. Thus, recovery of an injured OR can be demonstrated by examining changes in DTI parameters and/or configuration on follow-up DTI scans or via DTT of the injured OR. Herein, we review nine DTI-based studies that demonstrated recovery of OR injuries. The results reported in these studies suggest that an OR injury has a potential for recovery. Moreover, the results of these studies can form a basis for elucidating the recovery mechanisms of injured OR. These studies have suggested two recovery mechanisms for OR injury: recovery via the original OR pathway or via the transcallosal fibers of the corpus callosum. However, only nine studies on this topic have been conducted to date and six of those nine studies were case reports. Therefore, further studies involving larger numbers of subjects and reporting precise evaluations of changes in OR injury during recovery are warranted.

Vasomodulation of peripheral blood flow by focused ultrasound potentiates improvement of diabetic neuropathy

ObjectiveEffective treatment methods for diabetic peripheral neuropathy are still lacking. Here, a focused ultrasound (FUS) technique was developed to improve blood flow in diabetic peripheral vessels and potentially treat diabetic peripheral neuropathy.Research design and methodsMale adult Sprague-Dawley rats at 4 weeks poststreptozotocin injections were adopted as models for diabetic neuropathic rats. For single FUS treatment, blood perfusion in the skin of the pad of the middle toe was measured before, during, and after the medial and lateral plantar arteries were treated by FUS. For multiple FUS treatments, blood perfusion measurements, von Frey and hot plate testing and nerve conduction velocity measurements were performed before ultrasonic treatment on the first day of each week, and the microvascular and neural fiber densities in the pad of the toe were measured on the first day of the last week.ResultsThe blood perfusion rate significantly increased for 7–10 min in the control and neuropathic rats after a single ultrasound exposure. Multiple ultrasound treatments compared with no treatments significantly increased blood perfusion at the second week and further enhanced perfusion at the third week in the neuropathic rats. Additionally, the paw withdrawal force and latency significantly increased from 34.33±4.55 g and 3.96±0.25 s at the first week to 39.10±5.02 g and 4.77±0.71 s at the second week and to 41.13±2.57 g and 5.24±0.86 s at the third week, respectively. The low nerve conduction velocity in the diabetic rats also improved after the ultrasound treatments. Additionally, ultrasound treatments halted the decrease in microvessel and neural fiber densities in the skin of the diabetic toes. Histologic analysis indicated no damage to the treated arteries or neighboring tissue.ConclusionsFUS treatment can increase upstream arterial blood flow in diabetic feet, ameliorate the decrease in downstream microvessel perfusion and halt neuropathic progression.

White Matter Fiber Tractography Using Nonuniform Rational B-Splines Curve Fitting

The study of neural connectivity has grown rapidly in the past decade. Revealing brain anatomical connection improves not only clinical measures but also cognition understanding. In order to achieve this goal, we have to track neural fiber pathways first. Aiming to estimate 3D fiber pathways more accurately from orientation distribution function (ODF) fields, we presented a novel tracking method based on nonuniform rational B-splines (NURBS) curve fitting. First, we constructed ODF fields from high angular resolution diffusion imaging (HARDI) datasets using diffusion orientation transform (DOT) method. Second, under the angular and length constraints, the consecutive diffusion directions were extracted along each fiber pathway starting from a seed voxel. Finally, after the coordinates of the control points and their corresponding weights were determined, NURBS curve fitting was employed to track fiber pathways. The performance of the proposal has been evaluated on the tractometer phantom and real brain datasets. Based on several measure metrics, the resulting fiber pathways show promising anatomic consistency.

Continuum Mechanics for Coordinating Massive Microrobot Swarms

This chapter addresses the problem of coordinating the behavior of very large numbers of microrobots to assemble complex, hierarchically structured physical objects. The approach is patterned after morphogenetic processes during embryological development, in which masses of simple agents (cells) coordinate to produce complex three-dimensional structures. To ensure that the coordination mechanisms scale up to hundreds of thousands or millions of microrobots, the swarm is treated as a continuous mass using partial differential equations. A morphogenetic programming notation permits algorithms to be developed for coordinating dense masses of microrobots. The chapter presents algorithms and simulations for assembling segmented structures (artificial spines and legs) and for routing artificial neural fiber bundles. These algorithms scale over more than four orders of magnitude.