Avoiding a Collision in Gamma Knife Radiosurgery : A Modified Mask Fixation Method

Objective@#: The latest version of the Leksell Gamma Knife IconTM allows for mask- and frame-based fixation. Although mask fixation provides fractionated treatment and immobilization using a noninvasive method, it is not free from collision. The authors investigated the collision problem with a modified mask fixation method. @*Methods@#: This study presents a case of two meningiomas in the frontal area, where a collision occurs in the occipital area. A modified mask fixation method was introduced to avoid the collision : first, the edges of the head cushion were cut off and polystyrene beads with a diameter of approximately 5 cm were removed. Next, the head cushion was sealed using a stapler. Finally, the head cushion was flattened in the adapter. We compared the shot coordinates, 3-dimensional (3D) error, clearance distance, and vertical depth of the head cushion between the initial and modified mask fixations. @*Results@#: When comparing the initial and modified mask fixations, the difference in the shot coordinates was +10.5 mm along the y-axis, the difference in the 3D error was approximately 18 mm, and the difference in clearance was -10.2 mm. The head cushion was approximately 8 mm deeper in the modified mask fixation. @*Conclusion@#: Based on these findings, we recommend a modified mask fixation method for gamma knife radiosurgery using ICON with a collision.

An Optimization of AAV-82Q-Delivered Rat Model of Huntington’s Disease

Objective@#: No optimum genetic rat Huntington model both neuropathological using an adeno-associated virus (AAV-2) vector vector has been reported to date. We investigated whether direct infection of an AAV2 encoding a fragment of mutant huntingtin (AV2-82Q) into the rat striatum was useful for optimizing the Huntington rat model. @*Methods@#: We prepared ten unilateral models by injecting AAV2-82Q into the right striatum, as well as ten bilateral models. In each group, five rats were assigned to either the 2×1012 genome copies (GC)/mL of AAV2-82Q (×1, low dose) or 2×1013 GC/mL of AAV2-82Q (×10, high dose) injection model. Ten unilateral and ten bilateral models injected with AAV-empty were also prepared as control groups. We performed cylinder and stepping tests 2, 4, 6, and 8 weeks after injection, tested EM48 positive mutant huntingtin aggregates. @*Results@#: The high dose of unilateral and bilateral AAV2-82Q model showed a greater decrease in performance on the stepping and cylinder tests. We also observed more prominent EM48-positive mutant huntingtin aggregates in the medium spiny neurons of the high dose of AAV2-82Q injected group. @*Conclusion@#: Based on the results from the present study, high dose of AAV2-82Q is the optimum titer for establishing a Huntington rat model. Delivery of high dose of human AAV2-82Q resulted in the manifestation of Huntington behaviors and optimum expression of the huntingtin protein in vivo.

Characterization of Tetrodes Coated with Au Nanoparticles (AuNPs) and PEDOT and Their Application to Thalamic Neural Signal Detection in vivo

Tetrodes, consisting of four twisted micro-wires can simultaneously record the number of neurons in the brain. To improve the quality of neuronal activity detection, the tetrode tips should be modified to increase the surface area and lower the impedance properties. In this study, tetrode tips were modified by the electrodeposition of Au nanoparticles (AuNPs) and dextran (Dex) doped poly (3,4-ethylenedioxythiophene) (PEDOT). The electrochemical properties were measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A decrease in the impedance value from 4.3 MΩ to 13 kΩ at 1 kHz was achieved by the modified tetrodes. The cathodic charge storage capacity (CSC(C)) of AuNPs-PEDOT deposited tetrodes was 4.5 mC/cm², as determined by CV measurements. The tetrodes that were electroplated with AuNPs and PEDOT exhibited an increased surface area, which reduced the tetrode impedance. In vivo recording in the ventral posterior medial (VPM) nucleus of the thalamus was performed to investigate the single-unit activity in normal rats. To evaluate the recording performance of modified tetrodes, spontaneous spike signals were recorded. The values of the L-ratio, isolation distance and signal-to-noise (SNR) confirmed that electroplating the tetrode surface with AuNPs and PEDOT improved the recording performance, and these parameters could be used to effectively quantify the spikes of each cluster.

Comparison of 3 and 7 Tesla Magnetic Resonance Imaging of Obstructive Hydrocephalus Caused by Tectal Glioma

Obstructive hydrocephalus caused by tectal glioma, which relived by neuroendoscopy, have been described using 3.0 Tesla magnetic resonance imaging (3T MRI) so far, we present the results obtained from 3T and 7T MRI in this patient. A 21-year-old woman presented at our hospital with gait disturbance, hormonal insufficiency, and urinary incontinence that began prior to 6 years of age. 3.0T MRI revealed a non-enhancing tectal mass along with obstructive hydrocephalus. The mass measured approximately 1.1×1.0×1.2 cm. An endoscopic third ventriculostomy was performed to relieve the hydrocephalus. We compared hydrocephalus and cerebrospinal fluid (CSF) flow findings from 3T and 7T MRI, both preoperative and postoperative at 1, 6 months. Intraventricular CSF voiding on T2-weighted images obtained with 7T MRI showed greater fluid inversion than those obtained with 3T MRI. This study shows that 7T brain MRI can provide detailed information on hydrocephalus caused by tectal glioma. Further studies are needed to develop refined 7T MRI protocols for better images of hydrocephalus.