The Poised Cannula Technique Reduces the Stereotactic Error of the Fiducial-Less Frameless DBS Procedure.

BACKGROUND: In this study, we describe a technique of optimizing the accuracy of frameless deep brain stimulation (DBS) lead placement through the use of a cannula poised at the entry to predict the location of the fully inserted device. This allows real-time correction of error prior to violation of the deep gray matter. METHODS: We prospectively gathered data on radial error during the operative placements of 40 leads in 28 patients using frameless fiducial-less DBS surgery. Once the Nexframe had been aligned to target, a cannula was inserted through the center channel of the BenGun until it traversed the pial surface and a low-dose O-arm spin was obtained. Using 2 points along the length of the imaged cannula, a trajectory line was projected to target depth. If lead location could be improved, the cannula was inserted through an alternate track in the BenGun down to target depth. After intraoperative microelectrode recording and clinical assessment, another O-arm spin was obtained to compare the location of the inserted lead with the location predicted by the poised cannula. RESULTS: The poised cannula projection and the actual implant had a mean radial discrepancy of 0.75 ± 0.64 mm. The poised cannula projection identified potentially clinically significant errors (avg 2.07 ± 0.73 mm) in 33% of cases, which were reduced to a radial error of 1.33 ± 0.66 mm (p = 0.02) after correction using an alternative BenGun track. The final target to implant error for all 40 leads was 1.20 ± 0.52 mm with only 2.5% of errors being >2.5 mm. CONCLUSION: The poised cannula technique results in a reduction of large errors (>2.5 mm), resulting in a decline in these errors to 2.5% of implants as compared to 17% in our previous publication using the fiducial-less method and 4% using fiducial-based methods of DBS lead placement.

An Embedded Sensor System for Real-Time Detecting 5-DOF Error Motions of Rotary Stages.

The geometric error motions of rotary stages greatly affect the accuracy of constructed machines such as machine tools, measuring instruments, and robots. In this paper, an embedded sensor system for real-time measurement of two radial and three angular error motions of a rotary stage is proposed, which makes use of a rotary encoder with multiple scanning heads to measure the rotational angle and two radial error motions and a miniature autocollimator to measure two tilt angular errors of the axis of rotation. The assembly errors of the grid disc of the encoder and the mirror for autocollimator are also evaluated and compensated. The developed measuring device can be fixed inside the rotary stage. In the experiments, radial error motions of two points on the axis (h = 5 mm and 60 mm) were measured and calibrated with LVDTs, and the data showed that the radial error motions of the axis were less than 20 µm, and the calibration residual errors were less than 2 µm. When intermittent external forces were applied to the stage, the change of the stage's error motion could also be monitored accurately.

Variable training: effects on velocity and accuracy in the tennis serve.

Variable practice has been shown to be an effective strategy to improve open motor skills. However, the usefulness of this procedure in closed motor skills remains controversial. The following study has the objective of analysing the effects of variability practice in the improvement of a closed skill. The skill studied has been the tennis serve. Thirty young tennis players (13 ± 1.52 years), divided in two groups, took part in this study. One group practiced in variable conditions and the other group in consistency conditions. Both groups performed 12 training sessions (60 serves/session). The variable practice group improved their accuracy significantly compared with the consistency group (F3.25 = 3.078; P = 0.035). The velocity of serve increased after training in both groups (F3.25 = 15.890; P = 0.001). The practice in variable conditions seems to be effective in improving the performance of the tennis serve.

The impact of skull thickness on pediatric stereoencephalography electrode implantation and technical considerations.

OBJECTIVE: One consideration in pediatric stereoencephalography (SEEG) is decreased skull thicknesses compared with adults, which may limit traditional bolt-based anchoring of electrodes. The authors aimed to investigate the safety profile, complication rates, and technical adaptations of placing SEEG electrodes in pediatric patients. METHODS: The authors retrospectively reviewed all patients aged 12 years or younger at the time of SEEG implantation at their institution. Postimplantation CT scans were used to measure skull thickness at the entry point of each SEEG lead. Postimplantation lead accuracy was also assessed. RESULTS: Fifty-three patients were reviewed. The median skull thickness was 4.1 (interquartile range [IQR] 3.15-5.2) mm. There were 5 total complications: 1 retained bolt fragment, 3 asymptomatic subdural hematomas, and 1 asymptomatic intracranial hemorrhage. Median radial error from the lead target was 3.5 (IQR 2.24-5.25) mm. Linear regression analysis revealed that increasing skull thickness decreased the deviation from the intended target, implying an improved accuracy to target at thicker skull entry points; this trended towards improved accuracy, but did not achieve statistical significance (p = 0.54). CONCLUSIONS: This study found a 1.9% hardware complication rate and a 9.4% asymptomatic hemorrhage rate. Suturing electrodes to the scalp may represent a reasonable option if there are concerns of young age or a thin skull. These data indicate that invasive SEEG evaluation is safe among patients 12 years old or younger.

Accuracy of Subthalamic Nucleus Electrode Implantation in Deep Brain Stimulation Surgery for Parkinson's Disease Treatment and Affecting Factors: Outcomes at Two Centers in Vietnam.

BACKGROUND: Deep brain stimulation (DBS) surgery for Parkinson's Disease (PD) has become more and more popular in Vietnam. However, the accuracy of implantation and affecting factors are under investigation. The objective of this study is to evaluate the accuracy of the subthalamic nucleus (STN)-DBS electrode implantation technique for treatment PD at Nguyen Tri Phuong Hospital and University Medical Center. To investigate factors related to accuracy. METHODS: We carried out a retrospective analysis of 58 patients with advanced PD who underwent STN-DBS surgery at Nguyen Tri Phuong Hospital and University Medical Center in Ho Chi Minh City, Viet Nam between June 2014 and July 2021 (115 leads total). All patients underwent the procedure with standard frame-based techniques under local anesthesia with microelectrode recording and macrostimuation test. RESULTS: Twenty-six female (44.8%) and thirty-two male (55.2%) patients with a mean age of 60.4 ± 8.3 years old (40-76 years) were included. Of total of 115 electrodes implanted, the mean target error (ΔT), radial error (ΔR), angle error (Δθ) were 1.94 ± 0.73 mm; 1.16 ± 0.69 mm; 2.22 ± 4.24 degrees, respectively. Vector error on each coordinate axis ΔX, ΔY, ΔZ were -0.35 ± 1.02 mm, +0.99 ± 0.82 mm, +0.73 ± 0.99 mm, respectively. There was a statistically significant correlation between subdural air volume, cortical shift, intracranial electrode bending, and accuracy. CONCLUSIONS: The current STN-DBS electrode implantation technique applied in our centers was quite accurate with acceptable error. More clinical trials are necessary to directly compare affecting factors to the accuracy of electrode implantation.

In Situ Measurement of Spindle Radial Error for Ultra-Precision Machining Based on Three-Point Method.

The radial error is an important parameter to evaluate the performance of ultra-precision spindles. The three-point method has not yet been well applied in nanometer-scale measurement due to its disadvantages of harmonic suppression and the complicated error separation process. In order to verify that the three-point method can realize the nanometer-scale measurement of the radial error in the machining environment, an in situ measurement and evaluation system is established. Experiments are performed using the system, and a comparative experiment is conducted to verify the accuracy of the system. The average value and standard deviation of the measurement results are 23.096 nm and 0.556 nm, respectively. The in situ measurement result was in good agreement with the Donaldson reversal method using a commercially available spindle analyzer.

The application of augmented reality-based navigation for accurate target acquisition of deep brain sites: advances in neurosurgical guidance.

OBJECTIVE: The objective of this study is to quantify the navigational accuracy of an advanced augmented reality (AR)-based guidance system for neurological surgery, biopsy, and/or other minimally invasive neurological surgical procedures. METHODS: Five burr holes were drilled through a plastic cranium, and 5 optical fiducials (AprilTags) printed with CT-visible ink were placed on the frontal, temporal, and parietal bones of a human skull model. Three 0.5-mm-diameter targets were mounted in the interior of the skull on nylon posts near the level of the tentorium cerebelli and the pituitary fossa. The skull was filled with ballistic gelatin to simulate brain tissue. A CT scan was taken and virtual needle tracts were annotated on the preoperative 3D workstation for the combination of 3 targets and 5 access holes (15 target tracts). The resulting annotated study was uploaded to and launched by VisAR software operating on the HoloLens 2 holographic visor by viewing an encrypted, printed QR code assigned to the study by the preoperative workstation. The DICOM images were converted to 3D holograms and registered to the skull by alignment of the holographic fiducials with the AprilTags attached to the skull. Five volunteers, familiar with the VisAR, used the software/visor combination to navigate an 18-gauge needle/trocar through the series of burr holes to the target, resulting in 70 data points (15 for 4 users and 10 for 1 user). After each attempt the needle was left in the skull, supported by the ballistic gelatin, and a high-resolution CT was taken. Radial error and angle of error were determined using vector coordinates. Summary statistics were calculated individually and collectively. RESULTS: The combined angle of error of was 2.30° ± 1.28°. The mean radial error for users was 3.62 ± 1.71 mm. The mean target depth was 85.41 mm. CONCLUSIONS: The mean radial error and angle of error with the associated variance measures demonstrates that VisAR navigation may have utility for guiding a small needle to neural lesions, or targets within an accuracy of 3.62 mm. These values are sufficiently accurate for the navigation of many neurological procedures such as ventriculostomy.

Effect of Different Shooting Techniques in Floorball on Accuracy and Velocity in Experienced Male Floorball Players.

The aims of this study were to investigate the effect of four different shooting techniques (slap, sweeper, drag, and wrist shots) in floorball on velocity and accuracy in experienced floorball players, and to investigate whether target height has an influence on these shooting performances. Ten experienced male floorball players (age, 21 ± 4 years; body mass, 81.5 ± 10 kg; body height, 1.85 ± 0.07 m; and years of experience, 6.9 ± 3.1 years) shot as hard as possible and tried to hit the upper and lower targets with four different shooting techniques from a 4-m distance. The main findings were that shooting techniques and target height could influence ball velocity in the expected way from slap to sweeper shots and drag to wrist shots, whereas accuracy did not change, and thereby, did not follow any velocity-accuracy trade-off like Fitts' law.