Biomechanical testing of ex vivo porcine tendons following high intensity focused ultrasound thermal ablation.

INTRODUCTION: Magnetic resonance-guided focused ultrasound (MRgFUS) has been demonstrated to be able to thermally ablate tendons with the aim to non-invasively disrupt tendon contractures in the clinical setting. However, the biomechanical changes of tendons permitting this disrupting is poorly understood. We aim to obtain a dose-dependent biomechanical response of tendons following magnetic resonance-guided focused ultrasound (MRgFUS) thermal ablation. METHODS: Ex vivo porcine tendons (n = 72) were embedded in an agar phantom and randomly assigned to 12 groups based on MRgFUS treatment. The treatment time was 10, 20, or 30s, and the applied acoustic power was 25, 50, 75, or 100W. Following each MRgFUS treatment, tendons underwent biomechanical tensile testing on an Instron machine, which calculated stress-strain curves during tendon elongation. Rupture rate, maximum treatment temperature, Young's modulus and ultimate strength were analyzed for each treatment energy. RESULTS: The study revealed a dose-dependent response, with tendons rupturing in over 50% of cases when energy delivery exceeded 1000J and 100% disruption at energy levels beyond 2000J. The achieved temperatures during MRgFUS were directly proportional to energy delivery. The highest recorded temperature was 56.8°C ± 9.34 (3000J), while the lowest recorded temperate was 18.6°C ± 0.6 (control). The Young's modulus was highest in the control group (47.3 MPa ± 6.5) and lowest in the 3000J group (13.2 MPa ± 5.9). There was no statistically significant difference in ultimate strength between treatment groups. CONCLUSION: This study establishes crucial thresholds for reliable and repeatable disruption of tendons, laying the groundwork for future in vivo optimization. The findings prompt further exploration of MRgFUS as a non-invasive modality for tendon disruption, offering hope for improved outcomes in patients with musculotendinous contractures.

Noninvasive release of tendons using MRI guided focused ultrasound: a hybrid therapy using long-pulse focused ultrasound followed by thermal ablation.

INTRODUCTION: Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thermal ablation is an effective noninvasive ultrasonic therapy to disrupt in vivo porcine tendon but is prone to inducing skin burns. We evaluated the safety profile of a novel hybrid protocol that minimizes thermal spread by combining long-pulse focused ultrasound followed by thermal ablation. METHODS: In-vivo Achilles tendons (hybrid N = 15, thermal ablation alone N = 21) from 15 to 20 kg Yorkshire pigs were randomly assigned to 6 treatment groups in two studies. The first (N = 21) was ablation (600, 900, or 1200 J). The second (N = 15) was hybrid: pulsed FUS (13.5 MPa peak negative pressure) followed by ablation (600, 900, or 1200 J). Measurements of ankle range of motion, tendon temperature, thermal dose (240 CEM43), and assessment of skin burn were performed in both groups. RESULTS: Rupture was comparable between the two protocols: 1/5 (20%), 5/5 (100%) and 5/5 (100%) for hybrid protocol, compared to 2/7 (29%), 6/7 (86%) and 7/7 (100%) for the ablation-only protocol with energies of 600, 900, and 1200 J, respectively. The hybrid protocol produced lower maximum temperatures, smaller areas of thermal dose, fewer thermal injuries to the skin, and fewer full-thickness skin burns. The standard deviation for the area of thermal injury was also smaller for the hybrid protocol, suggesting greater predictability. CONCLUSION: This study demonstrated a hybrid MRgFUS protocol combining long-pulse FUS followed by thermal ablation to be noninferior and safer than an ablation-only protocol for extracorporeal in-vivo tendon rupture for future clinical application for noninvasive release of contracted tendon.

Intraoperative changes in large-scale thalamic circuitry following laser ablation of hypothalamic hamartomas.

BACKGROUND AND OBJECTIVES: Gelastic seizures due to hypothalamic hamartomas (HH) are challenging to treat, in part due to an incomplete understanding of seizure propagation pathways. Although magnetic resonance imaging-guided laser interstitial thermal therapy (MRgLITT) is a promising intervention to disconnect HH from ictal propagation networks, the optimal site of ablation to achieve seizure freedom is not known. In this study, we investigated intraoperative post-ablation changes in resting-state functional connectivity to identify large-scale networks associated with successful disconnection of HH. METHODS: Children who underwent MRgLITT for HH at two institutions were consecutively recruited and followed for a minimum of one year. Seizure freedom was defined as Engel score of 1A at the last available follow-up. Immediate pre- and post- ablation resting-state functional MRI scans were acquired while maintaining a constant depth of general anesthetic. Multivariable generalized linear models were used to identify intraoperative changes in large-scale connectivity associated with seizure outcomes. RESULTS: Twelve patients underwent MRgLITT for HH, five of whom were seizure-free at their last follow-up. Intraprocedural changes in thalamocortical circuitry involving the anterior cingulate cortex were associated with seizure-freedom. Children who were seizure-free demonstrated an increase and decrease in connectivity to the pregenual and dorsal anterior cingulate cortices, respectively. In addition, children who became seizure-free demonstrated increased thalamic connectivity to the periaqueductal gray immediately following MRgLITT. DISCUSSION: Successful disconnection of HH is associated with intraoperative, large-scale changes in thalamocortical connectivity. These changes provide novel insights into the large-scale basis of gelastic seizures and may represent intraoperative biomarkers of treatment success.

Clinical characteristics of upper cervical spine injuries in children: a retrospective case series.

OBJECTIVE: Pediatric cervical spine injuries (CSI) can be devastating, and children < 8 years are particularly at risk for upper CSI given unique anatomical differences. Diagnosis of these injuries can be delayed due to variable clinical presentations and a paucity of existing literature. The authors aimed to characterize the spectrum of pediatric upper CSI. METHODS: This was a retrospective, single-center case series of trauma patients aged < 16 years who were assessed at a level I pediatric trauma center and diagnosed with upper CSI between 2000 and 2020. Patients were included if they had evidence of bony or ligamentous injury from the occiput to C2 on imaging or autopsy. Data were obtained from manual chart review and analyzed using descriptive statistics. RESULTS: In total, 502 patients were screened and 202 met inclusion criteria. Of these, 31 (15%) had atlanto-occipital (AO) joint distractions, 10 (5%) had atlanto-axial (AA) joint distractions, 31 (15%) had fractures of C1-2, and 130 (64%) had ligamentous injury without joint distraction. Of the patients with AO injury, 15 patients had complete dislocation. They presented as hemodynamically unstable with signs of herniation and 14 died (93%). In contrast, 16 had incomplete dislocation (subluxation). They usually had stable presentations and survived with good outcomes. Of the patients with AA injury, 2 had complete dislocation, presented with arrest and signs of herniation, and died. In contrast, 8 patients with subluxation mostly presented as clinically stable and all survived with little residual disability. The most common fractures of C1 were linear fractures of the lateral masses and of the anterior and posterior arches. The most common fractures of C2 were synchondrosis, hangman, and odontoid fractures. Overall, these patients had excellent outcomes. Ligamentous injuries frequently accompanied other brain or spine injuries. When these injuries were isolated, patients recovered well. CONCLUSIONS: Among upper CSI, AO and AA joint injuries emerged as particularly severe with high mortality rates. Both could be divided into complete dislocations or incomplete subluxations, with clear clinical differences and the former presenting with much more severe injuries. Lateral cervical spine radiography should be considered during resuscitation of unstable trauma patients to assess for these CSI subtypes. Fractures and ligamentous injuries were clinically heterogeneous, with presentations and outcomes depending on severity and associated injuries.

Complications following resection of primary and recurrent pediatric posterior fossa ependymoma.

OBJECTIVE: Extent of resection (EOR) is the most important modifiable prognostic variable for pediatric patients with posterior fossa ependymoma. An understanding of primary and recurrent ependymoma complications is essential to inform clinical decision-making for providers, patients, and families. In this study, the authors characterize postsurgical complications following resection of primary and recurrent pediatric posterior fossa ependymoma in a molecularly defined cohort. METHODS: The authors conducted a 20-year retrospective single-center review of pediatric patients undergoing resection of posterior fossa ependymoma at the Hospital for Sick Children in Toronto, Canada. Complications were dichotomized into major and minor groups; EOR was compared across complication categories. The association between complication occurrence with length of stay (LOS) and mortality was also assessed using multivariable regressions. RESULTS: There were 60 patients with primary resection included, 41 (68%) of whom were alive at the time of data collection. Gross-total resection was achieved in 33 (58%) of 57 patients at primary resection. There were no 30-day mortality events following primary and recurrent ependymoma resection. Following primary resection, 6 patients (10%) had posterior fossa syndrome (PFS) and 36 (60%) developed cranial neuropathies, 56% of which recovered within 1 year. One patient (1.7%) required a tracheostomy and 9 patients (15%) required gastrostomy tubes. There were 14 ventriculoperitoneal shunts (23%) inserted for postoperative hydrocephalus. Among recurrent cases, there were 48 recurrent resections performed in 24 patients. Complications included new cranial neuropathy in 10 patients (21%), of which 5 neuropathies resolved within 1 year. There were no cases of PFS following resection of recurrent ependymoma. Gastrostomy tube insertion was required in 3 patients (6.3%), and 1 patient (2.0%) required a tracheostomy. Given the differences in the location of tumor recurrence, a direct comparison between primary and recurrent resection complications was not feasible. Following multivariate analysis adjusting for sex, age, molecular status, and EOR, occurrence of major complications was found to be associated with prolonged LOS but not mortality. CONCLUSIONS: These results detail the spectrum of postsurgical morbidity following primary and recurrent posterior fossa ependymoma resection. The crude complication rate following resection of infratentorial recurrent ependymoma was lower than that of primary ependymoma, although a statistical comparison revealed no significant differences between the groups. These results should serve to inform providers of the morbidity profile following surgical management of posterior fossa ependymoma and inform perioperative counseling of patients and their families.

An augmented hybrid multibaseline and referenceless MR thermometry motion compensation algorithm for MRgHIFU hyperthermia.

PURPOSE: A hybrid principal component analysis and projection onto dipole fields (PCA-PDF) MR thermometry motion compensation algorithm was optimized with atlas image augmentation and validated. METHODS: Experiments were conducted on a 3T Philips MRI and Profound V1 Sonalleve high intensity focused ultrasound (high intensity focused ultrasound system. An MR-compatible robot was configured to induce motion on custom gelatin phantoms. Trials with periodic and sporadic motion were introduced on phantoms while hyperthermia was administered. The PCA-PDF algorithm was augmented with a predictive atlas to better compensate for larger sporadic motion. RESULTS: During periodic motion, the temperature SD in the thermometry was improved from 1 . 1 ± 0 . 1 $$ 1.1\pm 0.1 $$ to 0 . 5 ± 0 . 1 ∘ $$ 0.5\pm 0.{1}^{\circ } $$ C with both the original and augmented PCA-PDF application. For large sporadic motion, the augmented atlas improved the motion compensation from the original PCA-PDF correction from 8 . 8 ± 0 . 5 $$ 8.8\pm 0.5 $$ to 0 . 7 ± 0 . 1 ∘ $$ 0.7\pm 0.{1}^{\circ } $$ C. CONCLUSION: The PCA-PDF algorithm improved temperature accuracy to <1°C during periodic motion, but was not able to adequately address sporadic motion. By augmenting the PCA-PDF algorithm, temperature SD during large sporadic motion was also reduced to <1°C, greatly improving the original PCA-PDF algorithm.

Development and Evaluation of a High-Fidelity Rhinoplasty Simulator.

SUMMARY: Rhinoplasty is a challenging procedure with a steep learning curve. Surgical simulators provide a safe platform to gain hands-on experience without compromising patient outcomes. Therefore, rhinoplasty is an ideal procedure to benefit from an effective surgical simulator. A high-fidelity rhinoplasty simulator was developed using three-dimensional computer modeling, three-dimensional printing, and polymer techniques. The simulator was tested by six surgeons with experience in rhinoplasty to assess realism, anatomic accuracy, and value as a training tool. The surgeons performed common rhinoplasty techniques and were provided a Likert-type questionnaire assessing the anatomic features of the simulator. A variety of surgical techniques were performed successfully using the simulator, including open and closed approaches. Bony techniques performed included endonasal osteotomies and rasping. Submucous resection with harvest of septal cartilage, cephalic trim, and tip suturing, as well as grafting techniques including alar rim, columellar strut, spreader, and shield grafts, were performed successfully. Overall, there was agreement on the simulator's anatomic accuracy of bony and soft-tissue features. There was strong agreement on the simulator's overall realism and value as a training tool. The simulator provides a high-fidelity, comprehensive training platform to learn rhinoplasty techniques to augment real operating experience without compromising patient outcomes.

Postoperative cerebellar mutism syndrome is an acquired Autism-like network disturbance.

BACKGROUND: Cerebellar mutism syndrome (CMS) is a common and debilitating complication of posterior fossa tumour surgery in children. Affected children exhibit communication and social impairments that overlap phenomenologically with subsets of deficits exhibited by children with Autism spectrum disorder (ASD). Although both CMS and ASD are thought to involve disrupted cerebro-cerebellar circuitry, they are considered independent conditions due to an incomplete understanding of their shared neural substrates. METHODS: In this study, we analyzed post-operative cerebellar lesions from 90 children undergoing posterior fossa resection of medulloblastoma, 30 of whom developed CMS. Lesion locations were mapped to a standard atlas, and the networks functionally connected to each lesion were computed in normative adult and paediatric datasets. Generalizability to ASD was assessed using an independent cohort of children with ASD and matched controls (n=427). RESULTS: Lesions in children who developed CMS involved the vermis and inferomedial cerebellar lobules. They engaged large-scale cerebellothalamocortical circuits with a preponderance for the prefrontal and parietal cortices in the paediatric and adult connectomes, respectively. Moreover, with increasing connectomic age, CMS-associated lesions demonstrated stronger connectivity to the midbrain/red nuclei, thalami and inferior parietal lobules and weaker connectivity to prefrontal cortex. Importantly, the CMS-associated lesion network was independently reproduced in ASD and correlated with communication and social deficits, but not repetitive behaviours. CONCLUSIONS: Our findings indicate that CMS-associated lesions result in an ASD-like network disturbance that occurs during sensitive windows of brain development. A common network disturbance between CMS and ASD may inform improved treatment strategies for affected children.

Noninvasive magnetic resonance-guided focused ultrasound for tendon disruption: an in vivo Animal study.

PURPOSE: Surgical resection of the tendon is an effective treatment for severe contracture. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) is a non-invasive ultrasonic therapy which produces a focal increase in temperature, subsequent tissue ablation and disruption. We evaluated MRgFUS as a clinically translatable treatment modality to non-invasively disrupt in vivo porcine tendons. MATERIAL AND METHODS: In vivo Achilles tendons (n = 28) from 15-20kg Yorkshire pigs (n = 16) were randomly assigned to 4 treatment groups of 600, 900, 1200 and 1500 J. Pretreatment range of motion (ROM) of the ankle joint was measured with the animal under general anesthesia. Following MRgFUS treatment, success of tendon rupture, ROM increase, temperature, thermal dosage, skin burn, and histology analyses were performed. RESULTS: Rupture success was found to be 29%, 86%, 100% and 100% for treatment energies of 600, 900, 1200 and 1500 J respectfully. ROM difference at 90° flexion showed a statistically significant change in ROM between 900 J and 1200 J from 16° to 27°. There was no statistical significance between other groups, but there was an increase in ROM as more energy was delivered in the treatment. For each of the respective treatment groups, the maximal temperatures were 58.4 °C, 63.3 °C, 67.6 °C, and 69.9 °C. The average areas of thermal dose measured were 24.3mm2, 53.2mm2, 77.8mm2 and 91.6mm2. The average areas of skin necrosis were 5.4mm2, 21.8mm2, 37.2mm2, and 91.4mm2. Histologic analysis confirmed tissue ablation and structural collagen fiber disruption. CONCLUSIONS: This study demonstrated that MRgFUS is able to disrupt porcine tendons in vivo without skin incisions.

An adaptive targeting algorithm for magnetic resonance-guided high-intensity focused ultrasound controlled hyperthermia.

BACKGROUND: Mild hyperthermia has been demonstrated to improve the efficacy of chemotherapy, radiation, and immunotherapy in various cancer types. One localized, non-invasive method of administering mild hyperthermia is magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU). However, challenges for ultrasound such as beam deflection, refraction and coupling issues may result in a misalignment of the HIFU focus and the tumor during hyperthermia. Currently, the best option is to stop the treatment, wait for the tissue to cool, and redo the treatment planning before restarting the hyperthermia. This current workflow is both time-consuming and unreliable. PURPOSE: An adaptive targeting algorithm was developed for MRgHIFU controlled hyperthermia treatments for cancer therapeutics. This algorithm executes in real time while hyperthermia is being administered to ensure that the focus is within our target region. If a mistarget is detected, the HIFU system will electronically steer the focus of the HIFU beam to the correct target. The goal of this study was to quantify the accuracy and precision of the adaptive targeting algorithm's ability to correct a purposely misplanned hyperthermia treatment in real-time using a clinical MRgHIFU system. METHODS: A gelatin phantom with acoustic properties matched to the average speed of sound in human tissue was used to test the adaptive targeting algorithm's accuracy and precision. The target was purposely offset 10 mm away from the focus at the origin, in four orthogonal directions, allowing the algorithm to correct for this mistarget. In each direction, 10 data sets were collected for a total sample size of 40. Hyperthermia was administered with a target temperature set at 42°C. The adaptive targeting algorithm was run during the hyperthermia treatment and 20 thermometry images were collected after the beam steering occurred. The location of the focus was quantified by calculating the center of heating on the MR thermometry data. RESULTS: The average calculated trajectory passed to the HIFU system was 9.7 mm ± 0.4 mm where the target trajectory was 10 mm. The accuracy of the adaptive targeting algorithm after the beam steering correction was 0.9 mm and the precision was 1.6 mm. CONCLUSION: The adaptive targeting algorithm was implemented successfully and was able to correct the 10 mm mistargets with high accuracy and precision in gelatin phantoms. The results demonstrate the capability to correct the MRgHIFU focus location during controlled hyperthermia.

Sinus pericranii in the setting of a posterior fossa pilocytic astrocytoma: illustrative case.

BACKGROUND: Sinus pericranii (SP) is a rare vascular anomaly, with an uncertain etiology. Often discovered as superficial lesions, they can be primary or secondary in nature. Herein, we report a rare case of SP in the setting of a large posterior fossa pilocytic astrocytoma associated with a significant venous network. OBSERVATIONS: A 12-year-old male presented with acute clinical deterioration in extremis with a 2-month history of lethargy and headaches. Outside plain computed tomography imaging revealed a large posterior fossa cystic lesion, probably a tumor, with severe hydrocephalus. There was also a midline small skull defect at the opisthocranion, without visible vascular anomalies. An external ventricular drain was placed with rapid recovery. Contrast imaging revealed a large midline SP emanating from occipital bone with a large intraosseous, and subcutaneous venous plexus in the midline draining inferiorly into venous plexus around the craniocervical junction. A posterior fossa craniotomy without contrast imaging could have resulted in catastrophic hemorrhage. A small modified off-center craniotomy provided access to the tumor with a gross total excision. LESSONS: SP is a rare but significant phenomenon. Its presence does not necessarily preclude resection of underlying tumors, provided that a careful preoperative assessment of the venous anomaly is undertaken.

Outcomes following management of relapsed pediatric posterior fossa ependymoma in the molecular era.

PURPOSE: The overall survival and prognostic factors for children with multiply recurrent posterior fossa ependymoma are not well understood. We aimed to assess prognostic factors associated with survival for relapsed pediatric posterior fossa ependymoma. METHODS: An institutional database was queried for children with a primary diagnosis of posterior fossa ependymoma from 2000 to 2019. Kaplan-Meier survival analysis and Cox-proportional hazard regression were used to assess the relationship between treatment factors and overall survival. RESULTS: There were 60 patients identified; molecular subtype was available for 56, of which 49 (87.5%) were PF-A and 7 (12.5%) were PF-B. Relapse occurred in 29 patients (48%) at a mean time of 24 months following primary resection. Median 50% survival was 12.3 years for all patients and 3.3 years following diagnosis of first relapsed disease. GTR was associated with significantly improved survival following primary resection (HR 0.373, 95% CI 0.14-0.96). Presence of recurrent disease was significantly associated with worse survival (p < 0.0001). At recurrent disease diagnosis, disseminated disease was a negative prognostic factor (HR 11.0 95% CI 2.7-44) while GTR at first relapse was associated with improved survival HR 0.215 (95% CI: 0.048-0.96, p = 0.044). Beyond first relapse, the impact of GTR was not significant on survival, though surgery compared to no surgery was favorable with HR 0.155 (95% CI: 0.04-0.59). CONCLUSIONS: Disseminated disease at recurrence and extent of resection for first relapsed disease were important prognostic factors. Surgery compared to no surgery was associated with improved survival for the multiply recurrent ependymoma cohort.

Design and validation of a hemispherectomy simulator for neurosurgical education.

OBJECTIVE: Early adaptors of surgical simulation have documented a translation to improved intraoperative surgical performance. Similar progress would boost neurosurgical education, especially in highly nuanced epilepsy surgeries. This study introduces a hands-on cerebral hemispheric surgery simulator and evaluates its usefulness in teaching epilepsy surgeries. METHODS: Initially, the anatomical realism of the simulator and its perceived effectiveness as a training tool were evaluated by two epilepsy neurosurgeons. The surgeons independently simulated hemispherotomy procedures and provided questionnaire feedback. Both surgeons agreed on the anatomical realism and effectiveness of this training tool. Next, construct validity was evaluated by modeling the proficiency (task-completion time) of 13 participants, who spanned the experience range from novice to expert. RESULTS: Poisson regression yielded a significant whole-model fit (χ2 = 30.11, p < 0.0001). The association between proficiency when using the training tool and the combined effect of prior exposure to hemispherotomy surgery and career span was statistically significant (χ2 = 7.30, p = 0.007); in isolation, pre-simulation exposure to hemispherotomy surgery (χ2 = 6.71, p = 0.009) and career length (χ2 = 14.21, p < 0.001) were also significant. The mean (± SD) task-completion time was 25.59 ± 9.75 minutes. Plotting career length against task-completion time provided insights on learning curves of epilepsy surgery. Prediction formulae estimated that 10 real-life hemispherotomy cases would be needed to approach the proficiency seen in experts. CONCLUSIONS: The cerebral hemispheric surgery simulator is a reasonable epilepsy surgery training tool in the quest to increase preoperative practice opportunities for neurosurgical education.

A robotic MR-guided high-intensity focused ultrasound platform for intraventricular hemorrhage: assessment of clot lysis efficacy in a brain phantom.

OBJECTIVE: Intraventricular hemorrhage (IVH) is a neurovascular complication due to premature birth that results in blood clots forming within the ventricles. Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU) has been investigated as a noninvasive treatment to lyse clots. The authors designed and constructed a robotic MRgHIFU platform to treat the neonatal brain that facilitates ergonomic patient positioning. The clot lysis efficacy of the platform is quantified using a brain phantom and clinical MRI system. METHODS: A thermosensitive brain-mimicking phantom with ventricular cavities was developed to test the clot lysis efficacy of the robotic MRgHIFU platform. Whole porcine blood was clotted within the phantom's cavities. Using the MRgHIFU platform and a boiling histotripsy treatment procedure (500 W, 10-msec pulse duration, 1.0% duty cycle, and 40-second duration), the clots were lysed inside the phantom. The contents of the cavities were vacuum filtered, and the remaining mass of the solid clot particles was used to quantify the percentage of clot lysis. The interior of the phantom's cavities was inspected for any collateral damage during treatment. RESULTS: A total of 9 phantoms were sonicated, yielding an average (± SD) clot lysis of 97.0% ± 2.57%. Treatment resulted in substantial clot lysis within the brain-mimicking phantoms that were apparent on postsonication T2-weighted MR images. No apparent collateral damage was observed within the phantom after treatment. The results from the study showed the MRgHIFU platform was successful at lysing more than 90% of a blood clot at a statistically significant level. CONCLUSIONS: The robotic MRgHIFU platform was shown to lyse a large percentage of a blood clot with no observable collateral damage. These results demonstrate the platform's ability to induce clot lysis when targeting through simulated brain matter and show promise toward the final application in neonatal patients.

Preservation of endocrine function after Ommaya reservoir insertion in children with cystic craniopharyngioma.

INTRODUCTION: Children with craniopharyngiomas (CP) can experience significant morbidities caused by extensive surgery and/or radiation. Ommaya reservoir insertion (ORI) into cystic CP represents a minimally invasive approach allowing immediate decompression and aims to avoid additional injuries. The purpose of this study was to determine the surgical outcome and relevance of upfront ORI (± intracystic treatment) for preservation of endocrine function. METHODS: We performed a retrospective chart review of children with CP treated at the Hospital for Sick Children between 01/01/2000 and 15/01/2020. Endocrine function was reviewed at the time of initial surgery and throughout follow-up. New endocrinological deficits related to the index procedure were defined as immediate failure (IF), whereas postoperative duration of endocrinological stability (ES) was analyzed using the Kaplan-Meier method. The rate of IF and ES was compared between the treatment groups. RESULTS: Seventy-nine patients were included and had a median age of 8.3 years (range 2.1-18.0 years); 31 were males. Fifty-three patients with upfront surgical treatment, including 29 ORI and 24 gross total or partial resections had sufficient endocrinological follow-up data. Endocrine dysfunction occurring immediately after the index procedure (IF) was observed in 15 patients (62.5%) in the resection group compared to two patients (6.8%) in the ORI group, odds ratio: 0.05 (CI: 0.01-0.26, p < 0.0001). Excluding those with immediate endocrinological deficits, mean ES after ORI was 19.4 months (CI: 11.6-34.2), compared to 13.4 months (CI:10.6-NA) after surgical resection. CONCLUSIONS: Endocrine function was preserved in patients with upfront ORI (± intracystic treatment), which was confirmed as a minimally invasive procedure with an overall low morbidity profile.

Moderate procedural confidence improvement following hands-on practice using the hemispherectomy simulator.

INTRODUCTION: Pediatric hemispherectomy is a technically demanding procedure with significant risk. There are relatively few opportunities for surgeon trainees to gain confidence in this nuanced surgery solely through traditional apprenticeship prior to independent practice. Surgeon confidence has been linked to better intraoperative performance and surgical simulation has, according to literature, resulted in improved surgeon confidence. This manuscript measures the effect of epilepsy simulation on the procedural confidence of neurosurgical trainees as a marker of future improved intraoperative performance. METHODS: Eleven neurosurgery residents and fellows were allowed to practice on a novel hemispherectomy simulator. Pre- and post-simulation procedural confidence was measured using a 10-item questionnaire, with total scores ranging from 10 (least confident) to 50 (most confident). Matched pair t-testing was performed to determine participant mean difference between the pre- and post-procedural data sets. RESULTS: The assessment tool bore a high reliability coefficient (Cronbach's α = 0.93). The procedural confidence of all the study participants increased following simulation (p value < 0.001). The overall mean increase in confidence was 7.2 ± 4.0 (mean ± standard deviation), 7.5 ± 4.7 among fellows and 6.8 ± 3.6 among residents. Procedural confidence values were higher among the fellows (26.9 ± 8.1) compared to the residents (19.0 ± 7.4). This difference in means was statistically significant (p value 0.03). A positive association was calculated between the perceived confidence and the postgraduate year of training (p value 0.005, r = 0.57). CONCLUSION: The hemispherectomy simulator moderately improves perceived confidence among neurosurgical trainees and may augment pre-operative surgical practice opportunities.

Preliminary Study of a Modular MR-Compatible Robot for Image-Guided Insertion of Multiple Needles.

Percutaneous needle-based interventions such as transperineal prostate brachytherapy require the accurate placement of multiple needles to treat cancerous lesions within the target organ. To guide needle placement, magnetic resonance imaging (MRI) offers excellent visualization of the target lesion without the need for ionizing radiation. To date, multi-needle insertion relies on a grid template, which limits the ability to steer individual needles. This work describes an MR-compatible robot designed for the sequential insertion of multiple non-parallel needles under MR guidance. The 6-DOF system is designed with an articulated arm to extend the reach of the robot. This strategy presents a novel approach enabling the robot to maneuver around existing needles while minimizing the footprint of the robot. Forward kinematics as well as optimization-based inverse kinematics are presented. The impact of the robot on image quality was tested for four sequences (T1w-TSE, T2w-TSE, THRIVE and EPI) on a 3T Philips Achieva system. Quantification of the signal-to-noise ratio showed a 46% signal loss in a gelatin phantom when the system was powered on but no further adverse effects when the robot was moving. Joint level testing showed a maximum error of 2.10 ± 0.72°s for revolute joints and 0.31 ± 0.60 mm for prismatic joints. The theoretical workspace spans the proposed clinical target surface of 10 x 10 cm. Lastly, the feasibility of multi-needle insertion was demonstrated with four needles inserted under real-time MR-guidance with no visible loss in image quality.

Fabrication of Customizable Intraplaque Hemorrhage Phantoms for Magnetic Resonance Imaging.

PURPOSE: Magnetic resonance (MR) imaging detection of methemoglobin, a molecular marker of intraplaque hemorrhage (IPH), in atherosclerotic plaque is a promising method of assessing stroke risk. However, the multicenter imaging studies required to further validate this technique necessitate the development of IPH phantoms to standardize images acquired across different scanners. This study developed a set of phantoms that modeled methemoglobin-laden IPH for use in MR image standardization. PROCEDURES: A time-stable material mimicking the MR properties of methemoglobin in IPH was created by doping agarose hydrogel with gadolinium and sodium alginate. This material was used to create a phantom that consisted of 9 cylindrical IPH sites (with sizes from 1 to 8 mm). Anatomical replicas of IPH-positive atherosclerosis were also created using 3D printed molds. These plaque replicas also modeled other common plaque components including a lipid core and atheroma cap. T1 mapping and a magnetization-prepared rapid acquisition gradient echo (MPRAGE) carotid imaging protocol were used to assess phantom realism and long-term stability. RESULTS: Cylindrical phantom IPH sites possessed a T1 time of 335 ± 51 ms and exhibited little change in size or MPRAGE signal intensity over 31 days; the mean (SD) magnitude of changes in size and signal were 6.4 % (2.7 %) and 7.3 % (6.7 %), respectively. IPH sites incorporated into complex anatomical plaque phantoms exhibited contrast comparable to clinical images. CONCLUSIONS: The cylindrical IPH phantom accurately modeled the short T1 time characteristic of methemoglobin-laden IPH, with the IPH sites exhibiting little variation in imaging properties over 31 days. Furthermore, MPRAGE images of the anatomical atherosclerosis replicas closely matched those of clinical plaques. In combination, these phantoms will allow for IPH imaging protocol standardization and thus facilitate future multicenter IPH imaging.

The Hydrocephalus Clinical Research Network quality improvement initiative: the role of antibiotic-impregnated catheters and vancomycin wound irrigation.

OBJECTIVE: Two previous Hydrocephalus Clinical Research Network (HCRN) studies have demonstrated that compliance with a standardized CSF shunt infection protocol reduces shunt infections. In this third iteration, a simplified protocol consisting of 5 steps was implemented. This analysis provides an updated evaluation of protocol compliance and evaluates modifiable shunt infection risk factors. METHODS: The new simplified protocol was implemented at HCRN centers on November 1, 2016, for all shunt procedures, excluding external ventricular drains, ventricular reservoirs, and subgaleal shunts. Procedures performed through December 31, 2019, were included (38 months). Compliance with the protocol, use of antibiotic-impregnated catheters (AICs), and other variables of interest were collected at the index operation. Outcome events for a minimum of 6 months postoperatively were recorded. The definition of infection was unchanged from the authors' previous report. RESULTS: A total of 4913 procedures were performed at 13 HCRN centers. The overall infection rate was 5.1%. Surgeons were compliant with all 5 steps of the protocol in 79.4% of procedures. The infection rate for the protocol alone was 8.1% and dropped to 4.9% when AICs were added. Multivariate analysis identified having ≥ 2 complex chronic conditions (odds ratio [OR] 1.76, 95% confidence interval [CI] 1.26-2.44, p = 0.01) and a history of prior shunt surgery within 12 weeks (OR 1.84, 95% CI 1.37-2.47, p < 0.01) as independent risk factors for shunt infection. The use of AICs (OR 0.70, 95% CI 0.50-0.97, p = 0.05) and vancomycin irrigation (OR 0.36, 95% CI 0.21-0.62, p < 0.01) were identified as independent factors protective against shunt infection. CONCLUSIONS: The authors report the third iteration of their quality improvement protocol to reduce the risk of shunt infection. Compliance with the protocol was high. These updated data suggest that the incorporation of AICs is an important, modifiable infection prevention measure. Vancomycin irrigation was also identified as a protective factor but requires further study to better understand its role in preventing shunt infection.