Repeat single-fraction stereotactic radiosurgery for recurrent vestibular schwannoma.

Background: Data are scarce on the efficacy of a second radiosurgery (SRS) treatment of vestibular schwannoma that has progressed following initial treatment with SRS. We sought to report the outcome of our repeat SRS series with long-term imaging follow-up. Materials and methods: We retrospectively analyzed 6 patients who met the following criteria: Repeat SRS at our institution between 1995 and 2018; solitary unilateral tumor; no evidence of neurofibromatosis; and magnetic resonance (MR) planning for both SRS treatments. All treatments were delivered with a linear accelerator-based system using head frame immobilization. The prescribed dose to the periphery of the tumor was 12.5 Gy in all initial and repeat SRS treatments, except for one repeat treatment to 10 Gy. Results: Follow-up with MR scan following the second SRS treatment was a median 8.4 years. The tumor control rate (lack of progression) following the second SRS treatment was 83% (5/6). Actuarial 10-year outcomes following repeat SRS were: tumor control, 80%; absolute survival, 80%; and cause-specific survival, 100%. Of the patients with at least minimal hearing retention before initial SRS, none had ipsilateral hearing preservation after initial radiation treatment. Improvement in any pretreatment cranial nerve deficits was not seen. The only permanent grade ≥ 3 toxicity from repeat SRS was a case of infraorbital nerve deficit. No patient developed a stroke, malignant transformation, induced second tumor, or facial nerve deficit. Conclusion: There was excellent overall survival, tumor control, and low morbidity in our series for recurrent vestibular schwannoma submitted to repeat single-fraction SRS, supporting additional studies of this treatment strategy.

Variability in commercially available deformable image registration: A multi-institution analysis using virtual head and neck phantoms.

PURPOSE: The purpose of this study was to evaluate the performance of three common deformable image registration (DIR) packages across algorithms and institutions. METHODS AND MATERIALS: The Deformable Image Registration Evaluation Project (DIREP) provides ten virtual phantoms derived from computed tomography (CT) datasets of head-and-neck cancer patients over a single treatment course. Using the DIREP phantoms, DIR results from 35 institutions were submitted using either Velocity, MIM, or Eclipse. Submitted deformation vector fields (DVFs) were compared to ground-truth DVFs to calculate target registration error (TRE) for six regions of interest (ROIs). Statistical analysis was performed to determine the variability between each DIR software package and the variability of users within each algorithm. RESULTS: Overall mean TRE was 2.04 ± 0.35 mm for Velocity, 1.10 ± 0.29 mm for MIM, and 2.35 ± 0.15 mm for Eclipse. The MIM mean TRE was significantly different than both Velocity and Eclipse for all ROIs. Velocity and Eclipse mean TREs were not significantly different except for when evaluating the registration of the cord or mandible. Significant differences between institutions were found for the MIM and Velocity platforms. However, these differences could be explained by variations in Velocity DIR parameters and MIM software versions. CONCLUSIONS: Average TRE was shown to be <3 mm for all three software platforms. However, maximum errors could be larger than 2 cm indicating that care should be exercised when using DIR. While MIM performed statistically better than the other packages, all evaluated algorithms had an average TRE better than the largest voxel dimension. For the phantoms studied here, significant differences between algorithm users were minimal suggesting that the algorithm used may have more impact on DIR accuracy than the particular registration technique employed. A significant difference in TRE was discovered between MIM versions showing that DIR QA should be performed after software upgrades as recommended by TG-132.

Three-Dimensional Printing for Construction of Tissue-Equivalent Anthropomorphic Phantoms and Determination of Conceptus Dose.

OBJECTIVE: The purpose of this study was to develop a road map for rapid construction of anthropomorphic phantoms from computational human phantoms for use in diagnostic imaging dosimetry studies. These phantoms are ideal for performing pregnant-patient dosimetry because the phantoms imitate the size and attenuation properties of an average-sized pregnant woman for multiple gestational periods. MATERIALS AND METHODS: The method was derived from methods and materials previously described but adapted for 3D printing technology. A 3D printer was used to transform computational models into a physical duplicate with small losses in spatial accuracy and to generate tissue-equivalent materials characterized for diagnostic energy x-rays. A series of pregnant abdomens were selected as prototypes because of their large size and complex modeling. The process involved the following steps: segmentation of anatomy used for modeling; transformation of the computational model into a printing file format; preparation, characterization, and introduction of phantom materials; and model removal and phantom assembly. RESULTS: The density of the homogenized soft tissue-equivalent substitute was optimized by combining 9.0% by weight of urethane filler powder and 91.0% urethane polymer, which resulted in a mean density of 1.041 g/cm3 measured over 20 samples. Density varied among all of the samples by 0.0026 g/cm3. The total variation in density was 0.00261 g/cm3. The half-value layer of the bone material was measured to be 1.7 mm of bone material at 120 kVp and when simulated by use of the density of the bone tissue-equivalent substitute (1.60 g/cm3) was determined to be 1.61 mm of bone tissue. For dosimetry purposes the phantom provided excellent results for evaluating a site's protocol based on scan range. CONCLUSION: The 3D printing technology is applicable to the fabrication of phantoms used for performing dosimetry. The tissue-equivalent materials used to substitute for the soft tissue were developed to be highly adaptable for optimization based on the dosimetry application. Use of this method resulted in more automated phantom construction with decreased construction time and increased out-of-slice spatial resolution of the phantoms.

Mapping hematopoiesis in a fully regenerative vertebrate: the axolotl.

Hematopoietic stem cell (HSC)-derived cells are involved in wound healing responses throughout the body. Unfortunately for mammals, wound repair typically results in scarring and nonfunctional reparation. Among vertebrates, none display such an extensive ability for adult regeneration as urodele amphibians, including 1 of the more popular models: the axolotl. However, a lack of knowledge of axolotl hematopoiesis hinders the use of this animal for the study of hematopoietic cells in scar-free wound healing and tissue regeneration. We used white and cytomegalovirus:green fluorescent protein(+) transgenic white axolotl strains to map sites of hematopoiesis and develop hematopoietic cell transplant methodology. We also established a fluorescence-activated cell sorter enrichment technique for major blood lineages and colony-forming unit assays for hematopoietic progenitors. The liver and spleen are both active sites of hematopoiesis in adult axolotls and contain transplantable HSCs capable of long-term multilineage blood reconstitution. As in zebrafish, use of the white axolotl mutant allows direct visualization of homing, engraftment, and hematopoiesis in real time. Donor-derived hematopoiesis occurred for >2 years in recipients generating stable hematopoietic chimeras. Organ segregation, made possible by embryonic microsurgeries wherein halves of 2 differently colored embryos were joined, indicate that the spleen is the definitive site of adult hematopoiesis.

Benchmarking of five commercial deformable image registration algorithms for head and neck patients.

Benchmarking is a process in which standardized tests are used to assess system performance. The data produced in the process are important for comparative purposes, particularly when considering the implementation and quality assurance of DIR algorithms. In this work, five commercial DIR algorithms (MIM, Velocity, RayStation, Pinnacle, and Eclipse) were benchmarked using a set of 10 virtual phantoms. The phantoms were previously developed based on CT data collected from real head and neck patients. Each phantom includes a start of treatment CT dataset, an end of treatment CT dataset, and the ground-truth deformation vector field (DVF) which links them together. These virtual phantoms were imported into the commercial systems and registered through a deformable process. The resulting DVFs were compared to the ground-truth DVF to determine the target registration error (TRE) at every voxel within the image set. Real treatment plans were also recalculated on each end of treatment CT dataset and the dose transferred according to both the ground-truth and test DVFs. Dosimetric changes were assessed, and TRE was correlated with changes in the DVH of individual structures. In the first part of the study, results show mean TRE on the order of 0.5 mm to 3 mm for all phan-toms and ROIs. In certain instances, however, misregistrations were encountered which produced mean and max errors up to 6.8 mm and 22 mm, respectively. In the second part of the study, dosimetric error was found to be strongly correlated with TRE in the brainstem, but weakly correlated with TRE in the spinal cord. Several interesting cases were assessed which highlight the interplay between the direction and magnitude of TRE and the dose distribution, including the slope of dosimetric gradients and the distance to critical structures. This information can be used to help clinicians better implement and test their algorithms, and also understand the strengths and weaknesses of a dose adaptive approach.

The risk of malignancy anywhere in the body after linear accelerator (LINAC) stereotactic radiosurgery.

BACKGROUND: Despite the conformity of stereotactic radiosurgery (SRS) treatment, there are concerns about the risk of malignancy. OBJECTIVE: We compared the number of cancer cases observed after treatment in a group of SRS patients to the number of cancer cases that would be expected in an age- and gender-matched group. METHODS: We collected data from the University of Florida SRS database for patients treated for meningiomas, intracranial schwannomas, arteriovenous malformations (AVMs), trigeminal neuralgia, pituitary adenomas, cavernous angiomas, and metastases. We used the Florida Cancer Data System (FCDS) to determine the actual cancer rates for SRS-treated patients, and we compared these to the cancer rates in similar groups of non-SRS-treated patients based on rates available from the SEER (surveillance epidemiology and end results) database. RESULTS: A total of 2,369 patients were analyzed. Of these, 862 were patients with metastases who were analyzed only to ensure the sensitivity of using the FCDS to determine malignancy rates. The results for patients with more than 5 years of follow-up are reported. Without the metastases patients, a total of 627 patients had more than 5 years of follow-up data. Follow-up in patient-years was 1,711 for the meningioma patients, 1,851 for the schwannoma patients, 1,407 for the AVM patients and 338 for patients with a diagnosis of 'other'. The observed cancer rate in the meningioma patients was 3.96% compared to the expected rate of 10% (binomial 95% confidence interval, CI = 1.85-7.94). The observed cancer rate in the schwannoma patients was 4.93% compared to the expected rate of 12.5% (95% CI = 2.61-8.89). The observed cancer rate in the AVM patients was 3.64% compared to the expected rate of 4.43% (95% CI = 1.49-8.10). The observed cancer rate in patients treated for other diagnoses (e.g. pituitary adenoma or trigeminal neuralgia) was 0% compared to the expected rate of 6.36% (95% CI = 0-11.7). CONCLUSIONS: In a large population of SRS-treated patients, there was no increased risk of malignancy compared to the general population.

Stereotactic Radiosurgery for Vestibular Schwannoma With Radiographic Brainstem Compression.

OBJECTIVE: The safety of single-treatment stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) with radiographic evidence of brainstem compression but without motor deficit is controversial. Data on linear accelerator (linac)-based SRS in this setting are scarce. We address this with an outcomes report from an unselected series of patients with VS with radiographic brainstem compression treated with linac SRS. METHODS: We included 139 patients with unilateral VS (any size) with radiographic brainstem compression (all without serious brainstem neurological deficits). The SRS prescription dose was 12.5 Gy (single fraction) using 6MV linac-produced photon beams, delivered with a multiple arc technique. Inclusion criteria required at least 1 year of radiographic follow-up with magnetic resonance imaging. The primary endpoint was freedom from serious brainstem toxicity (≥grade 3 Common Terminology Criteria for Adverse Events v5); the secondary was freedom from enlargement (tumor progression or any requiring intervention). We assessed serious cranial nerve complications, excluding hearing loss, defined as Common Terminology Criteria for Adverse Events v5 grade 3 toxicity. RESULTS: Median magnetic resonance imaging follow-up time was 5 years, and median tumor size was 2.5 cm in greatest axial dimension and 5 ml in volume. The median brainstem D0.03 ml=12.6 Gy and median brainstem V10 Gy=0.4 ml. At 5 years, the actuarial freedom from serious brainstem toxicity was 100%, and freedom from tumor enlargement (requiring surgery and/or due to progression) was 90%. Severe facial nerve damage in patients without tumor enlargement was 0.9%. CONCLUSION: Linac-based SRS, as delivered in our series for VS with radiographic brainstem compression, is safe and effective.

Delineation of motor and somatosensory thalamic subregions utilizing probabilistic diffusion tractography and electrophysiology.

PURPOSE: To employ and compare probabilistic diffusion tractography (PDT) for the explicit localization of connections from the thalamus to somatosensory cortex (S1) and primary motor cortex (M1) / supplementary motor area (SMA) with microelectrode electrophysiology in patients undergoing deep brain stimulation (DBS) surgery. MATERIALS AND METHODS: These tractography-derived connections were used to categorize voxels in the thalamus as corresponding to sensory or motor physiology. A novel model (referred to in this work as the "mixture" model) to delineate PDT-based thalamic functional subregions by thresholding fiber intensities, ie, connectivity-defined regions (CDR), was devised. Regions created using this classification method were compared with the most commonly used model (referred to in this work as the "separation" or "winner takes all" model) for defining CDRs. RESULTS: Electrophysiology data corresponded better for S1 CDRs created using the mixture model for both sensory and motor cells. Separation model CDRs showed poor correspondence against electrophysiology, with few sensory cells corresponding to the S1 separation model CDR. CONCLUSION: Mixture model-based CDRs may offer a significant improvement in delineation of functional subregions of subcortical structures.

A silicone-based support material eliminates interfacial instabilities in 3D silicone printing.

Among the diverse areas of 3D printing, high-quality silicone printing is one of the least available and most restrictive. However, silicone-based components are integral to numerous advanced technologies and everyday consumer products. We developed a silicone 3D printing technique that produces precise, accurate, strong, and functional structures made from several commercially available silicone formulations. To achieve this level of performance, we developed a support material made from a silicone oil emulsion. This material exhibits negligible interfacial tension against silicone-based inks, eliminating the disruptive forces that often drive printed silicone features to deform and break apart. The versatility of this approach enables the use of established silicone formulations in fabricating complex structures and features as small as 8 micrometers in diameter.

Cognition and mood in Parkinson's disease in subthalamic nucleus versus globus pallidus interna deep brain stimulation: the COMPARE trial.

OBJECTIVE: Our aim was to compare in a prospective blinded study the cognitive and mood effects of subthalamic nucleus (STN) vs. globus pallidus interna (GPi) deep brain stimulation (DBS) in Parkinson disease. METHODS: Fifty-two subjects were randomized to unilateral STN or GPi DBS. The co-primary outcome measures were the Visual Analog Mood Scale, and verbal fluency (semantic and letter) at 7 months post-DBS in the optimal setting compared to pre-DBS. At 7 months post-DBS, subjects were tested in four randomized/counterbalanced conditions (optimal, ventral, dorsal, and off DBS). RESULTS: Forty-five subjects (23 GPi, 22 STN) completed the protocol. The study revealed no difference between STN and GPi DBS in the change of co-primary mood and cognitive outcomes pre- to post-DBS in the optimal setting (Hotelling's T(2) test: p = 0.16 and 0.08 respectively). Subjects in both targets were less "happy", less "energetic" and more "confused" when stimulated ventrally. Comparison of the other 3 DBS conditions to pre-DBS showed a larger deterioration of letter verbal fluency in STN, especially when off DBS. There was no difference in UPDRS motor improvement between targets. INTERPRETATION: There were no significant differences in the co-primary outcome measures (mood and cognition) between STN and GPi in the optimal DBS state. Adverse mood effects occurred ventrally in both targets. A worsening of letter verbal fluency was seen in STN. The persistence of deterioration in verbal fluency in the off STN DBS state was suggestive of a surgical rather than a stimulation-induced effect. Similar motor improvement were observed with both STN and GPi DBS.

Prevalence of Twiddler's syndrome as a cause of deep brain stimulation hardware failure.

We reviewed our deep brain stimulation patient database to describe hardware complications which resulted from implantable pulse generator mobility, a phenomenon referred to as Twiddler's syndrome. A prospectively collected database of adverse events for all patients operated on at the University of Florida was queried searching for hardware malfunctions. Of 362 total leads implanted in 226 patients since 2002, there were 17 hardware malfunctions. Three of them were due to Twiddler's syndrome, representing 1.3% of patients (3 of 226 patients) and 1.4% of leads (5 of 362 leads). The subjects had characteristic presentations including re-emergence of symptoms, pain along the path of the hardware, abnormal impedances/current drain and radiographic signs of twisting/fracture. In all cases securing the implantable pulse generator within the chest pocket resolved the issue. Twiddler's syndrome in the population of movement disorder patients treated with deep brain stimulation is an uncommon but important adverse event. It possesses a characteristic presentation and with appropriate diagnostic evaluation it is treatable and future occurrences are preventable.

Impact of Extent of Resection on Incidence of Postoperative Complications in Patients With Glioblastoma.

BACKGROUND: Extent of resection (EOR) is well established as correlating with overall survival in patients with glioblastoma (GBM). The impact of EOR on reported quality metrics such as patient safety indicators (PSIs) and hospital-acquired conditions (HACs) is unknown. OBJECTIVE: To perform a retrospective study to evaluate possible associations between EOR and the incidence of PSIs and HACs. METHODS: We queried all patients diagnosed with GBM who underwent surgical resection at our institution between January 2011 and May 2017. Pre- and postoperative magnetic resonance images were analyzed for EOR. Each chart was reviewed to determine the incidence of PSIs and HACs. RESULTS: A total of 284 patients met the inclusion criteria. EOR ranged from 39.00 to 100%, with a median of 99.84% and a mean of 95.7%. There were 16 PSI, and 13 HAC, events. There were no significant differences in the rates of PSIs or HACs when compared between patients stratified by gross total resection (EOR ≥ 95%) and subtotal resection (EOR < 95%). The odds of encountering a PSI or HAC were 2.5 times more likely in the subtotal resection group compared to the gross total resection group (P = .58). After adjusting for confounders, the odds of encountering a PSI or HAC in the subtotal resection group were 3.9 times greater than for the gross total resection group (P < .05). CONCLUSION: Gross total resection of GBM is associated with a decreased incidence of PSIs and HACs, as compared to subtotal resection.

A high resolution and high contrast MRI for differentiation of subcortical structures for DBS targeting: the Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR).

DBS depends on precise placement of the stimulating electrode into an appropriate target region. Image-based (direct) targeting has been limited by the ability of current technology to visualize DBS targets. We have recently developed and employed a Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR) 3T MRI sequence to more reliably visualize these structures. The FGATIR provides significantly better high resolution thin (1 mm) slice visualization of DBS targets than does either standard 3T T1 or T2-weighted imaging. The T1 subcortical image revealed relatively poor contrast among the targets for DBS, though the sequence did allow localization of striatum and thalamus. T2 FLAIR scans demonstrated better contrast between the STN, SNr, red nucleus (RN), and pallidum (GPe/GPi). The FGATIR scans allowed for localization of the thalamus, striatum, GPe/GPi, RN, and SNr and displayed sharper delineation of these structures. The FGATIR also revealed features not visible on other scan types: the internal lamina of the GPi, fiber bundles from the internal capsule piercing the striatum, and the boundaries of the STN. We hope that use of the FGATIR to aid initial targeting will translate in future studies to faster and more accurate procedures with consequent improvements in clinical outcomes.

Linear accelerator radiosurgery for cavernous sinus meningiomas.

OBJECTIVE: In this paper, the authors review the results of a single-center experience using linear accelerator (LINAC) radiosurgery for the treatment of cavernous sinus meningiomas. METHODS: This is a retrospective analysis with a median follow-up of 50 months. All patients were treated on an outpatient basis. Fifty-five patients were treated and 6 patients were lost to follow-up. Changes in preradiosurgery cranial nerve deficits and symptoms as well as actuarial local tumor control were evaluated. RESULTS: The actuarial local tumor control was 100% at 5 years and 98% at 10 years. One patient had enlargement of tumor. Sixty-five percent had improvement in preradiosurgery cranial nerve deficits, 31% were unchanged and 1 patient (3.5%) was worse. Only 1 patient developed a new neurologic deficit. CONCLUSIONS: This is the largest LINAC radiosurgery experience for cavernous sinus meningiomas reported to date. Radiosurgery appears to offer greatly superior tumor control and much lower morbidity than surgical resection of cavernous sinus meningiomas.

Stereotactic radiosurgery and the linear accelerator: accelerating electrons in neurosurgery.

The search for efficacious, minimally invasive neurosurgical treatment has led to the development of the operating microscope, endovascular treatment, and endoscopic surgery. One of the most minimally invasive and exciting discoveries is the use of targeted, high-dose radiation for neurosurgical disorders. Radiosurgery is truly minimally invasive, delivering therapeutic energy to an accurately defined target without an incision, and has been used to treat a wide variety of pathological conditions, including benign and malignant brain tumors, vascular lesions such as arteriovenous malformations, and pain syndromes such as trigeminal neuralgia. Over the last 50 years, a tremendous amount of knowledge has been garnered, both about target volume and radiation delivery. This review covers the intense study of these concepts and the development of linear accelerators to deliver stereotactic radiosurgery. The fascinating history of stereotactic neurosurgery is reviewed, and a detailed account is given of the development of linear accelerators and their subsequent modification for radiosurgery.

Rapid fabrication of custom patient biopsy guides.

Image guided surgery is currently performed using frame-based as well as frameless approaches. In order to reduce the invasive nature of stereotactic guidance as well as to reduce the cost in both equipment and time required within the operating room we investigated the use of rapid prototyping (RP) technology. In our approach we fabricated custom patient specific face-masks and guides that can be applied to the patient during surgery. These guides provide a stereotactic reference for the accurate placement of surgical tools to a pre-planned target along a pre-planned trajectory. While the use of RP machines has previously been shown to be satisfactory for the accuracy standpoint, one of our design criteria, completing the entire built and introduction into the sterile field in less than 120 minutes, was unobtainable. Our primary problems were the fabrication time and the non-resistance of the built material to high-temperature sterilization. In the current study, we have investigated the use of subtractive rapid prototyping (SRP) machines to perform the same quality of surgical guidance while improving the fabrication time and allowing for choosing materials suitable for sterilization. Because SRP technology does not offer the same flexibility as RP in term of prototype shape and complexity, our software program was adapted to provide new guide designs suitable for SRP fabrication. The biopsy guide was subdivided for a more efficient built with the parts being uniquely assembled to form the final guide. The accuracy of the assembly was then assessed using a modified Brown-Roberts-Wells phantom base that allows measuring the position of a biopsy needle introduced into the guide and comparing it with the actual planned target. These tests showed that 1) SRP machines provide an average accuracy of 0.77 mm with a standard deviation of 0.05 mm (plus or minus one image pixel) and 2) SRP allows for fabrication and sterilization within three and a half hours after diagnostic image acquisition and we are confident that that further improvements can reduce this time to less than two hours. Further tests will determine the accuracy of the positioning of the face mask on the patient's head under an IRB-approved trial judged against actual frame-based and frameless systems.

CXCR1- or CXCR2-modified CAR T cells co-opt IL-8 for maximal antitumor efficacy in solid tumors.

Chimeric antigen receptor (CAR) T-cell therapy targeting solid tumors has stagnated as a result of tumor heterogeneity, immunosuppressive microenvironments, and inadequate intratumoral T cell trafficking and persistence. Early (≤3 days) intratumoral presentation of CAR T cells post-treatment is a superior predictor of survival than peripheral persistence. Therefore, we have co-opted IL-8 release from tumors to enhance intratumoral T-cell trafficking through a CAR design for maximal antitumor activity in solid tumors. Here, we demonstrate that IL-8 receptor, CXCR1 or CXCR2, modified CARs markedly enhance migration and persistence of T cells in the tumor, which induce complete tumor regression and long-lasting immunologic memory in pre-clinical models of aggressive tumors such as glioblastoma, ovarian and pancreatic cancer.

Anniversary Paper: the role of medical physicists in developing stereotactic radiosurgery.

This article is a tribute to the pioneering medical physicists over the last 50 years who have participated in the research, development, and commercialization of stereotactic radiosurgery (SRS) and stereotactic radiotherapy utilizing a wide range of technology. The authors have described the evolution of SRS through the eyes of physicists from its beginnings with the Gamma Knife in 1951 to proton and charged particle therapy; modification of commercial linacs to accommodate high precision SRS setups; the multitude of accessories that have enabled fine tuning patients for relocalization, immobilization, and repositioning with submillimeter accuracy; and finally the emerging technology of SBRT. A major theme of the article is the expanding role of the medical physicist from that of advisor to the neurosurgeon to the current role as a primary driver of new technology that has already led to an adaptation of cranial SRS to other sites in the body, including, spine, liver, and lung. SRS continues to be at the forefront of the impetus to provide technological precision for radiation therapy and has demonstrated a host of downstream benefits in improving delivery strategies for conventional therapy as well. While this is not intended to be a comprehensive history, and the authors could not delineate every contribution by all of those working in the pursuit of SRS development, including physicians, engineers, radiobiologists, and the rest of the therapy and dosimetry staff in this important and dynamic radiation therapy modality, it is clear that physicists have had a substantial role in the development of SRS and theyincreasingly play a leading role in furthering SRS technology.

A case-based review of troubleshooting deep brain stimulator issues in movement and neuropsychiatric disorders.

OBJECTIVE: To review the spectrum of problems that can occur in the DBS patient and to suggest potential troubleshooting tips for identification and management of DBS related issues. BACKGROUND: Deep brain stimulation (DBS) has become commonplace for the treatment of medication-refractory neurological disorders. There remains no consensus on the best practices for screening, surgical techniques, and post-operative care. There are few experienced DBS programmers and scarce resources available describing approaches for troubleshooting DBS problems. METHODS: We present a case-based review that offers practical tips for the management and troubleshooting of difficult to manage DBS cases. We present 10 cases to demonstrate common issues encountered in DBS management. RESULTS: There are many important difficulties that may be encountered with DBS devices, and practitioners should be aware of these potential problems, as well as rational management solutions. The following areas should be emphasized as potential causes of difficulties: a non-ideal initial DBS candidate, inadequate multidisciplinary team care, failure of perceived expectations, DBS procedural complication, hardware complication, suboptimal lead placement, programming, access to care, disease progression, and tolerance/habituation. CONCLUSION: Neurologists seeing DBS patients should become familiar with issues involved in difficult to manage DBS cases. Many "DBS failures" are currently treatable by appropriate medicine, programming, and surgical approaches.

Techniques to Ensure Accurate Targeting for Delivery of Awake Laser Interstitial Thermotherapy.

BACKGROUND: Magnetic resonance imaging (MRI) guided laser interstitial thermal therapy (LITT) is an emerging neurosurgical treatment modality that is typically performed under general anesthesia. We describe a novel workflow developed at the University of Florida to deliver LITT in conscious patients without the use of general anesthesia. OBJECTIVE: To describe a novel workflow for LITT implementation in the awake patient with equivalent treatment results when compared to procedures performed under general anesthesia. METHODS: For trajectories near a post of the Cosman-Roberts-Wells (CRW) frame (Integra LifeSciences, Plainsboro, New Jersey), we used preoperative MRI imaging to 3-dimensional-print a patient-specific mask with a trajectory guide to indicate the planned entry point during headframe placement. Otherwise, routine headframe placement and stereotactic registration were performed. Stereotactic biopsy and placement of the cranial bolt were performed in a standard neurosurgical operating room. The patient was transferred to a diagnostic MRI suite and positioned in the MRI scanner using beanbags and a custom molded thermoplastic mask. LITT was delivered with the patient conscious in the MRI scanner according to the manufacturer's recommendations. We collected patient demographics, treatment time, length of stay, and calculated preoperative tumor volume and postoperative ablation volumes. RESULTS: Ten sequential patients were treated with LITT from January 2016 until March 2017. The average preoperative tumor volume was 6.9 cm3. The average tissue volume ablated was 18.3 cm3. The mean operative time was 31 min (standard deviation [SD] 10 min) and mean time with laser delivery in MRI was 79 min (SD 27 min). The mean length of stay was 1.4 d (SD 0.9). There were no major complications. CONCLUSION: Using trajectory preplanning, customized face masks, and noninvasive head immobilization, LITT can be delivered to patients safely and accurately without general anesthesia.