Mahesh B. Shenai

Virtual interactive presence and augmented reality (VIPAR) for remote surgical assistance.

BACKGROUND: Surgery is a highly technical field that combines continuous decision-making with the coordination of spatiovisual tasks. OBJECTIVE: We designed a virtual interactive presence and augmented reality (VIPAR) platform that allows a remote surgeon to deliver real-time virtual assistance to a local surgeon, over a standard Internet connection. METHODS: The VIPAR system consisted of a “local” and a “remote” station, each situated over a surgical field and a blue screen, respectively. Each station was equipped with a digital viewpiece, composed of 2 cameras for stereoscopic capture, and a high-definition viewer displaying a virtual field. The virtual field was created by digitally compositing selected elements within the remote field into the local field. The viewpieces were controlled by workstations mutually connected by the Internet, allowing virtual remote interaction in real time. Digital renderings derived from volumetric MRI were added to the virtual field to augment the surgeons reality. For demonstration, a fixed-formalin cadaver head and neck were obtained, and a carotid endarterectomy (CEA) and pterional craniotomy were performed under the VIPAR system. RESULTS: The VIPAR system allowed for real-time, virtual interaction between a local (resident) and remote (attending) surgeon. In both carotid and pterional dissections, major anatomic structures were visualized and identified. Virtual interaction permitted remote instruction for the local surgeon, and MRI augmentation provided spatial guidance to both surgeons. Camera resolution, color contrast, time lag, and depth perception were identified as technical issues requiring further optimization. CONCLUSION: Virtual interactive presence and augmented reality provide a novel platform for remote surgical assistance, with multiple applications in surgical training and remote expert assistance.

The use of multiplanar trajectory planning in the stereotactic placement of depth electrodes.

OBJECTIVE To assess the value of multiplanar reconstruction software in trajectory planning for depth electrode insertion in medically refractory epilepsy. METHODS A series of 29 patients undergoing frame-based hippocampal depth electrode insertion were identified. In 19 patients, preoperative trajectory planning was conducted in axial, coronal, and sagittal planes using standard-axis software. In 10 patients, preoperative trajectory planning was conducted with multiplanar reconstruction software. Postoperative magnetic resonance imaging scans were evaluated to study the quality of insertion. Target accuracy was assessed by measuring the mean shortest distance to strictly defined hippocampal borders in the coronal plane (“coronal deviation”). Additionally, the number of electrode contacts placed within the amygdalohippocampal structure was assessed. RESULTS With the use of multiplanar reconstruction software, there was a statistically insignificant increase in coronal deviation (standard-axis software group, 0.09 ± 0.50 mm; multiplanar reconstruction group, 0.37 ± 1.16 mm). However, the use of multiplanar planning strategies resulted in approximately one additional electrode contact inserted in the amygdalohippocampal structure (standard-axis software group, 3.42 ± 0.89; multiplanar reconstruction group, 4.36 ± 0.93; P < 0.01). CONCLUSION The use of reconstructed planes in preoperative trajectory planning allows for the insertion of additional electrode contacts within the target structure.

Spatial topographies of unilateral subthalamic nucleus deep brain stimulation efficacy for ipsilateral, contralateral, midline, and total Parkinson disease motor symptoms.

BACKGROUND: Subthalamic nucleus (STN) deep brain stimulation is a successful intervention for medically refractory Parkinson disease, although its efficacy depends on optimal electrode placement. Even though the predominant effect is observed contralaterally, modest improvements in ipsilateral and midline symptoms are also observed. OBJECTIVE: To elucidate the role of contact location of unilateral deep brain stimulation on contralateral, ipsilateral, and axial subscores of Parkinson disease motor symptoms. METHODS: Eighty-six patients receiving first deep brain stimulation STN electrode placements were identified, yielding 73 patients with 3-month follow-up. Total preoperative and postoperative Unified Parkinson Disease Rating Scale Part III scores were obtained and divided into contralateral, ipsilateral, and midline subscores. Contact location was determined on immediate postoperative magnetic resonance imaging. A 3-dimensional ordinary “kriging” algorithm generated spatial interpolations for total, ipsilateral, contralateral, and midline symptom categories. Interpolative reconstructions were performed in the axial planes (z = −0.5, −1.0, −1.5, −3.5, −4.5, −6.0) and a sagittal plane (x = 12.0). Interpolation error and significance were quantified by use of a cross-validation technique and quantile-quantile analysis. RESULTS: There was an overall reduction in Unified Parkinson Disease Rating Scale Part III symptoms: total = 37.0 ± 24.11% (P < .05), ipsilateral = 15.9 ± 51.8%, contralateral = 56.2 ± 26.8% (P < .05), and midline = 26.5 ± 34.7%. Kriging interpolation was performed and cross-validated with quantile-quantile analysis with high correlation (R2 > 0.92) and demonstrated regions of efficacy for each symptom category. Contralateral symptoms demonstrated broad regions of efficacy across the peri-STN area. The ipsilateral and midline regions of efficacy were constrained and located along the dorsal STN and caudal zona incerta. CONCLUSION: We provide evidence for a unique functional topographic window in which contralateral, ipsilateral, and midline structures may achieve the best efficacy. Although there are overlapping regions, laterality demonstrates distinct topographies. Surgical optimization should target the intersection of optimal regions for these symptom categories. ABBREVIATIONS: AC, anterior commissure DBS, deep brain stimulation PC, posterior commissure ROE, region of efficacy STN, subthalamic nucleus SW, Schaltenbrand-Wahren UPDRS, Unified Parkinson Disease Rating Scale

Construction of Relational Topographies from the Quantitative Measurements of Functional Deep Brain Stimulation Using a ‘Roving Window’ Interpolation Algorithm

The delivery of stimulus by a deep brain stimulation (DBS) contact electrode at a particular location may lead to a quantifiable physiologic effect, both intraoperatively and postoperatively. Consequently, measured data values can be attributed to discrete scattered points in neuroanatomic space, allowing for interpolative techniques to generate a topographic map of spatial patterns. Ultimately, by relating the topographies of various intraoperative measurements to the postoperative counterparts and neuroanatomic atlases, outcome-guided adjustments to electrode position can be pursued intraoperatively. In this study, 52 Parkinson’s disease patients were tested with a postoperative trial of stimulation and thresholds were recorded for motor adverse effects. A ‘roving window’ interpolation algorithm was adapted to generate a topographic map of voltage threshold along selected axial, coronal and sagittal planes. By developing these relational topographies for a variety of intraoperative and postoperative effects, a multivariable approach towards DBS optimization emerges.

Telemedicine with mobile devices and augmented reality for early postoperative care

Advanced features are being added to telemedicine paradigms to enhance usability and usefulness. Virtual Interactive Presence (VIP) is a technology that allows a surgeon and patient to interact in a “merged reality” space, to facilitate both verbal, visual, and manual interaction. In this clinical study, a mobile VIP iOS application was introduced into routine post-operative orthopedic and neurosurgical care. Survey responses endorse the usefulness of this tool, as it relates to The virtual interaction provides needed virtual follow-up in instances where in-person follow-up may be limited, and enhances the subjective patient experience.

The Relationship of Electrophysiologic Subthalamic Nucleus Length as a Predictor of Outcomes in Deep Brain Stimulation for Parkinson Disease

Background: Intraoperative measurement of subthalamic nucleus (STN) width through microelectrode recording (MER) is a common proxy for optimal electrode location during deep brain stimulation (DBS) surgery for Parkinson disease. We assessed whether the MER-determined STN width is a predictor of postoperative Unified Parkinson Disease Rating Scale (UPDRS) improvement. Methods: Records were reviewed for patients who underwent single-sided STN DBS placement for Parkinson disease between 2005 and 2010 at the UAB Medical Center. Reviews of preoperative and 3-month postoperative UPDRS part III, intraoperative MER records, and postoperative MRI scans were conducted. Results: The final cohort consisted of 73 patients (mean age 59 ± 9.7 years, length of disease 13 ± 9.7 years). STN widths were defined as depths associated with increased background activity and motor-driven, spiking action potentials on MER. The mean contralateral UPDRS improvement was 58% (± 24). The mean STN width was 5.1 mm (± 1.6, min = 0.0, max = 8.7). No significant relationship between STN width and UPDRS improvement was found, with and without AC-PC normalization (R2 < 0.05). Conclusion: This analysis raises questions about seeking the maximal electrophysiological width of STN as a proxy for optimal outcome in DBS for PD. We suggest this strategy for DBS placement in Parkinson disease be subject to more robust prospective investigation.

A method to project clinical outcome topographies onto preoperative MRI to guide direct DBS targeting

The use of intraoperative MR and direct DBS targeting, relies on anatomical rather than functional data. Historical clinical outcome databases that have recorded stimulation location and magnitude of effect, can provide a useful adjunct in DBS targeting strategies. We present a method for generating clinical outcome topographies, and merging regions of effect onto a pre-operative MR, for surgical planning. The clinical outcome topographies are consistent with more intuitive strategies used by neurosurgeons. This method provides theoretical guidance during DBS target planning.