MRI-guided stereotactic neurosurgical procedures in a diagnostic MRI suite: Background and safe practice recommendations

Feasibility and performance of a frameless stereotactic system for targeting subcortical nuclei in nonhuman primates

OBJECTIVE

Deep brain stimulation (DBS) is an effective therapy for different neurological diseases, despite the lack of comprehension of its mechanism of action. The use of nonhuman primates (NHPs) has been historically important in advancing this field and presents a unique opportunity to uncover the therapeutic mechanisms of DBS, opening the way for optimization of current applications and the development of new ones. To be informative, research using NHPs should make use of appropriate electrode implantation tools. In the present work, the authors report on the feasibility and accuracy of targeting different deep brain regions in NHPs using a commercially available frameless stereotactic system (microTargeting platform).

METHODS

Seven NHPs were implanted with DBS electrodes, either in the subthalamic nucleus or in the cerebellar dentate nucleus. A microTargeting platform was designed for each animal and used to guide implantation of the electrode. Imaging studies were acquired preoperatively for each animal, and were subsequently analyzed by two independent evaluators to estimate the electrode placement error (EPE). The interobserver variability was assessed as well.

RESULTS

The radial and vector components of the EPE were estimated separately. The magnitude of the vector of EPE was 1.29 ± 0.41 mm and the mean radial EPE was 0.96 ± 0.63 mm. The interobserver variability was considered negligible.

CONCLUSIONS

These results reveal the suitability of this commercial system to enhance the surgical insertion of DBS leads in the primate brain, in comparison to rigid traditional frames. Furthermore, our results open up the possibility of performing frameless stereotaxy in primates without the necessity of relying on expensive methods based on intraoperative imaging.

Adapting to Space Limitations During Prone Real-Time Magnetic Resonance Imaging-Guided Stereotaxic Laser Ablation: Technical Pearls

BACKGROUND

New techniques of intraoperative magnetic resonance imaging (MRI)-guided stereotaxy enable minimally invasive approaches to intracranial pathology. Laser interstitial thermal therapy (LITT), convection-enhanced drug delivery, and stereotactic biopsy can be performed with a real-time confirmation of location and the ability to adjust for intracranial shift during the procedure. However, these procedures are constrained by patient positioning and the need for trajectories that avoid collision between stereotactic elements and the small MRI bore. To our knowledge, this is the first report to outline the technical details of safe intraoperative MRI (iMRI)-guided stereotaxy, performed with prone positioning.

OBJECTIVE

To present technical pearls to guide the safe conduction of iMRI-guided stereotaxy and LITT while in the prone position.

METHODS

The details of the positioning and trajectories for a series of patients who underwent Clearpoint® (MRI Interventions Inc) frameless real-time MRI-guided stereotaxis using a posterior approach were reviewed.

RESULTS

In this series, 5 patients underwent selective amygdalohippocampectomy, and 2 underwent tumor biopsy/ablation while in the prone position without any complications.

CONCLUSION

Prone iMRI procedures can be performed safely even in a 60-cm MRI bore.

The interventional magnetic resonance imaging suite: Experience in the design, development, and implementation in a pre-existing radiology space and review of concepts

BACKGROUND

Intraoperative magnetic resonance imaging (ioMRI) has led to significant advancements in neurosurgery with improved accuracy, assessment of the extent of resection, less invasive surgical alternatives, and real-time confirmation of targeting as well delivery of therapies. The costs associated with developing ioMRI units in the surgical suite have been obstacles to the expansion of their use. More recently, the development of hybrid interventional MRI (iMRI) units has become a viable alternative. The process of designing, developing, and implementing operations for these units requires the careful integration of environmental, technical, and safety elements of both surgical and MR practices. There is a paucity of published literature providing guidance for institutions looking to develop a hybrid iMRI unit, especially with a limited footprint in the radiology department.

METHODS

The experience of designing, developing, and implementing an iMRI in a preexisting space for neurosurgical procedures at a single institution in light of available options and the literature is described.

RESULTS

The development of the unit was accomplished through the engagement of a multidisciplinary team of stakeholders who utilized existing guidelines and recommendations and their own professional experience to address issues including physical layout, equipment selection, operations planning, infection control, and oversight/review, among others.

CONCLUSION

Successful creation of an iMRI program requires multidisciplinary collaboration in integrating surgical and MR practice. The authors' aim is that the experience described in this article will serve as an example for facilities or neurosurgical departments looking to navigate the same process.

The local thermal effect of using monopolar electrosurgery in the presence of a deep brain stimulator: Cadaveric studies on a lamb brain

In 2001, a patient with a deep brain stimulator (DBS) died following treatment with medical diathermy. Manufacturers have since advised against all forms of diathermy except bipolar electrosurgery in DBS patients. This effective ban on monopolar electrosurgery has an impact on the 150,000 patients treated with DBS to date, a number that is set to progressively increase. Analysis of the events, technical specifications, and literature suggests that the original ban was based on extrapolation from medical diathermy to electrosurgery, two very different treatment modalities. This prompted novel work exploring the impact of electrosurgery on DBS systems. Monopolar electrosurgery was employed on an animal cadaveric model with a DBS system paired with a thermocouple at the brain implant site. Prolonged use of monopolar, including at settings higher than normal surgical practice, resulted in a maximum mean temperature increase of only 2.6 °C. Microscopic post-event analysis showed no evidence of thermal injury at the implant site. The implication is that there may be limits within which monopolar electrosurgery use is safe in patients with DBS.