A Patient-Specific Reference Tracker for Noninvasive Electromagnetic Navigation of Endoscopic Skull Base Surgery.

BACKGROUND: Owing to the possibility of nonrigid head fixation, electromagnetic navigation (EM) is a mainstay for endoscopic skull base surgery. The currently available dynamic reference trackers (RTs) are invasive or inaccurate. OBJECTIVE: To investigate the feasibility and stability of this innovative oral tracker (OT), which is adhesive to the hard palate in comparison with a commercially available skin adhesive tracker (ST). METHODS: A prospective series of 31 patients with intrasellar lesions who underwent surgery between 2019 and 2021 using a pure endoscopic transsphenoidal approach were evaluated. A patient-specific palatal mold was designed from preoperative computed tomography data. The OT was cast using a biocompatible algin with an integrated EM tracker assembly. In comparison with a skull-mounted RT, which served as a gold standard, the deviations of OT vs those of the ST with the RT were continuously assessed. RESULTS: The OT showed significantly lower deviations from the RT than the ST during the surgical steps: start of endoscopic surgery (OT vs ST: 0.62 mm, IQR 0.36-0.89 vs 1.65 mm, IQR 1.35-2.32, P < .001), drilling phase (OT vs ST: 0.81 mm, IQR 0.51-1.32 vs 1.89 mm, IQR 1.6-2.74, P < .001), and end of endoscopic surgery (OT vs ST: 1.1 mm, IQR 0.68-1.64 vs 1.9 mm, IQR 1.6-2.72, P < .001). CONCLUSION: The OT showed significantly higher intraoperative stability than the ST. Therefore, this noninvasive and patient-specific tool could be used to achieve accurate EM guidance during endoscopic skull base surgeries.

Development of a miniaturized robotic guidance device for stereotactic neurosurgery.

OBJECTIVE: Consistently high accuracy and a straightforward use of stereotactic guidance systems are crucial for precise stereotactic targeting and a short procedural duration. Although robotic guidance systems are widely used, currently available systems do not fully meet the requirements for a stereotactic guidance system that combines the advantages of frameless surgery and robotic technology. The authors developed and optimized a small-scale yet highly accurate guidance system that can be seamlessly integrated into an existing operating room (OR) setup due to its design. The aim of this clinical study is to outline the development of this miniature robotic guidance system and present the authors' clinical experience. METHODS: After extensive preclinical testing of the robotic stereotactic guidance system, adaptations were implemented for robot fixation, software usability, navigation integration, and end-effector application. Development of the robotic system was then advanced in a clinical series of 150 patients between 2013 and 2019, including 111 needle biopsies, 13 catheter placements, and 26 stereoelectroencephalography (SEEG) electrode placements. During the clinical trial, constant modifications were implemented to meet the setup requirements, technical specifications, and workflow for each indication. For each application, specific setup, workflow, and median procedural accuracy were evaluated. RESULTS: Application of the miniature robotic system was feasible in 149 of 150 cases. The setup in each procedure was successfully implemented without adding significant OR time. The workflow was seamlessly integrated into the preexisting procedure. In the course of the study, procedural accuracy was improved. For the biopsy procedure, the real target error (RTE) was reduced from a mean of 1.8 ± 1.03 mm to 1.6 ± 0.82 mm at entry (p = 0.05), and from 1.7 ± 1.12 mm to 1.6 ± 0.72 mm at target (p = 0.04). For the SEEG procedures, the RTE was reduced from a mean of 1.43 ± 0.78 mm in the first half of the procedures to 1.12 ± 0.52 mm (p = 0.002) at entry in the second half, and from 1.82 ± 1.13 mm to 1.57 ± 0.98 mm (p = 0.069) at target, respectively. No healing complications or infections were observed in any case. CONCLUSIONS: The miniature robotic guidance device was able to prove its versatility and seamless integration into preexisting workflow by successful application in 149 stereotactic procedures. According to these data, the robot could significantly improve accuracy without adding time expenditure.

The endonasal patient reference tracker: a novel solution for accurate noninvasive electromagnetic neuronavigation.

OBJECTIVE: Electromagnetic (EM) navigation provides the advantages of continuous guidance and tip-tracking of instruments. The current solutions for patient reference trackers are suboptimal, as they are either invasively screwed to the bone or less accurate if attached to the skin. The authors present a novel EM reference method with the tracker rigidly but not invasively positioned inside the nasal cavity. METHODS: The nasal tracker (NT) consists of the EM coil array of the AxiEM tracker plugged into a nasal tamponade, which is then inserted into the inferior nasal meatus. Initially, a proof-of-concept study was performed on two cadaveric skull bases. The stability of the NT was assessed in simulated surgical situations, for example, prone, supine, and lateral patient positioning and skin traction. A deviation ≤ 2 mm was judged sufficiently accurate for clinical trial. Thus, a feasibility study was performed in the clinical setting. Positional changes of the NT and a standard skin-adhesive tracker (ST) relative to a ground-truth reference tracker were recorded throughout routine surgical procedures. The accuracy of the NT and ST was compared at different stages of surgery. RESULTS: Ex vivo, the NT proved to be highly stable in all simulated surgical situations (median deviation 0.4 mm, range 0.0-2.0 mm). In 13 routine clinical cases, the NT was significantly more stable than the ST (median deviation at procedure end 1.3 mm, range 0.5-3.0 mm vs 4.0 mm, range 1.2-11.2 mm, p = 0.002). The loss of accuracy of the ST was highest during draping and flap fixation. CONCLUSIONS: Application of the EM endonasal patient tracker was found to be feasible with high procedural stability ex vivo as well as in the clinical setting. This innovation combines the advantages of high precision and noninvasiveness and may, in the future, enhance EM navigation for neurosurgery.

Frameless Stereotactic Brain Biopsies: Comparison of Minimally Invasive Robot-Guided and Manual Arm-Based Technique.

BACKGROUND: Most brain biopsies are still performed with the aid of a navigation-guided mechanical arm. Due to the manual trajectory alignment without rigid skull contact, frameless aiming devices are prone to considerably lower accuracy. OBJECTIVE: To compare a novel minimally invasive robot-guided biopsy technique with rigid skull fixation to a standard frameless manual arm biopsy procedure. METHODS: Accuracy, procedural duration, diagnostic yield, complication rate, and cosmetic result were retrospectively assessed in 40 consecutive cases of frameless stereotactic biopsies and compared between a minimally invasive robotic technique using the iSYS1 guidance device (iSYS Medizintechnik GmbH) (robot-guided group [ROB], n = 20) and a manual arm-based technique (group MAN, n = 20). RESULTS: Application of the robotic technique resulted in significantly higher accuracy at entry point (group ROB median 1.5 mm [0.4-3.2 mm] vs manual arm-based group (MAN) 2.2 mm [0.2-5.2 mm], P = .019) and at target point (group ROB 1.5 mm [0.4-2.8 mm] vs group MAN 2.8 mm [1.4-4.9 mm], P = .001), without increasing incision to suture time (group ROB 30.0 min [20-45 min vs group MAN 32.5 min [range 20-60 min], P = .09) and significantly shorter skin incision length (group ROB 16.3 mm [12.7-23.4 mm] vs group MAN 24.2 mm [18.0-37.0 mm], P = .008). CONCLUSION: According to our data, the proposed technique of minimally invasive robot-guided brain biopsies can improve accuracy without increasing operating time while being equally safe and effective compared to a standard frameless arm-based manual biopsy technique.