Freehand Stereotactic Image-Guidance Tailored to Neurotologic Surgery.

Schneider, Daniel; Anschuetz, Lukas; Mueller, Fabian; Hermann, Jan; O'Toole Bom Braga, Gabriela; Wagner, Franca; Weder, Stefan; Mantokoudis, Georgios; Weber, Stefan; Caversaccio, Marco (2021). Freehand Stereotactic Image-Guidance Tailored to Neurotologic Surgery. Frontiers in Surgery, 8(742112), p. 742112. Frontiers 10.3389/fsurg.2021.742112

fsurg-08-742112.pdf - Published Version
Available under License Creative Commons: Attribution (CC-BY).

Download (4MB) | Preview

Hypothesis: The use of freehand stereotactic image-guidance with a target registration error (TRE) of μTRE + 3σTRE < 0.5 mm for navigating surgical instruments during neurotologic surgery is safe and useful. Background: Neurotologic microsurgery requires work at the limits of human visual and tactile capabilities. Anatomy localization comes at the expense of invasiveness caused by exposing structures and using them as orientation landmarks. In the absence of more-precise and less-invasive anatomy localization alternatives, surgery poses considerable risks of iatrogenic injury and sub-optimal treatment. There exists an unmet clinical need for an accurate, precise, and minimally-invasive means for anatomy localization and instrument navigation during neurotologic surgery. Freehand stereotactic image-guidance constitutes a solution to this. While the technology is routinely used in medical fields such as neurosurgery and rhinology, to date, it is not used for neurotologic surgery due to insufficient accuracy of clinically available systems. Materials and Methods: A freehand stereotactic image-guidance system tailored to the needs of neurotologic surgery-most importantly sub-half-millimeter accuracy-was developed. Its TRE was assessed preclinically using a task-specific phantom. A pilot clinical trial targeting N = 20 study participants was conducted ( ID: NCT03852329) to validate the accuracy and usefulness of the developed system. Clinically, objective assessment of the TRE is impossible because establishing a sufficiently accurate ground-truth is impossible. A method was used to validate accuracy and usefulness based on intersubjectivity assessment of surgeon ratings of corresponding image-pairs from the microscope/endoscope and the image-guidance system. Results: During the preclinical accuracy assessment the TRE was measured as 0.120 ± 0.05 mm (max: 0.27 mm, μTRE + 3σTRE = 0.27 mm, N = 310). Due to the COVID-19 pandemic, the study was terminated early after N = 3 participants. During an endoscopic cholesteatoma removal, a microscopic facial nerve schwannoma removal, and a microscopic revision cochlear implantation, N = 75 accuracy and usefulness ratings were collected from five surgeons each grading 15 image-pairs. On a scale from 1 (worst rating) to 5 (best rating), the median (interquartile range) accuracy and usefulness ratings were assessed as 5 (4-5) and 4 (4-5) respectively. Conclusion: Navigating surgery in the tympanomastoid compartment and potentially in the lateral skull base with sufficiently accurate freehand stereotactic image-guidance (μTRE + 3σTRE < 0.5 mm) is feasible, safe, and useful. Clinical Trial Registration:, identifier: NCT03852329.

Item Type:

Journal Article (Original Article)


10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research
10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Image Guided Therapy
04 Faculty of Medicine > Department of Head Organs and Neurology (DKNS) > Clinic of Ear, Nose and Throat Disorders (ENT)
04 Faculty of Medicine > Department of Radiology, Neuroradiology and Nuclear Medicine (DRNN) > Institute of Diagnostic and Interventional Neuroradiology

UniBE Contributor:

Schneider, Daniel, Anschütz, Lukas Peter, Müller, Fabian Matthias, Hermann, Jan, O'Toole Bom Braga, Gabriela, Wagner, Franca, Weder, Stefan Andreas, Mantokoudis, Georgios, Weber, Stefan (B), Caversaccio, Marco


500 Science > 570 Life sciences; biology
600 Technology > 610 Medicine & health








Martin Zbinden

Date Deposited:

15 Nov 2021 15:58

Last Modified:

29 Mar 2023 23:37

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

accurate navigation in neurotology clinical trial image-guidance lateral skull lateral skull base neurotology surgical navigation temporal bone




Actions (login required)

Edit item Edit item
Provide Feedback