Accuracy of Image-Guided Surgical Systems at the Lateral Skull Base as Clinically Assessed Using Bone-Anchored Hearing Aid Posts as Surgical Targets

Abstract

Objective Image-guided surgical (IGS) technology has been clinically available for over a decade. To date, no acceptable standard exists for reporting the accuracy of IGS systems, especially for lateral skull base applications. We present a validation method that uses the post from bone anchored hearing aid (BAHA) patients as a target. We then compare the accuracy of two IGS systems—one using laser skin-surface scanning (LSSS) and another using a non-invasive fiducial frame (FF) attached to patient via dental bite-block (DBB) for registration. Study design Prospective. Setting Tertiary referral center. Patients Six BAHA patients who had adequate dentition for creation of a DBB. Intervention(s) For each patient, a dental impression was obtained, and a customized DBB was made to hold a FF. Temporal bone CT scans were obtained with the patient wearing the DBB, FF, and a customized marker on the BAHA post. In a mock OR, CT scans were registered to operative anatomy using two methods: (a) LSSS, (b) FF. Main outcome measure(s) For each patient and each system, the position of the BAHA marker in the CT scan and in the mock OR (using optical measurement technology) were compared and the distances between them are reported to demonstrate accuracy. Results Accuracy (mean ± standard deviation) was 1.54 ± 0.63 mm for DBB registration and 3.21 ± 1.02 mm for LSSS registration. Conclusions An IGS system using FF registration is more accurate than one using LSSS (p = 0.03, two-sided Student's t-test). BAHA patients provide a unique patient population upon which IGS systems may be validated.

Quantitative error analysis for computer assisted navigation: A feasibility study

“…Recently Balachandran 32,33 and Fitzpatrick 10 have introduced the Target Localization Error (TLE), the error associated with the physical localization of a locus on a patient (a marker, a screw, or an anatomical feature).This yields an overall estimate of the application error of clinical navigation in quadrature, the Total Target Error, TTE 10 , of (4) Here <TLE 2 >, <FLE 2 >, and <TRE 2 > are assumed to be independent random variables. TRE(r) with anisotropic noise covariance 27 can be predicted as (5) δ ij is the Kronecker delta, ε the smallness parameter of the perturbation-theoretic approach, are the components of the FLE covariance matrix Σ FLE , r i are the coordinates of a point r expressed in the principal axes coordinate system of the fiducials; are the i-th singular values of the fiducial configuration in the principal axes.…”

Image guided surgery of the lateral skull base: Testing a new dental splint registration device

“…In contrast, insufficient accuracy was reported in an in vitro model of mastoidectomy when using a navigation bow with integrated registration markers fixed to the upper jaw [15]. A major problem with the existing devices is the large bilateral extraoral reference frame [17,29,31], which does not allow the patient's head to be positioned on one side for surgery -a prerequisite for surgery at the lateral skull base. Furthermore, depending on the size and weight of the extensions, the extraoral parts might act as a lever, leading to dislocation of the maxillary splint and poor registration accuracy.…”

“…Although the more distant targets yielded slightly larger values, confirming the significant impact of the distance between the registration and target points on the accuracy [7,8,21], even the maximum deviation of 1.2 mm is still within the range (1 to 2 mm) that is often considered ''clinically acceptable'' for navigation system accuracy [1,21,25,26]. Maxillary splint-based systems with extraoral extensions for reference markers have been used previously with sufficient navigational accuracy in neurosurgery (0.29-0.86 mm [17], 0.0-2.0 mm [27]), in sinus surgery (1.56 AE 0.76 mm [28]), and in the temporal region (0.73 AE 0.25 mm [17,29]); however, only a few of these systems have been tested for targets in the lateral skull base region [15,29,30,31]. Bale et al used a mouthpiecebased registration template held in place by a vacuum system to successfully cannulate the foramen ovale [30], but did not test its applicability for Figure 3.…”

Accuracy Assessment of Different Registration and Imaging Methods on Image-Guided Surgery of Lateral Skull Base

“…During surgery, all target points were far from the surface, so the system is applicable. The microscope distance was preserved near 300 mm to surgical field, as previously done by Bernardeschi et al (10) The bone implanted markers, Fiducial marker, are accepted as the gold standard for registration (9,11). The totally fixed titanium screw with central head cavity was very suitable for accurate registration and point defining and decreased the error of measurement.…”