Skin shift and its effect on navigation accuracy in image-guided neurosurgery

Abstract

Neuronavigation systems have been developed for image-guided neurosurgery to aid in the accurate resection of malignant brain tumors. Therefore, the accuracy of the neuronavigation is important. However, many factors can reduce the navigation accuracy during surgery. Before craniotomy, the patient's head is secured to a head frame with head pins; this fixation may cause displacement of fiducial markers and reduce the accuracy. We term this phenomenon skin shift. In this study, the extent of skin shift and its effect on navigation accuracy were determined by use of both preoperative magnetic resonance imaging (MRI) scans acquired before fixation and intraoperative MRI scans acquired after fixation. We measured the displacement of the fiducial markers by using fusion images obtained by integrating preoperative and intraoperative MRI scans. We also evaluated the navigation accuracy of registration based on preoperative and on intraoperative MRI. The mean (± SD) extent of skin shift was 5.34 (± 2.65) mm. The navigation accuracy of registration based on preoperative MRI was 4.06 (± 2.25) mm, and that of registration based on intraoperative MRI was 2.51 (± 1.32) mm. No significant correlation was observed between the extent of skin shift and the distance between the head pins and fiducial markers (p > 0.05). The navigation accuracy of registration based on intraoperative MRI was significantly higher than that of registration based on preoperative MRI (p < 0.001). The results indicated that skin shift was caused by the fixation, and that this shift reduced the navigation accuracy. Intraoperative MRI can correct the effect of skin shift.

Subject position affects EEG magnitudes

“…As the precision of anatomically accurate models improve, concerns expressed in Ramon et al (2006) that head models generated from supine MRI scans may lead to errors in EEG source localizations may be warranted, an effect that might add to the confounding effect of "skin shift" (Mitsui et al, 2011). Indeed, anatomically accurate models of current flows in the context of transcranial stimulation have shown that small errors in CSF thickness lead to significant changes in the resulting current flows (Datta et al, 2009).…”

Navigation-assisted Surgery for Bone and Soft Tissue Tumors With Bony Extension

“…In neurosurgery, skin shifting is a problem when head pins are used [22]. The use of bone-anchored screw markers has been recommended for better accuracy [14].…”

Can coffee improve image guidance?

“…This is a reasonable hypothesis, since it has previously been experimentally shown that skin mobility with respect to the skull bone can range from 1.3-13.1 mm, with a mean of 5.34 ± 2.65 mm under load 16 . Figure 2 illustrates two ways loads can be applied to the skin that would cause relative motion between the optical tracking rigid body and the patient's skull.…”