Current accuracy of surface matching compared to adhesive markers in patient-to-image registration

Abstract

Object In the past, the accuracy of surface matching has been shown to be disappointing. We aimed to determine whether this had improved over the years by assessing application accuracy of current navigation systems, using either surface matching or point-pair matching. Methods Eleven patients, scheduled for intracranial surgery, were included in this study after a power analysis had shown this small number to be sufficient. Prior to surgery, one additional fiducial marker was placed on the scalp, the “target marker,” where the entry point of surgery was to be expected. Using one of three different navigation systems, two patient-to-image registration procedures were performed: one based on surface matching and one based on point-pair matching. Each registration procedure was followed by the digitization of the target marker’s location, allowing calculation of the target registration error. If the system offered surface matching improvement, this was always used; and for the two systems that routinely offer an estimate of neuronavigation accuracy, this was also recorded. Results The error in localizing the target marker using point-pair matching or surface matching was respectively 2.49 mm and 5.35 mm, on average ( p < 0.001). In those four cases where an attempt was made to improve the surface matching, the error increased to 6.35 mm, on average. For the seven cases where the system estimated accuracy, this estimate did not correlate with target registration error ( R 2 = 0.04, p = 0.67). Conclusion The accuracy of navigation systems has not improved over the last decade, with surface matching consistently yielding errors that are twice as large as when point-pair matching with adhesive markers is used. These errors are not reliably reflected by the systems own prediction, when offered. These results are important to make an informed choice between image-to-patient registration strategies, depending on the type of surgery at hand.

Are fiducial registration error and target registration error correlated? SciKit-SurgeryFRED for teaching and research

“…8,29 Surface based registration has long been proposed as a way to improve registration accuracy for neurosurgery 15 and is is now integrated into commercial systems with mixed results. 16 SciKit-SurgeryFRED could be extended to include different registration methods, though obviously would require a more inclusive name. As we move to non rigid and probabilistic registrations, the correct interpretation of registration uncertainty will become more challenging.…”

Reliable navigation registration in cranial and spine surgery based on intraoperative computed tomography

“…A recent study analyzing the effect of additional skin surface matching showed a worsening of registration accuracy with an in- crease in the mean registration errors from 5.3 mm to 6.3 mm. 19 While in cranial surgery skin surface matching leads only to mediocre registration accuracy, in spine surgery for a single vertebra surface matching-based registration is an established strategy for spinal implantation of pedicle screws. This is due to the direct identification of the bony surface by sampling at least 20 points on the lamina of a vertebra with the tip of a navigation pointer, 28 which in phantom measurements achieves low registration errors of 1.1 ± 0.61 mm but markedly increases in adjacent levels.…”

“…Registration errors in fiducial-based registration have been reported to range from 1.4 to 5.8 mm, 22 which is comparable to a recent study with errors ranging from 0.55 to 4.8 mm. 7 Skin surface matching in cranial surgery resulted in even worse mean registration errors of 5.3 mm, 19 while in spine surgery, bone surface matching achieved lower registration errors of 1.1 ± 0.61 mm, which markedly increased in adjacent levels. 32 These results were obtained in Sawbones phantom experiments.…”

Virtual splint registration for electromagnetic and optical navigation in orbital and craniofacial surgery

“…In image-guided surgical navigation, registration is a prerequisite to determine the position of a surgical navigation instrument relative to the patient’s position and visualize this position in the pre-operative imaging data 1 – 5 . The coordinate system associated with the pre-operative imaging data is registered to the position of the dynamic reference frame and thus the position of the patient’s anatomy within the OR.…”