Preliminary trials of trackerless augmented reality in endoscopic endonasal surgery

PurposeWe present a novel method for augmented reality in endoscopic endonasal surgery. Our method does not require the use of external tracking devices and can show hidden anatomical structures relevant to the surgical intervention.MethodsOur method registers a preoperative 3D model of the nasal cavity to an intraoperative 3D model by estimating a scaled-rigid transformation. Registration is based on a two-stage ICP approach on the reconstructed nasal cavity. The hidden structures are then transferred from the preoperative 3D model to the intraoperative one using the estimated transformation, projected and overlaid into the endoscopic images to obtain the augmented reality.ResultsWe performed qualitative and quantitative validation of our method on 12 clinical cases. Qualitative results were obtained from an ENT surgeon from visual inspection of the hidden structures in the augmented images. Quantitative results were obtained by measuring a target registration error using a novel transillumination-based approach. The results show that the hidden structures of interest are augmented at the expected locations in most cases.ConclusionOur method was able to augment the endoscopic images in a sufficiently precise manner when the intraoperative nasal cavity did not deform considerably with respect to its preoperative state. This is a promising step towards trackerless augmented reality in endonasal surgery.