Optical tracking of the three-dimensional position of an ablative focused laser beam

Abstract

The primary treatment for brain tumors with infiltrating margins is surgical resection. However at the present time this method is limited by visual discrimination between normal and neoplastic marginal tissues during surgery. Imaging modalities such as CT, MRI, PET, and optical imaging techniques can accurately localize tumor margins. We hypothesize that coupling the fine resolution of current imaging techniques with the precise cutting of mid-infrared lasers through image-guided neurosurgery has the potential to enhance tumor margin resection. This paper describes a feasibility study designed to optically track in three-dimensional space the articulated arm delivery of a non-contact ablative laser beam. Infrared-emitting diodes (IRED's) were attached to the handheld probe of an articulated arm to enable optical tracking of the laser beam focus in the operating room. Crosstalk between the infrared laser beam and the tracking diodes was measured. The geometry of the adapted laser probe was characterized to allow tracking the laser beam focus projected in front of the articulated arm. The target localization accuracy was assessed. Stray laser light did not affect optical tracking accuracy. The mean target registration errors while optically tracking the laser beam focus was 3.16 m 1.04 mm. Analysis of target localization errors indicated that precise optical tracking of a laser beam focus in three-dimensional space is feasible. However, since the projected beam focus is spatially defined relative to the tracking diodes, tracking accuracy is highly sensitive to laser beam delivery geometry and beam trajectory/alignment out of the articulated arm.