N-localizer

The N-localizer or N-bar is a device that enables guidance of stereotactic surgery or radiosurgery using tomographic images that are obtained via computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). The N-localizer comprises a diagonal rod that spans two vertical rods to form an N-shape (Figure 1) that permits calculation of the point where a tomographic image plane intersects the diagonal rod. Attaching three N-localizers to a stereotactic instrument allows calculation of three points where a tomographic image plane intersects three diagonal rods (Figure 2). These points determine the spatial orientation of the tomographic image plane relative to the stereotactic instrument. The N-localizer or N-bar is a device that enables guidance of stereotactic surgery or radiosurgery using tomographic images that are obtained via computed tomography (CT), magnetic resonance imaging (MRI), or positron emission tomography (PET). The N-localizer comprises a diagonal rod that spans two vertical rods to form an N-shape (Figure 1) that permits calculation of the point where a tomographic image plane intersects the diagonal rod. Attaching three N-localizers to a stereotactic instrument allows calculation of three points where a tomographic image plane intersects three diagonal rods (Figure 2). These points determine the spatial orientation of the tomographic image plane relative to the stereotactic instrument. An alternative to the N-localizer is the Sturm-Pastyr localizer that comprises three rods wherein two diagonal rods form a V-shape and a vertical rod is positioned midway between the two diagonal rods. Compared to the N-localizer, the Sturm-Pastyr localizer requires more elaborate calculations to determine the spatial orientation of the tomographic image plane; and in contrast to the N-localizer, calculations for the Sturm-Pastyr localizer require accurate specification of the pixel size in the tomographic image.