The N-localizer[3] is a device that enables guidance of stereotactic surgery or radiosurgery using tomographic images that are obtained via computed tomography (CT),[4] magnetic resonance imaging (MRI),[5] or positron emission tomography (PET).

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 frame.

[7] The N-localizer is integrated with the Brown-Roberts-Wells (BRW),[8] Kelly-Goerss,[9] Leksell,[10] Cosman-Roberts-Wells (CRW),[11] Micromar-ETM03B, FiMe-BlueFrame, Macom, and Adeor-Zeppelin[12] stereotactic frames and with the Gamma Knife radiosurgery system.

[15] Compared to the N-localizer, the Sturm-Pastyr localizer is less accurate and necessitates more elaborate calculations to determine the spatial orientation of the tomographic image plane relative to the stereotactic frame.