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).[6] The N-localizer comprises a diagonal rod that spans two vertical rods to form an N-shape (Figure 1) and 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 frame.[7]
N-localizer | |
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Specialty | neurosurgery, radiation oncology |
Intervention | stereotactic surgery, radiosurgery |
Inventor(s) | Russell A. Brown[2] |
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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.[13]
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 third, vertical rod is positioned midway between the two diagonal rods (Figure 3).[14] The Sturm-Pastyr localizer is integrated with the Riechert-Mundinger and Zamorano-Dujovny stereotactic frames.[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.[16] In contrast to the N-localizer that does not require specification of the pixel size in a tomographic image,[17] the Sturm-Pastyr localizer requires precise specification of the pixel size.[18]
Research conducted four decades after the introduction of the N-localizer[19] and Sturm-Pastyr localizer[20] has revealed computational techniques that improve the accuracy of both localizers.