N-localizer

The N-localizer[3] or N-bar 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) 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.[7]

N-localizer
Three N-localizers attached to a stereotactic instrument.[1]
Specialtyneurosurgery, radiation oncology
Interventionstereotactic surgery, radiosurgery
Inventor(s)Russell A. Brown[2]

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.[8] Compared to the N-localizer, the Sturm-Pastyr localizer requires more elaborate calculations to determine the spatial orientation of the tomographic image plane;[9] and in contrast to the N-localizer, calculations for the Sturm-Pastyr localizer require accurate specification of the pixel size in the tomographic image.[10]

Figures
Figure 1. Depiction of the N-localizer and its intersection with the tomographic image plane. (A) Side view of the N-localizer. The tomographic image plane intersects two vertical rods and one diagonal rod. (B) Tomographic image. The intersection of the tomographic image plane with the N-localizer creates two fiducial circles and one fiducial ellipse. The relative spacing between the ellipse and the two circles varies with the height at which the tomographic image plane intersects the diagonal rod.
Figure 2. Depiction of three N-localizers and their intersection with the tomographic image plane. The quadrilateral represents the tomographic image plane. The oval and the arch represent the stereotactic instrument. The vertical and diagonal lines attached to the oval represent three N-localizers. The three points where the tomographic image plane intersects the diagonal rods are depicted by the dots. These points of intersection determine the spatial orientation of the tomographic image plane relative to the stereotactic instrument.

References
  1. Arle, J (2009). "Development of a Classic: The Todd-Wells Apparatus, the BRW, and the CRW Stereotactic Frames". In Lozano, AM; Gildenberg, PL; Tasker, RR (eds.). Textbook of Stereotactic and Functional Neurosurgery. Berlin: Springer-Verlag. pp. 456–460. doi:10.1007/978-3-540-69960-6. ISBN 978-3-540-69959-0.
  2. "System Using Computed Tomography as for Selective Body Treatment". U.S. Patent 4608977. 1986.
  3. Galloway, RL Jr. (2015). "Introduction and Historical Perspectives on Image-Guided Surgery". In Golby, AJ (ed.). Image-Guided Neurosurgery. Amsterdam: Elsevier. pp. 2–4. doi:10.1016/B978-0-12-800870-6.00001-7. ISBN 978-0-12-800870-6.
  4. Thomas DG, Anderson RE, du Boulay GH (1984). "CT-guided stereotactic neurosurgery: experience in 24 cases with a new stereotactic system". Journal of Neurology, Neurosurgery & Psychiatry. 47 (1): 9–16. doi:10.1136/jnnp.47.1.9. PMC 1027634. PMID 6363629.
  5. Heilbrun MP, Sunderland PM, McDonald PR, Wells TH Jr, Cosman E, Ganz E (1987). "Brown-Roberts-Wells stereotactic frame modifications to accomplish magnetic resonance imaging guidance in three planes". Applied Neurophysiology. 50 (1–6): 143–152. doi:10.1159/000100700. PMID 3329837.
  6. Maciunas RJ, Kessler RM, Maurer C, Mandava V, Watt G, Smith G (1992). "Positron emission tomography imaging-directed stereotactic neurosurgery". Stereotactic and Functional Neurosurgery. 58 (1–4): 134–140. doi:10.1159/000098986. PMID 1439330.
  7. Gildenberg, PL; Krauss, JK (2009). "History of Stereotactic Surgery". In Lozano, AM; Gildenberg, PL; Tasker, RR (eds.). Textbook of Stereotactic and Functional Neurosurgery. Berlin: Springer-Verlag. p. 23. doi:10.1007/978-3-540-69960-6. ISBN 978-3-540-69959-0.
  8. Sturm V, Pastyr O, Schlegel W, Scharfenberg H, Zabel HJ, Netzeband G, Schabbert S, Berberich W (1983). "Stereotactic computer tomography with a modified Riechert-Mundinger device as the basis for integrated stereotactic neuroradiological investigations". Acta Neurochirurgica. 68 (1–2): 11–17. doi:10.1007/BF01406197. PMID 6344559.
  9. Dai J, Zhu Y, Qu H, Hu Y (2001). "An algorithm for stereotactic localization by computed tomography or magnetic resonance imaging". Physics in Medicine and Biology. 46 (1): N1–N7. doi:10.1088/0031-9155/46/1/401. PMID 11197682.
  10. Weaver K, Smith V, Lewis JD, Lulu B, Barnett CM, Leibel SA, Gutin P, Larson D, Phillips T (1990). "A CT-based computerized treatment planning system for I-125 stereotactic brain implants". International Journal of Radiation Oncology, Biology, Physics. 18 (2): 445–454. doi:10.1016/0360-3016(90)90114-Y. PMID 2406230.

Further reading
  • Tse, VCK; Kalani, MYS; Adler, JR (2015). "Techniques of Stereotactic Localization". In Chin, LS; Regine, WF (eds.). Principles and Practice of Stereotactic Radiosurgery. New York: Springer. pp. 25–32. doi:10.1007/978-1-4614-8363-2. ISBN 978-1-4614-8362-5.
  • Saleh, H; Kassas, B (2014). "Developing Stereotactic Frames for Cranial Treatment". In Benedict, SH; Schlesinger, DJ; Goetsche, SJ; Kavanagh, BD (eds.). Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy. Boca Raton: CRC Press. pp. 156–159. doi:10.1201/b16776. ISBN 978-1-4398-4198-3.
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