title: Marker-CT assisted surgery using household key ring: A simple substitute to frameless stereotaxy for developing countries.
abstract: BACKGROUND
  Operative localization systems such as stereotactic frames and neuronavigation are prohibitively expensive to be of use in many centers in developing countries. Here, we present a modified version of marker-computed tomography (CT) assisted technique using a household key ring, which can be performed in any operative set-up lacking modern amenities.
  
  
  METHODS
  For a patient who presents with left posterior frontal lesion, the approximate entry point for the shortest and perpendicular trajectory to the lesion is marked on the scalp using a household key ring and fixed in place. Helical CT is obtained and reconstruction performed in two planes perpendicular to the ring and mutually perpendicular to each other. Based on the measurements of the lesion in relation to the radiologic pointers of the ring, and the location of the corrected entry point with respect to the center of the ring, the shortest perpendicular depth of approach is determined. Freehand technique perpendicular to the surface at the predetermined entry point and depth is employed for the surgical approach. The advantages of key ring over other markers are its simplicity, conformity to the shape of the head, and paucity of artifacts in CT.
  
  
  CONCLUSIONS
  The relatively effortless estimation and three-dimensional visual impression renders this method easy enough to be employed anywhere for the operative localization of superficial intracranial lesions both for biopsy as well as resection.
authors.affiliation: Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Sivashanmugam
authors.initials: S
authors.lastname: Dhandapani
authors.affiliation: Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Harnarayan
authors.initials: H
authors.lastname: Singh
keywords: Marker-CT; neuronavigation; operative localization; stereotaxy
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