Comparison of frameless stereotactic systems: Accuracy, precision, and applications

Ethan A. Benardete, Michael A. Leonard, Howard L. Weiner, Kim J. Burchiel, Nathan R. Selder, Philip L. Gildenberg, Andres M. Lozano

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


OBJECTIVE: Frameless stereotactic systems have become an integral part of neurosurgical practice. At our center, we recently introduced for clinical use a small, portable, frameless stereotactic system, namely the Cygnus PFS system (Compass International, Rochester, MN). The purpose of this study was to compare the accuracy of the Cygnus PFS system with that of two larger systems that are also currently in use at our institution, i.e., the SMN system (Zeiss, Oberkochen, Germany) and the ISG viewing wand (ISG Technologies, Toronto, Canada). These systems represent three kinds of frameless stereotactic technologies that are commercially available. Each system uses a different method of spatial localization, i.e., mechanical linkage (ISG system), magnetic field digitization (Cygnus system), or optical technology (SMN system). METHODS: Using a stereotactic "phantom," we measured the accuracies of all three systems with identical data sets. The errors in localization in three-dimensional space for nine targets were calculated by using 10 magnetic resonance imaging data sets. The precision of each system was also calculated. RESULTS: With this experimental protocol, the Cygnus system attained a mean accuracy of 1.90 ± 0.7 mm, the ISG viewing wand system a mean accuracy of 1.67 ± 0.43 mm, and the SMN microscope a mean accuracy of 2.61 ± 0.99 mm. The precision values were not significantly different among the systems. CONCLUSION: We observed only small differences in accuracy and precision among these three systems. We briefly review the advantages and disadvantages of each system and note that other factors, such as portability, ease of use, and microscope integration, should influence the selection of a frameless stereotactic system.

Original languageEnglish (US)
Pages (from-to)1409-1416
Number of pages8
Issue number6
StatePublished - Jan 1 2001
Externally publishedYes


  • Accuracy
  • Precision
  • Stereotactic techniques

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology


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