Comparison of laser surface scanning and fiducial marker–based registration in frameless stereotaxy

Technical note

Restricted access

✓The authors compared the accuracy of laser surface scanning patient registration using the commercially available Fazer (Medtronic, Inc.) with the conventional registration procedure based on fiducial markers (FMs) in computer-assisted surgery.

Four anatomical head specimens were prepared with 10 titanium microscrews placed at defined locations and scanned with a 16-slice spiral computed tomography unit. To compare the two registration methods, each method was applied five times for each cadaveric specimen; thus data were obtained from 40 registrations. Five microscrews (selected following a randomization protocol) were used for each FM-based registration; the other five FMs were selected for coordinate measurements by touching with a point measurement stylus. Coordinates of these points were also measured manually on the screen of the navigation computer. Coordinates were measured in the same manner after laser surface registration.

The root mean square error as calculated by the navigation system ranged from 1.3 to 3.2 mm (mean 1.8 mm) with the Fazer and from 0.3 to 1.8 mm (mean 1.0 mm) with FM-based registration. The overall mean deviations (the arithmetic mean of the mean deviations of measurements on the four specimens) were 3.0 mm (standard deviation [SD] range 1.4–2.6 mm) with the Fazer and 1.4 mm (SD range 0.4–0.9 mm) with the FMs. The Fazer registration scans 300 surface points. Statistical tests showed the difference in the accuracy of these methods to be highly significant.

In accordance with the findings of other groups, the authors concluded that the inclusion of a larger number of registration points might improve the accuracy of Fazer registration.

Abbreviations used in this paper:ANOVA = analysis of variance; CT = computed tomography; FM = fiducial marker; RMSE = root mean square error; SD = standard deviation.

Article Information

Address reprint requests to: Kurt Schicho, D.Sc., University Hospital for Craniomaxillofacial and Oral Surgery, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria. email:

© AANS, except where prohibited by US copyright law.



  • View in gallery

    Photograph illustrating some of the titanium microscrews inserted into the anatomical specimen at defined locations for fiducial-based registration and measurement of coordinates.

  • View in gallery

    Photograph showing a head rigidly fixed in the Vertek biopsy system for measurement.

  • View in gallery

    Screen shot showing the FM-based registration. Following a randomization protocol, five FMs were selected from the total of 10 during every registration process. Coordinate measurements were performed at FMs that were not used in this registration. The grid sphere in the lower right part of the screen indicates an area where an intraoperative accuracy of 1.0 mm can be expected. The RMSE of the registration (0.9 mm in this example) is displayed on the navigation panel (right side of the figure).

  • View in gallery

    Screen shot illustrating coordinate measurements. After the centers of the FMs are manually identified, the system displays the x, y, and z coordinates. The pixel values must then be converted into millimeter values.

  • View in gallery

    Left: Photograph of the Fazer. The Fazer measures the distance to the surface with a laser beam. Light-emitting diodes in the device serve as reference points for the active optical tracking system. Right: Screen shot showing the Fazer-generated points. With this method, a set of points is generated on the surface of the patient's skin.

  • View in gallery

    Bar graphs depicting RMSEs as calculated by the system after registration of the four specimens for Fazer-based (upper) and FM-based (lower) registration.

  • View in gallery

    Bar graphs showing the deviations for Fazer-based (upper) and FM-based (lower) registration. Values on the y axis represent deviation measurements in millimeters.

  • View in gallery

    Box-and-whisker plots showing the RMSEs for Fazer-based and FM-based registration. The boxes indicate the interquartile range, the horizontal lines within the boxes indicate the median values, and the vertical lines (whiskers) designate the ranges that extend 1.5 × the interquartile ranges above and below the hinges of the boxes. The circles indicate outliers. Values on the y axis indicate deviation measurements in millimeters. The designators on the x axis indicate type of registration and specimen number. F = Fazer-based registration; M = FM-based registration.


  • 1

    Adler JR JrMurphy MJChang SDHancock SL: Image-guided robotic radiosurgery. Neurosurgery 44:129913071999

  • 2

    Amin DVKanade TDiGioia AM IIIJaramaz B: Ultrasound registration of the bone surface for surgical navigation. Comp Aided Surg 8:1162003

  • 3

    Amstutz CCaversaccio MKowal JBachler RNolte LPHausler R: A-mode ultrasound-based registration in computer-aided surgery of the skull. Arch Otolaryngol Head Neck Surg 129:131013162003

  • 4

    Birkfellner WSeemann RFigl MHummel JEde CHomolka P: Wobbled splatting—a fast perspective volume rendering method for simulation of x-ray images from CT. Phys Med Biol 50:N73N842005

  • 5

    Birkfellner WSolar PGahleitner AHuber KKainberger FKettenbach J: In-vitro assessment of a registration protocol for image guided implant dentistry. Clin Oral Implants Res 12:69782001

  • 6

    Birkfellner WWirth JBurgstaller WBaumann BStaedele HHammer B: A faster method for 3D/2D medical image registration—a simulation study. Phys Med Biol 48:266526792003

  • 7

    Cash DMSinha TKChapman WCTerawaki HDawant BMGalloway RL: Incorporation of a laser range scanner into image-guided liver surgery: surface acquisition, registration, and tracking. Med Phys 30:167116822003

  • 8

    Marmulla RHassfeld SLuth TMende UMuhling J: Soft tissue scanning for patient registration in image-guided surgery. Comput Aided Surg 8:70812003

  • 9

    Marmulla RLuth TMuhling JHassfeld S: Automated laser registration in image-guided surgery: evaluation of the correlation between laser scan resolution and navigation accuracy. Int J Oral Maxillofac Surg 33:6426482004

  • 10

    Marmulla RLuth TMuhling JHassfeld S: Markerless laser registration in image-guided oral and maxillofacial surgery. J Oral Maxillofac Surg 62:8458512004

  • 11

    Marmulla RMuhling JWirtz CRHassfeld S: High-resolution laser surface scanning for patient registration in cranial computer-assisted surgery. Minim Invasive Neurosurg 47:72782004

  • 12

    Raabe AKrishnan RWolff RHermann EZimmermann MSeifert V: Laser surface scanning for patient registration in intracranial image-guided surgery. Neurosurgery 50:7978032002

  • 13

    Schlaier JWarnat JBrawanski A: Registration accuracy and practicability of laser-directed surface matching. Comput Aided Surg 7:2842902002




All Time Past Year Past 30 Days
Abstract Views 126 126 10
Full Text Views 146 146 3
PDF Downloads 47 47 3
EPUB Downloads 0 0 0


Google Scholar