Localization accuracy of sphere fiducials in computed tomography images

Jan-Philipp Kobler; Jesus Díaz Díaz; J. Michael Fitzpatrick; G. Jakob Lexow; Omid Majdani; Tobias Ortmaier

doi:10.1117/12.2043472

12 March 2014 Localization accuracy of sphere fiducials in computed tomography images

Jan-Philipp Kobler, Jesus Díaz Díaz, J. Michael Fitzpatrick, G. Jakob Lexow, Omid Majdani, Tobias Ortmaier

Author Affiliations +

Proceedings Volume 9036, Medical Imaging 2014: Image-Guided Procedures, Robotic Interventions, and Modeling; 90360Z (2014) https://doi.org/10.1117/12.2043472
Event: SPIE Medical Imaging, 2014, San Diego, California, United States

Abstract

In recent years, bone-attached robots and microstereotactic frames have attracted increasing interest due to the promising targeting accuracy they provide. Such devices attach to a patient's skull via bone anchors, which are used as landmarks during intervention planning as well. However, as simulation results reveal, the performance of such mechanisms is limited by errors occurring during the localization of their bone anchors in preoperatively acquired computed tomography images. Therefore, it is desirable to identify the most suitable fiducials as well as the most accurate method for fiducial localization. We present experimental results of a study focusing on the fiducial localization error (FLE) of spheres. Two phantoms equipped with fiducials made from ferromagnetic steel and titanium, respectively, are used to compare two clinically available imaging modalities (multi-slice CT (MSCT) and cone-beam CT (CBCT)), three localization algorithms as well as two methods for approximating the FLE. Furthermore, the impact of cubic interpolation applied to the images is investigated. Results reveal that, generally, the achievable localization accuracy in CBCT image data is significantly higher compared to MSCT imaging. The lowest FLEs (approx. 40 μm) are obtained using spheres made from titanium, CBCT imaging, template matching based on cross correlation for localization, and interpolating the images by a factor of sixteen. Nevertheless, the achievable localization accuracy of spheres made from steel is only slightly inferior. The outcomes of the presented study will be valuable considering the optimization of future microstereotactic frame prototypes as well as the operative workflow.

Citation Download Citation

Jan-Philipp Kobler, Jesus Díaz Díaz, J. Michael Fitzpatrick, G. Jakob Lexow, Omid Majdani, and Tobias Ortmaier "Localization accuracy of sphere fiducials in computed tomography images", Proc. SPIE 9036, Medical Imaging 2014: Image-Guided Procedures, Robotic Interventions, and Modeling, 90360Z (12 March 2014); https://doi.org/10.1117/12.2043472

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