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Erschienen in:
01.07.2014 | Original Article
A low-cost tracked C-arm (TC-arm) upgrade system for versatile quantitative intraoperative imaging
Erschienen in: International Journal of Computer Assisted Radiology and Surgery | Ausgabe 4/2014
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Purpose
C-arm fluoroscopy is frequently used in clinical applications as a low-cost and mobile real-time qualitative assessment tool. C-arms, however, are not widely accepted for applications involving quantitative assessments, mainly due to the lack of reliable and low-cost position tracking methods, as well as adequate calibration and registration techniques. The solution suggested in this work is a tracked C-arm (TC-arm) which employs a low-cost sensor tracking module that can be retrofitted to any conventional C-arm for tracking the individual joints of the device.
Methods
Registration and offline calibration methods were developed that allow accurate tracking of the gantry and determination of the exact intrinsic and extrinsic parameters of the imaging system for any acquired fluoroscopic image. The performance of the system was evaluated in comparison to an Optotrak\(^\mathrm{TM}\) motion tracking system and by a series of experiments on accurately built ball-bearing phantoms. Accuracies of the system were determined for 2D–3D registration, three-dimensional landmark localization, and for generating panoramic stitched views in simulated intraoperative applications.
Results
The system was able to track the center point of the gantry with an accuracy of \(1.5 \pm 1.2\) mm or better. Accuracies of 2D–3D registrations were \(2.3 \pm 1.1\) mm and \(0.2 \pm 0.2^{\circ }\). Three-dimensional landmark localization had an accuracy of \(3.1 \pm 1.3\%\) of the length (or \(4.4 \pm 1.9\) mm) on average, depending on whether the landmarks were located along, above, or across the table. The overall accuracies of the two-dimensional measurements conducted on stitched panoramic images of the femur and lumbar spine were 2.5 \(\pm \) 2.0 % \((3.1 \pm 2.5 \hbox { mm})\) and \(0.3 \pm 0.2^{\circ }\), respectively.
Conclusion
The TC-arm system has the potential to achieve sophisticated quantitative fluoroscopy assessment capabilities using an existing C-arm imaging system. This technology may be useful to improve the quality of orthopedic surgery and interventional radiology.