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. 2011 Nov 23;6(11):e27372. doi: 10.1371/journal.pone.0027372

Figure 1. Calibration and accuracy of electromagnetically-tracked CT/US.

Figure 1

(a) Relevant hardware for combined CT/US with the coordinate systems used to join the tracked US transducer and CT image space. The US plane, P space, is calibrated with respect to a position sensor, R space, attached to the US transducer. The sensor's location is known relative to an electromagnetic transmitter, T space, whose orientation relative to the CT image space, C, is determined by fiducial registration. (b) The combined imaging system is used to view B-mode US, the corresponding CT slice, the corresponding segmented CT slice, or any combination of these slices in real-time. (c) The magnitude of the error in calibration across 93 observations of a single point imaged from multiple angles with a mean of ∼0.94 ±0.5 mm. (d) Calibration data from (c) plotted in 3D to provide the spatial distribution of the error and indicate that the error is isotropic.