We assessed the targeting precision of a previously reported needle-based soft tissue navigation system in-vivo. Eight 2 ml agar nodules were implanted into the livers of two swine as tumor models. One medical expert with experience in punctures and one non-expert used the navigation system to target each nodule twice. The targeting error, which includes the system error and the user error, was defined as the distance between the applicator tip and the center of gravity of the lesions in computed tomography (CT) control scans and was 5.3C 2.2 mm (n = 16) for the expert, 3.2 +/- 1.3 mm (n = 16) for the non-expert, and 4.2 +/- 2.1 mm (n = 32) averaged over both subjects. A robust targeting precision of the order of magnitude of 4 mm could improve the treatment standard for CT-guided minimally invasive interventions in the liver dramatically.
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