Image-based guidance of percutaneous abdomen intervention based on markers for semi-automatic rigid registration.

INTRODUCTION: For percutaneous abdomen intervention (e.g. liver radiofrequency (RF) tumor ablation, liver biopsy), surgeons lack real-time visual feedback about the location of the needle on planning images, typically computed tomography (CT). One difficulty lies in tracking and synchronizing both the tool movement and the patient breathing motion. AIM: To verify the correspondence between rigid registration fiducial registration error signal and breathing phase.
MATERIAL AND METHODS: Designed markers that are clearly visible both in planning CT and on the patient during the intervention are proposed. Registration and breathing synchronization is then performed by a point-based approach. The method was tested in a clinical environment on 10 patients with liver cancer using 3D abdominal CT in the exhale position. Median rigid fiducial registration error (FRE) in the breathing cycle was used as a criterion to distinguish the inhale and exhale phase.
RESULTS: The correlation between breathing phase and FRE value can be observed for every patient. We obtained mean median FRE equal to 9.37 mm in exhale positions and 15.56 mm in the whole breathing cycle.
CONCLUSIONS: The presented real time approach, based on FRE calculation, was integrated in the clinical pipeline, and can help to select the best respiratory phase for needle insertion for percutaneous abdomen intervention, in cases where only 3D CT is performed. Moreover, this method allows semi-automated rigid registration to establish the correspondence between preoperative patient anatomical model and patient position.