Soft-tissue deformation and the potential of skin markers to facilitate accurate navigation in percutaneous renal ablation

Abstract

Purpose: In percutaneous renal ablation (PRA), reaching the target accurately is challenging due to target motion and limited real-time visualization of the target, requiring a suitable navigation strategy. In the context of this thesis research, skin markers are used in combination with an the Azurion C-arm system (Philips Healthcare, Best, The Netherlands), an image-guided therapy system, equipped with ClarifEye (Philips Healthcare, Best, The Netherlands), an Augmented Reality (AR) surgical navigation system. The skin markers are tracked by ClarifEye, virtually representing the position of the patient. This thesis aims to explore if skin markers can facilitate sufficiently accurate navigation in PRA by investigating the skin marker motion (SMM) and kidney tumor marker motion (TMM) during needle insertion, considering the insertion speed (IS) and level of perirenal fat (LPF). Methods: An ex-vivo porcine kidney model, with simulated skin, tumors and perirenal fat was developed and validated. A skin marker model was constructed on the model. Consequently, 60 robotic-assisted needle insertions were planned with ClarifEye (Philips Healthcare, Best, The Netherlands) navigation and performed on 8 kidney models (4 with low LPF (LLPF), 4 with high LPF (HLPF)), targeting 20 tumors at varying ISs: continuous insertions of 2.5 mm/s, 75 mm/s and consecutive 5 mm increments of 10 mm/s. Cone beam computed tomography (CBCT)-scans were made before and after insertion to analyze SMM and TMM. Results: The SMM (overall mean SMM = 0.16 mm, standard deviation (SD) = 0.14 mm) was smaller than the voxel-size (1D) of dViewX (dicom-viewer software, Philips Healthcare, Best, The Netherlands) (voxel-size 1D = 0.2425 mm), regardless of the direction of the SMM and regardless of the IS and LPF. The TMM values in the z-direction were predominantly negative. The IS and LPF did not impact the amount and direction of TMM.
Conclusion: Any local skin deformation caused by needle insertion resulted in negligible SMM. Although the skin markers do not account for the TMM caused by needle insertions, the median TMM values (1.2-1.9 mm) are still smaller than the minimally required clinical insertion accuracy of 3-5 mm. The acceptable TMM values, in combination with the negligible SMM values, imply that skin markers can be used to facilitate navigation in PRA.