Abstract: PD42-08
Sources of Funding: none

Introduction

Precise sonographically guided puncture remains a challenge especially in gaining access to undilated renal pelvises or for biopsy of very small renal masses. Existing systems for navigated ultrasound (US) guided punctures are rarely used due to their complex setup and the increased cost. Most of the systems use electromagnetic tracking facilitating a separate field generator (FG) to be placed next to the patients. We present a novel approach for navigated renal puncture using a mobile lightweight electromagnetic FG that is combined with a conventional US probe into one compact apparatus. The system's feasibility and accuracy for renal puncture was evaluated in an in-vitro and an in-vivo model.

Methods

The mobile FG has a rectangular frame shaped configuration, that allows for a centered mounting of the US probe. In-vitro evaluation took place in a biological model to teach percutaneous kidney access. Therefore, 10 porcine kidneys freshly removed after commercial slaughtering were used. Their ureters were canalized to simulate hydronephrosis, and then placed inside chicken carcasses of about 1 kg. Puncturing of the renal pelvis were performed both, with and without the assistance of navigation. In case of unsuccessful puncture attempts the puncture was repeated after the renal pelvis was dilated stepwise first to a diameter of 2 mm and if still necessary to 1cm. The correct placement of the needles was checked by CT afterwards._x000D_ For in-vivo evaluation of the system a ventilated porcine model was used. First a puncture without navigation was done to place a cylindric metal bead (1x2mm) within the renal parenchyma. Then a second puncturing was performed using navigation to guide the biopsy needle as close as possible to the bead. This procedure was done twice for each kidney of the model. For verification, a CT scan was performed after every sub-step. The accuracy was calculated as the distance between the metal bead and the biopsy needle's tip.

Results

In 0-2 mm dilated renal pelvises of the biological model successful puncture took place in 100% vs. 60% (navigated vs. conventional) of the cases (n=10, p≤0.021). The puncture duration was 49 vs. 40 sec. In the porcine model the mean distance of metal bead and biopsy needle (n=4) was 6.36±2.18 mm.

Conclusions

The innovative combination of FG and US probe enables reproducible and accurate needle navigation without having to use a separate FG. Navigated punctures are superior compared to conventional sonographic punctures.

Funding

none