PD4-03 A RANDOMIZED TRIAL OF ULTRASOUND VERSUS COMPUTED TOMOGRAPHY FOR IMAGING PATIENTS WITH SUSPECTED NEPHROLITHIASIS

Abstract

INTRODUCTION AND OBJECTIVES: We present the first application of a percutaneous navigation system (Translucent Medical, Inc.) which integrates GPS technology with a movable tablet display of virtual 3D models. Both the surgical tools and the movable tablet display are trackedbyGPStechnologyanddigitallyalignedwitheachother. In realtime, this system displays the internal anatomy, superimposed surgical tools, and navigation aids (such as predicted puncture line). The objective of our study was to assess the feasibility and accuracy of this system in a cadaver model for targeted interventions of the prostate and kidney. METHODS: Gold fiducial-markers (CIVCO Medical), which served as target center of the virtual tumor (Target-fiducial), were needle-implanted in kidney and prostate parenchyma. Then a preoperative CT scan was obtained, and CT-DICOM data were transferred to the system to construct 3D surgical models. A needle, with built-in GPS sensors, was used as the therapeutic puncture needle. When the system indicated coincidence of the needle-tip and target-fiducial, another gold fiducial (Treatment-fiducial) was placed through the outersheath of the therapeutic needle. A post-operative CT was acquired to measure distance between the Target and Treatment fiducials. For each Target-fiducial, two placements of a Treatment-fiducial were attempted (from two different skin incisions >2 cm apart). RESULTS: Real-time display of the needle puncture trajectory superimposed on the 3D model allowed successful navigation in all procedures. Navigation was further enhanced by color-coded changes to the needle-icon, which indicated whether or not the current trajectory was on-track to intersect the surgical target. Median time to target was 43 sec. Mean distance from needle-tip to target was 2.5mm (as calculated by the tracking system). Distance between the Targetand Treatment-fiducial was 16.6 mm in the prostate and 12 mm in the kidney. Distance between the paired Treatment-fiducials was 7.7mm. Analyzing each axial component, errors were significantly greater along z-axis (p<0.01), likely due to the intra-operative compression of the organ during puncture, resulting in possible rotation, shift, or deformation of the soft-tissue cadaveric organ. CONCLUSIONS: This virtual navigation system, integrating GPS-technology with movable tablet display, is promising for percutaneous interventions. In order to minimize possible errors, further work is needed to augment the tracking system for intra-corporeal organ motion/deformation.