MP20-03\u2003DEVELOPMENT AND VALIDATION OF PATIENT SPECIFIC HYDROGEL KIDNEY PHANTOMS IN PREDICTING PARTIAL NEPHRECTOMY SUCCESS FOR COMPLEX RENAL MASSES

Abstract

INTRODUCTION AND OBJECTIVES: Models generated from 3D printing technology are limited, by the lack of tissue realism, anatomical accuracy and vascular channels found within surgical target organs, allowing only limited tissue interaction. We present our unique technique, combining 3D printing and hydrogel casting to develop patient-specific kidney phantoms, which can be used as simulation platforms for preoperative rehearsals for cases with complex renal cancer. METHODS: Model creation: Patient’s DICOM files were imported into a segmentation software and converted to STL files to 3D-print injection molds. Individually fabricated tumors and hollow hilar structures were registered within the mold. Hydrogel (PVA) was injected to create the kidney parenchyma containing the tumor with functional arterial, venous, urine drainage systems. MECHANICAL TESTING: Uniaxial compression: An Instron MTA was used to compress 40 samples from fresh porcine kidneys and compared to 4 different conditions of PVA. Perfusion closure pressures: To replicate the closure forces during renorrhaphy, 5cm longitudinal defects were created in 4 porcine and PVA kidneys. Suture tensions, required to achieve hemostasis and to rip through the parenchyma, were measured. DETERMINING ANATOMICAL ACCURACY: 8 PVA kidney phantoms were reimaged (CT scan) and segmented to generate duplicate sets of STL files that were overlaid to perform a detailed quantitative analysis to determine distance errors in millimeters. Predictive validity: Full procedural rehearsals were performed on models of 8 complex cancer patients (nephrometry score > 8) after surrounding them with relevant organs defined by patient imaging. Warm ischemia time (WIT), estimated blood loss (EBL) and positive surgical margins were measured in the rehearsal and live cases. RESULTS: Stress-strain relationship for PVA at a concentration of 7% after 2 cycles produced the lowest root mean square error (RMSE=0.0003) compared to fresh porcine kidney tissues. The average RMSE discrepancy between the phantom and patient anatomy were -0.26mm, -0.2mm, 3.10mm, 0.61mm and 3.33mm for kidney parenchyma, tumor, artery, vein and calyx, respectively. Partial nephrectomy was successful in all 8 complex cases after rehearsals. A positive correlation was found in WIT and EBL between the simulated and live surgeries. Rehearsals improved surgeon’s confidence in predicting outcomes of these complex cases. CONCLUSIONS: Software that incorporates patient imaging into 3D printing applications, together with hydrogel molding techniques, are capable of creating human kidney phantoms with authentic anatomical, physical, and functional properties. Application of this versatile and reproducible technique may translate to improved clinical performance. Source of Funding: None