3D Printing Surgical Models for Kidney Cancer Care

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3D Prostate Model - McAlpine, University of Minnesota Twin Cities
3D Prostate Model - McAlpine, University of Minnesota Twin Cities

Jonathan Silberstein, MD, is chief of Urologic Oncology at Tulane University Medical Center in New Orleans. We spoke with Dr Silberstein about his fascinating research creating surgical models of the kidney using a 3D printer.

How do you 3D print surgical models of the kidney? Why should urologists and nephrologists find these technologies so exciting?

Bringing a 2D structure to life by creating a 3D physical model through printing is tremendously exciting. When I carry one of our models down the hallway, I'm stopped by just about every physician asking how we made the model and whether we think that the technology can be used to accomplish this or that goal.

Although 3D printers come in a variety of shapes and sizes, they all perform by layering successive thin sheets of materials on top of one another to create a 3D model. Cross-sectional imaging, in which successive pictures are taken at different anatomic levels, is ideally suited for use in 3D printing as each slice or cross section is used to make one layer of the structure the 3D printer creates. The finer the “cuts” on the CT or MRI, the higher the model's fidelity to the endogenous structure being recreated. Typically, the materials used to construct these models are plastic resins that become malleable when heated allowing them to be formed into the desired shape, then cooled and fixed.

How are these 3D printed models superior to other models?

A CT scan can be manipulated in a variety of ways and rendered in 3D, but there are situations especially for a surgeon in which a 2D structure is not as beneficial as a 3D object that you can feel. A generic 3D anatomical model has some value, but it is not specific to the patient. 3D-printed models on the other hand are completely individualized.

Currently, 3D printers are used to convert cross sectional imaging into 3D physical models of bony structures that have been injured or damaged to allow orthopedic or maxillofacial surgeons to aid in realignment and reconstruction. Newer types of 3D printers allow for the printing of objects with multiple colors, multiple textures, and multiple materials. We have created high-fidelity 3D models of renal tumors with surrounding normal parenchyma and vasculature to aid in pre-surgical planning.

How are 3D printed models of the kidney being used for partial nephrectomy?

Our studies show that patient-specific models benefit patients, students, trainees, and surgeons. Medical students and trainees learn to interpret radiographic imaging more quickly with the aid of 3D models.

For patients, holding a replica of their kidney permits a clearer understanding of their disease and the intended intervention, and may influence their decision to provide informed consent for surgery. For surgeons, manipulating a patient-specific model allows better and more rapid identification of the tumor and may improve surgical outcomes.

Now young surgeons can do a “dry run” of a surgical resection and repair on a model that mimics the real organ. Likewise, practicing surgeons who trained in a low volume program or before the robotic era, can rapidly improve their operative skills using models with no risk to the patient. Theoretically, surgeons can practice multiple times prior to operating on a patient.

Our group has trained 2 sets of residents using these models, and they have progressed to advanced robotic partial nephrectomies with high nephrometry scores and excellent outcomes. We believe this training improves patient outcomes and minimizes harm.

What are other potential applications?

The potential applications of 3D printing in medicine are endless. Any widget you can dream of can be made in minutes. If a surgeon envisions a novel tool that is just a little longer or wider, or has a slightly different angle, than an existing one, he can simply fire up the printer and have a prototype in his hands.

Or, if a patient needs an implant or prosthesis, one can be fabricated in an individualized fashion using a 3D printer. From penile implants to urinary sphincters there is the potential to create a specifically customized solution to every need.

For malignancies, the models may aid in organ-sparing surgery, or potentially for ablation by enabling a surgeon to perform a “dry run” to determine the location, depth and/or number of needles that need to be placed.

Similarly 3D models may aid in diagnosis of benign or malignant conditions by helping to determine the trajectory and depth needed to hit a specific target lesion.

From stoma appliances that specifically fit a person's body to customizable biopsy guides, 3D printing has the very real potential to change the way we practice urologic medicine.

3D printers are becoming more and more affordable and more and more user friendly. In the not too distant future, every hospital, every academic department, perhaps every home will have one of these tools.

Sources

1. Silberstein JL, Maddox MM, Feibus A, et al. Physical models of renal malignancies using standard cross-sectional imaging and three-dimensional printers: a pilot study. Urology. 2014;84:268­272.

2. Maddox MM, Feibus A, Lee BR, et al. Resectable physical 3­D models utilizing 3­D printer technology for robotic partial nephrectomy. Video abstract presented at the American Urological Association Annual Meeting in New Orleans, May 15­19, 2015. Video abstract 15­898.

3. Libby RS, Silberstein JL. Physical Model of Clear-Cell Renal Carcinoma With Inferior Vena Cava Extension Created From a 3-Dimensional Printer to Aid in Surgical Resection: A Case Report. Clin Genitourin Cancer. 2017;15:e867-e869.

4. Maddox MM, Feibus A, Lee BR, et al. 3-D printed soft tissue physical models of renal malignancies for individualized surgical simulation: a feasibility study. J Robot Surg. 2017 [Published online Jan 20, 2017]. doi: 10.1007/s11701-017-0680-6

5. Knoedler M, Feibus A, Lange A, et al. Individualized physical 3D kidney tumor models constructed from 3D printers result in improved trainee anatomic understanding. Urol. 2015;85:1257-1262.

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