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Page 2 of 12 Pecoraro et al. Mini-invasive Surg 2024;8:25 https://dx.doi.org/10.20517/2574-1225.2023.134

INTRODUCTION
Current guidelines recommend nephron-sparing surgery (NSS) as the treatment of choice in small renal
[1]
masses whenever technically feasible . Specifically, minimally invasive approach (laparoscopic or robotic)
should be preferred to minimize perioperative morbidity .
[2,3]
Many new technologies have been tested trying to broaden the indications for NSS to include larger and
more surgically challenging renal masses, including the use of intravenous dyes [e.g., indocyanine green
[4,5]
(ICG)] and hyper-accuracy three-dimensional virtual models (3DVMs) .

To improve planning and resection phase of the tumor, 3DVMs of the kidney and the tumor have been
introduced.

These models are obtained from preoperative computed tomography (CT) images and can be used through
different modalities such as holograms and intraoperative superimposition with augmented reality (AR)
[6-8]
technology .
Considering the tumor resection phase, AR has proven to be the most attractive technology for the surgeon.
This can be explained by the fact that this technology allows the real-time intraoperative superimposition of
3D models on real anatomy, enhancing the surgeon’s perception of anatomical relationship of the tumor
with the surrounding anatomical structures.

Additionally, 3DVMs seem to improve trifecta rates of the procedure, also in highly complex renal tumors,
by enhancing many surgical steps [6,9-12] .

We aimed to summarize the clinical applications of AR technology during the different sections of robot-
assisted partial nephrectomy (RAPN), from the renal pedicle approach to the resection and reconstructive
techniques.

3DVM AND AR
Workflow to obtain a high-definition 3D virtual model
A dedicated team of bioengineers is needed to obtain the final model in about 24-48 h. It is mandatory that
patients undergo four-phase (unenhanced corticomedullary, arterial, nephrographic, and urographic phase)
contrast-enhanced CT [13,14] . This necessitates a specific scanning protocol, with distinct scan delays for each
of the three phases: typically seven seconds for the arterial phase, 70 s for the nephrographic phase, and at
least 10 min for the urographic phase . Alternative imaging techniques such as magnetic resonance
[15]
imaging (MRI), ultrasound, and non-contrast CT, along with advanced processing methods, can achieve
similar levels of accuracy for patients with renal insufficiency. Studies have demonstrated the effectiveness
of MRI for creating detailed 3D models of kidney cancers [6,15,16] .

The following workflow [Table 1] helps summarize the step-by-step process for developing accurate and
high-quality 3D models, from initial imaging to final visualization or printing :
[16]

1. Image Acquisition: Multi-slice CT scans are preferred due to their detailed imaging and ability to export
in DICOM format. The slice thickness should be ≤ 5 mm to ensure high-fidelity 3D reconstruction. MRI
images can also be used, especially for soft tissue differentiation [Table 2].