3D mixed reality holograms for preoperative surgical planning of nephron-sparing surgery: evaluation of surgeons' perception.

Background: 3D reconstructions are gaining a wide diffusion in nephron-sparing surgery (NSS) planning. They have usually been studied on common 2D flat supports, with limitations regarding real depth comprehension and interaction. Nowadays, it is possible to visualize kidney 3D reconstructions as holograms in a "mixed reality" (MR) setting. The aim of this study was to test the face and content validity of this technology, and to assess the role of 3D holograms in aiding preoperative planning for highly complex renal tumors amenable by NSS.

Methods: We evaluated surgeons' perception of mixed reality for partial nephrectomy during a urological international meeting organized at our Institution in January 2019. Thanks to the images of preoperative CT, hyper-accuracy 3D (HA3D) reconstructions were performed. Then, a virtual environment was created, and it interacted with the models in mixed reality setting by using HoloLens. We submitted to all the attendees a questionnaire, expressed by the Likert scale (1-10), about their opinion over the use and application of the MR. Moreover, the attendees had the chance to perform a first-hand MR experience; then, they were asked to choose their clamping and resection approach.

Results: Overall 172 questionnaires were collected. The scores obtained regarding both surgical planning (scored 8/10) and anatomical accuracy (9/10) were very positive. High satisfaction toward the potential role of this technology in surgical planning and understanding of surgical complexity (both scored 9/10) were expressed. After a first-hand experience with HoloLens and MR, 64.4% and 44.4% of the surgeons changed their clamping and resection approach, respectively - compared to CT image visualization only - choosing a more selective one.

Conclusions: Our study suggests that surgeons perceive holograms and MR as a useful and interesting tool for the preoperative setting before partial nephrectomy, in the direction of an ever more precise surgery.