## 1 Introduction
The benefit of the second method is that each printout already contains the desired slice, however, there is a chance that not all the information is conveyed since there is a practical limit for how many printouts can be hung next to each other. Visualization technology in the operating room has continued to improve both surgical workflow and training practices. It has provided an opportunity for multimodal integration, enabling surgeons to maximize all the relevant information during the procedure. These visualization modalities include digital stereomicroscopy, virtual reality (VR), augmented reality (AR), and mixed reality (MR). Unlike VR, which only offers an effective platform for pre-procedural planning, AR allows a surgeon to visualize the live surgical field with an enriched virtual data overlay, including different sets of data deriving from different imaging modalities, such as tractography, or angiography, or ultrasound imaging [5; 14]. Yet, surgeons often cite the lack of tactile feedback and intuitive interaction as a limitation of AR technology. On the other hand, mixed reality holds the promise of providing digital enhancement to our vision while ensuring a fully immersed environment enabling the user to have an intuitive interaction with the overlaid digital contents [15; 16]. Despite these advantages, there has been little adoption of mixed reality into clinical interventions due to limitations in hardware, lack of streamlined methods to generate 3D data to render in the mixed reality environment, and an inability to provide real-time updates to the model due to events occurring during the procedure. Thus far, there are few publications on the use of AR systems in gynecologic surgery. Initially, [PERSON] et al. [17] presented the first AR-based image guidance system for assisted myoma localization in uterine laparoscopy. This study leveraged the reference and the update registration methods to achieve a nonrigid registration of the uterus and myomas from the MRI to the laparoscopic video. [PERSON] et al. [18] evaluated the potential benefits of an AR system for myometomy and reported that an AR system could enhance the accuracy of the localization of fibroids by a factor of about twenty. In two follow-up publications, [PERSON] et al. [19, 20] developed an AR system for the individual cases and demonstrated an improved laparoscopic myometomy and adenomyometomy upon implementing AR during surgery. In another study, [PERSON] et al. [21] proposed object-class occluding contour detection (OC2D) framework to register preoperative 3D MRI model to intraoperative laparoscopy 2D images, to achieve augmented reality in laparoscopy. A user study was carried out to evaluate the impact of OC2D against manually marked occluding contours in augmented laparoscopy. The OC2D reduced 3 min and 53 s in surgeon time without sacrificing registration accuracy, indicating that fully automatic augmented laparoscopy is feasible. It is clear that such works have shed light upon the success of adapting extended reality systems (VR/AR/MR) in gynecologic practices and given us an improved understanding of its significance. However, despite these, there is a paucity of literature detailing the technical development and the refinement which could enable the engineers and developers to build and test the environment for collaborating physicians. To this end, herein, we present the use of a mixed reality headset, Microsoft HoloLens2, as an intra-procedural image-guidance tool during a mock myometomy of an ex vivo animal model that was performed by a gynecologic surgeon at New York Presbyterian Hospital's Skills Acquisition and Innovation Laboratory (SAIL). We discuss the manual segmentation of uterine fibroids and overview the file preparation from a MRI scan. Additionally, we tested the use of 3D rendering projected on a 2D monitor and qualitatively compared it with the mixed reality hologram. Figure 1: Overview of intra-procedural MRI viewers.