# Review of Microsoft HoloLens Applications over the Past Five Years
## 3 Results
### Applications in Medical and Healthcare Fields
#### 3.1.1 Medical and Surgical Aids and Systems  
In medical and surgical aids and systems, AR-based HoloLens is used for purposes such as visualization of medical data, blood vessel search, targeting support for needles or drills and endoscope support. It is mainly used as an auxiliary means through which information related to the surgery is provided or the accuracy of the surgery is improved. [PERSON] et al. [29] evaluated the utility of Microsoft HoloLens in clinical and nonclinical applications of pathology. They tested virtual annotations during autopsy, 3D gross and microscopic pathology specimens, navigating entire slide images, telepathology and real-time pathology-radiology correlation. The pathology residents who performed the autopsy, while wearing the HoloLens, were instructed remotely with real-time diagrams, annotations and voice instructions; the 3D-scanned gross pathology specimen was implemented as a hologram, such that it could be manipulated easily. Additionally, the user could remotely contact the pathologist to receive guidance and register annotations in real time in the region of interest for the specimen. It was confirmed that the HoloLens is effective for autopsy and gross and microscopic examination; it can also support high-resolution imaging and has sufficient computing power to implement digital pathology. [PERSON] et al. [30] proposed an MR system for medical use that can superimpose medical data onto the physical surface of a patient by combining an Intel RealSense sensor and the Microsoft HoloLens HMD system. They used the denoised-resampled-weighted-and-perturbed-iterative closest points algorithm, which was developed in their study, to remove noise and outliers from the virtual medical data, before displaying the preoperative medical image data as a 3D image. The patient's 3D medical images were displayed in the same coordinate space as the real patient and it was confirmed that the proposed system could perform accurate and robust mapping, despite the presence of noise and outliers in the MR system. [PERSON] et al. [3] evaluated whether the HoloLens HMD could potentially replace the conventional monitor that is used in endoscopic surgery. The evaluation was conducted with 72 participants, i.e., with novices (\(n=28\)), intermediates (\(n=24\)) and experts (\(n=20\)). The participants performed ureteroscopy in an inflatable operating environment using a validated training model and the HoloLens MR device as a monitor (Figure 2). Consequently, even the novice group was able to complete the assigned task successfully. However, the experienced group found it difficult to complete the assigned task because the new device was unfamiliar to these participants. However, 97% of the participants agreed that HoloLens would play a useful role in surgical education and 95% of the participants strongly agreed that it could be introduced clinically. [PERSON] et al. [31] performed a qualitative user evaluation of an MR application. Furthermore, they described the detailed development and clinical-use workflows from acquisition to visualization in MR data. They also proposed an MR pilot for real-world use in surgical planning through clinical-use cases in laparoscopic liver resection and congenital heart surgery. The results from the clinical-use cases showed that the application of MR provides a better understanding of patient-specific anatomy and that it can improve surgical planning. [PERSON] et al. [32] proposed an AR approach that uses an improved alignment method for image-guided surgery, to provide physicians with the ability to observe the location of the lesion during the course of surgery. After building and establishing the patient's head surface information using an RGB-depth sensor in conjunction with a point cloud library, the preoperative medical imaging information, which was obtained using the proposed improved alignment algorithm, was visualized using AR. Then, this information was placed in the same world coordinate system as the patient's head surface information.