# Augmented Reality in Surgical Navigation: A Review of Evaluation and Validation Metrics
## 2 State of the Art AR Based Surgical Systems
### Laparoscopic Surgery  
Laparoscopy, in which physicians try surgical procedures through small incisions, is one of the most popular minimally invasive surgical treatments because of the development of video technology. However, despite the fact that a laparoscopic method is frequently favored over an open surgical approach due to the much lower patient morbidity and shortened recovery time [55], even for expert surgeons, it is highly difficult physically and cognitively. This is partly because of constraints in the typical arrangement, such as restricted flexibility in manipulation and poor depth perception in 2D displays, and partly because the surgeons' perception is dislocated from the action site. However, for many laparoscopic procedures, whether it be reconstruction of a bile duct while avoiding critical blood vessels or resection of a tumor located deep within an organ parenchyma, surgeons need to see hidden surgical targets. Keyhole techniques restrict the surgeon's 3D perception within the human body, despite the fact that minimally invasive surgery has several benefits [56; 57]. For instance, the surgeon's visual and tactile cues may be reduced by the restricted visual field of endoscopes and laparoscopes as well as the absence of haptic input.  
Augmented reality is a viable contender in the field of laparoscopic imaging [58; 59; 60; 61]. Given the standard endoscope or laparoscope's small field of vision, it makes perfect sense to supplement the video image with a model of the organ being inspected [62; 63]. This can include a depiction for internal organ features that are hidden in the typical laparoscopic picture or an extended surface view of the organ [64; 65; 66]. Many technical elements of correct registration and visualization of pre-operative imagery with the laparoscopic view, including the image registration, segmentation, calibration, tracking, and intra-operative imaging with MRI, CT, and ultrasound, have been addressed in [17; 67]. Recent advancements have revealed promising findings, suggesting that the proposed method requires substantially less cognitive and physical effort than the current 2D ultrasound imaging method utilized in the operating room [68].  
Figure 6 provides an example of visualization during laparoscopy through navigation system monitors. A thorough overview of the state of the art as well as the fundamentals of AR in laparoscopy is provided in [18], which makes it very useful. Several types of data, rendering, and display are accessible depending on the augmentation desired. A dependable technical foundation for laparoscopic liver resection is provided by the cutting-edge image navigation technology, as presented in [61]. Although the fundamental challenge facing laparoscopic AR is now its accuracy, the lack of accuracy necessitates the use of validation methods in surgical AR [1].  
Figure 6: An illustration of visualization during liver laparoscopy using navigation system [60] with (**a**) the surface fiducials being laparoscopically inserted on the surface of the liver, and (**b**) location of the surface fiducials being reprojected as AR objects.