**4. Augmented reality in renal cancer**

engineers [1]. Augmented reality (AR) has come a long way since, however the fundamental idea remains the same: working in a real-world environment where the components of the environment are enhanced by a digitally-created perception. This perception can include multiple sensory inputs including visual, auditory, haptic, somatosensory and olfactory senses. In healthcare, AR progression has involved a wide range of medical areas—from aiding clinic appointments by easy access to electronic health records and patient times, to wearable glasses that help teach life-skills to children on the autism spectrum [2]. However, it seems that the biggest expansion of AR is seen in enhancing surgical procedures. Project DR is one such development—internal organs as 3D reconstructions of the patient's anatomy are projected onto the patient's skin and this allows a constant view of the person's anatomy that moves with patient in real time. This is achieved by the amalgamation of CT/MRI imaging, motion-sensing infrared sensors and projectors all working as one unit [3]. Another example is the use of Microsoft's HoloLens glasses for trauma and plastic surgeries (Imperial College London and St Mary's Hospital). The "hologram" (made from pre-op imaging) through the lens of the glasses projects onto the patient's skin and allows a "mixed reality" which lets the surgeon track the pathways of the various blood vessels and bones to be operated upon [4]. This technology promises to let surgeons carefully plan and execute breast reconstruction surgeries in the future. Google glass is another extensively used example of AR. The 'glasses' allow an augmented field of view and surgeons have used these for all purposes from navigation tools to display ultra-

sound imaging, to remote videoconferencing in intraoperative communication [5].

Whilst augmented reality is technology that overlays on the reality that already exists around us, virtual reality (VR) is a complete replacement of the real world with a simulated one. This means that AR allows us to interact and work with the real world, whilst getting an enhanced

VR has shown to be a great teaching tool. Moglia et al. [6] found that subjects trained on virtual simulators were better than the control group (using conventional methods). An example is the Uro Tainer, a validated simulator for teaching transurethral resection of bladder tumours [7]. VR has not only shown promise in surgery, but also other areas like simulation of shock trauma centres (where surgeons can be trained in high pressured environments) [8] and Virtual Environment for Radiotherapy Training (VERT)—a system built to reduce anxiety in breast cancer patients [9].

Within renal cancer, a VR system has been developed by Rai et al. that enhances the novice's ability to localise renal tumour margins [10]. Specific to nephrectomies, Makiyama et al. [11] have developed a VR "rehearsal" simulator for surgeons that plans for anatomical abnormalities and incorporates haptic feedback for pre-operative training. Ueno et al. have developed VR addressing another aspect of nephrectomies—reducing postoperative urine leakage by predicting open urinary tracts on preoperative 3D CT—reconstructions [12]. Whereas, VR

**2. Augmented reality vs. virtual reality?**

input from an informed digital world.

94 Evolving Trends in Kidney Cancer

**3. VR in kidney cancer**

In renal cancer surgery, open nephrectomies for the most part, have been replaced by minimally invasive laparoscopic surgeries. This has led to many positive outcomes, including decreased intra-op blood loss and shorter hospital stay [13]. Furthermore, partial nephrectomies have shown an overall improved survival over radical nephrectomies, [14] and this has been made possible due to crucial development in laparoscopic and robotic-assisted surgery [15]. However, there have also been some drawbacks. One of these is the loss of haptic feedback that would usually allow the surgeon to manoeuvre intra-operatively and make instinctive decisions. AR can aid the loss in this feedback sense by replacing it with an enhancement in another—the visual sense.

AR systems exist that allow surgeons to see detailed anatomical structures on the surface of the organ by projecting pre-operative CT/MRI images onto a live laparoscopic video. This allows the view of the patient-unique renal anatomy, it's neighbouring structures and its relation to the rest of the intra-abdominal anatomy [16]. Having this added information can aid the surgeon in planning and executing an accurate and precise partial or total nephrectomy. Exact areas to be incised can be planned and damage to nearby delicate structures such as

**Figure 1.** An illustration showing the basic components involved in AR. "the basic method is to superimpose a computer generated image on a real-world imagery captured by a camera and displaying the combination of these on a computer, tablet PC or a video projector. The main advantage of AR is that the surgeon is not forced to look away from the surgical site as opposed to common visualisation techniques." Adapted from: 'Recent Development of Augmented Reality in Surgery: A Review' [20].

renal vasculature and ureters can be reduced. AR can also reduce excision margins—to spare as many well-functioning nephrons and reduce the risk and progression of chronic renal insufficiency [17] (**Figure 1**).

For an AR system to be ideal, the full length of a surgical procedure need to be "augmented." This requires 3 essential features (as adapted by a recent review by Hughes-Hallet et al. [18]): image registration, organ tracking and adapting to intra-operative tissue deformation. In the following chapter, I will describe, in detail, these aspects of AR specific to nephrectomies.
