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Background: Image guidance has been clinically available for over a period of 20 years. Although research increasingly has a translational emphasis, overall the clinical uptake of image guidance systems in surgery remains low. The objective of this review was to establish the metrics used to report on the impact of surgical image guidance systems used in a clinical setting., Methods: A systematic review of the literature was carried out on all relevant publications between January 2000 and April 2016. Ovid MEDLINE and Embase databases were searched using a title strategy. Reported outcome metrics were grouped into clinically relevant domains and subsequent sub-categories for analysis., Results: In total, 232 publications were eligible for inclusion. Analysis showed that clinical outcomes and system interaction were consistently reported. However, metrics focusing on surgeon, patient and economic impact were reported less often. No increase in the quality of reporting was observed during the study time period, associated with study design, or when the clinical setting involved a surgical specialty that had been using image guidance for longer., Conclusions: Publications reporting on the clinical use of image guidance systems are evaluating traditional surgical outcomes and neglecting important human and economic factors, which are pertinent to the uptake, diffusion and sustainability of image-guided surgery. A framework is proposed to assist researchers in providing comprehensive evaluation metrics, which should also be considered in the design phase. Use of these would help demonstrate the impact in the clinical setting leading to increased clinical integration of image guidance systems.

Purpose: The aim of this study is to propose a model that simulates patient-specific anatomical changes resulting from pneumoperitoneum, using preoperative data as input. The framework can assist the surgeon through a real-time visualisation and interaction with the model. Such could further facilitate surgical planning preoperatively, by defining a surgical strategy, and intraoperatively to estimate port positions., Methods: The biomechanical model that simulates pneumoperitoneum was implemented within the GPU-accelerated NVIDIA FleX position-based dynamics framework. Datasets of multiple porcine subjects before and after abdominal insufflation were used to generate, calibrate and validate the model. The feasibility of modelling pneumoperitoneum in human subjects was assessed by comparing distances between specific landmarks from a patient abdominal wall, to the same landmark measurements on the simulated model., Results: The calibration of simulation parameters resulted in a successful estimation of an optimal set parameters. A correspondence between the simulation pressure parameter and the experimental insufflation pressure was determined. The simulation of pneumoperitoneum in a porcine subject resulted in a mean Hausdorff distance error of 5-6 mm. Feasibility of modelling pneumoperitoneum in humans was successfully demonstrated., Conclusion: Simulation of pneumoperitoneum provides an accurate subject-specific 3D model of the inflated abdomen, which is a more realistic representation of the intraoperative scenario when compared to preoperative imaging alone. The simulation results in a stable and interactive framework that performs in real time, and supports patient-specific data, which can assist in surgical planning.

Purpose: To assist the rehearsal and planning of robot-assisted partial nephrectomy, a real-time simulation platform is presented that allows surgeons to visualise and interact with rapidly constructed patient-specific biomechanical models of the anatomical regions of interest. Coupled to a framework for volumetric deformation, the platform furthermore simulates intracorporeal 2D ultrasound image acquisition, using preoperative imaging as the data source. This not only facilitates the planning of optimal transducer trajectories and viewpoints, but can also act as a validation context for manually operated freehand 3D acquisitions and reconstructions., Methods: The simulation platform was implemented within the GPU-accelerated NVIDIA FleX position-based dynamics framework. In order to validate the model and determine material properties and other simulation parameter values, a porcine kidney with embedded fiducial beads was CT-scanned and segmented. Acquisitions for the rest position and three different levels of probe-induced deformation were collected. Optimal values of the cluster stiffness coefficients were determined for a range of different particle radii, where the objective function comprised the mean distance error between real and simulated fiducial positions over the sequence of deformations., Results: The mean fiducial error at each deformation stage was found to be compatible with the level of ultrasound probe calibration error typically observed in clinical practice. Furthermore, the simulation exhibited unconditional stability on account of its use of clustered shape-matching constraints., Conclusions: A novel position-based dynamics implementation of soft tissue deformation has been shown to facilitate several desirable simulation characteristics: real-time performance, unconditional stability, rapid model construction enabling patient-specific behaviour and accuracy with respect to reference CT images.

Purpose: In order to assist in the identification of renal vasculature and tumour boundaries in robot-assisted partial nephrectomy, robust ultrasound probe calibration and tracking methods are introduced. Contemporaneous image guidance during these crucial stages of the procedure should ultimately lead to improved safety and quality of outcome for the patient, through reduced positive margin rates, segmental clamping, shorter ischaemic times and nephron-sparing resection., Methods: Small KeyDot markers with circular dot patterns are attached to a miniature pickup ultrasound probe. Generic probe calibration is superseded by a more robust scheme based on a sequence of physical transducer measurements. Motion prediction combined with a reduced region-of-interest in the endoscopic video feed facilitates real-time tracking and registration performance at full HD resolutions., Results: Quantitative analysis confirms that circular dot patterns result in an improved translational and rotational working envelope, in comparison with the previous chessboard pattern implementation. Furthermore, increased robustness is observed with respect to prevailing illumination levels and out-of-focus images due to relatively small endoscopic depths of field., Conclusion: Circular dot patterns should be employed in this context as they result in improved performance and robustness. This facilitates clinical usage and interpretation of the combined video and ultrasound overlay. The efficacy of the overall system is demonstrated in the first human clinical case.

Background: Inattention blindness (IB) can be defined as the failure to perceive an unexpected object when attention is focussed on another object or task. The principal aim of this study was to determine the effect of cognitive load and surgical image guidance on operative IB., Methods: Using a randomised control study design, participants were allocated to a high or low cognitive load group and subsequently to one of three augmented reality (AR) image guidance groups (no guidance, wireframe overlay and solid overlay). Randomised participants watched a segment of video from a robotic partial nephrectomy. Those in the high cognitive load groups were asked to keep a count of instrument movements, while those in the low cognitive load groups were only asked to watch the video. Two foreign bodies were visible within the operative scene: a swab, within the periphery of vision; and a suture, in the centre of the operative scene. Once the participants had finished watching the video, they were asked to report whether they had observed a swab or suture., Results: The overall level of prompted inattention blindness was 74 and 10 % for the swab and suture, respectively. Significantly higher levels of IB for the swab were seen in the high versus the low cognitive load groups, but not for the suture (8 vs. 47 %, p < 0.001 and 90 vs. 91 %, p = 1.000, for swab and suture, respectively). No significant difference was seen between image guidance groups for attention of the swab or suture (29 vs. 20 %, p = 0.520 and 22 vs. 22 %, p = 1.000, respectively)., Conclusions: The overall effect of IB on operative practice appeared to be significant, within the context of this study. When examining for the effects of AR image guidance and cognitive load on IB, only the latter was found to have significance.

Many of the currently available stereo endoscopes employed during minimally invasive surgical procedures have shallow depths of field. Consequently, focus settings are adjusted from time to time in order to achieve the best view of the operative workspace. Invalidating any prior calibration procedure, this presents a significant problem for image guidance applications as they typically rely on the calibrated camera parameters for a variety of geometric tasks, including triangulation, registration and scene reconstruction. While recalibration can be performed intraoperatively, this invariably results in a major disruption to workflow, and can be seen to represent a genuine barrier to the widespread adoption of image guidance technologies. The novel solution described herein constructs a model of the stereo endoscope across the continuum of focus settings, thereby reducing the number of degrees of freedom to one, such that a single view of reference geometry will determine the calibration uniquely. No special hardware or access to proprietary interfaces is required, and the method is ready for evaluation during human cases. A thorough quantitative analysis indicates that the resulting intrinsic and extrinsic parameters lead to calibrations as accurate as those derived from multiple pattern views.

Transanal endoscopic microsurgery (TEM), i.e., the local excision of rectal carcinomas by way of a bimanual operating system with magnified binocular vision, is gaining acceptance in lieu of more radical total interventions. A major issue with this approach is the lack of information on submucosal anatomical structures. This paper presents an advanced navigation system, wherein the intraoperative 3D structure is stably estimated from multiple stereoscopic views. It is registered to a preoperatively acquired anatomical volume based on subject-specific priors. The endoscope motion is tracked based on the 3D scene and its field-of-view is visualised jointly with the preoperative information. Based on in vivo data, this paper demonstrates how the proposed navigation system provides intraoperative navigation for TEM1.

The Pico Lantern is proposed as a new tool for guidance in laparoscopic surgery. Its miniaturized design allows it to be picked up by a laparoscopic tool during surgery and tracked directly by the endoscope. By using laser projection, different patterns and annotations can be projected onto the tissue surface. The first explored application is surface reconstruction. The absolute error for surface reconstruction using stereo endoscopy and untracked Pico Lantern for a plane, cylinder and ex vivo kidney is 2.0 mm, 3.0 mm and 5.6 mm respectively. The absolute error using a mono endoscope and a tracked Pico Lantern for the same plane, cylinder and kidney is 0.8mm, 0.3mm and 1.5mm respectively. The results show the benefit of the wider baseline produced by tracking the Pico Lantern. Pulsatile motion of a human carotid artery is also detected in vivo. Future work will be done on the integration into standard and robot-assisted laparoscopic surgery.

Robotic partial nephrectomy is presently the fastest-growing robotic surgical procedure, and in comparison to traditional techniques it offers reduced tissue trauma and likelihood of post-operative infection, while hastening recovery time and improving cosmesis. It is also an ideal candidate for image guidance technology since soft tissue deformation, while still present, is localised and less problematic compared to other surgical procedures. This work describes the implementation and ongoing development of an effective image guidance system that aims to address some of the remaining challenges in this area. Specific innovations include the introduction of an intuitive, partially automated registration interface, and the use of a hardware platform that makes sophisticated augmented reality overlays practical in real time. Results and examples of image augmentation are presented from both retrospective and live cases. Quantitative analysis of registration error verifies that the proposed registration technique is appropriate for the chosen image guidance targets.

Local excision of rectal cancer with transanal endoscopic microsurgery has proved to be a viable alternative to conventional, more radical techniques, but the reduced sensory experience presents significant challenges for the surgeon. Accurate identification and complete removal of lesions and subsurface targets is currently a difficult task, often exacerbated by intraoperative tissue deformation. This work describes novel ultrasound calibration and effective visualisation methods designed to meet these requirements, relying solely on optical measurements and pattern tracking. Detailed quantitative phantom and porcine validation experiments confirm that the technique is both practical and an accurate means for assessing lesion thickness intraoperatively, leading directly to human clinical trials.

The recovery of 3D tissue structure and morphology during robotic assisted surgery is an important step towards accurate deployment of surgical guidance and control techniques in minimally invasive therapies. In this article, we present a novel stereo reconstruction algorithm that propagates disparity information around a set of candidate feature matches. This has the advantage of avoiding problems with specular highlights, occlusions from instruments and view dependent illumination bias. Furthermore, the algorithm can be used with any feature matching strategy allowing the propagation of depth in very disparate views. Validation is provided for a phantom model with known geometry and this data is available online in order to establish a structured validation scheme in the field. The practical value of the proposed method is further demonstrated by reconstructions on various in vivo images of robotic assisted procedures, which are also available to the community.

The use of physically-based models combined with image constraints for intraoperative guidance is important for surgical procedures that involve large-scale tissue deformation. A biomechanical model of tissue deformation is described in which surface positional constraints and internally generated forces are derived from endoscopic images and preoperative 4D CT data, respectively. Considering cardiac motion, a novel technique is presented which minimises the average registration error over one or more complete cycles. Features tracked in the stereo video stream provide surface constraints, and an inverse finite element simulation is presented which allows internal forces to be recovered from known preoperative displacements. The accuracy of surface texture, segmented mesh and volumetrically rendered overlays is evaluated with detailed phantom experiments. Results indicate that by combining preoperative and intraoperative images in this manner, accurate intraoperative tissue deformation modelling can be achieved.

Recently, much attention has been focused on heart motion analysis for minimally invasive beating-heart surgery. Unfortunately existing techniques usually require the camera(s) to be fixed during the motion analysis, which can restrict its usefulness during surgery. In this paper we present a novel method for heart motion analysis using geometric constraint, which can estimate the motion from a moving camera and employ multiple image features to improve robustness to noise. Our approach combines the benefits of geometry estimation for obtaining an accurate and robust solution with the proper treatment of respiratory motion. The proposed method can be applied to not only beating heart surgery, but also to other procedures involving periodic organ motion, such as lung and liver.