Evaluating a Novel 3D Stereoscopic Visual Display for Transanal Endoscopic Surgery

A Randomized Controlled Crossover Study

Aimee N. Di Marco, MA, MBBS, MRCS; Jenifa Jeyakumar, BSc; Philip J. Pratt, PhD; Guang-Zhong Yang, FREng; Ara W. Darzi, MD, FRS, FMedSci, FRCS, FACS

Disclosures

Annals of Surgery. 2016;263(1):36-42. 

In This Article

Abstract and Introduction

Abstract

Objective: To compare surgical performance with transanal endoscopic surgery (TES) using a novel 3-dimensional (3D) stereoscopic viewer against the current modalities of a 3D stereoendoscope, 3D, and 2-dimensional (2D) high-definition monitors.

Background: TES is accepted as the primary treatment for selected rectal tumors. Current TES systems offer a 2D monitor, or 3D image, viewed directly via a stereoendoscope, necessitating an uncomfortable operating position. To address this and provide a platform for future image augmentation, a 3D stereoscopic display was created.

Methods: Forty participants, of mixed experience level, completed a simulated TES task using 4 visual displays (novel stereoscopic viewer and currently utilized stereoendoscope, 3D, and 2D high-definition monitors) in a randomly allocated order. Primary outcome measures were: time taken, path length, and accuracy. Secondary outcomes were: task workload and participant questionnaire results.

Results: Median time taken and path length were significantly shorter for the novel viewer versus 2D and 3D, and not significantly different to the traditional stereoendoscope. Significant differences were found in accuracy, task workload, and questionnaire assessment in favor of the novel viewer, as compared to all 3 modalities.

Conclusions: This novel 3D stereoscopic viewer allows surgical performance in TES equivalent to that achieved using the current stereoendoscope and superior to standard 2D and 3D displays, but with lower physical and mental demands for the surgeon. Participants expressed a preference for this system, ranking it more highly on a questionnaire. Clinical translation of this work has begun with the novel viewer being used in 5 TES patients.

Introduction

Colorectal cancer is the fourth most common malignancy worldwide,[1] with rectal cancer accounting for over a third of these. Local transanal excision is an important alternative to radical surgical approaches to the rectum, that is, anterior resection and abdominoperineal excision for selected early cancers of the mid- and upper rectum, as it offers reduced operative time, fewer complications, less postoperative pain, and a shorter recovery period.[2–10] In addition, transanal endoscopic surgery (TES) is considered the gold standard for the treatment of benign rectal adenomas that cannot be excised endoscopically and risk malignant transformation if left behind, and it has an important role in the noncurative excision of advanced malignancies for palliation of symptoms and disease control in very comorbid patients.[10–12] The adoption of screening programs[13] for colorectal cancer, improved tumor downstaging with novel neoadjuvant therapies,[14] and an increasingly elderly and frail population are likely to make minimally invasive procedures, such as TES, increasingly important in the future.

The original platform, known as transanal endoscopic microsurgery (TEMS)[15] was pioneered by Dr Gerhard Buess and developed with Richard Wolf GmBH in the 1980s: this platform has changed little since its inception, but despite this, and competition from newer systems such as Karl Storz's Transanal Endoscopic Operating (TEO) system, and the rise of transanal minimally invasive surgery (TAMIS) using either standard laparoscopic instruments via a single incision (SILS) port or robotically with the daVinci Si,[16,17] the Wolf TEMS system has remained the most widely used. All of the platforms available for TES require a high degree of technical skill to overcome the issues of lack of triangulation and instrument clashes in the small workspace, and achieve a complete resection with clear margins: this is of paramount importance as salvage surgery for positive margins or local recurrence is associated with a worse prognosis than primary radical surgery.[18] In light of the potential growth of TES, improvements in any such system are required. This project sought to identify and improve upon the key area of visualization.

The Wolf TEMS system has a custom stereoendoscope, which offers a high-quality magnified 3D image of the operative field. The superior visualization afforded by this stereoendoscope is one reason for the system's continued popularity. However, a major associated drawback is that the operator can only obtain this image by viewing directly into the stereoendoscope, requiring the adoption of an uncomfortable position of neck flexion. An ancillary, "teaching" port on the stereoendoscope can be used to provide an image to a 2D flat screen for other personnel in the operating theater. Many experienced surgeons will, therefore, choose to operate using this 2D flat screen instead and switch to the stereoendoscope only if the procedure becomes challenging. This study sought to establish the relative merits of these 2 approaches against a novel 3D stereoscopic viewer and a flat 3D screen.

Creation of a Novel 3D Stereoscopic Viewing Device

A novel 3D stereoscopic viewer was designed and built, based on the principles of the Wheatstone stereoscope (Fig. 1).[19] A pair of high-definition (HD) laparoscopic camera heads (Storz UK Ltd) were mounted, with a custom-made bracket, onto the Wolf TEMS Stereoscope, to provide independent outputs to 2 small video monitors (5.6" TVLogic VFM-056W 1280 × 800). The monitors, with paired mirrors and lenses, were mounted on a machined aluminum plate and suspended from a stainless steel frame (Gallops, UK) (Fig. 1). This configuration of components in a box shape gave rise to its nickname among study participants—the "box viewer"—which is used in this article.

Figure 1.

The novel 3D stereoscopic ''box viewer.'' The upper image shows the external view of the complete viewer suspended from its custom-built frame. The lower image shows an internal view of a CAD model of the viewer, with one of the monitors and lenses removed for clarity.

The effect of the dual screens and mirrors, which is also utilized in Intuitive Surgical's daVinci console, is to mimic the most salient physiological depth cue of binocular disparity,[20,21] creating the illusion of a 3D object without the need for polarizing glasses.[22] This creates an immersive environment, which has previously been shown to benefit surgical performance.[23]

Previous Work on 3D Displays in Surgery

The work of previous groups on 3D surgical displays has shown that first-generation systems were associated with visual strain, headache, and facial discomfort.[24] However, improved second-generation systems have shown some benefits in ex vivo tasks.[25,26] Technical issues that can result in a suboptimal image include crosstalk between the 2 images of a stereoscope, which can be perceived as "ghosting" (a faint duplicate image), flicker, and vertical disparity, and lead to eye strain when continued compensation is required.[22,26] The development of 3D displays is further burdened by their inherent removal of a number of other depth cues such as accommodation and motion parallax.[22,24,26]

This is the first TES-specific study on 3D visualization that examines the performance of the novel stereoscopic 3D "box viewer" against the traditional Wolf stereoendoscope and standard 2D HD and 3D HD monitors. A pilot study of 10 surgeons was conducted before the full study and showed superior performance with the box viewer on a standardized PEG transfer model.

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