2016 Section 5 Green Book

TABLE I. Task Workload Assessment.

NASA-TLX Scores

NASA-TLX Subscale

Conventional Mean (SD)

LIVE-IGS Mean (SD)

P , Wilcoxon SR Test

Mental Demand

10.6 (4.9)

6.9 (3.3) 7.4 (3.1)

.006*

Physical Demand

9.3 (5.6)

.094

Temporal Demand

6.6 (4.5)

5.1 (2.4)

.19

Performance

5.4 (3.8) 9.8 (5.0)

4.6 (2.8) 6.1 (3.2)

.496

Effort

.011*

Frustration

7.7 (5.5)

4.6 (2.7)

.032*

Lower performance score indicates higher perceived performance. *Significant improvement with LIVE-IGS ( P < .05). LIVE-IGS 5 localized intraoperative virtual endoscopy image-guided surgery; NASA-TLX 5 National Aeronautics and Space Administration Task Load Index; SD 5 standard deviation; SR 5 signed rank.

each subject are summarized in Supplementary Appen- dix 1.

navigation of endoscopic and ablative instruments. Accu- racy was universally judged to be equal or superior to the current OR standards and sufficient for the applica- tions provided. The main benefit over a conventional system was the speed at which navigation assistance could be provided and interpreted during ablative tasks. Task Workload The NASA-TLX scores for mental demand, effort, and frustration were significantly reduced when using the LIVE-IGS system in comparison to conventional nav- igation ( P < .05). There was no significant difference in physical demand or perceived performance. Despite open feedback suggesting a potential operative time saving during real cases, no significant change in temporal demand was found during this trial ( P 5 0.19; Table I). Questionnaire The seven-point Likert scale questionnaire state- ments and median (IQR) responses are shown in Table II. No subject disagreed (score 1–3) with any of the statements. One gave a neutral response (score of 4) for question 1. There was universal agreement (score 5–7) for all other questions, with fairly uniform responses across the subjects. Below is a summary of the feedback gathered for each theme of investigation. Specific responses from

Ergonomics All subjects agreed that the laboratory layout and equipment were consistent with the OR. Minor changes, including mounting the reflective markers to face obliquely opposite the surgeon, were made to minimize optical tracking interference (Fig. 2d). Occasionally, the drill dropped out of vision when it was rotated; however, all of the surgeons were familiar with optical IGS systems and seemed to intuitively recognize when this was a problem. Visual Display Image guidance was provided in two ways: a 3D vir- tual view and cross-sectional, triplanar CT images. Three participants preferentially referenced the virtual view, stating that it was intuitive, allowed faster assess- ment of proximity to critical structures, and was easier to synthesize. Two preferred the triplanar views, as they were more often used to this display, and thought the virtual view was cluttered or lacked depth information and precision. The other two used both displays fairly equally; the virtual for a quick assessment and the tri- planar for fine detail. The contours were thought to be accurate, and there were mixed opinions as to whether the pixilation

TABLE II. Questionnaire Responses.

Statements for Questionnaire

Median (IQR)*

I felt it was faster to perform surgery when aided by the virtual view.

6 (5–6) 6 (6–6)

The system appeared to be sufficiently accurate for its intended use.

The dynamic tool tracking allowed me to quickly assess my proximity to critical structures without significantly interrupting dissection.

6 (5.5–7)

Proximity alerts increased my confidence during ablation close to critical structures.

6 (5.5–6)

The current technology is ready for clinical trial without significant changes.

5 (5–6)

*Based on a seven-point Likert scale (7 5 strongly agree, 1 5 strongly disagree). IQR 5 interquartile range.

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