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Force feedback is widely assumed to enhance performance in robotic surgery, but its benefits have not yet been systematically assessed. In this study we examine the effects of force feedback on a blunt dissection task. Twenty subjects used a telerobotic system to expose an artery in a synthetic model while viewing the operative site with a video laparoscope. Subjects were drawn from a range of surgical backgrounds, from inexperienced to attending surgeons. Performance was compared between three force feedback gains: 0% (no force feedback), 37%, and 75%. The absence of force feedback increased the average force magnitude applied to the tissue by at least 50%, and increased the peak force magnitude by at least 100%. The number of errors that damage tissue increased by over a factor of 3. The rate and precision of dissection were not significantly enhanced with force feedback. These results hold across all levels of previous surgical experience. We hypothesize that force feedback is helpful in this blunt dissection task because the artery is stiffer than the surrounding tissue. This mechanical contrast serves to constrain the subject's hand from commanding inappropriate motions that generate large forces.

BackgroundSPECT/CT combines high resolution anatomical 3D computerized tomography (CT) and single photon emission computerized tomography (SPECT) as functional imaging, which provides 3D information about biological processes into a single imaging modality. The clinical utility of SPECT/CT imaging has been recognized in a variety of medical fields and most recently in orthopaedics; however, clinical adoption has been limited due to shortcomings of analytical tools available. Specifically, SPECT analyses are mainly qualitative due to variation in overall metabolic uptake among patients. Furthermore, most analyses are done in 2D, although rich 3D data are available. Consequently, it is difficult to quantitatively compare the position, size, and intensity of SPECT uptake regions among patients, and therefore difficult to draw meaningful clinical conclusions.MethodsWe propose a method for normalizing orthopaedic SPECT/CT data that enables standardised 3D volumetric quantitative measurements and comparison among patients. Our method is based on 3D localisation using clinically relevant anatomical landmarks and frames of reference, along with intensity value normalisation using clinically relevant reference regions. Using the normalised data, we describe a thresholding technique to distinguish clinically relevant hot spots from background activity.ResultsUsing an exemplar comparison of two patients, we demonstrate how the normalised, 3D-rendered data can provide a richer source of clinical information and allow quantitative comparison of SPECT/CT measurements across patients. Specifically, we demonstrate how non-normalized SPECT/CT analysis can lead to different clinical conclusions than the normalized SPECT/CT analysis, and that normalized quantitative analysis can be a more accurate indicator of pathology.ConclusionsConventional orthopaedic frames of reference, 3D volumetric data analysis and thresholding are used to distinguish clinically relevant hot spots from background activity. Our goal is to facilitate a standardised approach to quantitative data collection and comparison of clinical studies using SPECT/CT, enabling more widespread clinical use of this powerful imaging tool.