MEMSurgery: an integrated test-bed for vascular surgery

Many surgical procedures require skillful manipulations of blood vessels, especially in conventional invasive or minimally invasive surgical procedures. Current surgical methods do not allow the surgeon to receive any real time feedback of the tissue properties when operating on the vessel. As a result, the unintentional application of excessive force may damage the blood vessel. To minimize such trauma, and to study the interaction of surgical instruments with the vessel structure, we have developed an integrated surgical testbed called MEMSurgery (Microelectromechanical Sensory augmented Surgery). The test-bed integrates four elements: a) force sensors mounted on surgical appliances, b) a feedback control mechanism utilizing the intrinsic mechanical properties of the blood vessel, c) feedback of the force applied on the tissue back to the surgeon through a haptic feedback device, and d) visual feedback by a graphical computer model of the vessel. Finally, we evaluate the performance of MEMSurgery by testing the hypothesis that the combination of haptic feedback, feedback control based on vascular mechanical properties, and real-time visual representation of the vessel will help the surgeon decrease the probability of applying excess force while occluding the blood vessel. To this end, we designed a rodent experimental model to obtain the ideal minimum occlusion force (MOF). After a series of human performance studies, and subsequent comparison to direct application of force on the forceps (without feedback), the results show that the probability of applying reasonable MOF increases from 35.5% to 80%. After a brief training period, the probability increases to 90%.     

Visual cues as a surrogate for tactile feedback during robotic‐assisted laparoscopic prostatectomy: posterolateral margin rates in 1340 consecutive patients

Study Type – Therapy (case series)
Level of Evidence 4

OBJECTIVE

To analyse consecutive cases of robotic‐assisted laparoscopic prostatectomy (RALP), present the incidence of nerve‐sparing‐related positive surgical margins (SM+), include visual cues that might assist in smoothly changing to the robotic platform, and discuss the scientific rationale for ‘intersensory integration’ which might explain the ‘reverse Braille’ phenomenon, i.e. the ability to feel when vision is greatly enhanced, as the lack of tactile feedback during RALP is often cited as a disadvantage of robotic surgery, interfering with a surgeon’s ability to make intraoperative oncological decisions.

PATIENTS AND METHODS

Data from 1340 consecutive patients undergoing RALP from one institution were analysed and trends for positive posterolateral SM+ (PLSM+) were correlated with oncological variables before and after RALP. A sample of patient slides were reviewed by a extramural pathologist. Multivariate regression modelling was used to compare the projected rates of PLSM+ vs the actual rate, given the effect of a conscious effort to use visual cues. Finally, video recordings of the procedure were systematically reviewed and correlated with anatomical and histopathological images in an integrated session involving the surgeon and the pathology team.

RESULTS

The incidence of PLSM+ was 2.1%, which gradually declined to 1.0% in the last 100 patients. The reduction in PLSM+ occurred despite an increased rate of high‐risk tumours operated on during this period. Forecasting analysis showed that the actual PLSM+ rate declined by half in the most recent 1000 patients, due to an integrated effort involving the use of visual cues during surgery. The following visual cues were considered important; appreciation of periprostatic (lateral prostatic) fascial compartments; colour and texture of the tissue; periprostatic veins as a landmark for athermal dissection; signs of inflammation; and a freely separating bloodless plane showing loose shiny areolar tissue.

CONCLUSION

Adapting to the robotic platform is easy and there is no compromise of the oncological safety of this procedure. Experienced surgeons can use visual cues to assist during nerve‐sparing RALP and achieve low PLSM+ rates.     

Haptic interaction in robot-assisted endoscopic surgery: a sensorized end-effector

Conventional endoscopic surgery has some drawbacks that can be addressed by using robots. The robotic systems used for surgery are still in their infancy. A major deficiency is the lack of haptic feedback to the surgeon. In this paper, the benefits of haptic feedback in robot-assisted surgery are discussed. A novel robotic end-effector is then described that meets the requirements of endoscopic surgery and is sensorized for force/ torque feedback. The endoscopic end-effector is capable of non-invasively measuring its interaction with tissue in all the degrees of freedom available during endoscopic manipulation. It is also capable of remotely actuating a tip and measuring its interaction with the environment without using any sensors on the jaws. The sensorized end-effector can be used as the last arm of a surgical robot to incorporate haptic feedback and/or to evaluate skills and learning curves of residents and surgeons in endoscopic surgery.     

Abnormal response recovery in the right somatosensory cortex of dyslexic adults

Somatosensory evoked fields (SEFs) to repetitive tactile stimuli were recorded from eight dyslexic and eight normal-reading adults. Three successive stimuli, produced by diaphragms driven by compressed air, were delivered to thumb, index finger and thumb in sequence, with stimulus-onset asynchronies (SOAs) of 100 and 200 ms in different runs. Both hands were stimulated alternatingly with an intertrain interval of 1 s, and the responses were recorded with a whole-scalp neuromagnetometer. Whereas the primary somatosensory cortex responses to the first stimuli of the trains did not differ between dyslexics and controls, responses to the second stimuli (and the ratios of second to first responses) were significantly smaller in dyslexic than in control subjects in the right hemisphere (differences 41 and 28% for response amplitudes at the 100 and 200 ms SOAs). The results agree with the proposed pansensory nature of temporal processing deficits in dyslexia, specifically demonstrating abnormal response recovery in the right somatosensory cortex.     

Structure of the excitatory receptive fields of infragranular forelimb neurons in the rat primary somatosensory cortex responding to touch

We quantitatively studied the excitatory receptive fields of 297 neurons recorded from the forelimb infragranular somatosensory cortex of the rat while touch stimuli were applied to discrete locations on the forelimbs. Receptive fields were highly heterogeneous, but they were regulated, on average, by an underlying spatio-temporal structure. We found the following. (i) Neurons responded with decreasing magnitude and increasing latency when the stimulus was moved from the primary location to secondary locations and to far ispilateral locations of their excitatory receptive fields, displaying smooth transitions from the primary location to secondary locations. (ii) Receptive field patterns revealed functional connectivity between the digits and ventral palm, which did not depend on whether the digits were stimulated dorsally or ventrally. (iii) The structure of the receptive fields (i.e. the neural responses to stimulation of secondary locations compared to the neural responses to stimulation of the primary location), reflected cortical (rather than body) distances. (iv) There was a functional separation between the forepaw and the rest of the forelimb. Namely: if the primary location was in the digits or palm, secondary locations were biased toward the digits and palm; if the primary location was in rest of the forelimb, secondary locations appeared equally distributed over forelimb, digits and palm. (v) More than 40% of neurons extended their receptive field to the ipsilateral forelimb, without any evident spatial organization. Overall, the stimuli evoked approximately 3 times more spikes from secondary responses than from primary responses. These results suggest that a rich repertoire of spatio-temporal responses is available for encoding tactile information. This highly distributed receptive field structure provides the electrophysiological architecture for studying organization and plasticity of cortical somatosensory processing.     

Intra-operative prostate examination: predictive value and effect on margin status

OBJECTIVE: To evaluate the ability of intra-operative prostate examination (IOPE) to predict extraprostatic extension (EPE) and its effect on margin status in the region of the neurovascular bundle (NVB) when combined with wide excision. PATIENTS AND METHODS: We retrospectively reviewed 403 patients with clinical stage T1c prostate adenocarcinoma undergoing radical retropubic prostatectomy (RRP). All patients had IOPE during RRP, and those with palpable abnormalities in the region of the NVB underwent wide excision. Pathological outcomes were analysed. RESULTS: Of 403 patients, 49 (12%) had a palpable abnormality in the region of the NVB. After wide excision, 18 (37%) of these 49 patients were found to have EPE at the site of the palpable abnormality; with wide excision of the NVB, only one of these 18 patients (6%) had a corresponding positive surgical margin (PSM). In 354 patients with a normal IOPE and who underwent bilateral NVB preservation, 30 were found to have EPE in the region of the NVB. The PSM rate in this subset was 23% (seven of 30). The positive predictive value of IOPE for detecting EPE was 37%. CONCLUSION: IOPE detects abnormalities in 12% of patients with preoperative stage T1c prostate cancer. Although the predictive value of this test is limited, IOPE may decrease PSMs in a subset of patients with EPE in the region of the NVB. The present study reaffirms the value of IOPE for assessing the risk of extraprostatic disease, and for guiding surgical management.