M. Silvestri

Magnetically Activated Stereoscopic Vision System for Laparoendoscopic Single-Site Surgery

In this paper, the authors present an innovative vision platform for laparoendoscopic single-site (LESS) surgery based on a wired and magnetically activated 5-degrees-of-freedom robot with stereovision. The stereoscopic vision module, developed using two off-the-shelf cameras and a light emitting diodes lighting system, is mounted on the robot tip. An autostereoscopic screen is adopted to display the surgical scenario as an alternative to 3-D helmets or polarizing glasses. A rough position of the stereocamera can be determined along the abdominal wall by dragging the robot with a set of external permanent magnets (EPMs). Once the camera is set in the desired position, the EPMs provide fixation, while the internal mechanism allows fine tilt adjustment. Considering the deformable round shape of the insufflated abdomen wall and in order to replicate the precise roll motion usually provided by the endoscopists hands, this prototype embeds an actuated mechanism that adjusts the stereocamera horizon and thus prevents any visual discomfort. Finally, the platform was preliminarily tested in vivo in a LESS scenario, demonstrating its advantages for eliminating potential conflicts with the operative tools and enabling the introduction of an additional instrument through the same access port used for stereoscopic vision.

Autostereoscopic Three-Dimensional Viewer Evaluation Through Comparison With Conventional Interfaces in Laparoscopic Surgery

In the near future, it is likely that 3-dimensional (3D) surgical endoscopes will replace current 2D imaging systems given the rapid spreading of stereoscopy in the consumer market. In this evaluation study, an emerging technology, the autostereoscopic monitor, is compared with the visualization systems mainly used in laparoscopic surgery: a binocular visor, technically equivalent from the viewer’s point of view to the da Vinci 3D console, and a standard 2D monitor. A total of 16 physicians with no experience in 3D interfaces performed 5 different tasks, and the execution time and accuracy of the tasks were evaluated. Moreover, subjective preferences were recorded to qualitatively evaluate the different technologies at the end of each trial. This study demonstrated that the autostereoscopic display is equally effective as the binocular visor for both low- and high-complexity tasks and that it guarantees better performance in terms of execution time than the standard 2D monitor. Moreover, an unconventional task, included to provide the same conditions to the surgeons regardless of their experience, was performed 22% faster when using the autostereoscopic monitor than the binocular visor. However, the final questionnaires demonstrated that 60% of participants preferred the user-friendliness of the binocular visor. These results are greatly heartening because autostereoscopic technology is still in its early stages and offers potential improvement. As a consequence, the authors expect that the increasing interest in autostereoscopy could improve its friendliness in the future and allow the technology to be widely accepted in surgery.

An innovative adaptive control strategy for sensorized left ventricular assist devices.

Nowadays advanced heart failure is mainly treated through heart transplantation. However, the low availability of donors makes the research of alternative therapies urgent. Continuous-flow left ventricular assist devices (LVADs) are going to assume a more significant role in assisting the failing heart. A recent challenge in clinical practice is the possibility to use LVAD as long-term therapy rather than as a bridge to transplantation. For this reason, more comfortable devices, able to dynamically adapt to the physiological cardiac demand in relation to the patient activity level, are needed in order to improve the life quality of patients with implants. Nevertheless, no control system has been developed yet for this purpose. This work proposes an innovative control strategy for a novel sensorized LVAD, based on the continuous collection of physical and functional parameters coming from implantable sensors and from the LVAD itself. Thanks to the proposed system, both the patient and the LVAD conditions are continuously monitored and the LVAD activity regulated accordingly. Specifically, a Proportional Integrative (PI) and a threshold control algorithms have been implemented, respectively based on flow and pressure feedbacks collected from the embedded sensors. To investigate the feasibility and applicability of this control strategy, an on-bench platform for LVADs sensing and monitoring has been developed and tested.

Experimental integration of Autoregulation Unit for left ventricular assist devices in a cardiovascular hybrid simulator

In this paper, an Autoregulation Unit (ARU) for left ventricular sensorized assist devices (LVAD) has been used with a cardiovascular hybrid simulator mimicking physiological and pathological patient conditions. The functionalities of the ARU have been demonstrating for the successful receiving and visualization of system parameters, sending of commands for LVAD speed changes, and enabling of the autonomous flow control algorithm. Experiments of speed changes and autoregulation are reported, showing the feasibility of the approach for both local and remote control of a LVAD.

An autoregulation unit for enabling adaptive control of sensorized left ventricular assist device

This paper describes an integrated system for facing heart failures (HF) in an innovative way. Existing left ventricular assist devices (LVAD or VAD) are usually devoted to blood pumping without the possibility to adapt the speed to patient conditions during everyday activities. This is essentially due to the lack of sensorization, bulkiness, and the need of relying on device-specific controllers with reduced computing ability for the existing ventricular assist systems. In this work, an innovative integrated and portable device, the ARU, is presented for enhancing VADs applicability as a long-term solution to HF. The ARU is an universal device able to fulfill with the needs of sensorized VADs in terms of data storing, continuous monitoring, autoregulation and adaptation to patient condition changes during daily activities. The ARU is able to wirelessly interface wearable devices for offering additional monitoring features from remote. The ARU functionalities on bench have been tested by the interfacing with a sensorized VAD platform in order to prove the feasibility of the approach. Experiments of local and remote VAD speed changes and autoregulation algorithms have been successfully tested showing response time of 1 s.

A hybrid cardiovascular simulator as test bench for VAD autoregulation control

Aim: Doppler ultrasound is standard for measurements of blood velocity. Aninherent limitation is that Doppler methods only measure the velocity parallelto the ultrasound beam. In Ultrasound Image Velocimetry (UIV) regions of two sequential B-mode images are cross-correlated to calculate 2-D velocity vectors. UIV results were compared with Doppler and transit-time flow measurements.Methods: In vitro experiments were performed in a pulsatile flow loop. Theworking fluid was water/glycerol with ultrasound contrast agent (microbubbles).The latex tube was imaged using an Ultrasonix RP500 and a novelimaging sequence was used to interleave two ultrasound frames, enabling ashort and variable (0.3-39 ms) interframe time separation (δt). A rabbit wasanaesthetised and imaged through the abdomen, with microbubbles administered via the ear vein. Radiofrequency data were post-processed offlineusing in-house code which calculates the local correlation between successiveframes, then sums correlation results for identical phases of all cardiaccycles.Results: Peak velocities >2 m/s were accurately measured across the entirefield-of-view in vitro, while peak systolic velocities in the rabbit were 0.99 m/sand 1.04 m/s with UIV and Doppler respectively. As δt was increased flow instability during deceleration caused the UIV velocity measurement to drop to zero. Comparing velocity measurements of decelerating flow with different values of δt leads to a new method for investigating flow instability.Conclusions: With short δt UIV and derived flow rates agreed excellently withDoppler and transit time flow rates.Aim: Topical application of ophthalmic drugs is very inefficient; contact lenses used as drug delivery devices could minimize the drug loss and side effects. Styrene-maleic acid copolymers (PSMA) can form polymer-phospholipid complexes with dipalmitoyl phosphatidylcholine (DMPC) in the form of nanometric vesicles, which can easily solubilise hydrophobic drugs. They can be dispersed on very thin contact lens coatings to immobilize the drug on their surface. Methods: Two types of complexes stable at different pH values (5 and 7 respectively) where synthesized and loaded with drugs of different hydrophilicities during their formation process. The drug release was studied in vitro and compared to the free drug. Results: The mean sizes of the complexes obtained by light scattering were 50 nm and 450 nm respectively with low polydispersities. However, they were affected by the drugs load and release. An increase was observed in the duration of the release in the case of hydrophobic drugs, from days to weeks, avoiding initial “burst” and with a lesser amount of total drug released due to the interaction of the drug with the phospholipid core. The size and charge of the different drugs and the complexes nature also affected the release profile. Conclusions: Polymer-phospholipid complexes in the form of nanoparticles can be used to solubilise and release hydrophobic drugs in a controlled way. The drug load and release can be optimised to reach therapeutic values in the eye.

A novel trocar-less, multi-point of view, magnetic actuated laparoscope

As a result of the rapid spreading of stereoscopy in the consumer market, three-dimensional (3D) vision systems are replacing two-dimensional devices. A fast growing technology in the 3D visualization systems market is multi-views autostereoscopic displays (ADs). However, these devices have not yet found a direct application in minimally invasive surgery (MIS), as it is really challenging to embed a high number of point-of-views in a device which has to pass through a MIS incision. The aim of this work is the development of a miniaturized vision acquisition system for MIS, which can be interfaced with multi-views ADs. The system is anchored by a magnetic link to the abdomen and freely moved by magnetic actuation to adjust the point of view and the horizon of the cameras. The laparoscope can embed up to 9 cameras, while matching typical MIS access incision size.