Results

Results - Motion Compensation

vaccarella.alberto@gmail.com (Administrator) — Fri, 13 Feb 2015 13:51:29 +0000

Motion compensation: accuracy

ACTIVE multirobot platform is dedicated to the coordinated motion of the master Active Headframe (AH) and the 2 slave arms (KUKA LWR), without the help of external tracking sensors for closed-loop visual servoing. All functional features (e.g. navigation, Active Constraints and surgical tool manipulation) are rendered in the floating skull compensated reference. The end-to-end accuracy of the 3 robots platform is therefore crucial for the overall accomplishment of the haptics features as well as for the general tool targeting.

The multi-robot system has multiple sources of kinematical inaccuracies, i.e. intrinsic calibration of robots, robot-robot registration, tool calibration, skull registration, alignment with the navigation system in the MRI reference, etc. The regular end-to-end error for such registration chain is normally in the range of 15-20mm for the integrated equipment.

CNR group developed an error compensation procedure that corrects the motion of slave arm TCPs on target true locations, with the result of 0.8±0.1 mm end-to-end accuracy in the static case (1:22 error reduction factor).

The procedure is performed offline, with the help of a ground-truth optical tracker, for the baseline compensation of the co-registration errors of the 3 coordinated robots. Errors are limited to an average 0.5mm/0.24deg, which is the performance of the general purpose robotic suite. Actual surgical tools and the positioning of a skull on the Active Headframe are defined intraoperative, introducing an additional 0.2-0.3mm to the end-to-end inaccuracy.

Results - Active Constraints

vaccarella.alberto@gmail.com (Administrator) — Mon, 26 Jan 2015 08:58:04 +0000

Dynamic Active Constraints for haptic augmentation during brain deformation

Several novel algorithms were developed for the application of dynamic active constraints to neurosurgery during brain shift and indentation. These algorithms allow efficient computation of the relative configuration between the surgical tool and anatomical model, and safe haptic forces and torques to be computed which prevent the surgeon from penetrating the protected region during teleoperation.

Results - Tribology

vaccarella.alberto@gmail.com (Administrator) — Mon, 26 Jan 2015 08:55:31 +0000

Development of a composite hydrogel brain tissue phantom and high resolution finite element models of brain shift and indentation

The group led by Dr. Dini at Imperial College has carried out different tests to identify the mechanical characteristics of the brain tissue (including porcine and human samples). The results led to the development of a novel composite hydrogel suitable for mimicking the mechanical the brain shift phenomenon and indentation procedures in a range of velocities spanning two orders of magnitude. With the same information, a new constitutive formulation to model tissue response has been implemented in state-of-the-art high resolution finite element model and used for brain shift and indentation simulations. A realistic life size brain phantom and a skull mock-up have also been produced and used in the context of the ACTIVE setup for testing, demonstration and model validation purposes. Development of a composite hydrogel brain tissue phantom and high resolution finite element models of brain shift and indentation

Results - Pre-surgical mapping

vaccarella.alberto@gmail.com (Administrator) — Thu, 22 Jan 2015 14:51:34 +0000

Results - Epileptogenic Zone Automatic Identification

vaccarella.alberto@gmail.com (Administrator) — Mon, 19 Jan 2015 09:05:40 +0000

Identification of the epileptogenic network in patients with focal cortical dysplasia

The leading role of the lesional zone may account for the good post-surgical outcome of patients with type II focal cortical dysplasia as resecting the dysplasia removes the epileptogenic zone responsible for seizure organization. Furthermore, our ﬁndings strongly suggest that advanced signal processing techniques aimed at characterizing brain networks could improve the pre-surgical evaluation of patients with focal epilepsyWe developed and validate a method to study complex brain networks from intracranial EEG signals (STEREO-EEG) in order to automatically identify the Epileptogenic Zone. This techniques have been applied to a group of patients with type II Focal Cortical Dysplasia, who underwent epilepsy Surgery. Our results showed that the focal dysplasia indeed acts as the initial generator of the ictal activity, presenting an abnormal pattern of connectivity, evident also in EEG activity far from seizures (Varotto et al., Neuroimage 2012).

Results - Enhanced Cooperative Control

vaccarella.alberto@gmail.com (Administrator) — Fri, 16 Jan 2015 09:37:40 +0000

Enhanced Cooperative Control

(a)

An admittance-controlled cooperative modality was developed and use to move the robots manually inside the intra-opeative workspace (a). Also two enhanced torque-based impedance control approaches, i.e. variable damping criterion and a force-feedback enhancement control, were proposed in combination with an image-based navigation system (b).

(b)

Results - System Behavior Supervisor

vaccarella.alberto@gmail.com (Administrator) — Fri, 16 Jan 2015 08:47:38 +0000

System Behavior Supervisor

Inside the Active project, the management of the incoming events from both sensors or users and the correspondent transitions in the architecture behavior are handled by a software supervisor module, called System Behavior Supervisor (SBS). The main purpose of the SBS is to act as a component aware of the workflow and of the status of each component of the architecture, letting the surgeon able to interact with the whole system.

At startup it is possible to choose the current procedure to be performed, loading the corresponding finite-state machine in the OSM component. The default interaction of the user with the system is through the next step button, which executes the predefined transitions in the pre-defined workflow. Both the current and the next step are shown to the user. At every moment of the procedure it is possible to request a deviation from the current workflow, pressing one of the button on the right side of the interface. Each workflow deviation needs to be acknowledged by the surgeon and the reprise it is possible through the next step button pressing.

Results - Intraoperative Brain Shift

vaccarella.alberto@gmail.com (Administrator) — Thu, 15 Jan 2015 17:18:57 +0000

Intra-operative Brain Deformation

Real-time brain deformations estimation: Stereo and video feature matching. Each row shows a video frame, and columns stand for the left and right cameras. Stereo matches are depicted by green arrows from the left to the right camera at time 0, and blue arrows show video matches for both cameras from time 0 to time 1. Each feature neighbourhood is depicted as a small numbered square.

(a)

(b)

(c)

Experimental setup of a deformable brain phantom for real-time modeling of intra-operative brain shift based on video tracking: (a) The whole phantom; (b) view through a mock craniotomy; (c) tracked features on a live brain.

(a)

(b)

(c)

Results of the brain shift simulation based on tracked feature points and the corresponding deformation of the 4×4×4 mm3 brain model: (a) green points: initially registered to the surface of a brain phantom; (b) Top right, red points: after 500 seconds of deformation tracking; (c) white points: after 1000 seconds of deformation tracking.