Arnaud Chanu

Automatic navigation of an untethered device in the artery of a living animal using a conventional clinical magnetic resonance imaging system

The feasibility for in vivo navigation of untethered devices or robots is demonstrated with the control and tracking of a 1.5mm diameter ferromagnetic bead in the carotid artery of a living swine using a clinical magnetic resonance imaging (MRI) platform. Navigation is achieved by inducing displacement forces from the three orthogonal slice selection and signal encoding gradient coils of a standard MRI system. The proposed method performs automatic tracking, propulsion, and computer control sequences at a sufficient rate to allow navigation along preplanned paths in the blood circulatory system. This technique expands the range of applications in MRI-based interventions.The feasibility for in vivo navigation of untethered devices or robots is demonstrated with the control and tracking of a 1.5mm diameter ferromagnetic bead in the carotid artery of a living swine using a clinical magnetic resonance imaging (MRI) platform. Navigation is achieved by inducing displacement forces from the three orthogonal slice selection and signal encoding gradient coils of a standard MRI system. The proposed method performs automatic tracking, propulsion, and computer control sequences at a sufficient rate to allow navigation along preplanned paths in the blood circulatory system. This technique expands the range of applications in MRI-based interventions.

MRI-based Medical Nanorobotic Platform for the Control of Magnetic Nanoparticles and Flagellated Bacteria for Target Interventions in Human Capillaries

Medical nanorobotics exploits nanometer-scale components and phenomena with robotics to provide new medical diagnostic and interventional tools. Here, the architecture and main specifications of a novel medical interventional platform based on nanorobotics and nanomedicine, and suited to target regions inaccessible to catheterization, are described. The robotic platform uses magnetic resonance imaging (MRI) for feeding back information to a controller responsible for the real-time control and navigation along pre-planned paths in the blood vessels of untethered magnetic carriers, nanorobots, and/or magnetotactic bacteria (MTB) loaded with sensory or therapeutic agents acting like a wireless robotic arm, manipulator, or other extensions necessary to perform specific remote tasks. Unlike known magnetic targeting methods, the present platform allows us to reach locations deep in the human body while enhancing targeting efficacy using real-time navigational or trajectory control. We describe several versions of the platform upgraded through additional software and hardware modules allowing enhanced targeting efficacy and operations in very difficult locations such as tumoral lesions only accessible through complex microvasculature networks.

Real-Time MRI-Based Control of a Ferromagnetic Core for Endovascular Navigation

This paper shows that even a simple proportional-integral-derivative (PID) controller can be used in a clinical MRI system for real-time navigation of a ferromagnetic bead along a predefined trajectory. Although the PID controller has been validated in vivo in the artery of a living animal using a conventional clinical MRI platform, here the rectilinear navigation of a ferromagnetic bead is assessed experimentally along a two-dimensional (2D) path as well as the control of the bead in a pulsatile flow. The experimental results suggest the likelihood of controlling untethered microdevices or robots equipped with a ferromagnetic core inside complex pathways in the human body.

Adapting the clinical MRI software environment for real-time navigation of an endovascular untethered ferromagnetic bead for future endovascular interventions

A dedicated software architecture for a novel interventional method allowing the navigation of ferromagnetic endovascular devices using a standard real‐time clinical MRI system is shown. Through a specially developed software environment integrating a tracking method and a real‐time controller algorithm, a clinical 1.5T Siemens Avanto MRI system is adapted to provide new functionality for potential automated interventional applications. The proposed software architecture was successfully validated through in vivo controlled navigation inside the carotid artery of a swine. Here we present how this MRI‐upgraded software environment could also be used in more complex vasculature models through the real‐time navigation of a 1.5 mm diameter chrome steel bead in two different MR‐compatible phantoms with flowless and quiescent flow conditions. The developed platform and software modules needed for such navigation are also presented. Real‐time tracking achieved through a dedicated positioning method based on an off‐resonance excitation technique has also been successfully integrated in the software platform while maintaining adequate real‐time performance. These preliminary feasibility experiments suggest that navigation of such devices can be achieved using a similar software architecture on other conventional clinical MRI systems at an operational closed‐loop control frequency of 32 Hz. Magn Reson Med 59:1287–1297, 2008.

A computer-assisted protocol for endovascular target interventions using a clinical MRI system for controlling untethered microdevices and future nanorobots.

The possibility of automatically navigating untethered microdevices or future nanorobots to conduct target endovascular interventions has been demonstrated by our group with the computer-controlled displacement of a magnetic sphere along a pre-planned path inside the carotid artery of a living swine. However, although the feasibility of propelling, tracking and performing real-time closed-loop control of an untethered ferromagnetic object inside a living animal model with a relatively close similarity to human anatomical conditions has been validated using a standard clinical Magnetic Resonance Imaging (MRI) system, little information has been published so far concerning the medical and technical protocol used. In fact, such a protocol developed within technological and physiological constraints was a key element in the success of the experiment. More precisely, special software modules were developed within the MRI software environment to offer an effective tool for experimenters interested in conducting such novel interventions. These additional software modules were also designed to assist an interventional radiologist in all critical real-time aspects that are executed at a speed beyond human capability, and include tracking, propulsion, event timing and closed-loop position control. These real-time tasks were necessary to avoid a loss of navigation control that could result in serious injury to the patient. Here, additional simulation and experimental results for microdevices designed to be targeted more towards the microvasculature have also been considered in the identification, validation and description of a specific sequence of events defining a new computer-assisted interventional protocol that provides the framework for future target interventions conducted in humans.

Real-time positioning and tracking technique for endovascular untethered microrobots propelled by MRI gradients

A real-time positioning and tracking technique for untethered devices or robots magnetically propelled by a clinical magnetic resonance imaging (MRI) system is described. The local magnetic field induced by the device, composed of a ferromagnetic material, is used as a signature to localize the device on three one-dimensional projections. A high-precision 3D circular-motion system was used to assess the precision and accuracy of this method. The integration of this technique inside propulsion and imaging MRI sequences was also achieved to demonstrate the feasibility of this tracking scheme in a closed-loop control scheme. Finally, in vivo tracking during automatic navigation of an untethered device in the carotid artery of a living animal is demonstrated.

Sequence Design and Software Environment for Real-time Navigation of a Wireless Ferromagnetic Device using MRI System and Single Echo 3D Tracking

Software architecture for the navigation of a ferromagnetic untethered device in a 1D and 2D phantom environment is briefly described. Navigation is achieved using the real-time capabilities of a Siemens 1.5 T Avanto MRI system coupled with a dedicated software environment and a specially developed 3D tracking pulse sequence. Real-time control of the magnetic core is executed through the implementation of a simple PID controller. 1D and 2D experimental results are presented

Real-time Software Platform Design for In-Vivo Navigation of a Small Ferromagnetic Device in a Swine Carotid Artery Using a Magnetic Resonance Imaging System

Using an 1.5 T Siemens clinical magnetic resonance imaging system (MRI), a 1.5 mm diameter ferromagnetic bead is moved across a pre-planned path in the carotid artery of a 25 kg living swine. The software architecture for the navigation and path planning is herein described. Using the real-time feedback capabilities of recent MRIs, the device is moved, controlled and tracked using the magnetic gradients coils already present for imaging purposes. Navigation of the ferromagnetic device has been achieved with a peak velocity of about 13 cm/s through a set of pre established 11 waypoints. The dedicated software architecture presented in this paper lies in a modified real-time MRI imaging sequence. The dedicated architecture permits the navigation of the ferromagnetic bead with an operating frequency of 24 Hz real-time control of the magnetic core is achieved through the implementation of a simple 2D PID controller incorporated in the presented software platform.

Medical and technical protocol for automatic navigation of a wireless device in the carotid artery of a living swine using a standard clinical MRI system

A 1.5 mm magnetic sphere was navigated automatically inside the carotid artery of a living swine. The propulsion force, tracking and real-time capabilities of a Magnetic Resonance Imaging (MRI) system were integrated into a closed loop control platform. The sphere was released using an endovascular catheter approach. Specially developed software is responsible for the tracking, propulsion, event timing and closed loop position control in order to follow a 10 roundtrips preplanned trajectory on a distance of 5 cm inside the right carotid artery of the animal. Experimental protocol linking the technical aspects of this in vivo assay is presented. In the context of this demonstration, many challenges which provide insights about concrete issues of future nanomedical interventions and interventional platforms have been identified and addressed.

MRI controlled magnetoelastic nano biosensor for in-vivo pH monitoring: A preliminary approach

Biosensors are a predominant research field and aim at providing small and novel methods for bio-recognition, bio-actuation and embedded data analysis to the medical and bioengineering domains. Typical biosensor technologies exploit optical, electrochemical or mechanical detection methods. Although many biosensors are designed to use biological samples for recognition and treatment, some are designed to be implantable on animals or human for direct detection. The presented work suggests the use of a magnetoelastic based biosensor for the wireless transmission of physiological data through the human body at capillary level. When excited by an external magnetic wave at a given frequency, the magnetoelastic core enters in a vibrating state and emits an alternative magnetic field in response. Using an external RF coils such as the one found in a magnetic resonance imaging (MRI) system, the magnetic flux generated by the magnetoelastic sensor core is received and analyzed during its transient response. Using a pH sensible functional polymer coated on the sensor core, physiological data fluctuations are translated into resonant frequency shifts which, in turn, are picked up by the coil. A preliminary approach for the sensor design and system architecture is presented.