MRI-Compatible Robotics

A body-mounted device for MRI-guided spinal therapy

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no cure and limited treatment options. Recent studies have shown that delivering cellular therapeutics to the ventral horn of the spinal cord can effectively halt neurodegeneration associated with ALS in small animal models.

METHODS

We developed a robotic system that assists with MRI-guided percutaneous injections to the spinal cord. The needle positioning robot consists of two linear axes with motorised translational sleds for two-degree-of-freedom (2-DOF) needle translation and a radial template for 2-DOF discrete rotation.

RESULTS

The robot's targeting capability, evaluated using phantom models and swine cadavers, showed mean targeting errors of 0.48 and 2.84 mm, respectively. The duration of the targeting procedure is approximately 60 min, with an extra 10 min for each additional injection.

CONCLUSIONS

The presented robot does not affect imaging quality during MRI-guided procedures, and it enables a simplified workflow for MRI-guided spinal therapy.

An fMRI Compatible Smart Device for Measuring Palmar Grasping Actions in Newborns

Grasping is one of the first dominant motor behaviors that enable interaction of a newborn infant with its surroundings. Although atypical grasping patterns are considered predictive of neuromotor disorders and injuries, their clinical assessment suffers from examiner subjectivity, and the neuropathophysiology is poorly understood. Therefore, the combination of technology with functional magnetic resonance imaging (fMRI) may help to precisely map the brain activity associated with grasping and thus provide important insights into how functional outcomes can be improved following cerebral injury. This work introduces an MR-compatible device (i.e., smart graspable device (SGD)) for detecting grasping actions in newborn infants. Electromagnetic interference immunity (EMI) is achieved using a fiber Bragg grating sensor. Its biocompatibility and absence of electrical signals propagating through the fiber make the safety profile of the SGD particularly favorable for use with fragile infants. Firstly, the SGD design, fabrication, and metrological characterization are described, followed by preliminary assessments on a preterm newborn infant and an adult during an fMRI experiment. The results demonstrate that the combination of the SGD and fMRI can safely and precisely identify the brain activity associated with grasping behavior, which may enable early diagnosis of motor impairment and help guide tailored rehabilitation programs.

SpinoBot: An MRI-Guided Needle Positioning System for Spinal Cellular Therapeutics

The neurodegenerative disease amyotrophic lateral sclerosis (ALS) results in the death of motor neurons in voluntary muscles. There are no cures for ALS and few available treatments. In studies with small animal models, injection of cellular therapeutics into the anterior horn of the spinal cord has been shown to inhibit the progression of ALS. It was hypothesized that spinal injection could be made faster and less invasive with the aid of a robot. The robotic system presented-SpinoBot-uses MRI guidance to position a needle for percutaneous injection into the spinal cord. With four degrees of freedom (DOF) provided by two translation stages and two rotational axes, SpinoBot proved capable of advanced targeting with a mean error of 1.12 mm and standard deviation of 0.97 mm in bench tests, and a mean error of 2.2 mm and standard deviation of 0.85 mm in swine cadaver tests. SpinoBot has shown less than 3% signal-to-noise ratio reduction in 3T MR imaging quality, demonstrating its compliance to the MRI environment. With the aid of SpinoBot, the length of the percutaneous injection procedure is reduced to less than 60 min with 10 min for each additional insertion. Although SpinoBot is designed for ALS treatment, it could potentially be used for other procedures that require precise access to the spine.

An MR-compatible gyroscope-based arm movement tracking system

BACKGROUND

Functional magnetic resonance imaging is well suited to link neural population activation with movement parameters of complex natural arm movements. However, currently existing MR-compatible arm tracking devices are not constructed to measure arm joint movement parameters of unrestricted movements. Therefore, to date most research focuses on simple arm movements or includes very little knowledge about the actual movement kinematics.

NEW METHOD

We developed a low cost gyroscope-based arm movement tracking system (GAMTS) that features MR-compatibility. The system consists of dual-axis analogue gyroscopes that measure rotations of upper and lower arm joints. After MR artifact reduction, the rotation angles of the individual arm joints are calculated and used to animate a realistic arm model that is implemented in the OpenSim platform. The OpenSim platform can then provide the kinematics of any point on the arm model.

RESULTS

In order to demonstrate the capabilities of the system, we first assessed the quality of reconstructed wrist movements in a low-noise environment where typical MR-related problems are absent and finally, we validated the reconstruction in the MR environment.

COMPARISON WITH EXISTING METHODS

The system provides the kinematics of the whole arm when natural unrestricted arm movements are performed inside the MR-scanner.

CONCLUSION

The GAMTS is reliably capable of reconstructing the kinematics of trajectories and the reconstruction error is small in comparison with the movement induced variation of speed, displacement, and rotation. Moreover, the system can be used to probe brain areas for their correlation with movement kinematics.

MR Safe Robot, FDA Clearance, Safety and Feasibility Prostate Biopsy Clinical Trial

Compatibility of mechatronic devices with the MR environment has been a very challenging engineering task. After over a decade of developments, we report the successful translation to clinical trials of our MR Safe robot technology. MrBot is a 6-degree-of-freedom, pneumatically actuated robot for transperineal prostate percutaneous access, built exclusively of electrically nonconductive and nonmagnetic materials. Its extensive pre-clinical tests have been previously reported. Here, we present the latest technology developments, an overview of the regulatory protocols, and technically related results of the clinical trial. The FDA has approved the MrBot for the biopsy trial, which was successfully performed in 5 patients. With no trajectory corrections, and no unsuccessful attempts to target a site, the robot achieved an MRI based needle targeting accuracy of 2.55 mm. To the best of our knowledge, this is the first robot approved by the FDA for the MR environment. The results confirm that it is possible to perform safe and accurate robotic manipulation in the MRI scanner, and the development of MR Safe robots is no longer a daunting technical challenge.

A novel infusion-drainage device to assess lower urinary tract function in neuro-imaging

OBJECTIVE

To evaluate the applicability and precision of a novel infusion-drainage device (IDD) for standardized filling paradigms in neuro-urology and functional magnetic resonance imaging (fMRI) studies of lower urinary tract (LUT) function/dysfunction.

SUBJECTS/PATIENTS AND METHODS

The IDD is based on electrohydrostatic actuation which was previously proven feasible in a prototype setup. The current design includes hydraulic cylinders and a motorized slider to provide force and motion. Methodological aspects have been assessed in a technical application laboratory as well as in healthy subjects (n=33) and patients with LUT dysfunction (n=3) undergoing fMRI during bladder stimulation. After catheterization, the bladder was pre-filled until a persistent desire to void was reported by each subject. The scan paradigm comprised automated, repetitive bladder filling and withdrawal of 100 mL body warm (37 °C) saline, interleaved with rest and sensation rating. Neuroimaging data were analysed using Statistical Parametric Mapping version 12 (SMP12).

RESULTS

Volume delivery accuracy was between 99.1±1.2% and 99.9±0.2%, for different flow rates and volumes. Magnetic resonance (MR) compatibility was demonstrated by a small decrease in signal-to-noise ratio (SNR), i.e. 1.13% for anatomical and 0.54% for functional scans, and a decrease of 1.76% for time-variant SNR. Automated, repetitive bladder-filling elicited robust (P = 0.05, family-wise error corrected) brain activity in areas previously reported to be involved in supraspinal LUT control. There was a high synchronism between the LUT stimulation and the blood oxygenation level-dependent (BOLD) signal changes in such areas.

CONCLUSION

We were able to develop an MR-compatible and MR-synchronized IDD to routinely stimulate the LUT during fMRI in a standardized manner. The device provides LUT stimulation at high system accuracy resulting in significant supraspinal BOLD signal changes in interoceptive and LUT control areas in synchronicity to the applied stimuli. The IDD is commercially available, portable and multi-configurable. Such a device may help to improve precision and standardization of LUT tasks in neuro-imaging studies on supraspinal LUT control, and may therefore facilitate multi-site studies and comparability between different LUT investigations in the future.

Review of MRI positioning devices for guiding focused ultrasound systems

BACKGROUND

This article contains a review of positioning devices that are currently used in the area of magnetic resonance imaging (MRI) guided focused ultrasound surgery (MRgFUS).

METHODS

The paper includes an extensive review of literature published since the first prototype system was invented in 1991.

RESULTS

The technology has grown into a fast developing area with application to any organ accessible to ultrasound. The initial design operated using hydraulic principles, while the latest technology incorporates piezoelectric motors. Although, in the beginning there were fears regarding MRI safety, during recent years, the deployment of MR-safe positioning devices in FUS has become routine. Many of these positioning devices are now undergoing testing in clinical trials.

CONCLUSION

Existing MRgFUS systems have been utilized mostly in oncology (fibroids, brain, liver, kidney, bone, pancreas, eye, thyroid, and prostate). It is anticipated that, in the near future, there will be a positioning device for every organ that is accessible by focused ultrasound.

Haptic fMRI: using classification to quantify task-correlated noise during goal-directed reaching motions

Neuroimaging artifacts in haptic functional magnetic resonance imaging (Haptic fMRI) experiments have the potential to induce spurious fMRI activation where there is none, or to make neural activation measurements appear correlated across brain regions when they are actually not. Here, we demonstrate that performing three-dimensional goal-directed reaching motions while operating Haptic fMRI Interface (HFI) does not create confounding motion artifacts. To test for artifacts, we simultaneously scanned a subject's brain with a customized soft phantom placed a few centimeters away from the subject's left motor cortex. The phantom captured task-related motion and haptic noise, but did not contain associated neural activation measurements. We quantified the task-related information present in fMRI measurements taken from the brain and the phantom by using a linear max-margin classifier to predict whether raw time series data could differentiate between motion planning or reaching. fMRI measurements in the phantom were uninformative (2σ, 45-73%; chance=50%), while those in primary motor, visual, and somatosensory cortex accurately classified task-conditions (2σ, 90-96%). We also localized artifacts due to the haptic interface alone by scanning a stand-alone fBIRN phantom, while an operator performed haptic tasks outside the scanner's bore with the interface at the same location. The stand-alone phantom had lower temporal noise and had similar mean classification but a tighter distribution (bootstrap Gaussian fit) than the brain phantom. Our results suggest that any fMRI measurement artifacts for Haptic fMRI reaching experiments are dominated by actual neural responses.

Haptic fMRI: accurately estimating neural responses in motor, pre-motor, and somatosensory cortex during complex motor tasks

Haptics combined with functional magnetic resonance imaging (Haptic fMRI) can non-invasively study how the human brain coordinates movement during complex manipulation tasks, yet avoiding associated fMRI artifacts remains a challenge. Here, we demonstrate confound-free neural activation measurements using Haptic fMRI for an unconstrained three degree-of-freedom motor task that involves planning, reaching, and visually guided trajectory tracking. Our haptic interface tracked subjects' hand motions, velocities, and accelerations (sample-rate, 350Hz), and provided continuous realtime visual feedback. During fMRI acquisition, we achieved uniform response latencies (reaching, 0.7-1.1s; tracking, 0.4-0.65s); minimized hand jitter (<;8mm); and ensured reliable motion trajectories (tracking, <;7mm root-mean-square error). In addition, our protocol decorrelated head motion from both hand speed (r=-0.03) and acceleration (r=-0.025), which reliably produced low head motion levels (<;0.4mm/s between scan volumes) and a low fMRI temporal noise-to-signal ratio (<;1%) across thirty-five scan runs. Our results address the primary outstanding Haptic fMRI confounds: motion induced low spatial-frequency magnetic field changes, which correlate neural activation across cortex; unreliable motions and response latencies, which reduce statistical power; and task-correlated head motion, which causes spurious fMRI activation. Haptic fMRI can thus reliably elicit and localize heterogeneous neural activation for different tasks in motor (movement), pre-motor (planning), and somatosensory (limb displacement) cortex, demonstrating that it is feasible to use the technique to study how the brain achieves three dimensional motor control.

MR compatible positioning device for guiding a focused ultrasound system for the treatment of brain deseases

BACKGROUND

A prototype magnetic resonance imaging (MRI)-compatible positioning device that navigates a high intensity focused ultrasound (HIFU) transducer is presented. The positioning device has three user-controlled degrees of freedom that allow access to brain targets using a lateral coupling approach. The positioning device can be used for the treatment of brain cancer (thermal mode ultrasound) or ischemic stroke (mechanical mode ultrasound).

MATERIALS AND METHODS

The positioning device incorporates only MRI compatible materials such as piezoelectric motors, ABS plastic, brass screws, and brass rack and pinion.

RESULT

The robot has the ability to accurately move the transducer thus creating overlapping lesions in rabbit brain in vivo. The registration and repeatability of the system was evaluated using tissues in vitro and gel phantom and was also tested in vivo in the brain of a rabbit.

CONCLUSION

A simple, cost effective, portable positioning device has been developed which can be used in virtually any clinical MRI scanner since it can be placed on the table of the MRI scanner. This system can be used to treat in the future patients with brain cancer and ischemic stroke.

Intraoperative magnetic resonance imaging–conditional robotic devices for therapy and diagnosis

Magnetic resonance imaging presents high-resolution preoperative scans of target tissue and allows for the availability of intraoperative real-time images without the exposure of patients to ionizing radiation. This has motivated scientists and engineers to integrate medical robotics with the magnetic resonance imaging modality to allow robot-assisted, image-guided diagnosis and therapy. This article provides a review of the state-of-the-art medical robotic systems available for use in conjunction with intraoperative magnetic resonance imaging. The robot functionalities and mechanical designs for a wide range of magnetic resonance imaging interventions are presented, including their magnetic resonance imaging compatibility, actuation, kinematics and the mechanical and electrical designs of the robots. Classification and comparative study of various intraoperative magnetic resonance image guided robotic systems are provided. The robotic systems reviewed are summarized in a table in detail. Current technologies for magnetic resonance imaging–conditional robotics are reviewed and their potential future directions are sketched.

Mapping stiffness perception in the brain with an fMRI-compatible particle-jamming haptic interface

We demonstrate reliable neural responses to changes in haptic stiffness perception using a functional magnetic resonance imaging (fMRI) compatible particle-jamming haptic interface. Our haptic interface consists of a silicone tactile surface whose stiffness we can control by modulating air-pressure in a sub-surface pouch of coarsely ground particles. The particles jam together as the pressure decreases, which stiffens the surface. During fMRI acquisition, subjects performed a constant probing task, which involved continuous contact between the index fingertip and the interface and rhythmic increases and decreases in fingertip force (1.6 Hz) to probe stiffness. Without notifying subjects, we randomly switched the interface's stiffness (switch time, 300-500 ms) from soft (200 N/m) to hard (1400 N/m). Our experiment design's constant motor activity and cutaneous tactile sensation helped disassociate neural activation for both from stiffness perception, which helped localized it to a narrow region in somatosensory cortex near the supra-marginal gyrus. Testing different models of neural activation, we found that assuming indepedent stiffness-change responses at both soft-hard and hard-soft transitions provides the best explanation for observed fMRI measurements (three subjects; nine four-minute scan runs each). Furthermore, we found that neural activation related to stiffness-change and absolute stiffness can be localized to adjacent but disparate anatomical locations. We also show that classical finger-tapping experiments activate a swath of cortex and are not suitable for localizing stiffness perception. Our results demonstrate that decorrelating motor and sensory neural activation is essential for characterizing somatosensory cortex, and establish particle-jamming haptics as an attractive low-cost method for fMRI experiments.

Surgical Robots

Information technology and robotics have been integrated into interventional medicine for over 25 years. Their primary aim has always been to provide patient benefits through increased precision, safety, and minimal invasiveness. Nevertheless, robotic devices should allow for sophisticated treatment methods that are not possible by other means. Several hundreds of different surgical robot prototypes have been developed, while only a handful passed clearance procedures, and was released to the market. This is mostly due to the difficulties associated with medical device development and approval, especially in those cases when some form of manipulation and automation is involved. This chapter is intended to present major aspects of surgical robotic prototyping and current trends through the analysis of various international projects. It spans across the phases from system planning, to development, validation, and clearance.

An fMRI compatible wrist robotic interface to study brain development in neonates

A comprehensive understanding of the mechanisms that underlie brain development in premature infants and newborns is crucial for the identification of interventional therapies and rehabilitative strategies. fMRI has the potential to identify such mechanisms, but standard techniques used in adults cannot be implemented in infant studies in a straightforward manner. We have developed an MR safe wrist stimulating robot to systematically investigate the functional brain activity related to both spontaneous and induced wrist movements in premature babies using fMRI. We present the technical aspects of this development and the results of validation experiments. Using the device, the cortical activity associated with both active and passive finger movements were reliably identified in a healthy adult subject. In two preterm infants, passive wrist movements induced a well localized positive BOLD response in the contralateral somatosensory cortex. Furthermore, in a single preterm infant, spontaneous wrist movements were found to be associated with an adjacent cluster of activity, at the level of the infant's primary motor cortex. The described device will allow detailed and objective fMRI studies of somatosensory and motor system development during early human life and following neonatal brain injury.

Development of BOLD signal hemodynamic responses in the human brain

In the rodent brain the hemodynamic response to a brief external stimulus changes significantly during development. Analogous changes in human infants would complicate the determination and use of the hemodynamic response function (HRF) for functional magnetic resonance imaging (fMRI) in developing populations. We aimed to characterize HRF in human infants before and after the normal time of birth using rapid sampling of the Blood Oxygen Level Dependent (BOLD) signal. A somatosensory stimulus and an event related experimental design were used to collect data from 10 healthy adults, 15 sedated infants at term corrected post menstrual age (PMA) (median 41 + 1 weeks), and 10 preterm infants (median PMA 34 + 4 weeks). A positive amplitude HRF waveform was identified across all subject groups, with a systematic maturational trend in terms of decreasing time-to-peak and increasing positive peak amplitude associated with increasing age. Application of the age-appropriate HRF models to fMRI data significantly improved the precision of the fMRI analysis. These findings support the notion of a structured development in the brain's response to stimuli across the last trimester of gestation and beyond.

Surgical Robots

Information technology and robotics have been integrated into interventional medicine for over 25 years. Their primary aim has always been to provide patient benefits through increased precision, safety, and minimal invasiveness. Nevertheless, robotic devices should allow for sophisticated treatment methods that are not possible by other means. Several hundreds of different surgical robot prototypes have been developed, while only a handful passed clearance procedures, and was released to the market. This is mostly due to the difficulties associated with medical device development and approval, especially in those cases when some form of manipulation and automation is involved. This chapter is intended to present major aspects of surgical robotic prototyping and current trends through the analysis of various international projects. It spans across the phases from system planning, to development, validation, and clearance.

Finite-element analysis for magnetic resonance image artifact evaluation

The static magnetic field of a magnetic resonance imaging scanner can be distorted by the presence of materials, perturbing the spatial encoding process in magnetic resonance imaging and often resulting in image artifacts. The relationship between the image artifact size and magnetic susceptibility of the material specimen is of interest to engineers for the design of devices that are to be compatible with the imaging volume of the scanner. In this study, a finite-element method was used to simulate the distorted magnetic field of samples with different susceptibilities. With the knowledge of the external- and self- magnetic field interactions, a Lorentz correction was applied to compute the magnetic field deviation. The simulated results were then validated by the corresponding experimental magnetic resonance images.

Multi-sensory and sensorimotor foundation of bodily self-consciousness - an interdisciplinary approach

Scientific investigations on the nature of the self have so far focused on high-level mechanisms. Recent evidence, however, suggests that low-level bottom-up mechanisms of multi-sensory integration play a fundamental role in encoding specific components of bodily self-consciousness, such as self-location and first-person perspective (Blanke and Metzinger, 2009). Self-location and first-person perspective are abnormal in neurological patients suffering from out-of-body experiences (Blanke et al., 2004), and can be manipulated experimentally in healthy subjects by imposing multi-sensory conflicts (Lenggenhager et al., 2009). Activity of the temporo-parietal junction (TPJ) reflects experimentally induced changes in self-location and first-person perspective (Ionta et al., 2011), and dysfunctions in TPJ are causally associated with out-of-body experiences (Blanke et al., 2002). We argue that TPJ is one of the key areas for multi-sensory integration of bodily self-consciousness, that its levels of activity reflect the experience of the conscious "I" as embodied and localized within bodily space, and that these mechanisms can be systematically investigated using state of the art technologies such as robotics, virtual reality, and non-invasive neuroimaging.

A simple 5-DoF MR-compatible motion signal measurement system

The purpose of this study was to develop a simple motion measurement system with magnetic resonance (MR) compatibility and safety. The motion measurement system proposed here can measure 5-DoF motion signals without deteriorating the MR images, and it has no effect on the intense and homogeneous main magnetic field, the temporal-gradient magnetic field (which varies rapidly with time), the transceiver radio frequency (RF) coil, and the RF pulse during MR data acquisition. A three-axis accelerometer and a two-axis gyroscope were used to measure 5-DoF motion signals, and Velcro was used to attach a sensor module to a finger or wrist. To minimize the interference between the MR imaging system and the motion measurement system, nonmagnetic materials were used for all electric circuit components in an MR shield room. To remove the effect of RF pulse, an amplifier, modulation circuit, and power supply were located in a shielded case, which was made of copper and aluminum. The motion signal was modulated to an optic signal using pulse width modulation, and the modulated optic signal was transmitted outside the MR shield room using a high-intensity light-emitting diode and an optic cable. The motion signal was recorded on a PC by demodulating the transmitted optic signal into an electric signal. Various kinematic variables, such as angle, acceleration, velocity, and jerk, can be measured or calculated by using the motion measurement system developed here. This system also enables motion tracking by extracting the position information from the motion signals. It was verified that MR images and motion signals could reliably be measured simultaneously.

Piezoelectric actuator design for MR elastography: implementation and vibration issues

BACKGROUND

MR elastography (MRE) is an emerging technique for tumor diagnosis. MRE actuation devices require precise mechanical design and radiofrequency engineering to achieve the required mechanical vibration performance and MR compatibility.

METHOD

A method of designing a general-purpose, compact and inexpensive MRE actuator is presented. It comprises piezoelectric bimorphs arranged in a resonant structure designed to operate at its resonant frequency for maximum vibration amplitude. An analytical model was established to understand the device vibration characteristics.

RESULTS

The model-predicted performance was validated in experiments, showing its accuracy in predicting the actuator resonant frequency with an error < 4%. The device MRI compatibility was shown to cause minimal interference to a 1.5 tesla MRI scanner, with maximum signal-to-noise ratio reduction of 7.8% and generated artefact of 7.9 mm in MR images.

CONCLUSIONS

A piezoelectric MRE actuator is proposed, and its implementation, vibration issues and future work are discussed.

Neuroscience robotics to investigate multisensory integration and bodily awareness

Humans experience the self as localized within their body. This aspect of bodily self-consciousness can be experimentally manipulated by exposing individuals to conflicting multisensory input, or can be abnormal following focal brain injury. Recent technological developments helped to unravel some of the mechanisms underlying multisensory integration and self-location, but the neural underpinnings are still under investigation, and the manual application of stimuli resulted in large variability difficult to control. This paper presents the development and evaluation of an MR-compatible stroking device capable of presenting moving tactile stimuli to both legs and the back of participants lying on a scanner bed while acquiring functional neuroimaging data. The platform consists of four independent stroking devices with a travel of 16-20 cm and a maximum stroking velocity of 15 cm/s, actuated over non-magnetic ultrasonic motors. Complemented with virtual reality, this setup provides a unique research platform allowing to investigate multisensory integration and its effects on self-location under well-controlled experimental conditions. The MR-compatibility of the system was evaluated in both a 3 and a 7 Tesla scanner and showed negligible interference with brain imaging. In a preliminary study using a prototype device with only one tactile stimulator, fMRI data acquired on 12 healthy participants showed visuo-tactile synchrony-related and body-specific modulations of the brain activity in bilateral temporoparietal cortex.

Mutual interferences and design principles for mechatronic devices in magnetic resonance imaging

PURPOSE

Robotic and mechatronic devices that work compatibly with magnetic resonance imaging (MRI) are applied in diagnostic MRI, image-guided surgery, neurorehabilitation and neuroscience. MRI-compatible mechatronic systems must address the challenges imposed by the scanner's electromagnetic fields. We have developed objective quantitative evaluation criteria for device characteristics needed to formulate design guidelines that ensure MRI-compatibility based on safety, device functionality and image quality.

METHODS

The mutual interferences between an MRI system and mechatronic devices working in its vicinity are modeled and tested. For each interference, the involved components are listed, and a numerical measure for "MRI-compatibility" is proposed. These interferences are categorized into an MRI-compatibility matrix, with each element representing possible interactions between one part of the mechatronic system and one component of the electromagnetic fields. Based on this formulation, design principles for MRI-compatible mechatronic systems are proposed. Furthermore, test methods are developed to examine whether a mechatronic device indeed works without interferences within an MRI system. Finally, the proposed MRI-compatibility criteria and design guidelines have been applied to an actual design process that has been validated by the test procedures.

RESULTS

Objective and quantitative MRI-compatibility measures for mechatronic and robotic devices have been established. Applying the proposed design principles, potential problems in safety, device functionality and image quality can be considered in the design phase to ensure that the mechatronic system will fulfill the MRI-compatibility criteria.

CONCLUSION

New guidelines and test procedures for MRI instrument compatibility provide a rational basis for design and evaluation of mechatronic devices in various MRI applications. Designers can apply these criteria and use the tests, so that MRI-compatibility results can accrue to build an experiential database.

Magnetic resonance elastography: a general overview of its current and future applications in brain imaging

Magnetic resonance elastography (MRE) has been developed over the last few years as a non-invasive means of evaluating the elasticity of biological tissues. The presence of the skull has always prevented semeiotic palpation of the brain, but MRE now offers the possibility of "palpating by imaging" in order to detect brain consistency under physiological and pathological conditions. The aim of this article is to review the current state-of-the-art of MRE imaging and discuss its possible future diagnostic applications in neuroscience.

An MRI-Compatible Needle Manipulator Concept Based on Elastically Averaged Dielectric Elastomer Actuators for Prostate Cancer Treatment: An Accuracy and MR-Compatibility Evaluation in Phantoms

A parallel manipulator concept using bistable polymer actuators has been developed to perform prostate cancer biopsy, and deliver therapy within the bore of a magnetic resonance imaging (MRI) scanner. The dielectric elastomer actuators (DEAs) used in this manipulator concept are promising for MRI-compatible robotics because they do not interfere with the high magnetic fields of MRI while having good mechanical performance and being low cost. In the past, these actuators have been plagued by robustness problems when used in a continuous manner. Recent studies show that reliability significantly improves when DEAs are used in a bistable manner, as proposed here. This paper investigates the potential of the proposed manipulator concept by evaluating the positioning accuracy and MRI compatibility of a laboratory prototype, developed for clinically relevant design criteria. An analytical model of the manipulator kinematics is presented. Analytical and experimental results validate that the proposed technology can provide an accurate needle placement required to perform prostate cancer treatments. The prototype’s MRI compatibility is validated in a 3 T clinical MRI scanner. The parallel manipulator concept using bistable polymer actuators is shown to be a viable approach to perform MRI-guided needle insertions for prostate cancer biopsy and therapy.

Magnetic resonance elastography hardware design: A survey

Magnetic resonance elastography (MRE) is an emerging technique capable of measuring the shear modulus of tissue. A suspected tumour can be identified by comparing its properties with those of tissues surrounding it; this can be achieved even in deep-lying areas as long as mechanical excitation is possible. This would allow non-invasive methods for cancer-related diagnosis in areas not accessible with conventional palpation. An actuating mechanism is required to generate the necessary tissue displacements directly on the patient in the scanner and three different approaches, in terms of actuator action and position, exist to derive stiffness measurements. However, the magnetic resonance (MR) environment places considerable constraints on the design of such devices, such as the possibility of mutual interference between electrical components, the scanner field, and radio frequency pulses, and the physical space restrictions of the scanner bore. This paper presents a review of the current solutions that have been developed for MRE devices giving particular consideration to the design criteria including the required vibration frequency and amplitude in different applications, the issue of MR compatibility, actuation principles, design complexity, and scanner synchronization issues. The future challenges in this field are also described.

Recent developments in biomedical engineering education and research in Brazil

The purpose of this paper is to present recent developments in Biomedical Engineering (BME) education & research in Brazil. The state-of-the-art in research in BME around the world is mentioned to highlight emerging technologies. A review of BME undergraduate, graduate & research programs in Brazil is presented. A roadmap of developing BME education in Brazil is outlined. Some critical implementation issues are mentioned.