Medical robots for MRI guided diagnosis and therapy

Magnetic Resonance Imaging (MRI) provides the capability of imaging tissue with fine resolution and superior soft tissue contrast, when compared with conventional ultrasound and CT imaging, which makes it an important tool for clinicians to perform more accurate diagnosis and image guided therapy. Medical robotic devices combining the high resolution anatomical images with real-time navigation, are ideal for precise and repeatable interventions. Despite these advantages, the MR environment imposes constraints on mechatronic devices operating within it. This thesis presents a study on the design and development of robotic systems for particular MR interventions, in which the issue of testing the MR compatibility of mechatronic components, actuation control, kinematics and workspace analysis, and mechanical and electrical design of the robot have been investigated. Two types of robotic systems have therefore been developed and evaluated along the above aspects. (i) A device for MR guided transrectal prostate biopsy: The system was designed from components which are proven to be MR compatible, actuated by pneumatic motors and ultrasonic motors, and tracked by optical position sensors and ducial markers. Clinical trials have been performed with the device on three patients, and the results reported have demonstrated its capability to perform needle positioning under MR guidance, with a procedure time of around 40mins and with no compromised image quality, which achieved our system speci cations. (ii) Limb positioning devices to facilitate the magic angle effect for diagnosis of tendinous injuries: Two systems were designed particularly for lower and upper limb positioning, which are actuated and tracked by the similar methods as the first device. A group of volunteers were recruited to conduct tests to verify the functionality of the systems. The results demonstrate the clear enhancement of the image quality with an increase in signal intensity up to 24 times in the tendon tissue caused by the magic angle effect, showing the feasibility of the proposed devices to be applied in clinical diagnosis

Quantitative propagation of chaos of McKean-Vlasov equations via the master equation

McKean-Vlasov stochastic differential equations (MVSDEs) are ubiquitous in kinetic theory and in controlled games with a large number of players. They have been intensively studied since McKean, as they pave a way to probabilistic representations for many important nonlinear/ nonlocal PDEs. Classically, their simulation involves using standard particle systems, which replace the evolving law in MVSDEs by the evolving empirical measure of the particles. However, this type of simulation is costly in terms of computational complexity, due to the interaction between the particles. Apart from classical techniques in stochastic analysis, the approach in this thesis relies heavily on the calculus on Wasserstein space, presented by P. Lions in his course at Collège de France. An important object in our study, is a PDE written on the product space of the space of time horizon and the Wasserstein space, which is a generalisation of the classical Feynman- Kac PDE. This PDE, namely the master equation, provides a new insight into the study of mean-field limits of particles and consequently allows us to solve many problems on MVSDEs that are very difficult/impossible to solve by classical techniques. The layout of the thesis is as follows. We start by a recap on classical results of MVSDEs (Chapter 2), followed by a full exposition of Wasserstein calculus on the results that we need (Chapter 3). Chapters 4 and 5 propose approximating systems to MVSDEs (as alternatives to the classical particle system) via Romberg extrapolation and Antithetic Multi-level Monte-Carlo estimation respectively, which are less costly in terms of computational complexity. Finally, in Chapter 6, we explore the converse: given a standard particle system, we hope to find an alternative mean-field limit that gives a better approximation to the standard particle system

Deep reinforcement learning for soft, flexible robots : brief review with impending challenges

The increasing trend of studying the innate softness of robotic structures and amalgamating it with the benefits of the extensive developments in the field of embodied intelligence has led to the sprouting of a relatively new yet rewarding sphere of technology in intelligent soft robotics. The fusion of deep reinforcement algorithms with soft bio-inspired structures positively directs to a fruitful prospect of designing completely self-sufficient agents that are capable of learning from observations collected from their environment. For soft robotic structures possessing countless degrees of freedom, it is at times not convenient to formulate mathematical models necessary for training a deep reinforcement learning (DRL) agent. Deploying current imitation learning algorithms on soft robotic systems has provided competent results. This review article posits an overview of various such algorithms along with instances of being applied to real-world scenarios, yielding frontier results. Brief descriptions highlight the various pristine branches of DRL research in soft robotics

Accepted and presented at The Design of Medical Devices Conference (DMD2016)

Magnetic resonance imaging (MRI) is an imaging approach to acquire high-resolution images of soft target tissue particularly for medical applications in both preoperative and intraoperative procedures Unlike electric and electromagnetic actuators, pneumatic motors demonstrate a few advantages. MR-compatible materials, such as plastic, ensure easy fabrication and customized design; the air supply of the pneumatic actuators can be found in most MR rooms; the compressed air does not interface with the MR imaging physics; furthermore, pneumatic actuators can provide little to no signal-to-noise ratio (SNR) reduction in MR images. These advantages result in the fast development of pneumatic actuation for MR-guided robotic interventions The device detailed in this paper is a pneumatic stepper motor. Previous stepper motor designs have generally relied on the intermeshing of different sets of "teeth" to create the rotation and stepwise effect. Chen et al. used a different approach creating a stepper motor composed of two cylinders and a supporting structure The pneumatic stepper motor presented in this paper can rotate 3.6 deg for each step and generate torque up to 918.75 mNÁm. The system setup, motor working principle, and calibration will be discussed in the Methods, and Results sections. Methods The compressed air supply was split into two lines with one line directed to the control box and the other to the switches. Depending on the direction of rotation, a signal was sent to one of two pneumatic valves in the control box to open the pneumatic valve. Then, air flows to the corresponding cylinder, and the cylinder pulls its connected switch to the open position. During a digital low, the pneumatic valve closes and exhausts the air that is trapped in between the valve and cylinder. The supply of air attached to the pneumatic switch flows into the continuous motor. The continuous motor rotates the main axle inside the housing. Attached to the main axle is a cam which flips the currently open switch back to the closed position, stopping air flow to the continuous motor, and causing the motor to slow to a stop. Also, the corresponding cylinder was reset since it is attached to the switch. Essentially, the motor turns itself off. After one rotation of the main shaft, the Geneva drive has advanced by one step. Since the Geneva drive has four slots, each step is equal to 90 deg of rotation. In order to increase the resolution of each step, a second series of planetary gears with a ratio of 25:1 was attached to the output of the Geneva drive resulting i

The Feasibility of Using a Smartphone Magnetometer for Assisting Needle Placement

Minimally invasive surgical procedures often require needle insertion. For these procedures, efficacy greatly depends on precise needle placement. Many methods, such as optical tracking and electromagnetic tracking, have been applied to assist needle placement by tracking the real-time position information of the needle. Compared with the optical tracking method, electromagnetic tracking is more suitable for minimally invasive surgery since it has no requirement of line-of-sight. However, the devices needed for electromagnetic tracking are usually expensive, which will increase the cost of surgery. In this study, we presented a low-cost smartphone-based permanent magnet tracking method compatible with CT imaging and designed a 3D printed operation platform to assist with needle placement prior to needle insertion during minimally invasive surgery. The needle positioning accuracy of this method was tested in an open air test and a prostate phantom test in a CT environment. For these two tests, the average radial errors were 0.47 and 2.25 mm, respectively, and the standard deviations were 0.29 and 1.63, respectively. The materials and fabrication required for the presented method are inexpensive. Thus, many image-guided therapies may benefit from the presented method as a low-cost option for needle positioning prior to needle insertion

Exploring magnetohydrodynamic voltage distributions in the human body : Preliminary results

BACKGROUND: The aim of this study was to noninvasively measure regional contributions of vasculature in the human body using magnetohydrodynamic voltages (VMHD) obtained from electrocardiogram (ECG) recordings performed inside MRI's static magnetic field (B0). Integrating the regional VMHD over the Swave-Twave segment of the cardiac cycle (Vsegment) provides a non-invasive method for measuring regional blood volumes, which can be rapidly obtained during MRI without incurring additional cost. METHODS: VMHD was extracted from 12-lead ECG traces acquired during gradual introduction into a 3T MRI. Regional contributions were computed utilizing weights based on B0's strength at specified distances from isocenter. Vsegment mapping was performed in six subjects and validated against MR angiograms (MRA). RESULTS: Fluctuations in Vsegment, which presented as positive trace deflections, were found to be associated with aortic-arch flow in the thoracic cavity, the main branches of the abdominal aorta, and the bifurcation of the common iliac artery. The largest fluctuation corresponded to the location where the aortic arch was approximately orthogonal to B0. The smallest fluctuations corresponded to areas of vasculature that were parallel to B0. Significant correlations (specifically, Spearman's ranked correlation coefficients of 0.96 and 0.97 for abdominal and thoracic cavities, respectively) were found between the MRA and Vsegment maps (p < 0.001). CONCLUSIONS: A novel non-invasive method to extract regional blood volumes from ECGs was developed and shown to be a rapid means to quantify peripheral and abdominal blood volumes

Applications of Wireless Power Transfer in Medicine : State-of-the-Art Reviews

Magnetic resonance within the field of wireless power transfer has seen an increase in popularity over the past decades. This rise can be attributed to the technological advances of electronics and the increased efficiency of popular battery technologies. The same principles of electromagnetic theory can be applied to the medical field. Several medical devices intended for use inside the body use batteries and electrical circuits that could be powered wirelessly. Other medical devices limit the mobility or make patients uncomfortable while in use. The fundamental theory of electromagnetics can improve the field by solving some of these problems. This survey paper summarizes the recent uses and discoveries of wireless power in the medical field. A comprehensive search for papers was conducted using engineering search engines and included papers from related conferences. During the initial search, 247 papers were found then non-relevant papers were eliminated to leave only suitable material. Seventeen relevant journal papers and/or conference papers were found, then separated into defined categories: Implants, Pumps, Ultrasound Imaging, and Gastrointestinal (GI) Endoscopy. The approach and methods for each paper were analyzed and compared yielding a comprehensive review of these state of the art technologies

Functional constituency members in Hong Kong's Legislative Council : a study of governance, legitimacy and accountability in action / y Cheung Hin Kei, Hankie, Ho Sing Yan, Simon, Li Man Pong, Charles, Tse Tsz Ying, Amy, Wong Man Ting, Mandy

published_or_final_versionPolitics and Public AdministrationMasterMaster of Public Administratio

Social Media Usage and Influenza Beliefs, Risk Perceptions and Behavioral Intentions Among Students at a University in Southeastern US

Background: To document social media usage for the retrieval of health information among college students; and to understand the beliefs, risk perceptions and behavioral intentions among participants who retrieved CDC influenza information via social media. Methods: We conducted an online survey to a convenience sample of students at a university in Southeastern United States during Spring 2015. The survey was self-administered and every matriculating student received an electronic invitation to participate at least once. Results: A total of 930 students completed the online survey. Most participants (n=905, 97.3%) reported that they had used a social networking site in the previous 12 months. However, only one-third (n=317, 34.1%) reported that they used social networking sites to read CDC health information or messages. Nearly one-fifth of participants (n=172, 18.5%) reported reading CDC influenza information during the 2014-15 influenza season. Among the subset of readers of CDC influenza information during the 2014-15 influenza season (N=153), 77 (50.99%) reported that it was likely they would get the influenza vaccine in the next 12 months. Women reported stronger risk perceptions and behavioral intentions than men. Blacks/African Americans reported more negative influenza-related beliefs and weaker risk perceptions compared to Whites. Conclusions: While social media penetration is high among university students in Southeastern US, only a minority of survey participants retrieved CDC influenza information via social media. Among these individuals, about half reported that they intended to vaccinate against influenza. Further research is needed to enhance CDC social media penetration among college students

Magnetic Alignment Detection Using Existing Charging Facility in Wireless EV Chargers

Wireless charging is a promising outlet to promote the electric vehicle (EV) industry due to its safe and noncontact manner. Wireless EV chargers require the secondary receiver coil to be well aligned with the primary station for efficient charging, which could require more of the driver’s time and attention when parking a vehicle. Therefore, this paper presents a magnetic alignment system to assist the EV driver during parking. The magnetic alignment approach uses the existing coil and frequency tracking control electronics of wireless chargers to detect the distance between the two coils while using 4 small auxiliary coils for direction and fine adjustment, leading to a cost effective detection method for coil alignment in electric vehicle wireless charging (EVWC). The testing results of a prototype show acceptable measurement correctness and the mean error for ten trials in range detection is within 0.25 cm at three different misalignment conditions (10.5, 15, and 20 cm). The positioning accuracy of coil alignment is within 1.2 cm for three different start positions with the auxiliary coils