16 research outputs found
Towards Privacy-Aware Research and Development in Wearable Health
Wearable sensor technology has the potential to transform healthcare. The investigation and testing of sensors in the commercial sector offer insight into ways to leverage biometric data, to improve individual health through the better products and to advance the public good through research. \ \ However, research with wearable sensor data must be done in a manner that is respectful of ethical considerations and privacy. Not only will the processes that govern this research define the potential public good derived from wearables, they will encourage user trust in wearables and promote participation. The research and development (R&D) teams at companies are not just engines of innovation but also have the potential to be an important part of our social infrastructure. The Center for Democracy & Technology (CDT) embarked on a yearlong partnership with Fitbit. CDT gained rare access to the company’s data policies and practices to build recommendations on privacy and ethics.
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Ultrasound Servoing of Catheters for Beating Heart Valve Repair
Robotic cardiac catheters have the potential to revolutionize heart surgery by extending minimally invasive techniques to complex surgical repairs inside the heart. However, catheter technologies are currently unable to track fast tissue motion, which is required to perform delicate procedures inside a beating heart. This paper presents an actuated catheter tool that compensates for the motion of heart structures like the mitral valve apparatus by servoing a catheter guidewire inside a flexible sheath. We examine design and operation parameters and establish that friction and backlash limit the tracking performance of the catheter system. Based on the results of these experiments, we implement compensation methods to improve trajectory tracking. The catheter system is then integrated with an ultrasound-based visual servoing system to enable fast tissue tracking. In vivo tests show RMS tracking errors of 0.77 mm for following the porcine mitral valve annulus trajectory. The results demonstrate that an ultrasound-guided robotic catheter system can accurately track the fast motion of the mitral valve.Engineering and Applied Science
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Haptic Noise Cancellation: Restoring Force Perception in Robotically-Assisted Beating Heart Surgery
Beating heart surgical methods have the potential to remove the
need for the heart-lung machine and its attendant side effects, but
must contend with the motion of the heart. Recent research in
robotically-assisted surgery has produced a handheld, actuated in-
strument that can track and compensate for heart motion; however,
the reaction forces caused by the actuation mechanism make it dif-
ficult for the surgeon to feel the heart during the operation, which
can lead to unsafe tissue manipulation. This paper investigates an
instrument design that negates reaction forces to the user by moving
a counterweight out of phase with the moving mass of the actuator.
The resulting instrument retains the tracking and motion compensa-
tion abilities of the current instrument, but reduces reaction forces
felt by the user by over 80%. Subjects used the new instrument
in an in vitro beating heart surgical contact task and performance
was compared to the previously existing instrument. The new in-
strument provided a 28% increase in user force sensitivity and im-
proved user reaction times by 51%, indicating that the new instru-
ment greatly enhances force perception in beating heart tasks.Engineering and Applied Science
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3D Ultrasound-Guided Motion Compensation System for Beating Heart Mitral Valve Repair
Beating heart intracardiac procedures promise significant benefits for patients, however, the fast motion of the heart poses serious challenges to surgeons. We present a new 3D ultrasound-guided motion (3DUS) compensation system that synchronizes instrument motion with the heart. The system utilizes the fact that the motion of some intracardiac structures, including the mitral valve annulus, is largely constrained to translation along one axis. This allows the development of a real-time 3DUS tissue tracker which we integrate with a 1 degree-of-freedom actuated surgical instrument, real-time 3DUS instrument tracker, and predictive filter to devise a system with synchronization accuracy of 1.8 mm RMSE. User studies involving the deployment of surgical anchors in a simulated mitral annuloplasty procedure demonstrate that the system increases success rates by over 100%. Furthermore, it enables more careful anchor deployment by reducing forces to the tissue by 50% while allowing instruments to remain in contact with the tissue for longer periods.Engineering and Applied Science
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Quasiperiodic predictive filtering for robot-assisted beating heart surgery
Beating heart procedures promise significant health benefits to patients but the fast motion of the heart poses a serious challenge to the surgeon. Robotic motion synchronization to heart movements could facilitate these surgeries, although for intracardiac procedures this requires the development of a predictive filter to compensate for the measurement noise and time delay present in 3D ultrasound imaging. In this paper, we present a quasiperiodic cardiac motion model and apply the extended Kalman filter to estimation of its parameters in real-time. We experimentally demonstrate high accuracy robot tracking to heart motion using this filter.Engineering and Applied Science
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Bayesian change-point analysis for atomic force microscopy and soft material indentation
Material indentation studies, in which a probe is brought into controlled physical contact with an experimental sample, have long been a primary means by which scientists characterize the mechanical properties of materials. More recently, the advent of atomic force microscopy, which operates on the same fundamental principle, has in turn revolutionized the nanoscale analysis of soft biomaterials such as cells and tissues. This paper addresses the inferential problems associated with material indentation and atomic force microscopy, through a framework for the changepoint analysis of pre- and post-contact data that is applicable to experiments across a variety of physical scales. A hierarchical Bayesian model is proposed to account for experimentally observed changepoint smoothness constraints and measurement error variability, with efficient Monte Carlo methods developed and employed to realize inference via posterior sampling for parameters such as Young’s modulus, a key quantifier of material stiffness. These results are the first to provide the materials science community with rigorous inference procedures and uncertainty quantification, via optimized and fully automated high-throughput algorithms, implemented as the publicly available software package BayesCP. To demonstrate the consistent accuracy and wide applicability of this approach, results are shown for a variety of data sets from both macro- and micro-materials experiments—including silicone, neurons, and red blood cells—conducted by the authors and others.Engineering and Applied Science
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Robotic Motion Compensation for Beating Heart Intracardiac Surgery
3D ultrasound imaging has enabled minimally invasive, beating heart intracardiac procedures. However, rapid heart motion poses a serious challenge to the surgeon that is compounded by significant time delays and noise in 3D ultrasound. This paper investigates the concept of using a one-degree-of-freedom motion compensation system to synchronize with tissue motions that may be approximated by 1D motion models. We characterize the motion of the mitral valve annulus and show that it is well approximated by a 1D model. The subsequent development of a motion compensation instrument (MCI) is described, as well as an extended Kalman filter (EKF) that compensates for system delays. The benefits and robustness of motion compensation are tested in user trials under a series of non-ideal tracking conditions. Results indicate that the MCI provides an approximately 50% increase in dexterity and 50% decrease in force when compared with a solid tool, but is sensitive to time delays. We demonstrate that the use of the EKF for delay compensation restores performance, even in situations of high heart rate variability. The resulting system is tested in an in vitro 3D ultrasound-guided servoing task, yielding accurate tracking (1.15 mm root mean square) in the presence of noisy, time-delayed 3D ultrasound measurements.Engineering and Applied Science
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A Robust Uniaxial Force Sensor for Minimally Invasive Surgery
This paper presents a novel, miniature uniaxial force sensor for use within a beating heart during mitral valve annuloplasty. The sensor measures 5.5 mm in diameter and 12 mm in length, and provides a hollow core to pass instrumentation. A soft elastomer flexure design maintains a waterproof seal. Fiber optic transduction eliminates electrical circuitry within the heart, and acetal components minimize ultrasound imaging artifacts. Calibration uses a nonlinear, viscoelastic method, and in vitro tests demonstrate a 0 to 4 N force range with RMS errors of 0.13 N (<3.2%). In vivo tests provide the first endocardial measurements of tissue-MIS instrument interaction forces in a beating heart.Engineering and Applied Science
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Bayesian Changepoint Detection Through Switching Regressions: Contact Point Determination in Material Indentation Experiments
Material indentation is a popular method for determining the mechanical properties of biomaterials. The basic premise of an indentation experiment is to physically displace the sample using an indenter that measures resistive force, in order to formulate a force-displacement curve. However, doing so requires estimating the initial contact event between the indenter and the sample-a statistical changepoint detection problem that has not been rigorously addressed in the biomaterials literature to date. Here we adopt a hierarchical Bayesian approach to contact point determination based on switching regressions, which generalizes an algorithm popular with practitioners and enables both hyperparameter estimation as well as uncertainty quantification. Results using several experimentally obtained silicone indentation data sets indicate that our approach outperforms existing techniques.Engineering and Applied Science