Journal of Medical Devices-Transactions of the Asme最新文献

Pediatric exoskeletons have the potential to aid the walking of children with neuromuscular conditions such as crouch gait. However, current exoskeleton devices often rely on bulky batteries and motors. Recent developments in 3D-printing technologies now allow the construction of lightweight yet stiff parts that are easy to customize and use for pediatric applications. We present the mechanical design of a 3D-printed and spring-powered knee exoskeleton for gait assistance. The device had a mass of ∼1.25 kg per leg and provided a knee extensor moment during the stance phase of gait, simulating the spring-like behavior of the knee. Conversely, the exoskeleton provided no resistance during swing to allow free motion of the joint. To validate the device, we recruited two neurologically intact children to walk on a treadmill with and without the exoskeleton while we recorded kinematics, kinetics, and muscle activity data. Our exoskeleton generated knee extensor moments proportional to its angular excursion and had a peak mean moment of ∼0.1 N·m/kg during stance. Kinetic data showed that subjects decreased their biological knee moment and joint spring-like behavior to compensate for the added exoskeleton moment and stiffness, respectively. We ultimately show that the device is robust and capable of generating extensor moments comparable to devices used to assist the knee in children with crouch gait.

We have previously verified the capabilities of a prototype magnetic nanoparticle (MNP) heater (called HYPER) that can perform spatially confined heating; however, the design lacked temperature control capabilities. In this work, we designed, verified, and validated a relay-based autotuning proportional-integral-derivative (PID) controller to be used with the HYPER during in vivo experiments. The PID controller is an autotuning, relay-based controller with several design constraints: The controller must: (1) maintain tumor temperature within hyperthermic range of 41-46 °C; (2) rise time ≤ 5 min; (3) steady-state temperature must be within ±0.5 °C of the setpoint; (4) standard deviation of steady-state temperature within ±0.5 °C; and (5) temperature overshoot within 5%. The relay-based autotuning PID controller was designed in LabVIEW^® with real-time thermal dose monitoring. Verification experiments were performed by heating aqueous suspensions of high-performance iron oxide MNPs. For validation, we injected the MNPs into tumor-bearing mice and analyzed the ability of the controller to maintain in vivo temperature. The results of the study show that controller was able to maintain the temperature within the hyperthermic range with a rise time ∼4 min and steady-state error ∼0.1 °C. Validation was performed on six mice, where four mice showed the temperature was maintained within design criteria and two mice partially met the design criteria. The autotuning controller can maintain the temperature within the design criteria and monitor thermal dose in real-time.

Dual X-ray absorptiometry (DEXA) scans are the current standard in assessing bone mineral density (BMD) and are used to identify patients who may need screw augmentation during spinal fusion. DEXA scans are not always available and tend to overestimate BMD. This paper describes the development of a dual-cantilever mechanical probe and tested in polyurethane foam blocks with varying compressive strengths. The probe was modeled after a 5.5 mm tap and foam block holes were prepared replicating intra-operative conditions. Calibration curves were acquired for each probe using six foam blocks (1.5-12.9 MPa). Verification tests were performed in a different set of four foam blocks (2.05-9.65 MPa). Four probes were machined and tested for repeatability. Three users separately acquired measurements of foam blocks to test for reliability. The root-mean-square error of all four probes measuring the 2.05 MPa, 3.65 MPa, 5.80 MPa, and 9.65 MPa samples were 0.89 MPa, 0.32 MPa, 1.41 MPa, and 1.71 MPa, respectively. There was not a significant difference between different probes or different users. The dual-cantilever probe provided measurements within the clinically relevant range of compressive strengths for vertebral trabecular bone. A targeted and reliable bone strength measurement technique could reduce the occurrence and revision surgeries and improve patient outcomes.

HeartLander is a miniature mobile robot designed to navigate on the surface of the heart using a crawling motion and is well-suited for delivering myocardial injections. Previous work has incorporated a cooling system to enable delivery of a thermally responsive anti-ventricular remodeling hydrogel to a target injection site. However, the previous setup required the saline coolant to be discharged at the distal end of the system and into the patient's pericardial space, hindering the hydrogel from forming a deposit at the target site, presenting an additional burden to the surgeon's workflow, and increasing the risk to the patient. To prevent this, we redesigned the system to include a return channel for the coolant, which discharges to a reservoir outside the patient. We validated this design with a multiphysics simulation, static water bath tests, and by demonstration of controlled injections in an ovine heart ex vivo at 37°C.

Focused ultrasound (FUS), especially when augmented by microbubbles (MBs), shows the potential for noninvasive ablation of deep-seated tumors, but its clinical adoption is hindered due to its dependency on multiple controllable parameters of FUS and MBs. To accelerate the clinical transition of this noninvasive and target therapy, a virtual lab featuring a two-way coupled Euler-Lagrange computation platform, capable of capturing physics down to individual MBs thus their nonlinear interactions, has been developed to accurately predict the acoustic and thermal fields for microbubble-augmented FUS (MBaFus), and subsequently the resultant temperature rise at the treatment spots. This technical brief concisely summarizes the main features of its numerical algorithms for prediction and high-performance computing schemes for speedup, as well as its preliminary validation against in vitro experiments. Recent progress on further evaluating the numerical virtual lab under ex vivo settings is reported, where FUS treatment for ex vivo porcine liver was conducted and MB augmentation effects to treatment outcome under different MB conditions were compared. It is found that the agreement between our numerical prediction and experimental measurements in the referred ex vivo study is reasonably satisfactory. Though more extensive validations are needed when extra ex vivo studies in the public domain become available, this intermediate progress illustrates the potential of this novel numerical platform serving as a virtual lab of microbubble-augmented FUS for noninvasive tumor ablation.

Tremor is a rhythmic, involuntary oscillatory movement that severely affects some aspects of a patient's daily life. The use of wearable tremor-suppressing orthoses has become an effective, noninvasive treatment method for controlling tremors. This article summarizes recent developments in upper limb tremor suppression orthoses, aiming to provide a foundation for future research. By analyzing the working mechanisms, degrees-of-freedom (DOFs), weight, and tremor suppression effectiveness of various types of orthoses, the following conclusions are drawn: We found that differences in the working mechanism and the number of suppression directions are related to the weight of the device; weight, in turn, is a major factor affecting the comfort of the orthoses; and the combination of the number and weight of the damping direction affects the effect of the damping equipment. Balancing these three factors should be a key focus of future research. Moreover, researchers are placing greater emphasis on the comfort of the wearer during the development of these orthoses.

Our group has developed a new nitinol endoluminal self-expandable device for microvascular anastomosis. It attaches to each vessel ending with opposite directed microspikes and reaches complete expansion at body temperature, using the nitinol shape memory capacity. The main purpose of this first in vivo trial is to evaluate the mechanical viability of the device and its immediate and early functionality. A recuperation study with seven New Zealand White rabbits was designed. A 1.96 mm outer diameter prototype of the new device was placed on the right femoral artery of each rabbit. Each anastomosis was reassessed on the seventh postoperative day to reevaluate the device function. The average anastomosis time with the new device was 18 min and 45 seg (±0.3 seg). It could be easily placed in all the cases with an average of 1.14 (1) complementary stitches needed to achieve a sealed anastomosis. Patency test was positive for all the cases on the immediate assessment. On the 1 week revision surgery, patency test was negative for the seven rabbits due to blood clot formation inside the device. The new device that we have developed is simple to use and shows correct immediate functionality. On the early assessment, the presence of a foreign body in the endoluminal space caused blood clot formation. We speculate that a heparin eluting version of the device could avoid thrombosis formation. We consider that the results obtained can be valuable for other endoluminal sutureless devices.

Magnetic resonance imaging (MRI) can provide high contrast soft tissue visualization without ionizing radiation, which makes it an attractive imaging modality for interventional procedures. However, the strong magnetic and radio frequency (RF) fields impose significant challenges to the development of robotic systems within the magnetic resonance environment. Consequently, designing MRI-compatible actuators is crucial for advancing MRI-guided robotic systems. This paper reports the design, control, and characterization of a gear-based pneumatic stepper motor. The motor is designed with three actuating piston units and a geared rotor. The three actuating pistons are driven sequentially by compressed air to push the geared rotor and to generate bidirectional stepwise motion. Experiments were conducted to characterize the motor in terms of torque, speed, control, and MRI compatibility. The results demonstrate that the motor can deliver a maximum continuous torque of 1300 mNm at 80 pounds per square inch (PSI) (0.55 MPa) with 9 m air hoses. The closed-loop control evaluation demonstrates the steady-state error of position tracking was 0.81±0.52 deg. The MRI compatibility study indicated negligible image quality degradation. Therefore, the proposed pneumatic stepper motor can effectively serve as an actuator for MRI-guided robotic applications.

During mechanical ventilation, lung function and gas exchange in structurally heterogeneous lungs may be improved when volume oscillations at the airway opening are applied at multiple frequencies simultaneously, a technique referred to as multifrequency oscillatory ventilation (MFOV). This is in contrast to conventional high-frequency oscillatory ventilation (HFOV), for which oscillatory volumes are applied at a single frequency. In the present study, as a means of fully realizing the potential of MFOV, we designed and tested a computer-controlled hybrid oscillatory ventilator capable of generating the flows, tidal volumes, and airway pressures required for MFOV, HFOV, conventional mechanical ventilation (CMV), as well as oscillometric measurements of respiratory impedance. The device employs an iterative spectral feedback controller to generate a wide range of oscillatory waveforms. The performance of the device meets that of commercial mechanical ventilators in volume-controlled mode. Oscillatory modes of ventilation also meet design specifications in a mechanical test lung, over frequencies from 4 to 20 Hz and mean airway pressure from 5 to 30 cmH₂O. In proof-of-concept experiments, the oscillatory ventilator maintained adequate gas exchange in a porcine model of acute lung injury, using combinations of conventional and oscillatory ventilation modalities. In summary, our novel device is capable of generating a wide range of conventional and oscillatory ventilation waveforms with potential to enhance gas exchange, while simultaneously providing less injurious ventilation.

Modification of cerebrospinal fluid (CSF) transport dynamics is an expanding method for treating central nervous system injury and diseases. One application of this route is to modify the distribution of solutes in the CSF; however, few tools currently exist for this purpose. The present study describes the use of a subject-specific in vitro CSF phantom to perform a parametric evaluation of the Neurapheresis™ CSF Management System (NP) for both CSF filtration and intrathecal drug circulation. An in vitro CSF phantom was constructed which included realistic anatomy for the complete subarachnoid space (SAS). This platform was configured to test multiple parametric modifications of a dual-lumen catheter and filtration system. Calibrated mapping of tracer distribution and area under the curve (AUC) measurements were used to compare filtration and intrathecal-circulation schemes using the NP device versus the clinical standards of care. The NP device showed potential advantages over lumbar drain (LD) for clearance of simulated subarachnoid hemorrhage (SAH), especially in the spinal canal. Use of the NP device in combination with simulated intracerebroventricular (ICV) drug infusion resulted in an increased extent and uniformity of tracer spread compared to ICV alone. NP improved clearance of simulated subarachnoid hemorrhage compared to LD and increased uniformity of tracer concentration via simulated ICV, providing support for NP use in these scenarios. The in vitro CSF phantom system presented here quantitatively described the effects of parametric boundary modification on solute distribution in the intrathecal space.