Automated three-dimensional vessel reconstruction based on deep segmentation and bi-plane angiographic projections.

Automated three-dimensional (3D) blood vessel reconstruction to improve vascular diagnosis and therapeutics is a challenging task in which the real-time implementation of automatic segmentation and specific vessel tracking for matching artery sequences is essential. Recently, a deep learning-based segmentation technique has been proposed; however, existing state-of-the-art deep architectures exhibit reduced performance when they are employed using real in-vivo imaging because of serious issues such as low contrast and noise contamination of the X-ray images. To overcome these limitations, we propose a novel methodology composed of the de-haze image enhancement technique as pre-processing and multi-level thresholding as post-processing to be applied to the lightweight multi-resolution U-shaped architecture. Specifically, (1) bi-plane two-dimensional (2D) vessel images were extracted simultaneously using the deep architecture, (2) skeletons of the vessels were computed via a morphology operation, (3) the corresponding skeleton structure between image sequences was matched using the shape-context technique, and (4) the 3D centerline was reconstructed using stereo geometry. The method was validated using both in-vivo and in-vitro models. The results show that the proposed technique could improve the segmentation quality, reduce computation time, and reconstruct the 3D skeleton automatically. The algorithm accurately reconstructed the phantom model and the real mouse vessel in 3D in 2 s. Our proposed technique has the potential to allow therapeutic micro-agent navigation in clinical practice, thereby providing the 3D position and orientation of the vessel.

Guide-Wired Helical Microrobot for Percutaneous Revascularization in Chronic Total Occlusion in-Vivo Validation.

OBJECTIVE: For the revascularization in small vessels such as coronary arteries, we present a guide-wired helical microrobot mimicking the corkscrew motion for mechanical atherectomy that enables autonomous therapeutics and minimizing the radiation exposure to clinicians. METHODS: The microrobot is fabricated with a spherical joint and a guidewire. A previously developed external electromagnetic manipulation system capable of high power and frequency is incorporated and an autonomous guidance motion control including driving and steering is implemented in the prototype. We tested the validity of our approach in animal experiments under clinical settings. For the in vivo test, artificial thrombus was fabricated and placed in a small vessel and atherectomy procedures were conducted. RESULTS: The devised approach enables us to navigate the helical robot to the target area and successfully unclog the thrombosis in rat models in vivo. CONCLUSION: This technology overcomes several limitations associated with a small vessel environment and promises to advance medical microrobotics for real clinical applications while achieving intact operation and minimizing radiation exposures to clinicians. SIGNIFICANCE: Advanced microrobot based on multi-discipline technology could be validated in vivo for the first time and that may foster the microrobot application at clinical sites.

Multifunctional Biodegradable Microrobot with Programmable Morphology for Biomedical Applications.

We described a magnetic chitosan microscaffold tailored for applications requiring high biocompatibility, biodegradability, and monitoring by real-time imaging. Such magnetic microscaffolds exhibit adjustable pores and sizes depending on the target application and provide various functions such as magnetic actuation and enhanced cell adhesion using biomaterial-based magnetic particles. Subsequently, we fabricated the magnetic chitosan microscaffolds with optimized shape and pore properties to specific target diseases. As a versatile tool, the capability of the developed microscaffold was demonstrated through in vitro laboratory tasks and in vivo therapeutic applications for liver cancer therapy and knee cartilage regeneration. We anticipate that the optimal design and fabrication of the presented microscaffold will advance the technology of biopolymer-based microscaffolds and micro/nanorobots.

Magnetic Control of a Flexible Needle in Neurosurgery.

Minimally invasive neurosurgery does not require large incisions and openings in the skull to access the desired brain region, which often results in a faster recovery with fewer complications than traditional open neurosurgery. For disorders treated by the implantation of neurostimulators and thermocoagulation probes, current procedures incorporate a straight rigid needle, which restricts surgical trajectories and limits the number of possible targets and degrees of freedom at the respective target. A steerable needle with a flexible body could overcome these limitations. In this paper, we present a flexible needle steering system with magnetic and fluoroscopic guidance for neurosurgical procedures. A permanent magnet at the proximal end of a flexible needle is steered by an external magnetic field, and the resultant tip-deflection angle bends the flexible body like a bevel-tip needle. We implemented a kinematic model for the magnetic needle derived from a nonholonomic bicycle model and a closed-loop control strategy with feed-forward and feed-back components using a chained-form transformation. The proposed needle steering method was investigated through in vitro and ex vivo experiments.

3D path planning for flexible needle steering in neurosurgery.

BACKGROUND: We propose a 3D path planning method to steer flexible needles along curved paths in the context of deep brain stimulation (DBS) procedures. METHODS: Our approach is based on a rapidly exploring random tree strategy, and it takes into account constraints coming from anatomical obstacles and physical constraints dictated by flexible needle kinematics. The strategy is evaluated in simulation on a realistic 3D CAD model of the brain. RESULTS: The subthalamic nucleus (STN) and the fornix can be reached along several curved paths from various entry points. As compared with the usual straight line path, these curved paths avoid tissue damage to important neural structures while allowing for a much greater selection of entry points. CONCLUSIONS: This path planning method offers alternative curved paths to reach DBS targets with flexible needles. The method potentially leads to safer paths and additional entry points capable of reaching the desired stimulation targets.

Programmable Locomotion Mechanisms of Nanowires with Semihard Magnetic Properties Near a Surface Boundary.

We report on the simplest magnetic nanowire-based surface walker that is able to change its propulsion mechanism near a surface boundary as a function of the applied rotating magnetic field frequency. The nanowires are made of CoPt alloy with semihard magnetic properties synthesized by means of template-assisted galvanostatic electrodeposition. The semihard magnetic behavior of the nanowires allows for programming their alignment with an applied magnetic field as they can retain their magnetization direction after premagnetizing them. By engineering the macroscopic magnetization, the nanowires' speed and locomotion mechanism are set to tumbling, precession, or rolling depending on the frequency of an applied rotating magnetic field. Also, we present a mathematical analysis that predicts the translational speed of the nanowire near the surface, showing a very good agreement with experimental results. Interestingly, the maximal speed is obtained at an optimal frequency (∼10 Hz), which is far below the theoretical step-out frequency (∼345 Hz). Finally, vortices are found by tracking polystyrene microbeads, trapped around the CoPt nanowire, when they are propelled by precession and rolling motion.

Multiwavelength Light-Responsive Au/B-TiO2 Janus Micromotors.

Conventional photocatalytic micromotors are limited to the use of specific wavelengths of light due to their narrow light absorption spectrum, which limits their effectiveness for applications in biomedicine and environmental remediation. We present a multiwavelength light-responsive Janus micromotor consisting of a black TiO2 microsphere asymmetrically coated with a thin Au layer. The black TiO2 microspheres exhibit absorption ranges between 300 and 800 nm. The Janus micromotors are propelled by light, both in H2O2 solutions and in pure H2O over a broad range of wavelengths including UV, blue, cyan, green, and red light. An analysis of the particles' motion shows that the motor speed decreases with increasing wavelength, which has not been previously realized. A significant increase in motor speed is observed when exploiting the entire visible light spectrum (>400 nm), suggesting a potential use of solar energy, which contains a great portion of visible light. Finally, stop-go motion is also demonstrated by controlling the visible light illumination, a necessary feature for the steerability of micro- and nanomachines.

Catalytic Locomotion of Core-Shell Nanowire Motors.

We report Au/Ru core-shell nanowire motors. These nanowires are fabricated using our previously developed electrodeposition-based technique, and their catalytic locomotion in the presence of H2O2 is investigated. Unlike conventional bimetallic nanowires that are self-electroosmotically propelled, our open-ended Au/Ru core-shell nanowires show both a noticeable decrease in rotational diffusivity and increase in motor speed with increasing nanowire length. Numerical modeling based on self-electroosmosis attributes decreases in rotational diffusivity to the formation of toroidal vortices at the nanowire tail, but fails to explain the speed increase with length. To reconcile this inconsistency, we propose a combined mechanism of self-diffusiophoresis and electroosmosis based on the oxygen gradient produced by catalytic shells. This mechanism successfully explains not only the speed increase of Au/Ru core-shell nanomotors with increasing length, but also the large variation in speed among Au/Ru, Au/Rh, and Rh/Au core-shell nanomotors. The possible contribution of diffusiophoresis to an otherwise well-established electroosmotic mechanism sheds light on future designs of nanomotors, at the same time highlighting the complex nature of nanoscale propulsion.

Inactivation of Escherichia coli O157:H7 in biofilm on food-contact surfaces by sequential treatments of aqueous chlorine dioxide and drying.

We investigated the efficacy of sequential treatments of aqueous chlorine and chlorine dioxide and drying in killing Escherichia coli O157:H7 in biofilms formed on stainless steel, glass, plastic, and wooden surfaces. Cells attached to and formed a biofilm on wooden surfaces at significantly (P ≤ 0.05) higher levels compared with other surface types. The lethal activities of sodium hypochlorite (NaOCl) and aqueous chlorine dioxide (ClO2) against E. coli O157:H7 in a biofilm on various food-contact surfaces were compared. Chlorine dioxide generally showed greater lethal activity than NaOCl against E. coli O157:H7 in a biofilm on the same type of surface. The resistance of E. coli O157:H7 to both sanitizers increased in the order of wood>plastic>glass>stainless steel. The synergistic lethal effects of sequential ClO2 and drying treatments on E. coli O157:H7 in a biofilm on wooden surfaces were evaluated. When wooden surfaces harboring E. coli O157:H7 biofilm were treated with ClO2 (200 µg/ml, 10 min), rinsed with water, and subsequently dried at 43% relative humidity and 22 °C, the number of E. coli O157:H7 on the surface decreased by an additional 6.4 CFU/coupon within 6 h of drying. However, when the wooden surface was treated with water or NaOCl and dried under the same conditions, the pathogen decreased by only 0.4 or 1.0 log CFU/coupon, respectively, after 12 h of drying. This indicates that ClO2 treatment of food-contact surfaces results in residual lethality to E. coli O157:H7 during the drying process. These observations will be useful when selecting an appropriate type of food-contact surfaces, determining a proper sanitizer for decontamination, and designing an effective sanitization program to eliminate E. coli O157:H7 on food-contact surfaces in food processing, distribution, and preparation environments.