1,720,989 research outputs found
AN INNOVATIVE SYSTEM BASED ON BIOIMPEDANCE MEASUREMENTS TO DEFINE THE BLADDER VOLUME
No full textObjectives: Alteration of the bladder sense of fullness due to spinal cord injury or radical cystectomy leads to the inability to plan micturition timing. The development of a system for the fullness detection would be highly desirable and would enable autonomous and spontaneous management of micturition by the patient. Here the design of an innovative system of bladder volume monitoring based on bioimpedance measurements is presented.
Methods: Bioimpedance measurements are performed on ex-vivo bladder tissue using traditional ECG sensors. Two couples of electrodes in different arrangements were applied on the bladder walls to detect degree of filling by 50ml step, from 0ml to 300ml. The bioimpedance values are obtained for frequencies ranging from 1 kHz to 2 MHz. Moreover, different compositions of artificial urine were tested, by varying relevant ions concentration.
Results: The impedance variations were recorded around 20ohm in average from empty to full status. However, the impedance variation was dependent to ion concentration in urine.
Discussion: The experiment shows the feasibility of this approach and the need to find the sensors arrangement able to normalize measurements with respect to urine composition.
Conclusions: A novel system to detect the bladder filling based on bioimpedence measures is reported. This approach could be feasible both in presence of natural or artificial/reconstructed bladder. Future work will target accurate volume estimation independently on urine composition, as well as combination with other sensing strategies.
Acknowledgements: The authors acknowledge INAIL (Istituto Nazionale Assicurazioni Infortuni sul Lavoro) for providing their collaboration within the BioSUP project
Ultrasound Acoustic Phase Analysis Enables Robotic Visual-Servoing of Magnetic Microrobots
Full text linkMicrorobots (MRs) have attracted growing interest for their potentialities in diagnosis and noninvasive intervention in hard-to-reach body areas. The safe operation of biomedical MRs requires fine control capabilities, which strongly depend on precise and robust feedback about their position over time. Ultrasound acoustic phase analysis (US-APA) may allow for a reliable feedback strategy for MR imaging and tracking in tissue. In this article, we combine task-specific magnetic actuation and related US-APA motion tracking to achieve closed-loop navigation of a magnetic MR, rolling on the boundary of a lumen in a tissue-mimicking phantom. A C-arm system attached to a robotic platform is used to precisely position the magnetic actuation source and US-APA detection unit within the workspace, thus enabling MR visual-servoing. In the first place, the proposed approach allows to perform supervised localization of the MR without any a-priori knowledge of its position. After localization, a robust real-time tracking enables closed-loop MR teleoperation in the phantom lumina over a travel distance of 80 mm (145 body lengths), both in static and counter flow, thus achieving an average position tracking error of 368 micron (0.67 body lengths). For the first time, our results validate US-APA as a reliable feedback strategy for visual-servoing control of MRs in simulated in-body environment
Urinary Bladder Volume Reconstruction Based on Bioimpedance Measurements: Ex Vivo and In Vivo Validation Through Implanted Patch and Needle Electrodes
Full text linkPreliminary Design and Validation of an Implantable Artificial Bladder
No full textSubstituting the functionalities of natural organs with artificial devices is an ambitious bioengineering challenge. This study proposes an artificial solution for the restoration of natural bladder functionalities (e.g. upon natural bladder removal for cancer treatment). The design of the artificial bladder system (ABS) is tailored around clinical needs. On one hand, a smart structural design enables to functionalize the internal walls with proper materials and to prevent reflux with custom unidirectional valves. On the other hand, a novel magnetic sensing strategy, combined with embedded electronics for efficient powering and wireless data transfer, allows to potentially restore bladder filling sensitivity. The performances of the system were validated preliminarily on the bench, achieving relative error in volume estimation below 12%. Finally, cadaver experiments allowed to demonstrate the implantability and the overall feasibility of the proposed solution, confirming the stability of wireless connection within a 100 cm distance from the implant
Real-time imaging and tracking of microrobots in tissues using ultrasound phase analysis
Full text linkUltrasound B-mode imaging has been employed to monitor single agents and collective swarms of microrobots in vitro and ex vivo in controlled experimental conditions. However, low contrast and spatial resolution still limit the effective employment of such a method in a medical microrobotic scenario. Doppler-based ultrasound appears as a promising tool for tracking microrobots in echogenic and dynamic environments as biological tissues. In this Letter, we demonstrate that microrobot displacements can be used as a special signature for their visualization within echogenic media, where B-mode fails. To this aim, we induced vibrations of a magnetic soft microrobot through alternated magnetic fields and used ultrasound phase analysis to derive microrobot features such as size and position over time. By exploiting vibrations, we were able to perform imaging and tracking of a low contrast microrobot both in tissue-mimicking phantom and in chicken breast. The axial resolution was 38 μm, which is four times smaller than the B-mode resolution with the employed equipment. We also performed real-time tracking of the microrobot's positions along linear trajectories with a linear velocity up to 1 mm/s. Overall, the reported results pave the way for the application of the proposed approach for the robust monitoring of medical microrobots in tissue
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Contrast-enhanced ultrasound tracking of helical propellers with acoustic phase analysis and comparison with color Doppler
Full text linkMedical microrobots (MRs) hold the potential to radically transform several interventional procedures. However, to guarantee therapy success when operating in hard-to-reach body districts, a precise and robust imaging strategy is required for monitoring and controlling MRs in real-time. Ultrasound (US) may represent a powerful technology, but MRs' visibility with US needs to be improved, especially when targeting echogenic tissues. In this context, motions of MRs have been exploited to enhance their contrast, e.g., by Doppler imaging. To exploit a more selective contrast-enhancement mechanism, in this study, we analyze in detail the characteristic motions of one of the most widely adopted MR concepts, i.e., the helical propeller, with a particular focus on its interactions with the backscattered US waves. We combine a kinematic analysis of the propeller 3D motion with an US acoustic phase analysis (APA) performed on the raw radio frequency US data in order to improve imaging and tracking in bio-mimicking environments. We validated our US-APA approach in diverse scenarios, aimed at simulating realistic in vivo conditions, and compared the results to those obtained with standard US Doppler. Overall, our technique provided a precise and stable feedback to visualize and track helical propellers in echogenic tissues (chicken breast), tissue-mimicking phantoms with bifurcated lumina, and in the presence of different motion disturbances (e.g., physiological flows and tissue motions), where standard Doppler showed poor performance. Furthermore, the proposed US-APA technique allowed for real-time estimation of MR velocity, where standard Doppler failed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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