Ultrasound-based visual servoing control of magnetic microrobot

Microrobots (MRs) hold the potential to revolutionize diagnosis and therapy. Thanks to their reduced dimensions, they have the ability to access and operate in hard-to-reach body districts performing submillimetric manipulation and targeted drug release. The safe operation of biomedical microrobots requires fine control capabilities, which strongly depends on precise and robust feedback about their position over time, and excellent movement abilities, essential to navigate in unstructured environments. In this thesis, a visual servoing platform for MR teleoperation has been developed. Magnetic actuation has been combined with ultrasound acoustic phase analysis (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 robotic arm was used to position the magnetic actuation source and US-APA detection unit within the workspace, thanks to a C-arm system. The end user interacts with the robotic platform thanks to an intuitive graphical user interface (GUI), setting several imaging parameters, and to a joystick-based human machine interface (HMI), enabling robotic arm teleoperation. In the first place, the proposed approach allowed to perform supervised localization of the MR without any a-priori knowledge of its position. After localization, a robust real-time tracking enabled 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). These results validate US-APA as a reliable feedback strategy for visual-servoing control of MRs in simulated in-body environment

Optical Flow and Acoustic Phase Analysis comparison in Ultrasound-based microrobot tracking

Micrometer-sized devices hold the potential to revolutionize medicine by improving diagnostic abilities, increasing therapeutic efficiency and reducing adverse effects. To safely operate microrobots (MRs) inside the human body, accurate localization strategies based on medical imaging should be adopted. Ultrasound (US) imaging has recently gained attention for medical robotics and microrobotics thanks to its noninvasiveness and real-time performances. In this letter we compare US Acoustic Phase Analysis (US-APA), a state-ofthe-art Phase tracking method, with US Optical Flow (US-OF), a computer vision Speckle tracking method. To this aim, different MRs dimensions, different locomotion strategies and working environments were considered. In particular, cylindrical magnetic MRs with diameters spanning from 1.20 down to 0.25 mm were fabricated. They were actuated in tissue-mimicking phantoms through a permanent magnet mounted on a robotic arm to reproduce intravascular rolling and in place vibration in tissue. US-OF proved to be comparable to US-APA in localizing vibrating MRs, achieving a tracking error comparable to one body length. It slightly improved localization during rolling, by consistently tracking the MR with errors lower than 0.6 body length. Additionally, US-OF outperformed US-APA in temporal performances, reaching an output rate forty times higher (about 40 Hz in USOF and about 1 Hz in US-APA). We believe that these results demonstrate the possible effective use of Optical Flow for MRs tracking, with a relevant advantage in terms of portability and intelligibility

A label-free immunoassay for Flavivirus detection by the Reflective Phantom Interface technology

Flaviviruses are widespread and cause clinically relevant arboviral diseases that impact locally and as imported travel-related infections. Direct detection of viraemia is limited, being typically undetectable at onset of symptoms. Therefore, diagnosis is primarily based on serology, which is complicated by high cross-reactivity across different species. The overlapping geographical distribution of the vectors in areas with a weak healthcare system, the increase of international travel and the similarity of symptoms highlight the need for rapid and reliable multi-parametric diagnostic tests in point-of-care formats. To this end we developed a bi-parametric serological microarray using recombinant NS1 proteins from Tick-borne encephalitis virus and West Nile virus coupled to a low-cost, label-free detection device based on the Reflective Phantom Interface (RPI) principle. Specific sequential detection of antibodies in solution demonstrates the feasibility of the approach for the surveillance and diagnosis of Flaviviruse

Pulmonary vascular function and exercise capacity in black sub-Saharan Africans.

Sex and age affect the pulmonary circulation.Whether there may be racial differences in pulmonary vascular function is unknown. Thirty white European Caucasian subjects (15 women) and age and body-size matched 30 black Sub-Saharan African subjects (15 women) underwent a cardio-pulmonary exercise test and exercise stress echocardiography with measurements of pulmonary artery pressure (PAP) and cardiac output (CO). A pulmonary vascular distensibility coefficient α was mathematically determined from the natural curvilinearity of multipoint mean PAP (mPAP)–CO plots. Maximum oxygen uptake (VO2max) and workload were higher in the whites, while maximum respiratory exchange ratio and ventilatory equivalents for CO2 were the same. Pulmonary hemodynamics were not different at rest. Exercise was associated with a higher maximum total pulmonary vascular resistance (TPVR), steeper mPAP-CO relationships and lower α coefficients in the blacks. These differences were entirely driven by higher slopes of mPAP-CO relationships (2.5 ± 0.7 vs 1.4 ± 0.7 mmHg/L/min, P < 0.001) and lower α coefficients (0.85 ± 0.33 vs 1.35 ± 0.51 %/mmHg, P < 0.01) in black men compared to white men. There were no differences in any of the hemodynamic variables between black and white women. In men only, the slopes of mPAP-CO relationships were inversely correlated to VO2max (P<0.01). Thus the pulmonary circulation is intrinsically less distensible in black sub-Saharan African men as compared to white Caucasian Europeans men, and this is associated with a lower exercise capacity. This study did not identify racial differences in pulmonary vascular function in women.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Réserve vasculaire pulmonaire et aptitude à l'effort chez les sujets noirs africains

info:eu-repo/semantics/publishe

Exercise Stress Echocardiography of Racial Differences in Pulmonary Vascular Function.

info:eu-repo/semantics/publishe

Effet de l’ethnicité sur la fonction vasculaire pulmonaire à l’effort: noirs Sub-sahariens vs caucasiens Européens

info:eu-repo/semantics/nonPublishe