RobUSt-An Autonomous Robotic Ultrasound System for Medical Imaging

Medical ultrasound (US) systems are widely used for the diagnosis of internal tissues. However, there are challenges associated with acquiring and interpreting US images, such as incorrect US probe placement and limited available spatial information. In this study, we expand the capabilities of medical US imaging using a robotic framework with a high level of autonomy. A 3D camera is used to capture the surface of an anthropomorphic phantom as a point cloud, which is then used for path planning and navigation of the US probe. Robotic positioning of the probe is realised using an impedance controller, which maintains stable contact with the surface during US scanning and compensates for uneven and moving surfaces. Robotic US positioning accuracy is measured to be 1.19 +/- 0.76mm. The mean force along US probe z-direction is measured to be 6.11 +/- 1.18N on static surfaces and 6.63 +/- 2.18N on moving surfaces. Overall lowest measured force of 1.58N demonstrates constant probe-to-surface contact during scanning. Acquired US images are used for the 3D reconstruction and multi-modal visualization of the surface and the inner anatomical structures of the phantom. Finally, K-means clustering is used to segment different tissues. Best segmentation accuracy of the jugular vein according to Jaccard similarity coefficient is measured to be 0.89. With such an accuracy, this system could substantially improve autonomous US acquisition and enhance the diagnostic confidence of clinicians

Intravascular Tracking of Micro-Agents Using Medical Ultrasound:Towards Clinical Applications

Objective: This study demonstrates intravascular micro-agent visualization by utilizing robotic ultrasound-based tracking and visual servoing in clinically-relevant scenarios. Methods: Visual servoing path is planned intraoperatively using a body surface point cloud acquired with a 3D camera and the vessel reconstructed from ultrasound (US) images, where both the camera and the US probe are attached to the robot end-effector. Developed machine vision algorithms are used for detection of micro-agents from minimal size of 250$\boldsymbol{\mu }$m inside the vessel contour and tracking with error recovery. Finally, real-time positions of the micro-agents are used for servoing of the robot with the attached US probe. Constant contact between the US probe and the surface of the body is accomplished by means of impedance control. Results: Breathing motion is compensated to keep constant contact between the US probe and the body surface, with minimal measured force of 2.02 N. Anthropomorphic phantom vessels are segmented with an Intersection-Over-Union (IOU) score of 0.93 $\pm$ 0.05, while micro-agent tracking is performed with up to 99.8% success rate at 28-36 frames per second. Path planning, tracking and visual servoing are realized over 80 mm and 120 mm long surface paths. Conclusion: Experiments performed using anthropomorphic surfaces, biological tissue, simulation of physiological movement and simulation of fluid flow through the vessels indicate that robust visualization and tracking of micro-agents involving human patients is an achievable goal

Intravascular Tracking of Micro-Agents Using Medical Ultrasound: Towards Clinical Applications

Objective: This study demonstrates intravascular micro-agent visualization by utilizing robotic ultrasound-based tracking and visual servoing in clinically-relevant scenarios. Methods: Visual servoing path is planned intraoperatively using a body surface point cloud acquired with a 3D camera and the vessel reconstructed from ultrasound (US) images, where both the camera and the US probe are attached to the robot end-effector. Developed machine vision algorithms are used for detection of micro-agents from minimal size of 250$\boldsymbol{\mu }$m inside the vessel contour and tracking with error recovery. Finally, real-time positions of the micro-agents are used for servoing of the robot with the attached US probe. Constant contact between the US probe and the surface of the body is accomplished by means of impedance control. Results: Breathing motion is compensated to keep constant contact between the US probe and the body surface, with minimal measured force of 2.02 N. Anthropomorphic phantom vessels are segmented with an Intersection-Over-Union (IOU) score of 0.93 $\pm$ 0.05, while micro-agent tracking is performed with up to 99.8% success rate at 28-36 frames per second. Path planning, tracking and visual servoing are realized over 80 mm and 120 mm long surface paths. Conclusion: Experiments performed using anthropomorphic surfaces, biological tissue, simulation of physiological movement and simulation of fluid flow through the vessels indicate that robust visualization and tracking of micro-agents involving human patients is an achievable goal

Optical and Electrical Simulations of Radiation-Hard Photodiode in 0.35μM High-Voltage CMOS Technology

Many imaging applications, like medical or space applications, require radiation-hard sensors. Generally, during radiation, many different defects are created, depending on the type of the radiation. With TCAD software, cross-section of a radiation-hard photodiode was simulated, and afterwards the impact of different physical parameters was simulated. Physical parameters like epitaxial layer thickness or the trap density in the bulk, play a huge role towards the responsivity of the photodiode. This paper presents a variation experiment, where relevant physical parameters are varied and analysis of the spectral responsivity and dark current of the photodiode is discussed

Impact of TCAD model parameters on optical and electrical characteristics of radiation-hard photodiode in 0.35 μ\mum CMOS technology

In this paper, a variability Design of Experiment (DoE) is performed on a radiation-hard photodiode structure in order to understand how the physical parameters of the device impact its spectral responsivity and dark current. The varied physical parameters describe the carrier mobility, lifetime, energy bandgap and recombination models. The electrical and optical performance of the device are simulated using TCAD software, as a function of varied physical parameters. The simulations are calibrated to the device measurements. The analysis of the design showed that the carrier lifetime is the most influencing parameter that impacts both the spectral responsivity and the dark current. Mobility parameters and Auger recombination parameters impact the spectral responsivity, while the energy bandgap at 340 K impacts the dark current. Finally, the model parameters that fit the measured dark current are obtained by the thorough variation simulations