Ruler Based Automatic C-Arm Image Stitching Without Overlapping Constraint.

In this paper, we propose a new method for stitching multiple fluoroscopic images taken by a C-arm instrument. We employ an X-ray radiolucent ruler with numbered graduations while acquiring the images, and the image stitching is based on detecting and matching ruler parts in the images to the corresponding parts of a virtual ruler. To achieve this goal, we first detect the regular spaced graduations on the ruler and the numbers. After graduation labeling, for each image, we have the location and the associated number for every graduation on the ruler. Then, we initialize the panoramic X-ray image with the virtual ruler, and we "paste" each image by aligning the detected ruler part on the original image, to the corresponding part of the virtual ruler on the panoramic image. Our method is based on ruler matching but without the requirement of matching similar feature points in pairwise images, and thus, we do not necessarily require overlap between the images. We tested our method on eight different datasets of X-ray images, including long bones and a complete spine. Qualitative and quantitative experiments show that our method achieves good results.

Correction to: On the reproducibility of expert-operated and robotic ultrasound acquisitions.

The original version of this article unfortunately contained a mistake.

On the reproducibility of expert-operated and robotic ultrasound acquisitions.

PURPOSE: We present the evaluation of the reproducibility of measurements performed using robotic ultrasound imaging in comparison with expert-operated sonography. Robotic imaging for interventional procedures may be a valuable contribution, but requires reproducibility for its acceptance in clinical routine. We study this by comparing repeated measurements based on robotic and expert-operated ultrasound imaging. METHODS: Robotic ultrasound acquisition is performed in three steps under user guidance: First, the patient is observed using a 3D camera on the robot end effector, and the user selects the region of interest. This allows for automatic planning of the robot trajectory. Next, the robot executes a sweeping motion following the planned trajectory, during which the ultrasound images and tracking data are recorded. As the robot is compliant, deviations from the path are possible, for instance due to patient motion. Finally, the ultrasound slices are compounded to create a volume. Repeated acquisitions can be performed automatically by comparing the previous and current patient surface. RESULTS: After repeated image acquisitions, the measurements based on acquisitions performed by the robotic system and expert are compared. Within our case series, the expert measured the anterior-posterior, longitudinal, transversal lengths of both of the left and right thyroid lobes on each of the 4 healthy volunteers 3 times, providing 72 measurements. Subsequently, the same procedure was performed using the robotic system resulting in a cumulative total of 144 clinically relevant measurements. Our results clearly indicated that robotic ultrasound enables more repeatable measurements. CONCLUSIONS: A robotic ultrasound platform leads to more reproducible data, which is of crucial importance for planning and executing interventions.

The First Interlaced Continuum Robot, Devised to Intrinsically Follow the Leader.

Flexible probes that are safely deployed to hard-to-reach targets while avoiding critical structures are strategic in several high-impact application fields, including the biomedical sector and the sector of inspections at large. A critical problem for these tools is the best approach for deploying an entire tool body, not only its tip, on a sought trajectory. A probe that achieves this deployment is considered to follow the leader (or to achieve follow-the-leader deployment) because its body sections follow the track traced by its tip. Follow-the-leader deployment through cavities is complicated due to a lack of external supports. Currently, no definitive implementation for a probe that is intrinsically able to follow the leader, i.e., without relying on external supports, has been achieved. In this paper, we present a completely new device, namely the first interlaced continuum robot, devised to intrinsically follow the leader. We developed the interlaced configuration by pursuing a conceptual approach irrespective of application-specific constraints and assuming two flexible tools with controllable stiffness. We questioned the possibility of solving the previously mentioned deployment problem by harnessing probe symmetry during the design process. This study examines the entire development of the novel interlaced probe: model-based conceptual design, detailed design and prototyping, and preliminary experimental assessment. Our probe can build a track with a radius of curvature that is as small as twice the probe diameter, which enables it to outperform state-of-the-art tools that are aimed at follow-the-leader deployment. Despite the limitations that are inherently associated with its original character, this study provides a prototypical approach to the design of interlaced continuum systems and demonstrates the first interlaced continuum probe, which is intrinsically able to follow the leader.

Dual-robot ultrasound-guided needle placement: closing the planning-imaging-action loop.

PURPOSE: Precise needle placement is an important task during several medical procedures. Ultrasound imaging is often used to guide the needle toward the target region in soft tissue. This task remains challenging due to the user's dependence on image quality, limited field of view, moving target, and moving needle. In this paper, we present a novel dual-robot framework for robotic needle insertions under robotic ultrasound guidance. METHOD: We integrated force-controlled ultrasound image acquisition, registration of preoperative and intraoperative images, vision-based robot control, and target localization, in combination with a novel needle tracking algorithm. The framework allows robotic needle insertion to target a preoperatively defined region of interest while enabling real-time visualization and adaptive trajectory planning to provide safe and quick interactions. We assessed the framework by considering both static and moving targets embedded in water and tissue-mimicking gelatin. RESULTS: The presented dual-robot tracking algorithms allow for accurate needle placement, namely to target the region of interest with an error around 1 mm. CONCLUSION: To the best of our knowledge, we show the first use of two independent robots, one for imaging, the other for needle insertion, that are simultaneously controlled using image processing algorithms. Experimental results show the feasibility and demonstrate the accuracy and robustness of the process.