Annular Fiber Probe for Interstitial Illumination in Photoacoustic Guidance of Radiofrequency Ablation

Unresectable liver tumors are commonly treated with percutaneous radiofrequency ablation (RFA). However, this technique is associated with high recurrence rates due to incomplete tumor ablation. Accurate image guidance of the RFA procedure contributes to successful ablation, but currently used imaging modalities have shortcomings in device guidance and treatment monitoring. We explore the potential of using photoacoustic (PA) imaging combined with conventional ultrasound (US) imaging for real-time RFA guidance. To overcome the low penetration depth of light in tissue, we have developed an annular fiber probe (AFP), which can be inserted into tissue enabling interstitial illumination of tissue. The AFP is a cannula with 72 optical fibers that allows an RFA device to slide through its lumen, thereby enabling PA imaging for RFA device guidance and ablation monitoring. We show that the PA signal from interstitial illumination is not affected by absorber-to-surface depth compared to extracorporeal illumination. We also demonstrate successful imaging of the RFA electrodes, a blood vessel mimic, a tumor-mimicking phantom, and ablated liver tissue boundaries in ex vivo chicken and bovine liver samples. PA-assisted needle guidance revealed clear needle tip visualization, a notable improvement to current US needle guidance. Our probe shows potential for RFA device guidance and ablation detection, which potentially aids in real-time monitoring.

A Novel Protocol of Continuous Navigation Guidance for Endoscopic Third Ventriculostomy

BACKGROUND: Although considered a standard neurosurgical procedure, endoscopic third ventriculostomy (ETV) is associated with a relatively high complication rate that is predominantly related to malpositioning of the trajectory. OBJECTIVE: To develop an advanced navigation protocol for ETV, assess its possible benefits over commonly used ETV trajectories, and apply this protocol during surgery. METHODS: After development of our advanced protocol, the imaging data of 59 patients who underwent ETV without navigation guidance was transferred to our navigation software. An individualized endoscope trajectory was created according to our protocol in all cases. This trajectory was compared with 2 standard trajectories, especially with regard to the distance to relevant neuronal structures: a trajectory manually measured on preoperative radiological images, as performed in all 59 cases, and a trajectory resulting from a commonly used fixed coronal burr hole. Subsequently, we applied the protocol in 15 ETVs to assess the feasibility and procedural complications. RESULTS: Our individualized trajectory resulted in a significantly greater distance to the margins of the foramen of Monro, and the burr hole was located more posteriorly from the coronal suture in comparison with the standard trajectories. The advanced ETV technique was feasible in all 15 procedures, and no major complications occurred in any procedure. In 1 patient, a fornix contusion without clinical correlation was observed. CONCLUSION: Our data indicate that the proposed navigation protocol for ETV optimizes the distance of the endoscope to important neuronal structures. Continuous endoscope and puncture device guidance may further add to the safety of this procedure.

Development of Operation Interface for Machine Tool Using 6-DOF Haptic Device - Guidance of Tool Movement Using Force Sense

In the previous report, the operation interface for multi-axis controlled machine tools was developed by using the haptic device that is used in the field of virtual reality and it was changed from a haptic device with 3-DOF to that with 6-DOF. In order to improve the system, more useful functions should be added. In this report, the function to guide the tool in consideration of the tools characteristics is developed. The square end mill cannot cut at its bottom part. So, when the bottom part contacts the removal shape, the square end mill should be guided into a posture contacting at the side part by the force sense. The experiment supposed that the machining of the curved surface had been done. In the case of using the developed function, the number of contacts at the bottom part of the tool was decreased. As a result, the usefulness of the developed function was confirmed.

Obstacle Detection System Based on Stereo Vision and a Structured Light

Obstacle detection is a crucial issue for pilotless device guidance function and it has to be performed with high reliability to avoid any potential collision with the front object. The vision-based obstacle detection systems are regarded perfect for this purpose because they require little on all kind of condition. In this paper, an obstacle detection system using stereo vision sensors and structured light is developed. This system realizes rapid feature matching and high precision measurement distance with the help of structured light, avoiding the time-consuming of the initial corresponding pairs. After the initial detection, the system executes the tracking light strip algorithm for the obstacles. The proposed system can detect a front obstacle in vision field and obtain the size of obstacle. The proposed obstacle detection system is set up and its performance is verified experimentally

Guidewire Reproducibilty and Modeling

The number of minimally invasive vascular interventions is increasing, and the device most frequently used is a guidewire, along which devices are delivered to the intervention site. Procedural failure can occur due to improper guidewire and∕or device selection. To facilitate guidewire and device guidance, we investigated the reproducibility of guidewire paths in vessel phantoms. Several trained users repeatedly passed guidewires of different flexibility through the phantoms under pulsatile flow conditions. Afterwards, the 3D paths were reconstructed and compared. In addition, the 3D paths were calculated using graph representation techniques. Points in the vessel lumen in planes perpendicular to the vessel centerline were generated. All points in adjacent planes were joined generating a vector set in a graph representation in which the edge weights were functions of the angle between contiguous vectors. The optimal path through this weighted directed graph was then determined using a Dijkstra’s (shortest path) algorithm. The guidewire paths appear reproducible across users but not across materials. The average RMS difference of repeated placements was 0.17±0.02mm (plastic-coated guidewire), 0.73±0.55mm (steel guidewire) and 1.15±0.65mm (steel vs plastic-coated). For the guidewire modeling, the average RMS distance between the actual and simulated guidewire path was 0.7mm; computation time was 3s. For a given guidewire, these results indicate that the guidewire path is relatively reproducible in shape and position. The ability to predict the guidewire path inside vessels may facilitate calculation of vessel-branch access and force estimation.