Analytical Computation of the Contact Force Jacobian for MRI-Actuated Robotic Catheter.

Contact force Jacobian relates the changes in the contact force to the changes in the actuation of a robotic catheter in contact with a surface. In this paper, we present an analytical method for calculating the contact force Jacobian for the Cosserat rod model of an MRI-actuated robotic catheter. First, the Cosserat rod model of the MRI-actuated robotic catheter under tip contact position constraint is introduced. For the analytical derivation of contact force Jacobian, the initial value problem parameter derivatives are defined and calculated analytically. Finally, simulation results show that the presented analytical method calculates the contact force Jacobian in significantly shorter computation time with comparable accuracy, compared to direct numerical computation.

Photoacoustic-based catheter tracking: simulation, phantom, and in vivo studies.

Catheters are commonly used in many procedures and tracking and localizing them is critical to patient safety and surgical success. The standard of care for catheter tracking is with the use of fluoroscopy. Alternatives using conventional tracking technologies such as electromagnetic trackers have been previously explored. This work explores the use of an emerging imaging modality, photoacoustics, as a means for tracking. A piezoelectric (PZT) sensor is placed at the tip of the catheter, allowing it to receive the acoustic signals generated from photoacoustic markers due to the photoacoustic effect. The locations of these photoacoustic markers are determined by a stereo-camera and the received acoustic signals are converted into distances between the PZT element and the photoacoustic markers. The location of the PZT sensor can be uniquely determined following a multilateration process. This work validates this photoacoustic tracking method in phantom, simulation, and in vivo scenarios using metrics including reconstruction precision, relative accuracy, estimated accuracy, and leave-out accuracy. Submillimeter tracking results were achieved in phantom experiments. Simulation studies evaluated various physical parameters relating to the photoacoustic source and the PZT sensor. In vivo results showed feasibility for the eventual deployment of this technology.

A novel robotic monofilament test for diabetic neuropathy.

OBJECTIVE: The use of the Semmes-Weinstein (SW) monofilament test is recommended as a screening method for diabetic neuropathy. It offers an important chance to prevent further complications of diabetic foot. We aimed to develop a prototype Robotic Monofilament Inspector that can be used as a standard machine for screening of diabetic neuropathy. METHODS: Development was divided into three parts: computer software, control box, and Robotic Monofilament Inspector. The examiner conducted the SW test (by hand and by robotic inspector), vibration perception threshold, and Toronto Clinical Scoring System without knowledge of patient information. The unpaired t test or Wilcoxon rank-sum test was used to determine the differences between independent groups in terms of continuous outcomes, while the χ(2) test was used to determine categorical outcomes. Agreement between the various diabetic neuropathy tests was measured using the kappa statistic. RESULTS: The SW test and vibration perception threshold were more valid tests for neuropathy than the Toronto test. The robotic test was in excellent agreement with the two former tests and appeared to be valid (kappa statistic, 0.35-0.81). Another indirect evidence for the validity of the robotic test was the finding that diabetic patients with foot ulcers had a higher prevalence of neuropathy (77%vs. 38%). This might indicate that the robotic test was more valid than the manual test. CONCLUSION: The Robotic Monofilament Inspector could be used as a simple screening machine. This prototype may be developed further for routine clinical use.