Intelligent magnetic manipulation for gastrointestinal ultrasound

Abstract

Diagnostic endoscopy in the gastrointestinal tract has remained largely unchanged for decades and is limited to the visualization of the tissue surface, the collection of biopsy samples for diagnoses, and minor interventions such as clipping or tissue removal. In this work, we present the autonomous servoing of a magnetic capsule robot for in-situ, subsurface diagnostics of microanatomy. We investigated and showed the feasibility of closed-loop magnetic control using digitized microultrasound (μUS) feedback; this is crucial for obtaining robust imaging in an unknown and unconstrained environment. We demonstrated the functionality of an autonomous servoing algorithm that uses μUS feedback, both on benchtop trials as well as in-vivo in a porcine model. We have validated this magnetic-μUS servoing in instances of autonomous linear probe motion and were able to locate markers in an agar phantom with 1.0 ± 0.9 mm position accuracy using a fusion of robot localization and μUS image information. This work demonstrates the feasibility of closed-loop robotic μUS imaging in the bowel without the need for either a rigid physical link between the transducer and extracorporeal tools or complex manual manipulation.

Fig. 1.. System Description.

(A) A conceptual image of the in-vivo RCE showing real-time acquisition of localized μUS images where ultrasonic features consistent with the histological layers of the bowel wall have been annotated. The RCE contains (a) μUS transducers, (b) an LED light source, (c) an irrigation channel, (d) a camera, (e) an I PM with circuitry that facilitates real-time pose estimation of the device, and (f) a soft, flexible tether. (B) The benchtop setup, showing key components, as well as a close-up view of the RCE prototype.

Fig. 2.. B-Scans generated during RCE benchtop trials.

(A) B-scan images with the corresponding tilt and tissue-coupling force, collected during a force sensitivity test. The black arrow identifies a wall-echo from our phantom. (B) Autonomous echo detection “Echo maintenance” routine with three disturbances. The wall-echo from the phantom is indicated by black arrows. The change in the observed depth of the back wall is attributed to variability in the phantom thickness, RCE contact force, RCE tilt, and thickness of coupling medium.

Fig. 3.. Experimental setup and results for in-vivo evaluation of our RCE.

(A) The in-vivo experimental setup in the endoscopy suite. (B) A B-Scan acquired during an in-vivo trial and the corresponding ESR with the set threshold (red dashed line). Features, characteristic of bowel wall layers, are annotated with black arrows. A deeper, tissue feature is shown with a white arrow.

Fig. 4.. System schematic.

A diagram that summarizes the major components in the system and the data flow between them.

Fig. 5.. Block diagram control schematic of our RCE system.

The US system components are shown in yellow, the magnetic control system is shown in blue, and the auxiliary inputs and outputs are shown in green.