Assistant Professor Vanderbilt University Nashville, Tennessee, United States
Introduction: Monitoring the elasticity of soft biological tissues in the gastrointestinal (GI) tract with minimal invasion holds promise for early diagnosis of intestinal fibrosis, colorectal cancer, and other diseases featuring abnormal elasticity. However, existing methods of sensing tissue elasticity have drawbacks such as insufficient resolution for elastography, and discomfort or the requirement of risky anesthesia for flexible endoscopes or implantable devices. Here we present a wirelessly actuated palpation mechanism integrated into a swallowable capsule robot, offering in situ tissue elasticity measurement with minimal invasiveness. Our approach employs a magnetic soft cantilever beam actuated by external magnetic fields to gently press against soft tissue. Mechanical stress and strain are monitored by an onboard magnetic sensor and a strain gauge, allowing for accurate assessment of tissue elasticity. Additionally, wireless modules utilizing Bluetooth Low Energy and powered by a battery facilitate real-time communication. The robot operates under external magnetic field control, which can move freely over soft tissues during examinations and palpate suspicious areas. We validate and assess the elasticity sensing mechanism on both phantom structures and ex vivo porcine colon tissues. Our capsule robot holds significant promise for assessing tissue physiological conditions and facilitating early disease diagnosis in hard-to-reach areas of the body.
Materials and
Methods: We present an overview of a palpation capsule robot designed for remote actuation and control through external magnetic fields, as depicted in Fig. 1. The capsule robot boasts compact dimensions, measuring 15 mm in diameter and 32 mm in length, tailored for effective disease diagnosis within the colon, as showcased in Fig. 1A. Fig. 1B illustrates the integration of a palpation unit within the capsule robot, enabling the sensing of local material elastic properties. This unit features a cantilever beam with a magnetic tip, facilitating deflection upon the application of an external magnetic field. This deflection allows for the palpation of soft tissues with a probe, converting bending motion into compression motion. The stress applied correlates with the strength of the external magnetic field, a parameter accurately measured by an on-board magnetic field sensor. Simultaneously, a strain gauge sensor mounted on the cantilever beam precisely measures the deflection. Fig. 1C demonstrates how materials of varying softness exhibit different deflection profiles under identical magnetic field conditions during palpation. An approximate magnetic actuation field strength of 30 mT is deemed necessary for deforming the cantilever beam adequately and generating palpation effects on soft materials, a feat achievable using a permanent magnet positioned at a specified distance. Equipped with an integrated battery and wireless communication capabilities via Bluetooth, the capsule robot can transmit real-time soft tissue information to mobile devices or cloud platforms for further analysis, as depicted in Fig. 1D. Figure 1E-F show the manufactured capsule robot with integrated wireless electronics.
Results, Conclusions, and Discussions: Our proposed capsule endoscope represents a significant advancement in medical technology, specifically tailored to efficiently sense tissue stiffness. The capsule shows a unique functionality of active navigation and palpation of soft tissue, all remotely actuated and controlled by an external magnetic field. The capsule’s navigation to the target area is achieved through a rolling locomotion. This approach enables precise navigation within the gastrointestinal (GI) tract, ensuring optimal positioning for thorough tissue examination. The, the gradient pulling force facilitates secure attachment of the capsule to soft tissue surfaces, guaranteeing stable readings throughout the sensing process. The captured tissue stiffness data is wirelessly transmitted via Bluetooth communication, enabling seamless, real-time transfer for convenient access and analysis by medical professionals. Therefore, our capsule endoscope embodies a potential solution for revolutionizing tissue examination, offering enhanced precision and efficiency in disease diagnostics.
Acknowledgements (Optional): [1] Kiyoung Kim, Steven Edwards, Kyle Fuxa, Honglu Lin, Hieu Vu, Shreya Shrestha, Joel Berinstein, Hutomo Tanoto, Rishi Naik, Yuxiao Zhou, Xiaoguang Dong, Mucosa-Interfacing Capsule Robot for In-Situ Sensing the Elasticity of Biological Tissues, under review. [2] Wang, C., Wu, Y., Dong, X., Armacki, M. and Sitti, M., In situ sensing physiological properties of biological tissues using wireless miniature soft robots. Science advances, 9(23), p.eadg3988, 2023.
