Tactile Sensor for Minimally Invasive Surgery Using Electrical Impedance Tomography

Abstract

Whilst offering numerous benefits to patients, minimally invasive surgery (MIS) has a disadvantage in the loss of tactile feedback to the surgeon, traditionally offering valuable qualitative tissue assessment, such as tumour identification and localisation. Tactile sensors aim to overcome this loss of sensation by detecting tissue characteristics such as stiffness, composition and temperature. Tactile sensors have previously been incorporated into MIS robotic end effectors, which require lengthy scanning procedures due to localised sensitivity. Distributed tactile sensors, or "artificial skin" offer a map of tissue properties in a single instance but are often not suitable for MIS applications due to limited biocompatibility or large collapsed volumes. We propose a deployable, soft, tactile sensor with a deformable saline chamber and integrated Electrical Impedance Tomography (EIT) electrodes. During contact with tissue, the saline is displaced from the chamber and the lesion size and stiffness can be inferred from the resultant impedance changes. Through optimisation of the EIT measurement protocol and hardware the sensor was capable of localising the centre of mass of palpation targets within 1.5 mm in simulation and 2.3-4.6mm in phantom experiments. Reconstructed image metrics differentiated target objects from 8-30 mm.

Open Source Sensor Interface for Soft Detectors in Surgical Simulators

“…Furthermore, research groups in similar disciplines often use commercially available data acquisition systems for measurements (e.g. soft E-skin tactile sensing [14], [15], strain mapping sensor by EIT [42], or tactile EIT sensors [18], [43], [44], [45]). Such systems are deliberately not used because they are neither cheap nor small and rarely portable.…”

“…Yoshimoto et al [52] could achieve an accuracy of 5.7 ± 2.8 % for position detection, and local pressure detection with error in the range of 0.027 − 0.051 N/mm 2 with their tomographic tactile electromechanically coupled conductor sensor system. Avery et al [44] were able to achieve an overall accuracy of 7.7−15.3 % for various perturbation diameters with their tactile EIT sensor. For comparison with a deep neural networkbased system, Park et al [53] obtained an error of 4.9±2.8 % for their large area robotic tactile sensing system.…”

Shape Self-Sensing With Mutual Inductance Sensor Array

“…Balloon catheters are used in minimally invasive surgery to open and fix patency to the blocked lumen inside the body. During percutaneous transluminal angioplasty (PTA) an inflated balloon is used to remove the blockage caused by a stricture or plaque in the periphery or coronary vessels [3], [4], [5]. So the exterior shape of the balloon is an important factor.…”

“…So the exterior shape of the balloon is an important factor. In [3] electrical impedance tomography sensor is proposed for such an application. Here we demonstrate the use of a magnetic inductive sensor array for such an application.…”