Purpose: We describe a comparative study between an enhanced air-cushion tactile sensor and a wheeled indentation probe. These laparoscopic tools are designed to rapidly locate soft-tissue abnormalities during minimally invasive surgery (MIS).
Materials and methods: The air-cushion tactile sensor consists of an optically based sensor with a 7.8 mm sphere "floating" on a cushion of air at the tip of a shaft. The wheeled indentation probe is a 10 mm wide and 5 mm in diameter wheel mounted to a force/torque sensor. A continuous rolling indentation technique is used to pass the sensors over the soft-tissue surfaces. The variations in stiffness of the viscoelastic materials that are detected during the rolling indentations are illustrated by stiffness maps that can be used for tissue diagnosis. The probes were tested by having to detect four embedded nodules in a silicone phantom. Each probe was attached to a robotic manipulator and rolled over the silicone phantom in parallel paths. The readings of each probe collected during the process of rolling indentation were used to achieve the final results.
Results: The results show that both sensors reliably detected the areas of variable stiffness by accurately identifying the location of each nodule. These are illustrated in the form of two three-dimensional spatiomechanical maps.
Conclusions: These probes have the potential to be used in MIS because they could provide surgeons with information on the mechanical properties of soft tissue, consequently enhancing the reduction in haptic feedback.