A sensor to measure hardness of human tissue

Abstract

Abstract-An innovative sensor is developed to evaluate hardness of human soft tissue. This sensor provides easy and accurate hardness measurements based on a unique sensing mechanism. Hardness of soft materials is often evaluated by using international standards of hardness such as IRHD (International Rubber Hardness Degree) and durometer hardness. However the conventional scales based on these standards requires a stable pressuring condition to the target. Therefore, these scales cannot be used for targets that are in motion or targets that require quick measurement such as human muscles during exercises and a liver exposed at a surgery. The prototyped sensor has a compact body and allows continuous hardness measurement with an arbitrary pressing force. This sensor always monitors the force exerted on the sensor and automatically eliminates the unintended effect from the fluctuation of the pressing force. Therefore, continuous time series of the hardness data is real-timely available. This paper reports results of a test as well as the detail of the mechanism and data processing technique of the latest version of the sensor.

Non-invasive control interfaces for intention detection in active movement-assistive devices

“…The measured force signals resulting from this phenomenon are known as myotonic (MT) [ 34 ] or myokinetic (MKT) [ 42 ] signals. These signals have been measured using arrays of force-sensitive resistors (FSRs) [ 42 ] or strain gauges [ 43 , 129 ]. A recent study by Castellini and Koiva [ 44 ] used a tactile sensor placed between the arm and the table to measure changes in pressure distribution at the ventral side of the forearm while performing a variable force task with the fingertip.…”

Implementation of Tactile Sensing for Palpation in Robot-Assisted Minimally Invasive Surgery: A Review

“…The characteristic feature of such devices is the limitation of its implementation method and design constraints, as a physical principle of construction does not allow any modifications. An example of such indentation device can be found in [68], (Fig. 6), it is using ring shaped airbag to detect contact force by measuring variable air pressure and to measure stiffness of liver.…”

“…In addition, to create a full representation of an 6. Schematic design and a prototype indentation device to measure liver stiffness [68].…”

Experimental Study of Hardness Measurement affected by a Cushion between Probe and PTF Pressure sensor

“…Hardness sensing especially for soft material is one of important problem in many fields such as foods industry and material science, including robotics [1][2][3][4][5][6][7][8][9][10][11].For application, the hardness sensing used many fields such as breast cancer diagnosis [6,12], tension-type headache from the musculoskeletal complaints [13,14], trapezius muscle hardness changes from the reason of visual display terminal height [15], muscle hardness measurements using ultrasound [16,17], hardness sensing using optical (IR frequency) techniques [18].As the force sensor, gauge sensor has been used for the hardness measurement. Since gauge sensor measures a distortion of metal, the accuracy of weak force range (0.1 to few N) inevitably drops, and it is considered difficult to measure the hardness of soft material [3,[19][20][21][22][23][24][25][26][27][28]. PTF sensor, on the other hand, is designed for weak force range (about 0.1 to 20 N), but the high reliability could not be realized by the instability of the contact area change of the two membranes inside the sensor (Fig.…”