To compensate for the lack of touch during minimally invasive and robotic surgeries, tactile sensors are integrated with surgical instruments. Surgical tools with tactile sensors have been used mainly for distinguishing among different tissues and detecting malignant tissues or tumors. Studies have revealed that malignant tissue is most likely stiffer than normal. This would lead to the formation of a sharp discontinuity in tissue mechanical properties. A hybrid piezoresistive-optical-fiber sensor is proposed. This sensor is investigated for its capabilities in tissue distinction and detection of a sharp discontinuity. The dynamic interaction of the sensor and tissue is studied using finite element method. The tissue is modeled as a two-term Mooney–Rivlin hyperelastic material. For experimental verification, the sensor was microfabricated and tested under the same conditions as of the simulations. The simulation and experimental results are in a fair agreement. The sensor exhibits an acceptable linearity, repeatability, and sensitivity in characterizing the stiffness of different tissue phantoms. Also, it is capable of locating the position of a sharp discontinuity in the tissue. Due to the simplicity of its sensing principle, the proposed hybrid sensor could also be used for industrial applications.
During conventional surgical tasks, surgeons use their tactile perception in their finger tips to sense the degree of softness of biological tissues to identify tissue types and to feel for any abnormalities. However, in robotic-assisted surgical systems, surgeons are unable to sense this information because only surgical tools interact with tissues. In order to provide surgeons with such useful tactile perception, therefore, a tactile sensor is required that is capable of simultaneously measuring contact force and resulting tissue deformation. Accordingly, this paper discusses the design, prototyping, testing, and validation of an innovative tactile sensor that is capable of measuring the degree of softness of soft objects such as tissues under both static and dynamic loading conditions and which is also magnetic resonance compatible and electrically passive. These unique characteristics of the proposed sensor would also make it a practical choice for use in robotic-assisted surgical platforms. The prototype version of this sensor was developed by using optical micro-systems technology and, thus far, experimental test results performed on the prototyped sensor have validated its ability to measure the relative softness of artificial tissues.
Currently, Minimally Invasive Surgery (MIS) performs through keyhole incisions using commercially available robotic
surgery systems. One of the most famous examples of these robotic surgery systems is the da Vinci surgical system. In
the current robotic surgery systems like the da Vinci, surgeons are faced with problems such as lack of tactile feedback
during the surgery. Therefore, providing a real-time tactile feedback from interaction between surgical instruments and
tissue can help the surgeons to perform MIS more reliably. The present paper proposes an optical tactile sensor to
measure the contact force between the bio-tissue and the surgical instrument. A model is proposed for simulating the
interaction between a flexible membrane and bio-tissue based on the finite element methods. The tissue is considered as
a hyperelastic material with the material properties similar to the heart tissue. The flexible membrane is assumed as a
thin layer of silicon which can be microfabricated using the technology of Micro Electro Mechanical Systems (MEMS).
The simulation results are used to optimize the geometric design parameters of a proposed MEMS tactile sensor for use
in robotic surgical systems to perform MIS.
The measurement of relative hardness of soft objects enables replication of human finger tactile perception capabilities.
This ability has many applications not only in automation and robotics industry but also in many other areas such as
aerospace and robotic surgery where a robotic tool interacts with a soft contact object. One of the practical examples of
interaction between a solid robotic instrument and a soft contact object occurs during robotically-assisted minimally
invasive surgery. Measuring the relative hardness of bio-tissue, while contacting the robotic instrument, helps the
surgeons to perform this type of surgery more reliably. In the present work, a new optical sensor is proposed to measure
the relative hardness of contact objects. In order to measure the hardness of a contact object, like a human finger, it is
required to apply a small force/deformation to the object by a tactile sensor. Then, the applied force and resulting
deformation should be recorded at certain points to enable the relative hardness measurement. In this work,
force/deformation data for a contact object is recorded at certain points by the proposed optical sensor. Recorded data is
used to measure the relative hardness of soft objects. Based on the proposed design, an experimental setup was
developed and experimental tests were performed to measure the relative hardness of elastomeric materials.
Experimental results verify the ability of the proposed optical sensor to measure the relative hardness of elastomeric
samples.
In conventional open surgery, using finger palpation, surgeons can distinguish between different types of tissues.
However, in the current commercially available minimally invasive robotic surgery (MIRS) systems, direct tactile
feedback is negligible. In the present paper, based on a novel concept, a new bend-type optical fiber tactile sensor is
proposed, designed, simulated, fabricated, and tested. In both dynamic and static loading conditions, the proposed tactile
sensor measures forces interacting between tissues and surgical tools whether they are distributed contact forces or
concentrated contact forces, or even if these forces are in combination. As a result, the sensor can identify the size and
the position of blood vessels or of abnormal tissues, one of which could be a tumorous lump within normal tissues. In
addition, the static force measurement provided by the sensor allows surgeons to maintain contact stability in any static
interactions between surgical tools and tissues while at the same time avoiding tissue damage because of excessive
contact force. In the meantime, because the sensor is based uniquely on optical fibers, it is insensitive to electromagnetic
fields. As a result, it is compatible with Magnetic Resonance Imaging (MRI) devices, which are currently in widespread
use in surgical operating rooms.
Mitral valve regurgitation (MR) is a condition in which heart's mitral valve does not close tightly, which allows blood to
leak back into the left atrium. Restoring the dimension of the mitral-valve annulus by percutaneous intervention surgery
is a common choice to treat MR. Currently, this kind of open heart annuloplasty surgery is being performed through
sternotomy with cardiomyopathy bypass. In order to reduce trauma to the patient and also to eliminate bypass surgery,
robotic assisted minimally invasive surgery (MIS) procedure, which requires small keyhole incisions, has a great
potential. To perform this surgery through MIS procedure, an accurate computer controlled catheter with wide-range
force feedback capabilities is required. There are three types of tissues at the site of operation: mitral leaflet, mitral
annulus and left atrium. The maximum allowable applied force to these three types of tissue is totally different. For
instance, leaflet tissue is the most sensitive one with the lowest allowable force capacity. For this application, therefore,
a wide-range force sensing is highly required. Most of the sensors that have been developed for use in MIS applications
have a limited range of sensing. Therefore, they need to be calibrated for different types of tissue. The present work,
reports on the design, modeling and simulation of a novel wide-range optical force sensor for measurement of contact
pressure between catheter tip and heart tissue. The proposed sensor offers a wide input range with a high resolution and
sensitivity over this range. Using Micro-Electro-Mechanical-Systems (MEMS) technology, this sensor can be
microfabricated and integrated with commercially available catheters.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.