Roozbeh Ahmadi

Discretely Loaded Beam-Type Optical Fiber Tactile Sensor for Tissue Manipulation and Palpation in Minimally Invasive Robotic Surgery

In traditional open surgery, surgeons use their fingertip palpation to investigate the hidden anatomical structures of tissue. However, in the current commercially available minimally invasive robotic surgery (MIRS) systems, while surgical instruments interact with tissues, surgeons do not sense any tactile information. Therefore, tactile sensors are required to be integrated into the tips of surgical instruments to mimic the perception of the surgeons fingertips. The electrically based tactile sensors that exist at present cannot usually operate under static loading conditions. In addition, they are not compatible with magnetic resonance imaging (MRI) devices. Therefore, this research was aimed at restoring tactile information by developing an MRI compatible optical fiber tactile sensor. The sensor consists of only one single moving part. Thanks to this novel design, the sensor does not require the use of an array of sensors to measure the distributed tactile information. This capability simplifies the integration of the sensor into any suitable space available at the tips of surgical instruments. In addition, the sensor performs under both static and dynamic loading conditions. A theoretical model of the sensor and a finite-element model of the sensor-tissue interaction were developed. To validate the sensor, a prototype of the sensor was fabricated and tested.

A piezoresistive tactile sensor for tissue characterization during catheter-based cardiac surgery

Currently, most of mitral valve annuloplasty surgeries are performed by using open heart surgery. However, if such operation would be performed by using minimally invasive surgery via catheter‐based techniques (CBT), it offers various advantages for both surgeons and patients.

Design, fabrication, and testing of a piezoresistive hardness sensor in Minimally Invasive Surgery

In the present paper, a novel and reliable tactile sensor is proposed to provide the required tactile feedback to the surgeon allowing the annuloplasty surgery to be performed by Minimally Invasive Surgery (MIS) techniques. The proposed sensor can differentiate between the hardness of different kind of elastomers. The structure of the sensor is very simple and it can easily be microfabricated, and integrated to various surgery devices such as catheters. The paper discusses the design, modeling, and fabrication of the sensor. Several hardness measuring tests are carried out on the sensor and the output is compared to a standard method of hardness measurement by a durometer. Two elastomers with hyperelastic behaviour, representing two different heart tissues were modelled mathematically to verify the sensors output. It is shown that the output of the sensor is reliable.

A new MRI-compatible optical fiber tactile sensor for use in minimally invasive robotic surgery systems

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.

A new hybrid catheter-tip tactile sensor with relative hardness measuring capability for use in catheter-based heart surgery

Mitral valve regurgitation (MR) is one of the common heart valve diseases. It can be fixed by surgical mitral valve repair. Currently, this type of surgery is performed using open heart bypass methods. If it would be performed using catheter-based techniques (CBT), it would offer both patients and surgeons many advantages. To perform it via CBT, it is necessary to include, on the tip of a catheter, tactile sensors that measure the relative hardness of contact tissues. The present paper discusses the design, modelling, and fabrication of a novel hybrid (Piezoresistive-Optical Fiber) catheter-tip tactile sensor that differentiates between the hardness of different kinds of elastomeric materials. In addition, finite element models of elastomeric materials, contacted at the tip of the catheter, were developed to verify the output of the sensor. Similarly, the experimental results confirm the relative hardness measurement of contact elastomeric materials.

A piezoresistive based tactile sensor for use in minimally invasive surgery

In the present paper, a novel tactile sensor is proposed for use in minimally invasive surgery to provide surgeons with tactile information. The sensing element of the sensor relies on a piezoresistive material. The proposed sensor measures contact force as well as the relative hardness of soft contact objects. A prototype of the sensor has been built, calibrated, and tested. Experimental test results confirm the ability of the sensor to distinguish between two different elastomeric materials. Such materials resemble two different biological tissues.

Innovative optical microsystem for static and dynamic tissue diagnosis in minimally invasive surgical operations

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.

Micro-optical force distribution sensing suitable for lump/artery detection.

Surgeons performing robotic-assisted surgical tasks need to establish the density and constituency of hidden tissue structures using only surgical tools. This is possible by integrating a miniaturized sensor into the end-effectors of robotic surgical systems. In this present work, optical microsystems technology is utilized to develop a miniature force-distribution sensor that can be integrated into surgical end-effectors. The sensing principle of the sensor is based on the mechanism of splice coupling. Since the device is fully optical, the sensor is magnetic-resonance compatible and is also electrically passive. The experimental results performed on the developed sensor confirm its ability to measure the distributed force information. Such information is used to detect different tissue structures such as lumps, arteries, or ureters during robotic-assisted surgical tasks.

Wide range force feedback for catheter insertion mechanism for use in minimally invasive mitral valve repair surgery

Mitral valve regurgitation (MR) is a condition in which hearts 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.

Optical fiber sensor array for artery/lump detection

In this study, a new optical fiber tactile sensor array is introduced for use in minimally invasive surgery systems. The proposed sensor helps surgeons to locate hidden harder tissues such as lumps and arteries within soft background tissues. Unlike currently available electrically-based tactile sensors, the proposed sensor is insensitive to electromagnetic fields and is electrically passive. It also performs under both dynamic and static loading conditions. The sensor was experimentally tested to locate a phantom solid artery/lump surrounded by an artificial soft background tissue.