Predicting Depth of Cut of Water-jet in Soft Tissue Simulants based on Finite Element Analysis with the Application to Fracture-directed Water-jet Steerable Needles

Water-jet technology has been used recently in medical applications including surgery, soft tissue resection, bone cutting, and wound debridement. The ability to measure the depth of cut of water-jet is important in these applications to selectively cut the desired tissue, and avoid damage to deeper layers. For fracture-directed water-jet steerable needles, one should be able to predict the depth of cut of water-jet in order to model the motion of the steerable needle. In this paper, the effect of tissue stiffness, water-jet flow rate, and nozzle diameter on depth of cut is studied experimentally and verified by finite element modeling. It is found that the depth of cut of water- jet has a direct relationship with flow rate, and an inverse relationship with elastic modulus of the tissue, and diameter of the needle. The proposed finite element model can predict the depth of cut with acceptable accuracy

Resultant Radius of Curvature of Stylet-and-Tube Steerable Needles Based on the Mechanical Properties of the Soft Tissue, and the Needle

Steerable needles have been widely researched in recent years, and they have multiple potential roles in the medical area. The flexibility and capability of avoiding obstacles allow the steerable needles to be applied in the biopsy, drug delivery and other medical applications that require a high degree of freedom and control accuracy. Radius of Curvature (ROC) of the needle while inserting in the soft tissue is an important parameter for evaluation of the efficacy, and steerability of these flexible needles. For our Fracture-directed Stylet-and-Tube Steerable Needles, it is important to find a relationship among the resultant insertion ROC, pre-set wire shape and the Young's Modulus of soft tissue to characterize this class of steerable needles. In this paper, an approach is provided for obtaining resultant ROC using stylet and tissue's mechanical properties. A finite element analysis is also conducted to support the reliability of the model. This work sets the foundation for other researchers to predict the insertion ROC based on the mechanical properties of the needle, and the soft tissue that is being inserted

Predicting Depth of Cut of Water-jet in Soft Tissue Simulants based on Finite Element Analysis with the Application to Fracture-directed Water-jet Steerable Needles

This paper is accepted and presented at 2019 International Symposium on Medical Robotics (ISMR).Water-jet technology has been used recently in medical applications including surgery, soft tissue resection, bone cutting, and wound debridement. The ability to measure the depth of cut of water-jet is important in these applications to selectively cut the desired tissue, and avoid damage to deeper layers. For fracture-directed water-jet steerable needles, one should be able to predict the depth of cut of water-jet in order to model the motion of the steerable needle. In this paper, the effect of tissue stiffness, water-jet flow rate, and nozzle diameter on depth of cut is studied experimentally and verified by finite element modeling. It is found that the depth of cut of water- jet has a direct relationship with flow rate, and an inverse relationship with elastic modulus of the tissue, and diameter of the needle. The proposed finite element model can predict the depth of cut with acceptable accuracy

Predictive Mechanics-based Model for Depth-of-Cut (DOC) of Waterjet in Soft-Tissue for Waterjet-assisted Medical Applications

The use of waterjet technology is now prevalent in medical applications including surgery, soft tissue resection, bone cutting, waterjet steerable needles, and wound debridement. The depth of the cut (DOC) of a waterjet in soft tissue is an important parameter that should be predicted in these applications. For instance, for waterjet- assisted surgery, selective cutting of tissue layers is a must to avoid damage to deeper tissue layers. For our proposed fracture-directed waterjet steerable needles, predicting the cut-depth of the waterjet in soft tissue is important to develop an accurate motion model, as well as control algorithms for this class of steerable needles. To date, most of the proposed models are only valid in the conditions of the experiments and if the soft tissue or the system properties change, the models will become invalid. The model proposed in this paper is formulated to allow for variation in parameters related to both the waterjet geometry and the tissue. In this paper, first the cut-depths of waterjet in soft tissue simulants are measured experimentally, and the effect of tissue stiffness, waterjet velocity, and nozzle diameter are studied on DOC. Then, a model based on the properties of the tissue and the waterjet is proposed to predict the DOC of waterjet in soft tissue. In order to verify the model, soft tissue properties (constitutive response, and fracture toughness) are measured using low strain rate compression tests, Split- Hopkinson-Pressure-Bar (SHPB) tests, and fracture toughness tests. The results show that the proposed model can predict the DOC of waterjet in soft tissue with acceptable accuracy if the tissue and waterjet properties are known

Predictive Mechanics-based Model for Depth-of-Cut (DOC) of Waterjet in Soft-Tissue for Waterjet-assisted Medical Applications

The paper entitled "Predictive Mechanics-based Model for Depth-of-Cut (DOC) of Waterjet in Soft-Tissue for Waterjet-assisted Medical Applications" is accepted to be published in the Journal of Medical & Biological Eng & Computing (MBEC).The use of waterjet technology is now prevalent in medical applications including surgery, soft tissue resection, bone cutting, waterjet steerable needles, and wound debridement. The depth of the cut (DOC) of a waterjet in soft tissue is an important parameter that should be predicted in these applications. For instance, for waterjet- assisted surgery, selective cutting of tissue layers is a must to avoid damage to deeper tissue layers. For our proposed fracture-directed waterjet steerable needles, predicting the cut-depth of the waterjet in soft tissue is important to develop an accurate motion model, as well as control algorithms for this class of steerable needles. To date, most of the proposed models are only valid in the conditions of the experiments and if the soft tissue or the system properties change, the models will become invalid. The model proposed in this paper is formulated to allow for variation in parameters related to both the waterjet geometry and the tissue. In this paper, first the cut-depths of waterjet in soft tissue simulants are measured experimentally, and the effect of tissue stiffness, waterjet velocity, and nozzle diameter are studied on DOC. Then, a model based on the properties of the tissue and the waterjet is proposed to predict the DOC of waterjet in soft tissue. In order to verify the model, soft tissue properties (constitutive response, and fracture toughness) are measured using low strain rate compression tests, Split- Hopkinson-Pressure-Bar (SHPB) tests, and fracture toughness tests. The results show that the proposed model can predict the DOC of waterjet in soft tissue with acceptable accuracy if the tissue and waterjet properties are known