Andrew C. Barnett

Compliant Needle Vibration Cutting of Soft Tissue

This work investigates the performance of a novel compliant needle for cutting tissue. The novel cutting geometry transfers axial vibration to transverse motion at the tip. The cutting edge of the geometry is defined in terms of the time-dependent inclination and rake angle. Finite element analysis was performed to determine the compliant geometry effect on the axial vibration modes of the needles. An ultrasonic transducer is used to apply the axial vibration. An ultrasonic horn was developed to increase the amplitude of vibration. Experiments were performed to determine the effectiveness of the compliant needle geometry. The motion of the compliant needle is measured with a stereomicroscope. The two compliant geometries developed transverse motion of 4.5 lm and 16.0 lm. The control needle with fixed geometry developed no measured transverse motion. The insertion force was recorded for two different compliant geometries and a control geometry inserted into a polyurethane sheet. The puncture force of the control needle with applied vibration and the two compliant needles was up to 29.5% lower than the control insertion without applied vibration. The compliant needles reduced the friction force up to 71.0%. The significant reduction of the friction force is explained by the compliant needles’ ability to create a larger crack in the material because of their transverse motion. [DOI: 10.1115/1.4033690]

Vibrating Needle Cutting Force

Needles are one of most commonly used medical devices, used to deliver drugs, biopsy tissue, draw blood, conduct brachytherapy cancer treatment and many other procedures. Maintaining a low insertion force of the needle is important to the success of these procedures. Utilizing vibratory cutting reduces the insertion force, thus improving the outcome of the procedure. This paper describes the experimental setup utilized to test the effectiveness of axial vibration in reducing the insertion force into porcine skin across a range of frequencies, amplitudes and needle sizes. Experiments showed the addition of the vibration was able to reduce the insertion force by up to 35%. The minimum insertion force occurred at lower maximum vibratory insertion speeds for larger diameter needles.Copyright

Modeling the cutting edge geometry of scalpel blades

Scalpel blades are commonly used in surgery to perform invasive medical procedures, yet there has been limited research on the geometry that makes up these cutting instruments. The goal of this article is to define scalpel blade geometry and examine the cutting forces and deflection between commonly used scalpel blades and phantom gel. The following study develops a generalized geometric model that describes the cutting edge geometry in terms of normal rake and inclination angle of any continuously differentiable scalpel cutting edge surface. The parameter of scalpel-tissue contact area is also examined. The geometry of commonly used scalpel blades (10, 11, 12, and 15) is compared to each other and their cutting force through phantom gel measured. It was found that blade 10 displayed the lowest average total steady-state cutting force of 0.52 N followed by blade 15, 11, and 12 with a cutting force of 1.17 N (125% higher than blade 10). Blade 10 also displayed the lowest normalized cutting force of 0.16 N/mm followed by blades 15, 12, and 11 with a force of 0.19 N/mm (17% higher than blade 10).

Needle geometry effect on vibration tissue cutting

Needle vibration tissue cutting is a method that has been shown to reduce tissue cutting force and thereby improve needle position accuracy inside the body. Needle accuracy is crucial for minimally invasive needle operations such as the radiation cancer treatment of brachytherapy. This article uniquely determines the importance of needle geometry in minimizing cutting force in needle vibration tissue cutting. This article also determines how vibration specifically affects cutting force. This new information was found by performing needle cutting experiments with five varying conical tipped needles being inserted into ex vivo bovine liver as well as a polyurethane sheet at varying vibratory amplitudes and frequencies. Results show that applying vibration to sharper needles greatly reduced the insertion force by up to 67%, where the blunter needles saw diminishing benefits. The tissue phantom experiments showed that vibration reduced the force needed to propagate the created crack but showed no improvement over the initial puncture force. This greater understanding of needle vibration tissue cutting can lead to improved needle geometry designs that work with vibration to reduce tissue cutting force.

Needle Insertion Force Model for Haptic Simulation

Percutaneous medical procedures rely upon clinicians performing precise needle insertion in soft tissue. The utility of haptic simulation systems in training clinicians for these procedures is highly dependent upon the ability to render accurate insertion force feedback. This paper presents a piecewise mathematical model for insertion force that does not require tissue material properties, detailed mechanical approximations, or complex computations. With manipulation of model parameters, a wide variety of insertion tasks and clinical scenarios can be modeled. Through needle insertion experiments and parameter estimation, this model was demonstrated to replicate the insertion forces associated with a variety of needle and tissue types. In 11 of 12 needle and tissue combinations tested, the model replicated the insertion force with an average absolute mean error of less than 0.065 N.Copyright

Vibration Needle Tissue Cutting With Varying Tip Geometry

Needles are one of most commonly used medical devices. They are used to deliver drugs, biopsy tissue, draw blood, conduct brachytherapy cancer treatment and many other procedures. Maintaining a low insertion force of the needle is important to the success of these procedures. Different geometries as well as utilizing vibratory cutting has been shown to reduce the insertion force, thus improving the outcome of the procedure; however, the effects of vibration and geometry of the needle together has yet to be explored. This paper describes the experimental setup utilized to test the effect of geometry on utilizing axial vibration in reducing the insertion force of needles into bovine liver across a range of frequencies and amplitudes. Three conical tipped needles with different grind angles were explored. Experiments showed the addition of the vibration was able to reduce the insertion force by up to 67%. Experiments showed that the insertion force for the bluntest needle was directly dependent on the amplitude of vibration, where the insertion force of the sharpest needle was more dependent on the maximum vibratory insertion speed of the needle.Copyright

Novel Instant Vacuum Biopsy Needle System

This paper explores the benefits of vacuum assistance to 18 gauge needle biopsy. Current biopsy methods are inefficient or have a high rate of failure, causing the need for further painful insertions. A novel needle insertion device was developed to create the vacuum in the needle. Using multiple pneumatic cylinders, a vacuum is created inside the end-cut needle by retracting the trocar while inserting the needle. Calculations were done to determine the force caused by the vacuum. Experiments inserting the needle into porcine kidney have shown that the vacuum assistance increases cutting efficiency.Copyright