Jason Z. Moore

Modeling of the Plane Needle Cutting Edge Rake and Inclination Angles for Biopsy

Hollow needles are one of the most common medical devices, yet little study has focused on the needle tip cutting geometry for biopsy, which is a tissue cutting process. This research develops mathematical models to calculate the inclination and rake angles along cutting edges on needle tips generated by planes. Three types of plane needle tips, the one-plane bias bevel, multi-plane symmetrical, and two-plane nonsymmetric needles, are investigated. The models show that the leading tip of a bias bevel needle has an inclination angle of 0 deg, the worst configuration for cutting. Symmetric multiplane needles on the other hand have very high inclination angles, 60, 56.3, and 50.8 deg, given a needle formed by two-, three-, and four-plane, respectively, for a bevel angle of 30 deg and can assist more effective needle biopsy. The rake angle is at its greatest value (the best configuration for cutting), which equals the 90 deg minus the bevel angle, at the initial cutting point for the bias bevel needle. Experiments are performed using three 11 gauge two-plane symmetric needles with 20, 25, and 30 deg bevel angles on bovine liver and demonstrate that the needle tip geometry affects biopsy performance, where longer biopsy samples are collected with needles of higher rake and inclination angle.

Effects of insertion speed and trocar stiffness on the accuracy of needle position for brachytherapy

PURPOSE In prostate brachytherapy, accurate positioning of the needle tip to place radioactive seeds at its target site is critical for successful radiation treatment. During the procedure, needle deflection leads to seed misplacement and suboptimal radiation dose to cancerous cells. In practice, radiation oncologists commonly use high-speed hand needle insertion to minimize displacement of the prostate as well as the needle deflection. Effects of speed during needle insertion and stiffness of trocar (a solid rod inside the hollow cannula) on needle deflection are studied. METHODS Needle insertion experiments into phantom were performed using a 2(2) factorial design (2 parameters at 2 levels), with each condition having replicates. Analysis of the deflection data included calculating the average, standard deviation, and analysis of variance (ANOVA) to find significant single and two-way interaction factors. RESULTS The stiffer tungsten carbide trocar is effective in reducing the average and standard deviation of needle deflection. The fast insertion speed together with the stiffer trocar generated the smallest average and standard deviation for needle deflection for almost all cases. CONCLUSIONS The combination of stiff tungsten carbide trocar and fast needle insertion speed are important to decreasing needle deflection. The knowledge gained from this study can be used to improve the accuracy of needle insertion during brachytherapy procedures.

Precision grid and hand motion for accurate needle insertion in brachytherapy

PURPOSE In prostate brachytherapy, a grid is used to guide a needle tip toward a preplanned location within the tissue. During insertion, the needle deflects en route resulting in target misplacement. In this paper, 18-gauge needle insertion experiments into phantom were performed to test effects of three parameters, which include the clearance between the grid hole and needle, the thickness of the grid, and the needle insertion speed. Measurement apparatus that consisted of two datum surfaces and digital depth gauge was developed to quantify needle deflections. METHODS The gauge repeatability and reproducibility (GR&R) test was performed on the measurement apparatus, and it proved to be capable of measuring a 2 mm tolerance from the target. Replicated experiments were performed on a 2(3) factorial design (three parameters at two levels) and analysis included averages and standard deviation along with an analysis of variance (ANOVA) to find significant single and two-way interaction factors. RESULTS Results showed that grid with tight clearance hole and slow needle speed increased precision and accuracy of needle insertion. The tight grid was vital to enhance precision and accuracy of needle insertion for both slow and fast insertion speed; additionally, at slow speed the tight, thick grid improved needle precision and accuracy. CONCLUSIONS In summary, the tight grid is important, regardless of speed. The grid design, which shows the capability to reduce the needle deflection in brachytherapy procedures, can potentially be implemented in the brachytherapy procedure.

Modeling cutting edge geometry for plane and curved needle tips

Hollow needles are commonly used in many areas of medicine, yet there has been limited research on needle tip geometry. A better understanding of needle tip geometry can lead to the creation of an optimized needle tip geometry design which would greatly benefit the procedure of biopsy, where a needle is used to cut and remove tissue from the body. The present research develops mathematical models to calculate the inclination and rake angle along the cutting edges of needle tips generated by curved surfaces. The parameters of needle insertion length and inner needle tip surface area are also examined. Needle insertion force is predicted based on needle geometry and calculated for curved and flat plane tip needles. A concave needle produced lower cutting forces than the convex and bias bevel needles. It is found that utilizing curved surface needle tip geometry, as opposed to flat plane geometry, allows for greater control in varying rake and inclination angles on the needle. This greater flexibility allows for more control in designing an optimized needle tip.

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).

Characterization of the Fluid Deaeration Device for a Hydraulic Hybrid Vehicle System

The attractiveness of the hydraulic hybrid concept stems from the high power density and efficiency of the pump/motors and the accumulator. This is particularly advantageous in applications to heavy vehicles, as high mass translates into high rates of energy flows through the system. Using dry case hydraulic pumps further improves the energy conversion in the system, as they have 1-4% better efficiency than traditional wet-case pumps. However, evacuation of fluid from the case introduces air bubbles and it becomes imperative to address the deaeration problems. This research develops a bubble elimination efficiency testing apparatus (BEETA) to establish quantitative results characterizing bubble removal from hydraulic fluid in a cyclone deaeration device. The BEETA system mixes the oil and air according to predetermined ratio, passes the mixture through a cyclone deaeration device, and then measures the concentration of air in the exiting fluid. Test results indicate the ability of the cyclone deaeration device to remove large bubbles with near 100% efficiency, while elimination of small (less than 1 mm diameter) bubbles proved to be a challenge. The explanation is provided through application of Stokes Law that shows a strong relationship between bubble size and bubble rise velocity. The theoretical analysis provides clear guidance regarding pathways towards improving the effectiveness of removing small bubbles.

Personalized Learning in Medical Education: Designing a User Interface for a Dynamic Haptic Robotic Trainer for Central Venous Catheterization

While Virtual Reality (VR) has emerged as a viable method for training new medical residents, it has not yet reached all areas of training. One area lacking such development is surgical residency programs where there are large learning curves associated with skill development. In order to address this gap, a Dynamic Haptic Robotic Trainer (DHRT) was developed to help train surgical residents in the placement of ultrasound guided Internal Jugular Central Venous Catheters and to incorporate personalized learning. In order to accomplish this, a 2-part study was conducted to: (1) systematically analyze the feedback given to 18 third year medical students by trained professionals to identify the items necessary for a personalized learning system and (2) develop and experimentally test the usability of the personalized learning interface within the DHRT system. The results can be used to inform the design of VR and personalized learning systems within the medical community.

Improving Medical Education Simulating Changes in Patient Anatomy Using Dynamic Haptic Feedback

Virtual simulation is an emerging field in medical education. Research suggests that simulation reduces complication rates and improves learning gains for medical residents. One benefit of simulators is their allowance for more realistic and dynamic patient anatomies. While potentially useful throughout medical education, few studies have explored the impact of dynamic haptic simulators on medical training. In light of this research void, this study was developed to examine how a Dynamic-Haptic Robotic Trainer (DHRT) impacts medical student self-efficacy and skill gains compared to traditional simulators developed to train students in Internal Jugular Central Venous Catheter (IJ CVC) placement. The study was conducted with 18 third year medical students with no prior CVC insertion experience who underwent a pre-test, simulator training (manikin, robotic, or mixed) and post-test. The results revealed the DHRT as a useful method for training CVC skills and supports further research on dynamic haptic trainers in medical education.