Developing a soft tissue surrogate for use in photoelastic testing

An improved skin tissue substitute for use in photoelastic testing is required to enable investigation of the mechanics of needle insertion into soft tissue. Current tissue substitutes are mainly used in large scale testing and can neglect the small scale mechanical properties of soft tissue. A series of experiments on konjac glucomannan are performed to characterise its mechanical properties, and the results are compared to published results from similar experiments on skin tissue. The optical properties of the gel, such as its strain optic coefficient, are also assessed using a grey field polariscope (GFP2500). A concentration of 1.5% konjac to water produced a viscoelastic gel whose mechanical response closely matches published data for skin. A strain optic coefficient was recorded and found ideal for the planned testing with a GFP2500. Overall konjac glucomannan was found to be a potential soft tissue surrogate for use in small scale photoelastic testing

Fabrication and Experimental Evaluation of Simple Tissue-Mimicking Phantoms with Realistic Electrical Properties for Impedance-Based Sensing

Venipuncture is one of the most often performed invasive clinical procedure. Nevertheless, complications still occur. One opportunity to counteract these complications is to indicate the insertion by electrical impedance measurement, which bases on the various electrical properties of different tissues. This paper presents the evaluation and reproducible fabrication of simple tissue-mimicking phantoms for investigation of impedance sensing techniques. Three different tissue-mimicking phantoms, representing blood, fat, and skin, were made on water-based recipes, including agar and gelatin as gelling agents. For evaluation of the electrical properties an electrode probe, made of hypodermic needles, was fabricated and characterized using six sodium chloride (NaCl) solutions of defined concentrations. For characterization of the phantoms, conductances were measured over a frequency range from 20 Hz up to 1 MHz using the self-fabricated electrodes. The calculated conductivities of the tissue-mimicking phantoms showed sufficient agreement with corresponding electrical literature data of native tissue. Tests with a layered tissue structure proved usability for impedance-based venous entry tests. However, the method proposed was not suitable for investigation of relative permittivity, which would be required for full electrical characterization

The Forces Associated with Bolus Injection and Continuous Infusion Techniques during Ultrasound-Targeted Nerve Contact:An Ex Vivo Study

Ultrasound-guided regional anaesthesia with real-time visualization of anatomical structures and needle trajectory has become the standard method for accurately achieving nerve block procedures. Nevertheless, ultrasound is particularly limited in accurately detecting the needle tip in tissues with complex echogenicity. Fat-filled circumneural fascial tissue provides a barrier to local anaesthetic diffusion. Injection during gentle needle nerve contact is more likely to spread under the circumneurium (halo sign). On the other hand, excessive force may cause hematoma or activate the piezo ion channels and intraneural calcium release. Therefore, it is vital to understand the mechanics of needle–tissue interaction for optimizing the procedural outcomes and patients’ safety. We hypothesised that continuous fluid infusion would reduce the needle force applied on the nerve compared to that of bolus injection. Thus, the primary objective of this study was to compare the forces associated with the bolus injection and continuous infusion techniques on the sciatic nerves of fresh lamb legs ex vivo. A needle combining pressure and force was inserted into six legs of lambs ex vivo using a motor stage at a constant velocity and imaged with a linear transducer. Saline injections were block randomised to bolus injection or infusion in the muscle upon gently touching and indenting of the epineurium at nine sites on six sciatic nerves at three angles (30°, 45° and 60°) in each location. The bolus was delivered over 6 s and infused for over 60 s. The result showed less force was generated during the infusion technique when gently touching the epineurium than that of the bolus technique, with p = 0.004, with significant differences observed at a 60° angle (0.49 N, p = 0.001). The injection pressure was also lower when light epineurium touches were applied (9.6 kPa, p = 0.02) and at 60° (8.9 kPa). The time to peak pressure varied across the insertion angles (p < 0.001), with the shortest time at 60° (6.53 s). This study explores future applications by emphasizing the significance of understanding needle–tissue interaction mechanics. This understanding is crucial for optimizing the procedural outcomes and enhancing patients’ safety in ultrasound-guided regional anaesthesia administration. Specifically, continuous infusion demonstrated a notable reduction in needle force compared to that of the bolus injection, especially during gentle epineurium contact

The Forces Associated with Bolus Injection and Continuous Infusion Techniques during Ultrasound-Targeted Nerve Contact:An Ex Vivo Study

Ultrasound-guided regional anaesthesia with real-time visualization of anatomical structures and needle trajectory has become the standard method for accurately achieving nerve block procedures. Nevertheless, ultrasound is particularly limited in accurately detecting the needle tip in tissues with complex echogenicity. Fat-filled circumneural fascial tissue provides a barrier to local anaesthetic diffusion. Injection during gentle needle nerve contact is more likely to spread under the circumneurium (halo sign). On the other hand, excessive force may cause hematoma or activate the piezo ion channels and intraneural calcium release. Therefore, it is vital to understand the mechanics of needle–tissue interaction for optimizing the procedural outcomes and patients’ safety. We hypothesised that continuous fluid infusion would reduce the needle force applied on the nerve compared to that of bolus injection. Thus, the primary objective of this study was to compare the forces associated with the bolus injection and continuous infusion techniques on the sciatic nerves of fresh lamb legs ex vivo. A needle combining pressure and force was inserted into six legs of lambs ex vivo using a motor stage at a constant velocity and imaged with a linear transducer. Saline injections were block randomised to bolus injection or infusion in the muscle upon gently touching and indenting of the epineurium at nine sites on six sciatic nerves at three angles (30°, 45° and 60°) in each location. The bolus was delivered over 6 s and infused for over 60 s. The result showed less force was generated during the infusion technique when gently touching the epineurium than that of the bolus technique, with p = 0.004, with significant differences observed at a 60° angle (0.49 N, p = 0.001). The injection pressure was also lower when light epineurium touches were applied (9.6 kPa, p = 0.02) and at 60° (8.9 kPa). The time to peak pressure varied across the insertion angles (p < 0.001), with the shortest time at 60° (6.53 s). This study explores future applications by emphasizing the significance of understanding needle–tissue interaction mechanics. This understanding is crucial for optimizing the procedural outcomes and enhancing patients’ safety in ultrasound-guided regional anaesthesia administration. Specifically, continuous infusion demonstrated a notable reduction in needle force compared to that of the bolus injection, especially during gentle epineurium contact

Development and evaluation of hand-held robotic technology for safe and successful peripheral intravenous catheterization on pediatric patients

Peripheral IntraVenous Catheterization (PIVC) is often required in hospitals to fulfil urgent needs of blood sampling or fluid/medication administration. Despite of the importance of a high success rate, the conventional PIVC operation suffers from low insertion accuracy especially on young pediatric patients. On average, each pediatric patient is submitted to 2.1 attempts before venous access is obtained, with around 50% failure for the first attempt. The risks of such multiple attempts can be severe and life-threatening as they can cause serious extravasation injuries. Given the levels of precision and controllability needed for PIVC, robotic systems show a good potential to effectively assist the operation and improve its success rate. Therefore, this study aims to provide such robotic assistance by focusing on the most challenging and error-prone parts of the operation. In order to understand the difficulties of a pediatric PIVC, a survey investigation is conducted with specialists at the beginning of this research. The feedbacks from this survey indicates an urgent need of a hand-held robot to assist in the catheter insertion control to precisely access the target vein. To achieve the above goal, a novel venipuncture detection system based on sensing the electrical impedance of the contacting tissue at the needle tip has been proposed and developed. Then several ex-vivo and in-vivo experiments were conducted to assess this detection system. Experimental results show that this system can be highly effective to detect venipuncture. Subsequently, based on this venipuncture detection system, four different handheld robots have been developed to provide different levels of autonomy and assistance while executing a PIVC insertion: 1. SVEI, short for \u2018Smart Venous Enter Indicator\u2019, is the simplest device without actuation. The user needs to do the whole PIVC operation, and this device only provides an indication of venipuncture by lighting up an LED. 5 2. SAID, short for \u2018Semi-Autonomous Intravenous access Device\u2019, integrates a motor to control the catheter insertion. The user is required to hold the device still and target it to a vein site. He/She then activates the device. The device inserts the catheter automatically and stops it when venipuncture is detected. 3. SDOP, short for \u2018Smart hand-held Device for Over-puncture Prevention\u2019, integrates a latch-based disengage mechanism to prevent over-puncture during PIVC. The user can keep the conventional way of operation and do the insertion manually. At the moment of venipuncture, the device automatically activates the disengage mechanism to stop further advancement of the catheter. 4. CathBot represents \u2018hand-held roBot for peripheral intravenous Catheterization\u2019. The device uses a crank-slider mechanism and a solenoid actuator to convert the complicated intravenous catheterization motion to a simple linear forward motion. The user just needs to push the device\u2019s handle forwards and the device completes the whole PIVC insertion procedure automatically. All the devices were characterized to ensure they can satisfy the design specifications. Then a series of comparative experiments were conducted to assess each of them. In the first experiment, 25 na\uefve subjects were invited to perform 10 trials of PIVC on a realistic baby arm phantom. The subjects were divided into 5 groups, and each group was asked to do the PIVC with one device only (SVEI, SAID, SDOP, CathBot and regular iv catheter). The experimental results show that all devices can provide the needed assistance to significantly facilitate and improve the success rates compared to the conventional method. People who have no experience of PIVC operation before can achieve considerably high success rates in robot-assisted PIVC (86% with SVEI, 80% with SAID, 78% with SDOP and 84% with CathBot) compared to the control group (12%) who used a regular iv catheter. Also, all 5 subjects using SVEI, 3 out of 5 subjects using SAID, 2 out of 5 subjects using SDOP and 4 out of 5 subjects using CathBot were able to successfully catheterize the baby arm phantom on their first attempt, while no subjects in the control group succeeded in their first attempts. Since SVEI showed the best results, it was selected for the second round of evaluation. In the second experiment, clinicians including both PIVC experts and general clinicians were invited to perform PIVC on a realistic baby arm phantom with 3 trials using SVEI and 3 trials in the conventional way. The results demonstrate that SVEI can bring great benefits to both specialists and general clinicians. The average success rates were found to be significantly improved from 48.3% to 71.7% when SVEI was used. The experimental results reveal that all experts achieved better or equal results with SVEI compared to the conventional method, and 9 out of 12 non-experts also had better or equal performance when SVEI was used. Finally, subjective feedback acquired through post-trial questionnaires showed that all devices were highly rated in terms of usability. Overall, the results of this doctoral research support continued investment in the technology to bring the handheld robotic devices closer to clinical us

下腹部を対象とした極細針によるCTガイド下高正確度穿刺プランニング

早大学位記番号:新8149早稲田大

Modelling, Materials and Methods Investigating Needle Insertion in Biomechanics

This project aimed to investigate the forces that both needle and tissue experienced during a needle insertion, and how they altered the needles trajectory. An investigation into the current literature showed that existing skin tissue surrogates did not perform similarly to real skin tissue in vivo during needle insertions. A new surrogate is required to aid with validation for computational models of needle insertions, while avoiding the ethical issues raised from testing real tissue. This study developed an improved skin tissue surrogate for use in photoelastic testing which focused on replicating the fracture mechanism observed during a needle insertion through human skin tissue. It is demonstrated that konjac glucomannan gel fractures in the same way as human skin tissue. Experimental assessments determined that at a concentration of 1.5% gel powder to water konjac jelly had a stiffness which closely matched the stiffness of human skin tissue in vivo. In order to use the surrogate in photoelastic analysis it must be clear and exhibit temporary birefringence, and it is shown that with careful preparation konjac satisfies these criteria. The strain optic coefficient for the gel is determined, which links the optical response to the strain and stress experienced by the surrogate. A variety of needle insertion experiments were conducted which assess how varying the insertion speed, needle length, and needle gauge affect the overall response. The results prove that konjac jelly accurately replicates needle insertion response through soft tissue better than existing surrogates. With use of the GFP2500 poleidoscope, a novel digital polariscope, full field and directional information from a needle insertion is obtained. The results identify never-before-seen locations of principal strain magnitude near the puncture surface. For the first time the forces directional response was reported, and show how a bending moment acts on the needle; resulting in deflection