Ultrasonic needles for bone biopsy

Bone biopsy is an invasive clinical procedure where a bone sample is recovered for analysis during the diagnosis of a medical condition. When the architecture of the bone tissue is required to be preserved, a core-needle biopsy is taken. Although this procedure is performed while the patient is under local anaesthesia, the patient can still experience significant discomfort. Additionally, large haematoma can be induced in the soft tissue surrounding the biopsy site due to the large axial and rotational forces which are applied through the needle to penetrate bone. It is well documented that power ultrasonic surgical devices offer advantages of low cutting force, high accuracy and preservation of soft tissues. This paper reports a study of the design, analysis and test of two novel power ultrasonic needles for bone biopsy that operate using different configurations to penetrate bone. The first utilises micrometric vibrations generated at the distil tip of a full-wavelength resonant ultrasonic device, while the second utilises an ultrasonic-sonic approach where vibrational energy generated by a resonant ultrasonic horn is transferred to a needle via the chaotic motion of a free-mass. It is shown that the dynamic behaviour of the devices identified through experimental techniques closely match the behaviour calculated through numerical and FEA methods, demonstrating that they are effective design tools for these devices. Both devices were able to recover trabecular bone from the metaphysis of an ovine femur, and the biopsy samples were found to be comparable to a sample extracted using a conventional biopsy needle. Furthermore, the resonant needle device was also able to extract a cortical bone sample from the central diaphysis, which is the strongest part of the bone, and the biopsy was found to be superior to the sample recovered by a conventional bone biopsy needle

A miniature surgical drill using ultrasonic/sonic frequency vibration

A study is presented of a miniature ultrasonic surgical drill designed for bone biopsy, based on an ultrasonic/sonic drill which converts high frequency to low frequency vibrations through a freely vibrating mass between an ultrasonic transducer-horn and a drill bit. For conventional surgical drilling using a rotary drill or an ultrasonic drill, considerable power is required to penetrate into bone and the efficiency is low. However, for ultrasonic/sonic drilling, sufficient acoustic energy is accumulated and then released through each impact to achieve precise drilling with a lower power requirement. The ultrasonic/sonic drill was originally invented for rock drilling in low gravity environments. In this study it is incorporated in a miniature ultrasonic surgical drill and the effective impulse delivered to the bone is used to evaluate the drilling performance. To develop a miniature surgical device based on maximising the effective impulse, optimisation of the ultrasonic horn and free-mass is first demonstrated. The shape and dimensions of the ultrasonic horn and free-mass are determined through FEA, which focuses on maximising the post-collision velocity of the free-mass. Then, the entire dynamic stack constituting the surgical drill device is modelled as a mass-spring-damper system to analyse the dynamic behaviour. The numerical model is validated through experiments, using a prototype drill, which record the velocity of the free-mass and the drilling force. The results of the numerical models and experiments indicate this miniature ultrasonic surgical drill can deliver sufficient impulse to penetrate bone and form the basis of an ultrasonically activated bone biopsy device

The application of ultrasound in neuroendoscopic procedures: first results with the new tool »NECUP-2« [Upotreba ultrazvuka u neuroendoskopskim procedurama: prvi rezultati s novim uređajem »NECUP-2«]

In this paper, our experience with originally constructed Neurosurgical Endoscopic Contact Ultrasound Probe »NECUP-2« in neuroendoscopy is reported. Between June 1997 and June 2007, 132 neuroendoscopic procedures have been performed: 102 endoscopic thrid ventriculostomies (ETV), 15 arachnoid cysts and 5 intraventricular tumours operations. The »NECUP-2« was applied effectively in all cases in which blunt perforation was not possible: 38/102 ETV, 10/10 septostomies, 15/15 arachnoid cysts. In five cases of intraventricular tumours, neuroendoscopic procedure was combined with open microsurgery for tumour removal with preservation of vascular structures. There were no »NECUP-2« related complications. Of postoperative complications, we had liquorrhea (9 patients), and symptoms of meningitis (6 patients). In the follow-up period (6 months to 6 years), we had a patency rate of 80% (50/63 patients). All patients improved in clinical status. According to the first results, it seems that ultrasonic contact probe NECUP-2 presents a new device in neurosurgical armamentarium that can be used in various fields of neurosurgery. With minimal and controlled lesion that is produced at the tip of the probe, it can be used in highly demanding operations such as third ventriculostomy and tumour resection

Ultrasonic bone cutting

This thesis reports on the design of ultrasonic bone cutting blades and the effect of various cutting parameters such as applied load, blade tip vibration velocity and frequency on cutting speed and temperature, two performance indicators used by orthopaedic clinicians. A range of high gain blades was developed to investigate the correlation between the frequency response predicted by finite element analysis (FEA) and the frequency response measured using an experimental model analysis (EMA) technique. It has been found that FEA frequency predictions are within 1.5% of measured frequencies. FEA has also been used to develop two novel ultrasonic cutting models which allow the effect of blade progression on cutting performance to be investigated. The models have been used to predict the relationship between applied load and cutting speed in single layer and multi-layer materials, and have shown that cutting speed decreases as cortical layer thickness increases, a trend also found from cutting experiments. Ongoing developments to predict temperature from both cutting models have produced a preliminary result which locates regions of maximum cutting temperature. The result influenced the design of blades with modified tip geometries that have been used to reduce cutting temperature. Ultrasonic cutting experiments were performed on bovine bone, two bone substitute materials and various grades of wood. Deep incisions were made for a range of applied loads and cutting speeds to investigate the effect of various cutting parameters on cutting temperature. Ultrasonic cutting has been successfully applied to perform deep incisions in bone whilst maintaining substrate temperature to within critical levels. Two innovative modelling techniques have been used to simulate ultrasonic cutting and demonstrate their potential for revolutionising blade design, and surgical trials

Design and Characterization of an Ultrasonic Surgical Tool Using d₃₁ PMN-PT Plate

AbstractAn ultrasonic surgical tool for tissue incision and dissection has been designed and characterized. The surgical tool is based on a simple geometry to which PMN-PT d31 plates are bonded directly. The performance of the surgical tool has been defined numerically with the Abaqus finite element analysis (FEA) package and practically with laser vibrometer and impedance spectroscopy. The results show the ability of FEA to accurately predict the behaviors of an ultrasonic device as numerical and practical analysis were found to be in a good agreement. The design of the tool presented has the ability to generate displacement amplitude high enough to carry out soft tissue incision with relatively low driving voltage

On the Application of Mechanical Vibration in Robotics-Assisted Soft Tissue Intervention

Mechanical vibration as a way of transmitting energy has been an interesting subject to study. While cyclic oscillation is usually associated with fatigue effect, and hence a detrimental factor in failure of structures and machineries, by controlled transmission of vibration, energy can be transferred from the source to the target. In this thesis, the application of such mechanical vibration in a few surgical procedures is demonstrated. Three challenges associated with lung cancer diagnosis and treatment are chosen for this purpose, namely, Motion Compensation, tumor targeting in lung Needle Insertion and Soft Tissue Dissection: A robotic solution is proposed for compensating for the undesirable oscillatory motion of soft tissue (caused by heart beat and respiration) during needle insertion in the lung. An impedance control strategy based on a mechanical vibratory system is implemented to minimize the tissue deformation during needle insertion. A prototype was built to evaluate the proposed approach using: 1) two Mitsubishi PA10-7C robots, one for manipulating the macro part and the other for mimicking the tissue motion, 2) one motorized linear stage to handle the micro part, and 3) a Phantom Omni haptic device for remote manipulation. Experimental results are given to demonstrate the performance of the motion compensation system. A vibration-assisted needle insertion technique has been proposed in order to reduce needle–tissue friction. The LuGre friction model is employed as a basis for the study and the model is extended and analyzed to include the impact of high-frequency vibration on translational friction. Experiments are conducted to evaluate the role of insertion speed as well as vibration frequency on frictional effects. In the experiments conducted, an 18 GA brachytherapy needle was vibrated and inserted into an ex-vivo soft tissue sample using a pair of amplified piezoelectric actuators. Analysis demonstrates that the translational friction can be reduced by introducing a vibratory low-amplitude motion onto a regular insertion profile, which is usually performed at a constant rate. A robotics-assisted articulating ultrasonic surgical scalpel for minimally invasive soft tissue cutting and coagulation is designed and developed. For this purpose, the optimal design of a Langevin transducer with stepped horn profile is presented for internal-body applications. The modeling, optimization and design of the ultrasonic scalpel are performed through equivalent circuit theory and verified by finite element analysis. Moreover, a novel surgical wrist, compatible with the da Vinci® surgical system, with decoupled two degrees-of-freedom (DOFs) is developed that eliminates the strain of pulling cables and electrical wires. The developed instrument is then driven using the dVRK (da Vinci® research kit) and the Classic da Vinci® surgical system

Nonlinear characterisation of power ultrasonic devices used in bone surgery

Ultrasonic cutting has existed in surgery since the 1950s. However, it was not until the end of the 20th century that advances in ultrasonic tool design, transduction and control allowed commercially viable ultrasonic cutting devices to enter the market. Ultrasonic surgical devices, like those in other power ultrasonic applications such as drilling and welding, require devices to be driven at high power to ensure sufficient output motion is produced to fulfil the application it is designed to perform. With the advent of novel surgical techniques surgeons require tuned ultrasonic tools which can reduce invasiveness while giving access to increasingly difficult to reach surgical sites. To fulfil the requirements of novel surgical procedures new tuned tools need to be designed. Meanwhile, it is well documented that power ultrasonic devices, whilst driven at high power, are inherently nonlinear and, if no attempt is made to understand and subsequently control these behaviours, it is likely that these devices will suffer from poor performance or even failure. The behaviour of the commercial ultrasonic transducer used in bone surgery (Piezosurgery® Device) is dynamically characterised through finite element and experimental methods whilst operating in conjunction with a variety of tuned inserts. Finite element analysis was used to predict modal parameters as well as stress levels within the tuned devices whilst operating at elevated amplitudes of vibration, while experimental modal analysis validated predicted resonant frequencies and mode shapes between 0-80kHz. To investigate the behaviour of tuned devices at elevated vibrational amplitudes near resonance, responses were measured whilst the device was excited via the burst sine sweep method. In an attempt to provide an understanding of the effects that geometry, material selection and wavelength of tuned assemblies have on the behaviour of an ultrasonic device, tuned inserts consisting of a simple rod horn design were characterised alongside more complex cutting inserts which are used in maxillofacial and craniofacial surgery. From these results the aim will be to develop guidelines for design of tuned inserts. Meanwhile, Langevin transducers, commonly known as sandwich or stack transducers, in their most basic form generally consist of four parts; a front mass, a back mass, a piezoceramic stack and a stud or bolt holding the parts together under a compressive pre-load. It is traditionally proposed that the piezoceramic stack is positioned at or close to the vibrational nodal point of the longitudinal mode, however, this also corresponds with the position of highest dynamic stress. It is also well documented that piezoceramic materials possess a low linear stress threshold, therefore this research, in part, investigates whether locating the piezoceramic stack away from a position of intrinsic high stress will affect the behaviour of the device. Through experimental characterisation it has been observed that the tuned devices under investigation exhibited; resonant frequency shifts, jump amplitudes, hysteretic behaviour as well as autoparametric vibration. The source of these behaviours have been found to stem from device geometry, but also from heating within the piezoceramic elements as well as joints with different joining torques

Experimental investigations of forces and torque in conventional and ultrasonically-assisted drilling of cortical bone

Bone drilling is widely used in orthopaedics and surgery; it is a technically demanding surgical procedure. Recent technological improvements in this area are focused on efforts to reduce forces in bone drilling. This study focuses on forces and a torque required for conventional and ultrasonically-assisted tool penetration into fresh bovine cortical bone. Drilling tests were performed with two drilling techniques, and the influence of drilling speed, feed rate and parameters of ultrasonic vibration on the forces and torque was studied. Ultrasonically-assisted drilling (UAD) was found to reduce a drilling thrust force and torque compared to conventional drilling (CD). The mechanism behind lower levels of forces and torque was explored, using high-speed filming of a drill–bone interaction zone, and was linked to the chip shape and character of its formation. It is expected that UAD will produce holes with minimal effort and avoid unnecessary damage and accompanying pain during the incision

Arterial Tissue Perforation Using Ultrasonically Vibrating Wire Waveguides

Chronic Total Occlusions (CTOs) are fibrous and calcified atherosclerotic lesions which completely occlude the artery. They are difficult to treat with standard dilation procedures as they cannot be traversed easily. Their treatment is also associated with a high risk of arterial perforation. Low frequency ultrasonic vibrations delivered via wire waveguides represent a minimally invasive treatment for CTOs and other tissue ablation applications. These devices typically operate at 20–50 kHz delivering wire waveguide distal tip amplitudes of vibration of 0-60 μm. The diseased tissue is ablated or disrupted by repetitive direct mechanical contact and cavitation. This research assesses the susceptibility of arterial tissue to perforation and residual damage under the action of ultrasonically energised wire waveguides. Using Finite Element Analysis (FEA), a linear acoustic model of the wire waveguide distal tips can predict the pressures for a range of operating parameters typically used for these devices. High mesh densities (140 EPW) were required to solve the entire acoustic field, including complex wave interactions. The FEA model was used to aid in the further design and modification of an ultrasonic apparatus and wire waveguide (0–34.3 μm at 22.5 kHz). Using a test rig, the effects of distal tip amplitudes of vibration, feedrate and angled entry on the perforation forces, energy and temperature were measured. The perforation forces reduced (≈ 60%, 6.13 N - 2.46 N mean) when the wire waveguide was energised at low amplitudes of vibrations (\u3c 27.8 μm). There were no significant change in tissue perforation forces above this or when the waveguide was operating above the cavitation threshold. Histological analysis also showed tissue removal. While this knowledge is useful in the prediction and avoidance of perforations during CTO operations; it is also envisaged that this information can aid in the design and development of generic ultrasonic wire waveguide tissue cutting tools