A surgical bone biopsy needle using ultrasonic-sonic frequency vibration

This thesis presents a surgical needle designed for bone biopsy, based on an ultrasonic-sonic drilling mechanism. Bone biopsy is an invasive diagnostic procedure where a bone sample is extracted for clinical analysis. For conventional bone biopsy methods, closed biopsy is normally adopted and uses a core needle. An intact and viable biopsy sample is required for clinical analysis. However, a particular limitation of closed biopsy is that the microarchitecture of the biopsy sample can be easily damaged due to the large force which is applied through the core needle to penetrate bone. In some cases, the bone biopsy samples are fractured or crushed during the biopsy process. Power ultrasonic surgical devices have improved many aspects of bone cutting procedures, such as lower cutting force, higher accuracy, and better preservation of the tissue around the cutting site. In this study, an ultrasonic-sonic needle (US needle) system is designed and used to extract an intact biopsy sample and the penetration performance is evaluated by the effective impulse delivered to the target. The ultrasonic-sonic drilling mechanism was originally invented for rock drilling in low environments. In the US needle system, a free mass oscillates between an ultrasonic transducer-horn and a surgical needle, converting the ultrasonic frequency vibration of the horn to sonic frequency vibration of the needle. Compared to other ultrasonic surgical devices that directly transfer the ultrasonic vibrations from the cutting tip to the tissue, the US needle allows sufficient time between impacts with the free mass for the tip vibration amplitude to be re-established in the horn. This can maintain penetration progress of the needle into bone, where the rate of progress has been shown to be proportional to the effective impulse delivered by the needle to the bone. To maximise the effective impulse, a numerical model is developed to simulate the dynamic behaviour of the needle system and optimise the US needle. To build the US needle system, the design and optimisation of the ultrasonic transducer-horn were investigated with the finite element method and experimental modal analysis, ensuring that the transducer-horn operates at the tuned frequency (50kHz) with a pure longitudinal mode. The configuration of the ultrasonic horn determines the momentum transferred to the free mass and hence also affects the effective impulse delivered to the target. The shape and dimensions of the ultrasonic horn were determined through the finite element model of the ultrasonic horn impacting the free mass, which focused on maximising the post-collision velocity of the free-mass. The dynamic components of the US needle were also investigated. A numerical model representing the dynamic behaviour of the needle system was developed, allowing the optimisation of each dynamic component, maximising the effective impulse delivered to the target. Each dynamic component of the US needle was modelled as a mass-spring-damper (MSD) system, which constituted the whole system dynamic model. The numerical model was validated by experiments using a prototype needle. The free-mass velocity, needle velocity and impact force predicted by the numerical model were compared with the results measured from experiments using 3D laser Doppler vibrometry, an ultra-high speed camera and a load cell, respectively. The numerical model results exhibit good agreement with the experimental results, indicating the numerical model can be used as a predictive tool to evaluate the performance of the US needle when different configurations are implemented. The configuration of the US needle is studied to maximise the effective impulse by the numerical model, through optimisation of the mass of the free mass, spring rate and spring pre-load. An optimised configuration of the US needle was determined by the numerical model and validated by experiments. The resulting prototype of the needle device was tested in ovine femur in vitro and was demonstrated to retrieve a cortical bone biopsy sample with a more cylindrical geometry, smoother surface and more intact sample than a cortical biopsy sample retrieved using a conventional trephine needle. Moreover, the penetration performance of the US needle was also compared with an ultrasonic resonant needle where the ultrasonic transducer and surgical needle resonate at the same frequency

Volume 19, issue 3

The mission of CJS is to contribute to the effective continuing medical education of Canadian surgical specialists, using innovative techniques when feasible, and to provide surgeons with an effective vehicle for the dissemination of observations in the areas of clinical and basic science research. Visit the journal website at http://canjsurg.ca/ for more.https://ir.lib.uwo.ca/cjs/1140/thumbnail.jp

'ACOUSTO-OPTIC SENSING FOR SAFE MRI PROCEDURES'

In this work, a novel sensor platform is developed for safer and more effective magnetic resonance imaging (MRI). This is achieved by tracking interventional devices, such as guidewires and catheters during interventional MRI procedures, and by measuring the radio frequency (RF) field to assess RF safety of patients with implants, such as pacemakers, during diagnostic MRI. The sensor is based on an acousto-optic modulator coupled with a miniature antenna. This structure is realized on an optical fiber which is immune to the RF field and eliminates the need for conducting lines. The acousto-optic modulator consists of a piezo-electric transducer and a fiber Bragg grating (FBG). The piezoelectric transducer is electrically connected to the miniature antenna and mechanically coupled to the FBG. Local RF signal received by the miniature antenna is converted to acoustic waves by the piezoelectric transducer. Acoustic waves change the grating geometry on the FBG, thus the reflected light from the FBG is modulated. For diagnostic imaging, short dipole antennas are used for sensing the local electric field, which is the primary cause of RF induced heating. For tracking purposes, small loop antennas are used for capturing local MRI signal which contains the location information. In this thesis, a comprehensive model for the acousto-optic modulator is developed and validated through sensitivity and linearity tests. Prototype RF field sensors are built and characterized: sensitivity of 1.36mV/nT and 98 μV/V/m with minimum detectable field strength of 8.2pT/√Hz and 2.7V/m/√Hz and dynamic range of 117dB/√Hz at 23MHz are achieved with 4mm single loop and 8mm short dipole antennas, respectively. These figures are competitive with commercial sensors with much larger form factors. Catheter tracking capability of the sensor under MRI is demonstrated in-vivo in swine in a 0.55T scanner using an 8F catheter in addition to phantom studies under 0.55T and 1.5T clinical MRI systems.Ph.D

Journal of Telecommunications and Information Technology

kwartalni

3D Innovations in Personalized Surgery

Current practice involves the use of 3D surgical planning and patient-specific solutions in multiple surgical areas of expertise. Patient-specific solutions have been endorsed for several years in numerous publications due to their associated benefits around accuracy, safety, and predictability of surgical outcome. The basis of 3D surgical planning is the use of high-quality medical images (e.g., CT, MRI, or PET-scans). The translation from 3D digital planning toward surgical applications was developed hand in hand with a rise in 3D printing applications of multiple biocompatible materials. These technical aspects of medical care require engineers’ or technical physicians’ expertise for optimal safe and effective implementation in daily clinical routines.The aim and scope of this Special Issue is high-tech solutions in personalized surgery, based on 3D technology and, more specifically, bone-related surgery. Full-papers or highly innovative technical notes or (systematic) reviews that relate to innovative personalized surgery are invited. This can include optimization of imaging for 3D VSP, optimization of 3D VSP workflow and its translation toward the surgical procedure, or optimization of personalized implants or devices in relation to bone surgery