Enhanced biopsy and regional anaesthesia through ultrasound actuation of a standard needle

摘要

There is an urgent and unmet clinical need to improve accuracy and safety during needle-based interventional procedures including regional anaesthesia and cancer biopsy. In ultrasound guided percutaneous needle procedures, there is a universal problem of imaging the needle, particularly the tip, especially in dense tissues and steep insertion angles. Poor visualization of the needle tip can have serious consequences for the patients including nerve damage and internal bleeding in regional anaesthesia and, in the case of biopsy, mis-sampling, resulting in misdiagnosis or the need for repeat biopsy. The aim of the work was to design and develop an ergonomic ultrasound device to actuate standard, unmodified needles such that the visibility of needle can be enhanced when observed under colour Doppler mode of ultrasound imaging. This will make the needle procedures efficient through accurate needle placement while reducing the overall procedure duration. The research reported in this thesis provides an insight into the new breed of piezoelectric materials. A methodology is proposed and implemented to characterize the new piezocrystals under ambient and extreme practical conditions. For the first time, the IEEE standard method (1987) was applied to an investigation of this type with binary (PMN-PT) and ternary (PIN-PMN-PT) compositions of piezocrystals. Using the existing data and the data obtained through characterization, finite element analysis (FEA) were carried to adequately design the ultrasound device. Various configurations of the device were modelled and fabricated, using both piezoceramic and piezocrystal materials, in order to assess the dependency of device’s performance on the configuration and type of piezoelectric material used. In order to prove the design concept and to measure the benefits of the device, pre-clinical trials were carried out on a range of specimens including the soft embalmed Thiel cadavers. Furthermore, an ultrasound planar cutting tool with various configurations was also designed and developed as an alternative to the existing cumbersome ultrasonic scalpels. These configurations were based on new piezocrystals including the Mn-doped ternary (Mn:PIN-PMN-PT) material.It is concluded that the needle actuating device can significantly enhance the visibility of standard needles and additionally benefits in reducing the penetration force. However, in order to make it clinically viable, further work is required to make it compliant with the medical environment. The piezocrystals tested under practical conditions although offer extraordinary piezoelectric properties, are vulnerable to extreme temperature and drive conditions. However, it is observed that newer piezocrystals, especially Mn:PIN-PMN-PT have shown the potential to replace the conventional piezoceramics in high power and actuator applications. Moreover, the d31-mode based planar cutting tool contrasts with the cumbersome design of mass-spring transducer structure and has the potential to be used in surgical procedures.