Novel Applications in Ultrasound Technology for Regional Anesthesia
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REGIONAL ANESTHESIA (CJ MCCARTNEY, SECTION EDITOR)
Novel Applications in Ultrasound Technology for Regional Anesthesia Shilpa Munirama • Graeme McLeod
Published online: 31 October 2013 Springer Science + Business Media New York 2013
Abstract Ultrasound-guided regional block (UGRA) of peripheral nerves is now common practice. Nerves, muscle, blood vessels and circumferential perineural spread of local anaesthetic are all seen in real time. However, the utility of B-Mode ultrasound may be limited when adjacent tissues have similar acoustic properties, and several diverse approaches have been taken to improve tissue contrast, particularly in cancer imaging. Examples include: 3D and 4D imaging, software modifications such as harmonics and beam steering, and clinical measurement of the fundamental properties of tissue such as stress and strain. Despite incorporation of new ultrasound technologies into cancer imaging, the practice of UGRA remains restricted to B-Mode ultrasound. Therefore, the objective of this review is to describe the principles of advanced ultrasound technologies, their application to cancer imaging, and their potential use within UGRA. Keywords Anesthesia Regional Ultrasound Needle 3D Elastography
Introduction Use of medical ultrasound can be traced back to as early as the Second World War, but it was not until the 1950s that the work of Professor Ian Donald from Glasgow led to S. Munirama (&) Department of Anaesthesia, Wythenshawe Hospital, South Manchester University Hospitals, Manchester M23 9LT, UK e-mail: [email protected] G. McLeod Institute of Academic Anaesthesia, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
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development in technology, its application giving birth to diagnostic medical ultrasound. In the following two decades, commercial ultrasound gained more widespread use. The introduction of microchip technology and more powerful signal processing by computers has revolutionised various aspects of ultrasound imaging. It was not until l994 that the use of ultrasound for regional anesthesia (supraclavicular block) was reported by Kapral et al. [1]. Since then, ultrasound is the only practical imaging modality that has been widely used to guide clinical practice while performing regional anesthesia. The obvious disadvantage of poor image quality with increasing depth and varying tissue characteristics demands the development of new technologies to overcome this problem. Furthermore, ultrasound-guided regional anesthesia is a dynamic process requiring real-time imaging. There are different variables influencing the quality of image which include operator skill, tissues characteristics (age, increasing body mass index, etc.), and echogenicity of the needles being used. Ultrasound images are formed from reflected echoes of ultrasound waves from tissues/boundaries which depends on its acoustic impedance (AI). AI is determined by density and stiffness of tissue. Biological tissue is more complex, with different physical properties such as d
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