High intensity focused ultrasound (HIFU) is an increasingly popular physical tool with a wide range of applications in medicine. One of the drivers of this advancement is the development of ultrasound phased arrays, which, although more complex and costly than the traditional single focused bowl transducers used in earlier studies, are capable of electronically controlled dynamic focusing. Such systems not only steer a single focus without movement of the array itself, but can also generate several foci simultaneously and create focal regions with complex configurations. This book addresses the design, research and development, and medical applications of both relatively small HIFU arrays that can be inserted into body cavities (so called linear arrays) and larger two dimensional arrays for extracorporeal use. A key safety issue in the design of these arrays is to ensure that only targeted tissue is exposed to high levels of acoustic intensity and in this regard, this book highlights the advantages of designs involving spatial randomization of array elements to reduce the level of potentially dangerous grating lobes. In particular, phased arrays with a random distribution of elements are discussed and compared to regular arrays, and methods for calculating ultrasound fields generated by different phased arrays including the generation of multiple simultaneous foci and focal regions with complex geometrical shapes are presented. A detailed discussion of the influence of the dimensions, number, and shape of individual elements, errors in phase setting at the elements, and the frequency modulation of the signal on the quality of the intensity distributions produced by random arrays is included. As well as addressing technical issues of ultrasound phased arrays, current and potential medical applications are discussed. Much clinical experience of HIFU has been gained in the treatment of prostate diseases, including prostate cancer, and uterine fibroids. The ability of phased arrays to sonicate through the skull and create a focal volume within the brain without excessive heating of the skull opens up the possibilities of non-invasive treatments of not only brain tumours but also neurological disorders, intracerebral haemorrhrage, and drug delivery across the blood-brain barrier whilst focusing acoustic energy at targets distal to the ribs provides an opportunity for HIFU ablation of cardiac tissue. Exciting new developments such as stimulation of neural structures leading to the development of tactile displays or a prosthesis of a degenerating retina are also included.
The book is aimed at not only at medical physicists and engineers interested in developing novel medical devices and systems to advance treatment of the above diseases and disorders but also physicians interested in applying these devices to their fields of clinical and experimental medicine. The information provided in this book will also be of interest to other professionals such as physiologists who use physical methods to study the origin, development and modification of different functions as well as to undergraduate and graduate students of all of these specialties. (Imprint: Nova)
“The authors, Leonid Gavrilov and Jeff Hand, are renown experts in investigation of High Intensity Focused Ultrasound (HIFU) and its application in medicine and physiology. This informative and very useful book summarizes the results of studies carried out in the field of ultrasound phased arrays specific to HIFU applications in medicine performed in the USA, Europe, and Asia. The monograph will be useful for specialists in physical and medical ultrasound, for engineers developing new devices for medical applications, for physicians applying these devices in different fields of clinical and experimental medicine, and for physiologists and biophysicists. Students and graduate students of all these specialties will also find the book to be useful.” - Reviewed by Professor Oleg Sapozhnikov, Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington.
"Gavrilov and Hand are amongst very few scientists internationally who have made ground-breaking contributions to the technical challenges associated with the clinical use of high-intensity ultrasound. This book sets out clearly the rationale and experimental solution to one specific challenge, grating-lobe exposure, by the use of random arrays, a technique pioneered by the authors. The text is rich in experimental detail, particularly from the authors’ own experience, and is well supported by references, a quarter of which are from the past 5 years. The book is essential for any scientist or clinical researcher who is taking a serious interest in this expanding field." - Reviewed by Francis A Duck, Professor, University of Bath, Claverton Down, Bath, UK.
"This book is written by world-known specialists in medical ultrasound Dr. Leonid Gavrilov (Acoustics Institute, Moscow) and Prof Jeffrey Hand (King's College London). The book addresses current state-of-the art in research, design, and development of multi-element phased arrays intended for medical applications. An important chapter of the book is related to the detail description of random therapeutic arrays, the approach that has been developing by the authors since the very beginning of 2000s. The elements of such arrays are randomly distributed over the array surface with the aim to minimize the level of secondary intensity maxima (so-called "grating lobes”). This approach has been realized in many clinical and research transducers. Another impressive and informative chapter of the book is related to various clinical applications of phased arrays, including data obtained in very recent years. In general, the book can be very useful for acousticians and medical physicists, engineers developing novel medical systems, and also for physiologists and biophysicists." - Reviewed by Professor Vera Khokhlova, Center for Industrial and Medical Ultrasound, University of Washington.