The International Acoustical Imaging Symposium has been held continuously since 1968 as a unique forum for advanced research in all areas of acoustical imaging. The interdisciplinary nature of the Symposium and the wide international participation are two of its main strengths. Scientists from around the world present papers in all fields of acoustical imaging in an informal environment conducive to lively discussion and cross-fertilization. Acoustical Imaging remains the unique Symposium in the world that promotes the sharing of technology, developments, methods and theory among all areas of acoustics. The fact that a loyal community of scientists has supported this Series since 1968 is evidence of its impact on the field. The Symposium Series continues to thrive in a busy calendar of scientific meetings without the infrastructure of a professional society. It does so because those who attend and those who rely on the Proceedings as a we- known reference work acknowledge its value. The 28th International Acoustical Imaging Symposium was held in San Diego, California USA during March 20–23, 2005. Volume 28 of the Proceedings contains an excellent collection of papers presented in six major categories: • Acoustic Microscopy • Components and Systems • Computed Tomography • Biological and Medical Applications • Non-Destructive Evaluation • Physics and Mathematics xv xvi Preface