Recent advances in micro-ultrasound

Over the past several decades, the maximum frequencies of ultrasound imaging devices have risen from about 10 MHz to over 60MHz. Similarly, in intravascular ultrasound imaging, frequencies have risen from 20 to as high as 60 MHz center frequencies. The push to higher frequencies is driven by the need for increased resolution in a diverse range of biological and medical applications. This talk will review the development of high frequency ultrasound and provide context for the current and potential application of these devices. Transducer technologies sit at the heart of all acoustic visualization applications. The evolution of transducer fabrication methods will be illustrated with examples of array devices based on conventional dice and fill methods and, more recently, using laser micro machining approaches. The development of novel devices such as dual-frequency probes and multi modality transducers will be reviewed. Examples of the latter will include dual frequency devices for angiography and intravascular ultrasound, photoacoustic devices, and combined IVUS-OCT devices. In each of these, specialized configurations of acoustic sensors and optical devices are required to achieve exceptional imaging performance. Applications of high frequency ultrasound are driven both by clinical needs in human applications and by the need for vastly improved in vivo imaging of biological systems used in discovery oriented biomedical research. Examples of applications of high frequency ultrasound imaging will be drawn from research in the areas of cancer and cardiovascular disease. Further discussion of the special issues related to detection of microbubble and nanoparticle contrast agents will also be included. Clinical translation will be described and illustrated with examples in neurosurgery, neonatology, and prostate imaging. Finally speculation on the future of the field will be presented.