Medical and Biological Physics(DMBP)
Physique médicale et biologique (DPMB)
Jeremy BROWN
Queen's University
Development and Applications of High Frequency Ultrasound Imaging Systems *
The non-destructive nature of ultrasonic waves has made ultrasound imaging one of the most popular diagnostic tools in medicine. Most commercial ultrasound systems operate in the frequency range from 3 to 5 MHz and can resolve structures approximately 1 mm in size. By increasing the frequency, the ultrasound wavelength is decreased and finer resolution can be obtained. Several high frequency (30-100 MHz) ultrasound systems have recently been developed for imaging the eye, skin, and vascular system with microscopic resolution (< 100 microns). Despite the improved resolution, high frequency systems are not routinely used in clinical practice or biological studies. A major problem is that the single element transducers that are currently available for high frequency imaging are geometrically shaped to focus the ultrasound energy. This introduces a tradeoff between the image resolution and depth of field. A significant improvement in image quality can be achieved by replacing the single element transducer with a transducer array and an electronic beamformer. This combination allows the ultrasound energy to be optimally focused at each depth within a tissue. Unfortunately, fabrication a high frequency transducer array is difficult since the dimensions of the array scale with the ultrasound wavelength. We have recently developed a technique for fabricating transducer arrays using a simple photolithographic process. The process is relatively simple and has allowed us to reproducibly fabricate miniature arrays. In this talk, I will provide a brief overview of high frequency ultrasound imaging and then describe our work in developing high frequency transducer arrays and beamformers.
*In collabaration with: F.S. Foster Sunnybrook Health Sciences Centre,G.R. Lockwood Queen's University.