High frequency ultrasound B-scan imaging

High frequency B-scan imaging or ultrasound biomiocroscopy (UBM) is a recent extention of the powerful methods of diagnostic ultrasound imaging. Operting in te 30 to 200 MHz range provides microscopic resolution but is limited to depths of penetration on the order of several millimetres. In spite of its' limited penetration, high frequency ultrasound B-scan imaging is finding clinical applictions in a number of areas where critical structures lie within the limited field of view. Imaging of the anterior segment of the eye, intraluminal imaging, skin imaging and imaging of cartilage are examples of UBM applications. In this paper, the physical principles applications of UBM imaging are explored with an emphasis on areas of current research and clinical applications. High frequency transducers and beamforming will be described together with basic system instrumentation. Resolution on the order of 50 microns laterally and 30 to 40 microns axially are readily achieved in the 60 MHz range. This permits visualization of disease processes in the very early stages. Examples of glaucauma an skin melanoma are used to illustrate this potential. The fundamental trade off between resolution and penetration is discussed and speculation on the development of new high frequency imaging technology such as high frequency Doppler techniques is presented.