Medical and Biological Imaging with High Frequency Ultrasound
Dr. Foster has been at the forefront of high-resolution, ultrasound development for small animal research since he developed the first high frequency imaging systems in the 1980s. Central to his effort has been his ability to extend the powerful B-mode backscatter methods developed for clinical imaging in the 3 - 10 MHz frequency range to much higher frequencies (20 - 200 MHz) thereby enabling tissue microimaging. This technique, called ultrasound biomicroscopy (UBM), enables biological structures to be imaged with resolutions ranging from 15 to 100 micrometres over fields of view ranging from 2 - 15 mm. This is the core foundation upon which the VisualSonics’ Vevo 770 imaging system was developed.

There are many clinical applications for high frequency ultrasound including ophthalmic, skin, and cartilage imaging. In the case of skin cancers such as malignant melanoma the stage at which the tumor changes from a lateral growth phase to a vertical growth phase is important in tumor grading. Osteoarthritis can change both the thickness, structure, and surface roughness of cartilage. Since such changes are typically only on the order of a few tens of microns, UBM is a useful means of quantifying this process. The management of surgical interventions and the assessment of treatment are important aspects of research in UBM.

Together with other U of T colleagues, Dr. Foster helped found the Mouse Imaging Centre (MICe) at the Hospital for Sick Children in Toronto. MICe is a Canada-wide resource for rapid phenotyping and disease modeling in the mouse. The biological applications of UBM are being investigated in combination with micro-MR, micro-CT and optical microscopies. These techniques greatly facilitate in vivo assessment of developmental and pathophysiological processes under highly controlled conditions. Disease models ranging from glaucoma to breast cancer are under investigation. Finally, the development of high frequency Doppler may offer a new dimension of information on blood flow at the arteriolar and capillary level to compliment the structural information in UBM images. Such developments are bound to have an important impact on the study of angiogenesis and disease progression.

Specific research areas include:

• >  Transducer array and imaging systems development
  
• >  Doppler studies of vascular morphology and hemodynamics in the microcirculation
  
• >  Ultrasonic propagation and fundamental interactions in tissues
  
• >  High frequency nonlinear propagation
  
• >  Microbubble and Nanoparticle contrast agents
  
• >  Imaging for genomics and disease models
  
  
  

Selected Publications:

• >  David E. Goertz, Emmanuel Cherin, Andrew Needles, Raffi Karshafian, Allison S. Brown, Peter N. Burns, and F. Stuart Foster , "High Frequency Nonlinear B-Scan Imaging of Microbubble Contrast Agents", Ultrasonics, Ferroelectrics, And Frequency Control, January 2005, Vol. 52.
  
  
• >  Le Floc'h J, Cherin E, Zhang MY, Akirav C, Adamson SL, Vray D, Foster FS., "Developmental changes in integrated ultrasound backscatter from embryonic blood in vivo in mice at high US frequency", Ultrasound Med Biol. 2004 Oct;30(10):1307-19.
  
  
• >  Yu-Qing Zhou, F. Stuart Foster, Brian J Nieman, Lorinda Davidson, X. Josette Chen, and R. Mark Henkelman, "Comprehensive transthoracic cardiac imaging in mice using ultrasound biomicroscopy with anatomical confirmation by magnetic resonance imaging", Physiological Genomics: 2004, April 27: 10.1152
  
  
• >  Zhou YQ, Davidson L, Henkelman RM, Nieman BJ, Foster FS, Yu LX, Chen XJ, "Ultrasound-guided left-ventricular catheterization: a novel method of whole mouse perfusion for microimaging", Nature Biotechnology, Lab Invest. 2004 Mar;84(3):385-9.
  
  
• >  Zhou YQ, Foster FS, Parkes R, and Adamson SL, "Developmental changes in left and right ventricular diastolic filling patterns in mice", Am J Physiol Heart Circ Physiol, 2003 June 12: 10.1152.
  
  
• >  F. S. Foster, C. J. Pavlin, K. A. Harasiewicz, D. A. Christopher, and D. H. Turnbull, “Advances in ultrasound biomicroscopy,” Journal of Ultrasound in Medicine and Biology, vol. 26, pp. 1-27, 2000.
  
  
• >  F. S. Foster, P. N. Burns, D. Hope-Simpson, S. R. Wilson, C. D.A., and D. E. Goertz, “Ultrasound for the visualization and quantification of tumour microcirculation,” Cancer Metastasis and Reviews, vol. 19, pp. 131-138, 2000.
  
  
• >  F. S. Foster, M. Y. Zhang, Y. Q. Zhou, G. Liu, J. Mehi, C. E., K. A. Harasiewicz, B. G. Starkoski, L. Zan, D. A. Knapik, and S. L. Adamson, “A new Ultrasound Instrument for in vivo microimaging of mice,” Ultrasound in Medicine and Biology, vol. 28, pp. 1165-1172, 2002.
  
  
• >  D. E. Goertz, J. L. Yu, R. S. Kerbel, P. N. Burns, and F. S. Foster, “High frequency Doppler ultrasound monitors the effects of antivascular therapy on tumor blood flow,” Cancer Research, vol. 62, pp. 6371-6375, 2002.
  
  
• >  D. E. Goertz, J. L. Yu, R. S. Kerbel, P. N. Burns, and F. S. Foster, “High frequency 3D color flow imaging of the microcirculation,” Ultrasound in Medicine and Biology, vol. In press, 2003.
  
  
• >  Y. Q. Zhou, F. S. Foster, D. W. Qu, M. Zhang, K. A. Harasiewicz, and S. L. Adamson, “Applications for multifrequency ultrasound biomicroscopy in mice from implantation to adulthood,” Physiol Genomics, vol. 10, pp. 113-126, 2002.
  
  
• >  R. Liu, K. A. Harasiewicz, and F. S. Foster, “Interdigital pair bonding for high frequency (20 - 50 MHz) ultrasonic composite transducers,” IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, vol. 48, pp. 299-306, 2001.
  
  
• >  M. Lukacs, M. Sayer, and F. S. Foster, “Single element high frequency (>50 MHz) sol gel composite ultrasound transducers,” IEEE Transactions on Ultrasonics Ferroeletrics and Frequency Control, vol. 47, pp. 148-159, 2000.