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How Vibro-Acoustography Ultrasound Is Making Waves
May 31, 2012
Azra Alizad, MD, associate professor at the Mayo Clinic College of Medicine, was the recipient of a 2008 Endowment for Education and Research grant. Her 2010 presentation, "A Novel Thyroid Imaging Method for Improving Specificity," delved into the many advantages of ultrasound vibro-acoustography (VA), including that the ultrasound energy used in VA can easily penetrate in dense tissues.

Vibro-acoustography is an innovative, noninvasive, and low cost imaging method that can visualize normal and abnormal soft tissue based on low-frequency (kilohertz-range) ultrasound. Dr Alizad recently sat down with the AIUM to discuss her research on high-contrast, speckle-free VA image displays and how VA technology may lead to a new clinical tool suitable for thyroid imaging.

How did you become interested in vibro-acoustography?

The technology of vibro-acoustography was invented by Dr Mostafa Fatemi and Dr James Greenleaf, in our lab (Ultrasound Research Laboratory) at the Mayo Clinic College of Medicine. I was fascinated by the potentials of this new technology and decided to explore its applications in clinical settings. I started by testing this new technology on phantoms and various excised human tissues. The promising results from excised tissue encouraged me to apply this methodology on humans.

What was the purpose and objective of this study?

The objective of this study was to evaluate the potential of VA for imaging of the thyroid. This method uses the radiation force of ultrasound to vibrate the tissue at a low frequency and records the resulting acoustic field to produce an image that is related to the stiffness of the tissue. VA is sensitive to object properties at ultrasound frequencies as well as low audio frequencies. The goals of this research can be described in two aims: (1) to determine if VA can perform at least similarly to conventional ultrasound imaging in detecting nodules in excised thyroid, and (2) to evaluate the performance of VA in imaging human thyroid.

What did you find out?

We had very promising results in the first aim of the study, which was conducted on excised thyroid tissues from cadaver. We were able to detect nodules and calcification with high contrast and resolution. The pilot study of the second aim, evaluating the performance of VA in imaging human thyroid, was done on 20 patients under an Institutional Review Board–approved protocol. The results showed the feasibility of vibro-acoustography for in vivo imaging of thyroid.

Were the results of your research as you expected?

This study proved the feasibility of in vivo VA imaging of humans, and we gained valuable experience in performing VA on a limited number of patients, which can be used to expand our research in this field. Further research with a larger sample size is needed to differentiate malignant and benign thyroid nodules. Results of this project serve as the starting point for expanded research on this new technique, followed by clinical studies, with the goal of introducing vibro-acoustography as a new tool for thyroid cancer imaging.

What do you think is the next step for research on this subject matter?

We will continue to test human thyroid in vivo on larger populations. Our future plan is to use these data to prepare an application for an extended grant, such as National Institutes of Health R01, to fully test our general hypothesis on a larger human subject population. Successful completion of such a project on human subjects will have a significant impact on thyroid imaging and cancer detection.

What impact has this grant had on your career, or what impact do you foresee this grant having on your career?

This award gave me the opportunity to explore vibro-acoustography imaging of thyroid tissue and testing this technique on a small number of patients. Without this award, I would not have been able to obtain such exciting results. Overall, this award has given me a chance to pursue a new line of research on thyroid imaging.

The full abstract of this study can be found under the 2010 Annual Convention Proceedings on page S6.