Page 60 - 2016Winter

TECHNICAL COMMITTEE REPORT
Biomedical Acoustics
tion, uses ultrasound and microbubbles to produce transient pores in cell membranes to enable the uptake of drugs or genes (Bouakaz et al., 2016). When preformed microbub- bles (ultrasound contrast agents) are injected systemically, the microbubble-ultrasound interactions are focused on the blood vessels. This approach can be used to enhance the de- livery of a thrombolytic agent into a blood clot or to directly break it up (Bader et al., 2016). In the central nervous sys- tem, microbubble-enhanced sonication can result in a tem- porary opening of the blood-brain barrier, which normally prevents most drugs from leaking out of the blood vessels (Burgess and Hynynen, 2016). At the May 2016 ASA meet- ing in Salt Lake City, we heard from a group in Norway who used a commercial ultrasound imaging system and a com- mercial ultrasound contrast agent to enhance the delivery of chemotherapy in patients with pancreatic cancer (Kotopou- lis et al., 2013). In tumors, hyperthermia can increase blood flow and drug delivery.
Another approach for targeted drug delivery with ultra- sound is to produce novel drugs or drug carriers to release a therapeutic payload on demand at specific targets (Sirsi and Borden, 2014). A number of researchers have developed drug-loaded microbubbles, echogenic liposomes, or perflu- orocarbon emulsions that release their cargoes when soni- cated. Others have developed agents that are heat sensitive. Thermosensitive liposomes are designed to undergo a phase change when a specific temperature is reached, enabling the rapid release of chemotherapy or other drugs to the desired targets.
Each of these treatments can have unique roles for acousti- cians and scientists in related fields at each stage of its de- velopment from concept to clinical use. For each treatment, we need to figure out how to safely deliver the acoustic en- ergy into the tissue, how to select the parameters to ensure the correct bioresponse, how to monitor and control what we are doing, and how to ensure that the treatment is suc- cessful. BATC members bring expertise in theoretical and experimental acoustics, electrical engineering, imaging (ul- trasound and otherwise), and control as well as in biology and drug development.
I hope that I have conveyed the breadth of research that is going on in relation to the biomedical applications of acous- tics. My favorite part of the ASA and the BATC has been the supportive environment for students and young inves- tigators. We all make an effort to be open and welcoming to students, providing an outlet for discussion and advice. We
are an engaged and friendly group, and I encourage every- one to attend our open meetings that are held at every ASA conference.
Biosketch
Nathan McDannold is an associ- ate professor in radiology at Harvard Medical School. He has been working in the Focused Ultrasound Laboratory at Brigham & Women’s Hospital since 1996. His work has been primarily con- cerned with the development and imple-
mentation of ultrasound-based therapies, image-guidance methods, and clinical focused ultrasound treatments. In re- cent years, a main focus of his work has been studying the use of ultrasound for temporary disruption of the blood- brain barrier, which may allow for targeted drug delivery to the brain. Dr. McDannold received his PhD in physics from Tufts University in 2002.
References
Bader, K. B., Bouchoux, G., and Holland, C. K. (2016). Sonothrombolysis. Advances in Experimental Medicine and Biology 880, 339-364.
Bouakaz, A., Zeghimi, A., and Doinikov, A. A. (2016). Sonoporation: Con- cept and mechanisms. Advances in Experimental Medicine and Biology 880, 175-189.
Burgess, A., and Hynynen, K. (2016). Microbubble-assisted ultrasound for drug delivery in the brain and central nervous system. Advances in Experi- mental Medicine and Biology 880, 293-308.
Garra, B. S. (2015). Elastography: History, principles, and technique com- parison. Abdominal Imaging 40, 680-697.
Kooiman, K., Vos, H. J., Versluis, M., and de Jong, N. (2014). Acoustic be- havior of microbubbles and implications for drug delivery. Advanced Drug Delivery Reviews 72, 28-48.
Kotopoulis, S., Dimcevski, G., Gilja, O. H., Hoem, D., and Postema, M. (2013). Treatment of human pancreatic cancer using combined ultra- sound, microbubbles, and gemcitabine: A clinical case study. Medical Physics 40, 072902.
Sirsi, S. R., and Borden, M. A. (2014). State-of-the-art materials for ul- trasound-triggered drug delivery. Advanced Drug Delivery Reviews 72, 3-14.
Vlaisavljevich, E., Lin, K. W., Maxwell, A., Warnez, M. T., Mancia, L., Singh, R., Putnam, A. J., Fowlkes, B., Johnsen, E., Cain, C., and Xu, Z. (2015). Effects of ultrasound frequency and tissue stiffness on the histotripsy in- trinsic threshold for cavitation. Ultrasound in Medicine and Biology 41, 1651-1667.
Wang, L. V., and Yao, J. (2016). A practical guide to photoacoustic tomogra- phy in the life sciences. Nature Methods 13, 627-638.
Xu, Z., Hall, T. L., Fowlkes, J. B., and Cain, C. A. (2007). Effects of acoustic parameters on bubble cloud dynamics in ultrasound tissue erosion (histo- tripsy). The Journal of the Acoustical Society of America 122, 229-236.
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