Description  Claims  Drawing  Cited references 

US2012055521A   [0004] 
US2007267176A   [0005] 
US2008073063A   [0005] 
US4375991A   [0006] 

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control   [0077] 
Applied Physics Letters   [0077] 
Phys. Med. Biol.   [0077] 
Nature, Scientific Reports   [0077]