A new methodology for focusing ultrasonic beams noninvasively in the presence of the rib cage is investigated. This investigation is motivated by the need to employ high intensity focused ultrasound (HIFU) using phased array applicators for the treatment of liver tumors partially shadowed by the rib obstacles. This approach enables us to efficiently perforn the ultrasound computational analysis and pattern synthesis in the interior region of the rib cage. The proposed technique consists of two main steps. First, a virtual array is introduced along the intercostal spacings between the solid ribs to generate the prespecified intensity levels at a set of control points within the target region. The second step involves the design of the actual feed array th it induces the virtual sources between the intercostal spaci igs. This design optimization is carried out via the pseudo-i iverse technique (minimum norm least squares solution) and by enforcing a constrained preconditioned pseudo-inv;rse method. The proposed procedure calculates the required primary sources (feed array) while maintaining minima power deposition over the solid obstacles.
|Original language||English (US)|
|Number of pages||12|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|State||Published - 1998|
Bibliographical noteFunding Information:
Manuscript received July 7, 1997; accepted February 20, 1998. This work was funded in part by a grant from the O ce of Vice President for Research at the University of Michigan and in part by grant and CA66602 from the National Institutes of Health.