title: Ex Vivo HIFU Experiments Using a $32 \times 32$ -Element CMUT Array.
abstract: High-intensity focused ultrasound (HIFU) has been used as noninvasive treatment for various diseases. For these therapeutic applications, capacitive micromachined ultrasonic transducers (CMUTs) have advantages that make them potentially preferred transducers over traditional piezoelectric transducers. In this paper, we present the design and the fabrication process of an 8 ×8 -mm232 ×32 -element 2-D CMUT array for HIFU applications. To reduce the system complexity for addressing the 1024 transducer elements, we propose to group the CMUT array elements into eight HIFU channels based on the phase delay from the CMUT element to the targeted focal point. Designed to focus at an 8-mm depth with a 5-MHz exciting frequency, this grouping scheme was realized using a custom application-specific integrated circuit. With a 40-V dc bias and a 60-V peak-to-peak ac excitation, the surface pressure was measured 1.2 MPa peak-to-peak and stayed stable for a long enough time to create a lesion. With this dc and ac voltage combination, the measured peak-to-peak output pressure at the focus was 8.5 MPa, which is expected to generate a lesion in a minute according to the temperature simulation. The following ex vivo tissue experiments successfully demonstrated its capability to make lesions in both bovine muscle and liver tissue.
authors.forename: Hyo-Seon
authors.initials: HS
authors.lastname: Yoon
authors.forename: Chienliu
authors.initials: C
authors.lastname: Chang
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Jang
authors.forename: Anshuman
authors.initials: A
authors.lastname: Bhuyan
authors.forename: Jung Woo
authors.initials: JW
authors.lastname: Choe
authors.forename: Amin
authors.initials: A
authors.lastname: Nikoozadeh
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Watkins
authors.forename: Douglas N
authors.initials: DN
authors.lastname: Stephens
authors.forename: Kim
authors.initials: K
authors.lastname: Butts Pauly
authors.forename: Butrus T
authors.initials: BT
authors.lastname: Khuri-Yakub
mesh_terms: D000818:Animals; D002417:Cattle; D003198:Computer Simulation; D004867:Equipment Design; D057086:High-Intensity Focused Ultrasound Ablation / Q000295:instrumentation* / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging; D009132:Muscles / Q000000981:diagnostic imaging; D014159:Transducers