title: Design and experimental evaluation of a 256-channel dual-frequency ultrasound phased-array system for transcranial blood-brain barrier opening and brain drug delivery.
abstract: Focused ultrasound (FUS) in the presence of microbubbles can bring about transcranial and local opening of the blood-brain barrier (BBB) for potential noninvasive delivery of drugs to the brain. A phased-array ultrasound system is essential for FUS-BBB opening to enable electronic steering and correction of the focal beam which is distorted by cranial bone. Here, we demonstrate our prototype design of a 256-channel ultrasound phased-array system for large-region transcranial BBB opening in the brains of large animals. One of the unique features of this system is the capability of generating concurrent dual-frequency ultrasound signals from the driving system for potential enhancement of BBB opening. A wide range of signal frequencies can be generated (frequency = 0.2-1.2 MHz) with controllable driving burst patterns. Precise output power can be controlled for individual channels via 8-bit duty-cycle control of transistor-transistor logic signals and the 8-bit microcontroller-controlled buck converter power supply output voltage. The prototype system was found to be in compliance with the electromagnetic compatibility standard. Moreover, large animal experiments confirmed the phase switching effectiveness of this system, and induction of either a precise spot or large region of BBB opening through fast focal-beam switching. We also demonstrated the capability of dual-frequency exposure to potentially enhance the BBB-opening effect. This study contributes to the design of ultrasound phased arrays for future clinical applications, and provides a new direction toward optimizing FUS brain drug delivery.
authors.forename: Hao-Li
authors.initials: HL
authors.lastname: Liu
authors.forename: Chen-Kai
authors.initials: CK
authors.lastname: Jan
authors.forename: Po-Chun
authors.initials: PC
authors.lastname: Chu
authors.forename: Jhong-Cing
authors.initials: JC
authors.lastname: Hong
authors.forename: Pei-Yun
authors.initials: PY
authors.lastname: Lee
authors.forename: Jyh-Duen
authors.initials: JD
authors.lastname: Hsu
authors.forename: Chung-Chih
authors.initials: CC
authors.lastname: Lin
authors.forename: Chiung-Ying
authors.initials: CY
authors.lastname: Huang
authors.forename: Pin-Yuan
authors.initials: PY
authors.lastname: Chen
authors.forename: Kuo-Chen
authors.initials: KC
authors.lastname: Wei
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000000981:diagnostic imaging; D016503:Drug Delivery Systems / Q000379:methods*; D004453:Echoencephalography; D004867:Equipment Design; D006801:Humans; D012886:Skull / Q000000981:diagnostic imaging; D013552:Swine; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*