A focused ultrasound (\u201cFUS\u201d} system capable of use in a small bore imaging system, such as a small bore magnetic resonance imaging (\u201cMRI\u201d} system is provided. a first silicon oxide layer of a first wafer, having flow features patterned in the first silicon oxide layer on an actuator chip in a first silicon substrate of the first wafer, to a second silicon oxide layer of a second wafer, defining a nozzle plate on a second silicon substrate of the second wafer. The current mirror circuit is used for providing a first current and third current. Then, after removing the resist and depositing an isolation oxide film on the whole surface, an isolation oxide film is flattened in good thickness precision in the height specified by the thickness of a silicon nitride film by performing CMP treatment which used the silicon nitride film as the polishing stopper. A normalized intrusion value is calculated based on the center strength value, the impact location, and a bumper stiffness factor.