A computerized tomography system for transcranial ultrasound imaging

Abstract

Hardware for tomographic imaging presents both challenge and opportunity for simplification when compared with traditional pulse-echo imaging systems. Specifically, point diffraction tomography does not require simultaneous powering of elements, in theory allowing just a single transmit channel and a single receive channel to be coupled with a switching or multiplexing network. In our ongoing work on transcranial imaging, we have developed a 512-channel system designed to transmit and/or receive a high voltage signal from/to arbitrary elements of an imaging array. The overall design follows a hierarchy of modules including a software interface, microcontroller, pulse generator, pulse amplifier, high-voltage power converter, switching mother board, switching daughter board, receiver amplifier, analog-to-digital converter, peak detector, memory, and USB communication. Two pulse amplifiers are included, each capable producing up to 400 Vpp via power MOSFETS. Switching is based around mechanical relays that allow passage of 200 V, while still achieving switching times of under 2 ms, with an operating frequency ranging from below 100 kHz to 10 MHz. The system is demonstrated through ex vivo human skulls using 1 MHz transducers. The overall system design is applicable to planned human studies in transcranial image acquisition, and may have additional tomographic applications for other materials necessitating a high signal output. [Work was supported by NIH R01 EB014296.]