Photoacoustic imaging of visually evoked cortical and subcortical hemodynamic activity in mouse brain: feasibility study with piezoelectric and capacitive micromachined ultrasonic transducer (CMUT) arrays

Abstract

This study investigates the feasibility of capturing visually evoked hemodynamic responses in the mouse brain using photoacoustic tomography (PAT) and ultrasound (US) dual-modality imaging. A commercial piezoelectric transducer array and a capacitive micromachined ultrasonic transducer (CMUT) array were compared using a programmable PAT-US imaging system. The system resolution was measured by imaging phantoms. We also tested the ability of the system to capture visually evoked hemodynamic responses in the superior colliculus as well as the primary visual cortex in wild-type mice. Results show that the piezoelectric transducer array and the CMUT array exhibit comparable imaging performance, and both arrays can capture visually evoked hemodynamic responses in subcortical as well as cortical regions of the mouse brain.

Label-free photoacoustic computed tomography of visually evoked responses in the primary visual cortex and four subcortical retinorecipient nuclei of anesthetized mice

“…Figure 1(a) shows a schematic of our PACT system for real-time brain imaging. This system was used in our previous study 16 and is briefly described here. A neodymium-doped yttrium aluminum garnet laser-pumped optical parametric oscillator (Phocus MOBILE, OPOTEK Inc., Carlsbad, California, United States) was used as the excitation source, with a pulse duration of 5 to 7 ns, a pulse repetition rate of 10 Hz, and a pulse energy variation below 5%.…”

“… 12 PACT has successfully recorded visual responses in V1 cortex of mice 13 and rats 14 , 15 and more recently in the mouse SC. 16 In PACT-US parallel imaging, the PACT images are naturally co-registered with the US images as the transducer array acquires both simultaneously, thereby allowing the HR to be easily superimposed onto the brain anatomies revealed by US imaging.…”

“…Our recent pilot study confirmed the feasibility of PACT-US parallel imaging to capture visually evoked HRs in V1 and SC of wild-type mice. 16 The present study used a linear array with a mechanical translation to cover major visual regions of high interest to researchers, including the V1, SC, LGd, suprachiasmatic nucleus (SCN), and olivary pretectal nucleus (OPN). In addition, we established a data processing method for isolating the visual-evoked responses from background signals.…”