Single-shot 3D photoacoustic computed tomography with a densely packed array for transcranial functional imaging

TL;DR

This paper presents a high-channel-count, single-shot 3D photoacoustic tomography system capable of transcranial brain imaging, overcoming skull attenuation and enabling real-time functional imaging in humans.

Contribution

The authors engineered a densely packed ultrasonic transducer array system that achieves single-shot 3D transcranial imaging, a significant advancement over previous limited-capability systems.

Findings

Achieved 9 cm light penetration depth in chicken tissue

Successfully performed transcranial imaging through ex vivo human skull

Enabled real-time 3D imaging at 20 Hz

Abstract

Photoacoustic computed tomography (PACT) is emerging as a new technique for functional brain imaging, primarily due to its capabilities in label-free hemodynamic imaging. Despite its potential, the transcranial application of PACT has encountered hurdles, such as acoustic attenuations and distortions by the skull and limited light penetration through the skull. To overcome these challenges, we have engineered a PACT system that features a densely packed hemispherical ultrasonic transducer array with 3072 channels, operating at a central frequency of 1 MHz. This system allows for single-shot 3D imaging at a rate equal to the laser repetition rate, such as 20 Hz. We have achieved a single-shot light penetration depth of approximately 9 cm in chicken breast tissue utilizing a 750 nm laser (withstanding 3295-fold light attenuation and still retaining an SNR of 74) and successfully performed transcranial imaging through an ex vivo human skull using a 1064 nm laser. Moreover, we have proven the capacity of our system to perform single-shot 3D PACT imaging in both tissue phantoms and human subjects. These results suggest that our PACT system is poised to unlock potential for real-time, in vivo transcranial functional imaging in humans.