  Matrix imaging paves the way towards a next revolution in wave physics. Based
on the response matrix recorded between a set of sensors, it enables an
optimized compensation of aberration phenomena and multiple scattering events
that usually drastically hinder the focusing process in heterogeneous media.
Although it gave rise to spectacular results in optical microscopy or seismic
imaging, the success of matrix imaging has been so far relatively limited with
ultrasonic waves because wave control is generally only performed with a linear
array of transducers. In this paper, we extend ultrasound matrix imaging to a
3D geometry. Switching from a 1D to a 2D probe enables a much sharper
estimation of the transmission matrix that links each transducer and each
medium voxel. Here, we first present an experimental proof of concept on a
tissue-mimicking phantom through ex-vivo tissues and then, show the potential
of 3D matrix imaging for transcranial applications.
