Correcting for sub-resolution tissue motion in localization optoacoustic tomography

Localization optoacoustic tomography (LOT) has recently been suggested for enhancing spatial resolution in optoacoustic imaging beyond the acoustic diffraction barrier and further enabling measuring blood flow velocity. LOT relies on tracking highly absorbing particles in a sequence of images acquired following intravenous injection. Much like for other high-resolution imaging methods, the achievable resolution is afflicted by physiological motion. Inter-frame displacements further hamper particle tracking and accurate velocity measurements. Herein, we propose a geometric-transformation-based approach to align motion-affected frames to a reference frame. This is achieved with a singular value decomposition (SVD) clutter filter, clustering the acquired sequence into low-order singular vectors representing blood-vessel background and high-order singular values related to flowing particles. Motion estimation is then performed in the background sequence, and localization and tracking are subsequently done in the flowing-particle sequence after motion correction. The enhanced performance achieved with the suggested approach is demonstrated in phantom experiments and LOT images of the mouse brain.