Two novel ultrasound imaging techniques with imaging contrast mechanisms are in the works: X-ray-induced acoustic computed tomography (XACT), and nanoscale photoacoustic tomography (nPAT). XACT has incredible potential in: (1) biomedical imaging, through which a 3D image can be generated using only a single X-ray projection, and (2) radiation dosimetry. nPAT as a new alternative of super-resolution microscopy can break through the optical diffraction limit and is capable of exploring sub-cellula