 A 2D image can be assembled a line-at-a-time by translating the focused transducer laterally along a linear path.A 3D image can be built up by scanning the transducer along a rectilinear path within a 2D plane.The ability to distinguish thermoacoustic signals "along" the line of focus ("axial" resolution) is superior to distinguishing thermoacoustic signals transverse to the line of focus ("lateral" resolution).