Spatial resolution in three-dimensional photo-acoustic reconstruction

We present an analytic explanation of the spatial resolution in three-dimensional photo-acoustic (also called opto-acoustic or thermo-acoustic) reconstruction. Based on rigorous reconstruction formulas, we analytically derive the point-spread functions (PSFs) for three types of specific recording geometries, including spherical, planar, and cylindrical surfaces. The PSFs as a function of the bandwidth of the measurement system and the finite size of the detector aperture, as well as the discrete sampling effect on the reconstruction, are investigated. The analyses clearly reveal that the dependence of the PSFs on the bandwidth of all of the recording geometries shares the same space-invariant expression while the dependence on the aperture size of the detector differs. The bandwidth affects both axial and lateral resolution; in contrast, the detector aperture blurs the lateral resolution greatly but the axial resolution only slightly. Under-sampling in the measurement causes significant aliasing artifacts in the reconstruction. A general sampling strategy to avoid aliasing is proposed.