This article reviews FFT algorithm-based approaches to holographic MMI (millimeter wave imaging). Approaches to holographic image reconstruction including indirect 2D image techniques, direct 3D techniques in the far field, slice-by-slice 3D techniques with far-field data and direct 3D techniques in the near field are all discussed briefly with a formal mathematical presentation for each approach and a discussion of advantages for direct 3D near-field reconstruction that make this approach compelling. Finally, the recording step is identified as a key bottleneck to achieving real-time imaging, and several innovative approaches are identified that expedite this step to advance real-time applications in security, biomedical and nondestructive testing applications.