The difficulties limit the direct application to electron tomography The tilt range has to be from -90 degree to +90 degree The number of projections in a tilt series needs to be 2N for an N*N object The grid points past the resolution circle cannot be experimentally determined These limitations are overcome by combining the PPFFT with an iterative process. Ref: http://www.physics.ucla.edu/research/imaging/EST/index.html
Electron microscopy, Programming and Fun!!!