Phase contrast tomography:: An alternative approach

Conventional microtomography is widely used for reconstructing the three-dimensional (3D) distribution of the absorption coefficient of a sample from a set of radiographic projections. The question here is whether the 3D distribution of the phase (refractive index) of a weakly absorbing object can be, alternatively to the combined phase retrieval-backprojection methods presented up to now, directly reconstructed from a single tomographic data set. In this letter a solution to this problem based on a direct filtered backprojection approach, derived from the transport of intensity equation, is investigated numerically and experimentally for monochromatic and polychromatic x rays. The results show that the contrast is increased, while keeping dose minimal and spatial resolution equivalent to the conventional absorption based technique. This method is therefore very promising for imaging of biological specimens. (c) 2006 American Institute of Physics.