3D Brain SPECT imagery is a well established functional imaging method which has become a great help to physicians in the diagnosis of several neurological and cerebrovascular diseases. However, mainly due to the effects of attenuation and the scattering of emitted photons, inherent to this imaging process, 3D SPECT images are generally blurred and exhibit poor spatial resolution. This leads to substantial errors in measurements of regional brain blood flow, and therefore in the estimations of brain activity. In order to improve the resolution of these images and then to facilitate their interpretation, we herein propose an original extension of the NAS-RIF (Recursive Inverse Filtering) deconvolution technique proposed by Kundur and Hatzinakos [1]. The proposed extension allows to efficiently integrate, in the deconvolution process, a set of soft constraints given by a probabilistic MRI atlas containing experts's prior knowledge about the spatial localization of the different bra...