Spect image restoration via Recursive Inverse Filtering constrained by a probabilistic MRI atlas

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 brain structures (or tissue classes). This extension has three interesting properties ; first it allows to exploit (or fuse) reliable anatomical and (high resolution) geometrical information extracted horn a probabilistic 3D MRI atlas. Second, it allows to incorporate, into the NAS-RIF method, a regularization term which efficiently stabilizes the inverse solution. Third and contrary to multi-modal restoration techniques, it does not require a MRI scan of the patient. This method has been successfully tested on numerous real brain SPECT images (of different patients suffering from epilepsy), yielding promising restoration results.