Multi-Exponential Relaxation Times Maps Reconstruction and Unsupervised Classification in Magnitude Magnetic Resonance Imaging

Christian El Hajj (1, 2) , Saïd Moussaoui (1) , Guylaine Collewet (2) , Maja Musse (2)

1 LS2N - Laboratoire des Sciences du Numérique de Nantes
2 UR OPAALE - Optimisation des procédés en Agriculture, Agroalimentaire et Environnement

In clinical and biological applications of T2 relaxom-etry, a multi-exponential decay model proved to be representative of the relaxation signal inside each voxel of the MRI images. However, estimating and exploiting the model parameters for magnitude data is a large-scale ill-posed inverse problem. This paper presents a parameter estimation method that combines a spatial regularization with a Maximum-Likelihood criterion based on the Rician distribution of the noise. In order to properly carry out the estimation on the image level, a Majorization-Minimization approach is implemented alongside an adapted non-linear least-squares algorithm. We propose a method for exploiting the reconstructed maps by clustering the parameters using a K-means classification algorithm applied to the extracted relaxation time and amplitude maps. The method is illustrated on real MRI data of food sample analysis.

Mots clés: K-means; MRI; multi-exponential model; Maximum- Likelihood; Majorization-Minimization

Domaines: Traitement du signal et de l'image [eess.SP]

Christian El Hajj, Saïd Moussaoui, Guylaine Collewet, Maja Musse. Multi-Exponential Relaxation Times Maps Reconstruction and Unsupervised Classification in Magnitude Magnetic Resonance Imaging. 27th European Signal Processing Conference, Sep 2019, La Corogne, Spain. ⟨hal-02318133⟩