In this group all the patients perform a 3 Tesla RMI. With these data, three methods will be used to calculate the ADC score : Siemens, PACS (picture archiving and communication system) Carestream, Osirix. The ADC scores obtained with these three post-processing softwares will be compared.

In this group all the patients perform a 1,5 Tesla RMI. With these data, three methods will be used to calculate the ADC score : Siemens, PACS Carestream, Osirix. The ADC scores obtained with these three post-processing softwares will be compared.

The MRI will be performed on the two groups of patients in the usual care. The intervention will be based on the ADC scores calculation. The scores will be obtained with three types of post-processing softwares : Siemens, PACS Carestream, Osirix.

The ADC Score will be calculated for each patient, with three different post-processing softwares : Siemens, PACS (picture archiving and communication system) Carestream, Osirix. The scores will be compared, because the aim of this study is to demonstrate the variability of this score, according to the post-processing software used.

Apparent diffusion coefficient (ADC) is a measure of the magnitude of diffusion (of water molecules) within tissue, and is commonly clinically calculated using Magnetic resonance imaging (MRI) with diffusion weighted imaging (DWI). An ADC of a tissue is expressed in units of mm2/s. There is no unanimity regarding the boundaries of the range of normal diffusion, but ADC values less than 1.0 to 1.1 x 10-3 mm2/s (or 1000-1100 x 10-6 mm2/s) are generally acknowledged in adults as indicating restriction.

The ADC Score will also be compared to the intensity of the Magnetic resonance imaging (MRI) performed for each patient. Half have received a MRI of 1,5 Tesla and the other hand a 3 Tesla MRI. The variability between these two groups will be compared in the secondary outcome.