A method for quantifying iron deposits in tissues using diffusion-weighted Magnetic Resonance Imaging with a high accuracy, comprising the steps of: - acquiring a first series of MRI images of a Field Of View of a biological tissue by using a MonoPolar pulse-diffusion Gradient sequence as a MonoPolar pulse-diffusion Gradient Spin-Echo sequence (PGSE), and by varying a programmed gradient attenuation factor b over a first plurality of values, the programmed gradient attenuation factor depending only on the set of the diffusion gradient pulses of the first sequence; - acquiring a second series of MRI images of the same Field of View FOV of the biological tissue by using as a BiPolar pulse-diffusion Gradient sequence a cross-term-free pulse-diffusion gradient spin echo sequence having a similar diffusion time as the MPG sequence, this BPG sequence having its diffusion-sensitizing gradients and RF pulses arranged so that the cross terms between the local magnetic field gradients induced by iron and the gradient pulses within the BPG sequence are equal to zero at the echo time TE period, and by varying a programmed gradient attenuation factor b over a second plurality of values, the programmed gradient attenuation factor depending only on the set of the diffusion gradient pulses of the BPG sequence; - providing an attenuation model of the diffusion MRI attenuated signal S/S 0 representative of the observed tissue expressed as a model function f(x) depending on a variable x equal to the product of an apparent model diffusion coefficient ADC and the programmed gradient attenuation factor b used; - on a one-per-one voxel basis or on a predetermined Region Of Interest including a set of voxels, - estimating a first apparent diffusion coefficient ADC MPG by fitting the MRI images acquired by using the MPG sequence and the first plurality of programmed gradient attenuation factors b with the model function f(b.ADC); - estimating a second apparent diffusion coefficient ADC BPG by fitting the MRI images acquired by using the BPG sequence and the second plurality of programmed gradient attenuation factors b with the model function f(b.ADC); characterized in that the method further comprises the step of: - calculating a local gradient factor ξ Fe quantitatively reflecting the iron load in each voxel or ROI from the estimated values of the first apparent diffusion coefficient ADC MPG and the second apparent diffusion coefficient ADC BPG through the relationship: ξ Fe = 1 − ADC MPG ADC BPG; said local gradient factor ξ Fe giving the absolute quantification of iron, the concentration [Fe] and/or the amount of iron stored in the ROI or each voxel of the tissue being determined from the calculated iron induced local gradient factor ξ Fe through a predetermined monotonic conversion function g -1 ( ξ Fe) of the iron induced local gradient factor ξ Fe. - acquiring a first series of MRI images of a Field Of View of a biological tissue by using a MonoPolar pulse-diffusion Gradient sequence as a MonoPolar pulse-diffusion Gradient Spin-Echo sequence (PGSE), and by varying a programmed gradient attenuation factor b over a first plurality of values, the programmed gradient attenuation factor depending only on the set of the diffusion gradient pulses of the first sequence; - acquiring a second series of MRI images of the same Field of View FOV of the biological tissue by using as a BiPolar pulse-diffusion Gradient sequence a cross-term-free pulse-diffusion gradient spin echo sequence having a similar diffusion time as the MPG sequence, this BPG sequence having its diffusion-sensitizing gradients and RF pulses arranged so that the cross terms between the local magnetic field gradients induced by iron and the gradient pulses within the BPG sequence are equal to zero at the echo time TE period, and by varying a programmed gradient attenuation factor b over a second plurality of values, the programmed gradient attenuation factor depending only on the set of the diffusion gradient pulses of the BPG sequence; - providing an attenuation model of the diffusion MRI attenuated signal S/S 0 representative of the observed tissue expressed as a model function f(x) depending on a variable x equal to the product of an apparent model diffusion coefficient ADC and the programmed gradient attenuation factor b used; - on a one-per-one voxel basis or on a predetermined Region Of Interest including a set of voxels, - estimating a first apparent diffusion coefficient ADC MPG by fitting the MRI images acquired by using the MPG sequence and the first plurality of programmed gradient attenuation factors b with the model function f(b.ADC); - estimating a second apparent diffusion coefficient ADC BPG by fitting the MRI images acquired by using the BPG sequence and the second plurality of programmed gradient attenuation factors b with the model function f(b.ADC); - calculating a local gradient factor ξ Fe quantitatively reflecting the iron load in each voxel or ROI from the estimated values of the first apparent diffusion coefficient ADC MPG and the second apparent diffusion coefficient ADC BPG through the relationship: ξ Fe = 1 − ADC MPG ADC BPG; said local gradient factor ξ Fe giving the absolute quantification of iron, the concentration [Fe] and/or the amount of iron stored in the ROI or each voxel of the tissue being determined from the calculated iron induced local gradient factor ξ Fe through a predetermined monotonic conversion function g -1 ( ξ Fe) of the iron induced local gradient factor ξ Fe.