A method of determining a quantization value of the deviation of the average value of a distribution of severity difference between an initial time and a time after the initial time, the contrast-dependent severity between areas receiving a treatment and areas receiving a vehicle, comprising steps in which: at least one patient, at an initial time and at at least one time subsequent to the initial time, acquires at least one hyper-spectral image comprising at least one at least one of a sick area receiving the treatment, a healthy area receiving the treatment, a sick area receiving the vehicle and a healthy area receiving the vehicle, determining a decomposition into independent components of the hyper-spectral images, is determined for each image, among the independent components, a representative component that maximizes the difference between healthy and pathological zones, it is in this image, a representative component corrected for the average of the representative components, a value of the severity difference is determined as a function of the corrected representative components of the acquired hyper-spectral images, for each patient and for each instant of measurement, and determining a quantization value of the deviation of the mean value between a severity difference distribution at the initial time and a distribution of the severity difference at a time subsequent to the initial time as a function of the value the severity difference for each patient at the initial time and the posterior moment.Procédé de détermination d'une valeur de quantification de la déviation de la valeur moyenne d'une distribution de l'écart de sévérité entre un instant initial et un instant postérieur à l'instant initial, la sévérité dépendant du contraste entre des zones recevant un traitement et des zones recevant un véhicule, comprenant des étapes au cours desquelles : on acquiert, pour au moins un patient, à un instant initial et à au moins un instant postérieur à l'instant i
