1. A method of acquiring an image biomarker suitable for prognosis of a blood-related disease, comprising the steps of: a) using an analyzing unit to acquire physical parameter sets, each including at least two physical parameters, respectively from time-signal intensity curves, the time-signal intensity curves being respectively obtained from magnetic resonance image sets of different subjects that are diagnosed as having the blood-related disease, each of the magnetic resonance image sets being acquired through magnetic resonance imaging (MRI) scanning using one of first and second configuration parameter sets; b) using a parameter significance-evaluating unit to analyze the physical parameter sets thus acquired with reference to prognoses of the different subjects so as to evaluate significance of each of the physical parameters and obtain weight values corresponding to the physical parameters; and c) configuring a computing unit to establish a risk score function that is a sum of products of each of the physical parameters and the corresponding weight value, wherein a risk score obtained using the risk score function serves as the image biomarker suitable for prognosis of the blood-related disease.