A magnetic resonance imaging apparatus comprising: an imaging unit (31, 40) configured to perform an inversion recovery, IR, prescan, the prescan involving the application of an IR pulse and the acquisition of a plurality of MR data sets from an object, each MR data set being acquired at one of a plurality of mutually different inversion times TI after the IR pulse, a calculation unit configured to calculate an optimum inversion time (TI opt) for an imaging scan of the object by analyzing the plurality of MR data sets of the prescan; and the imaging unit (31, 40) being configured to perform the imaging scan using an inversion recovery sequence, wherein an IR pulse is applied and an MR data acquisition is started when the optimum inversion time (TI opt) has elapsed from the application time of the IR pulse; wherein the calculation unit is configured to determine the optimum inversion time (TI opt) by applying a fitting curve to a plot of signal intensity over time of image data reconstructed from the plurality of MR data sets of the prescan in a region of interest or plural regions of interest, wherein the optimum inversion time (TI opt) is given as the time when the signal intensity of the fitted curve becomes zero; CHARACTERISED IN THAT: the calculation unit is configured to perform the curve fitting by using real-part signals of image data reconstructed from the plurality of MR data sets of the prescan obtained after phase correction; and in that the calculation unit is further configured to perform said phase correction by calculating the phase of an image signal of the MR data set of the prescan which was acquired using the longest inversion time TI and by correcting the phase of all MR data sets of the prescan by the calculated phase. an imaging unit (31, 40) configured to perform an inversion recovery, IR, prescan, the prescan involving the application of an IR pulse and the acquisition of a plurality of MR data sets from an object, each MR data set being acquired at one of a plurality of mutually different inversion times TI after the IR pulse, a calculation unit configured to calculate an optimum inversion time (TI opt) for an imaging scan of the object by analyzing the plurality of MR data sets of the prescan; and the imaging unit (31, 40) being configured to perform the imaging scan using an inversion recovery sequence, wherein an IR pulse is applied and an MR data acquisition is started when the optimum inversion time (TI opt) has elapsed from the application time of the IR pulse; wherein the calculation unit is configured to determine the optimum inversion time (TI opt) by applying a fitting curve to a plot of signal intensity over time of image data reconstructed from the plurality of MR data sets of the prescan in a region of interest or plural regions of interest, wherein the optimum inversion time (TI opt) is given as the time when the signal intensity of the fitted curve becomes zero; CHARACTERISED IN THAT: the calculation unit is configured to perform the curve fitting by using real-part signals of image data reconstructed from the plurality of MR data sets of the prescan obtained after phase correction; and in that the calculation unit is further configured to perform said phase correction by calculating the phase of an image signal of the MR data set of the prescan which was acquired using the longest inversion time TI and by correcting the phase of all MR data sets of the prescan by the calculated phase. the calculation unit is configured to perform the curve fitting by using real-part signals of image data reconstructed from the plurality of MR data sets of the prescan obtained after phase correction; and in that the calculation unit is further configured to perform said phase correction by calculating the phase of an image signal of the MR data set of the prescan which was acquired using the longest inversion time TI and by correcting the phase of all MR data sets of the prescan by the calculated phase.