A medical image diagnostic system according to an embodiment includes processing circuitry configured: to acquire a trained model generated by using, as learning data, at least one selected from among a first group of time-series images acquired by performing a first pre-scan on a first patient injected with a contrast agent in a first examination using the medical image diagnostic system, a first group of time-series partial images being generated on the basis of the first group of time-series images and corresponding to a first region of interest of the first patient, and first time-series information about signal intensities in the first region of interest generated on the basis of the first group of time-series images, as well as timing information about timing of a transition from the first pre-scan to a first main scan in the first examination, and information about appropriateness of the timing； and to determine, in a second examination different from the first examination, appropriate timing of a transition from a second pre-scan to a second main scan by inputting, to the trained model, at least one selected from among a second group of time-series images acquired by performing the second pre-scan on a second patient injected with a contrast agent in the second examination different from the first examination, a second group of time-series partial images being generated on the basis of the second group of time-series images and corresponding to a second region of interest of the second patient, and second time-series information about signal intensities in the second region of interest generated on the basis of the second group of time-series images.
