1. A medical image processing apparatus, comprising: setting circuitry configured to set a region of interest (ROI) of each of a plurality of sagittal plane images of medical images resulting from scanning an examinee; calculation circuitry configured to calculate an evaluation index based on a bipolarity feature of each block in the ROI related to change of pixel values and a similarity feature among the blocks; and recognition circuitry configured to select the ROI according to the calculation result of the calculation circuitry and recognize a sagittal plane image in which the selected ROI is located as a target sagittal plane image of a median sagittal plane passing through a spine.