1. A medical image processing apparatus, comprising: processing circuitry configured to extract an emphysema region that is at least part of a lung from three-dimensional image data, extract bronchi in the extracted emphysema region, calculate area ratios, each area ratio being between a lumen and a wall of each of the extracted bronchi, and identify a responsible bronchus that is within a prescribed distance from the emphysema region from among the bronchi, select an area ratio, corresponding to the responsible bronchus, from among the area ratios, allocate pixel values, corresponding to the selected area ratio, to corresponding positions on a bronchus image indicating the responsible bronchus so as to generate a superimposed image in which an area ratio image indicating the selected area ratio is superimposed on the bronchus image; and cause a display to display the superimposed image.