1. A medical image processing apparatus comprising: a first extraction means that extracts an air region from volume data after receiving volume data representing a region including an organ under observation, an adding means that adds pixel values of pixels within the air region in the volume data along a predetermined projection direction to generate projection image data representing the distribution of the added value of the pixel values, a first specifying means that specifies a first characteristic point from the projection image data, and a second specifying means that specifies, as a second characteristic point, a point on a line passing the first characteristic point in the air region.