1. A medical image processing apparatus which generates an image based on data acquired by using a medical imaging device, the apparatus comprising: a region specifying unit which specifies a nodule region in an image; a setting unit which sets a display type mode by selecting a nodule candidate region priority mode or an extended nodule candidate region priority mode; a parameter setting unit which executes statistical processing concerning an image in the nodule region and sets an opacity curve of the image based on a result of the statistical processing according to the set display type mode, wherein the statistical processing includes generating a histogram of an extracted volume of interest, and the opacity curve is set based on a first maximum H.U. value in a positive region on the histogram when the nodule candidate region priority mode is selected, and the opacity curve is set based on a second maximum H.U. value in a negative region on the histogram when the extended nodule candidate region priority mode is selected; and an image generating unit which generates a projection image based on the set opacity curve.