A medical image processing apparatus, comprising: a cardiac cavity region specifying part configured to receive volume data representing a heart and specify a position of a cardiac cavity region represented in the volume data; an axis setting part configured to set an axis intersecting the cardiac cavity region; an image generation plane setting part configured to set an image generation plane including the axis in the volume data; a first image generator configured to, based on the volume data, execute a rendering process with a direction orthogonal to the image generation plane as a view direction, on the data excluding the data included in the cardiac cavity region of the volume data to generate two-dimensional image data that represents a boundary of the cardiac cavity region, which is a boundary of one of regions of the cardiac cavity region divided by the image generation plane; characterised by further comprising a second image generator configured to, based on the data excluding the data included in the cardiac cavity region of the volume data, execute a Multi Planar Reconstruction process to generate two-dimensional image data that two-dimensionally represents a myocardial region in the image generation plane; and a display controller configured to generate synthesized image data by synthesizing the two-dimensional image data that represents the boundary of the cardiac cavity region and the two-dimensional image data that two-dimensionally represents the myocardial region in the image generation plane, and cause a display to display a synthesized image based on the synthesized image data, wherein upon reception of designation of an optional point on the synthesized image displayed on the display, the image generation plane setting part is configured to obtain a line that passes through the designated point and is orthogonal to the image generation plane, obtain an intersection of the line and the boundary of the cardiac cavity region, and set a plane including the intersection and the axis as a new image generation plane in place of the image generation plane, the first image generator is configured to generate new two-dimensional image data by using the new image generation plane, the second image generator is configured to generate new two-dimensional image data in the new image generation plane, and the display controller is configured to generate new synthesized image data by synthesizing the new two-dimensional image data generated by the first image generator and the new two-dimensional image data generated by the second image generator, and cause the display to display a synthesized image based on the new synthesized image data. a cardiac cavity region specifying part configured to receive volume data representing a heart and specify a position of a cardiac cavity region represented in the volume data; an axis setting part configured to set an axis intersecting the cardiac cavity region; an image generation plane setting part configured to set an image generation plane including the axis in the volume data; a first image generator configured to, based on the volume data, execute a rendering process with a direction orthogonal to the image generation plane as a view direction, on the data excluding the data included in the cardiac cavity region of the volume data to generate two-dimensional image data that represents a boundary of the cardiac cavity region, which is a boundary of one of regions of the cardiac cavity region divided by the image generation plane; characterised by further comprising a second image generator configured to, based on the data excluding the data included in the cardiac cavity region of the volume data, execute a Multi Planar Reconstruction process to generate two-dimensional image data that two-dimensionally represents a myocardial region in the image generation plane; and a display controller configured to generate synthesized image data by synthesizing the two-dimensional image data that represents the boundary of the cardiac cavity region and the two-dimensional image data that two-dimensionally represents the myocardial region in the image generation plane, and cause a display to display a synthesized image based on the synthesized image data, wherein upon reception of designation of an optional point on the synthesized image displayed on the display, the image generation plane setting part is configured to obtain a line that passes through the designated point and is orthogonal to the image generation plane, obtain an intersection of the line and the boundary of the cardiac cavity region, and set a plane including the intersection and the axis as a new image generation plane in place of the image generation plane, the first image generator is configured to generate new two-dimensional image data by using the new image generation plane, the second image generator is configured to generate new two-dimensional image data in the new image generation plane, and the display controller is configured to generate new synthesized image data by synthesizing the new two-dimensional image data generated by the first image generator and the new two-dimensional image data generated by the second image generator, and cause the display to display a synthesized image based on the new synthesized image data.