1. A dynamic image processing system comprising: an imaging unit that carries out dynamic imaging of a target part of a human body under examination and generates a plurality of frames of images indicating a dynamic condition of the target part of the human body under examination; a calculation unit that calculates from said frames of images a dynamic feature amount of the target part of the human body under examination; a display unit that displays on a display screen the plurality of frames of images; and a display control unit that displays at least one of the plurality of frames of images and the calculated dynamic feature amount on the display screen concurrently; wherein said display control unit, according to a result of calculation of the dynamic feature amount by said calculation unit adds information to at least one among the plurality of frames of images, or modifies a part of at least one among the plurality of frames of images, and displays on said display screen; wherein said display control unit, according to the result of calculation of the dynamic feature amount by the calculation unit colors at least one frame of image among the plurality of frames of images and displays on the display screen; wherein said display control unit has a dynamic image display mode for a motion display of the plurality of frames of images indicating a dynamic condition on the display screen, and a still image display mode for a still image display of the plurality of frames of images indicating a dynamic condition arranging the plurality of frame of images next to one another on the display screen, and wherein the dynamic image processing system is provided with an operation unit for selecting the dynamic image display mode or the still image display mode; wherein said calculation unit calculates, as the dynamic feature amount, an area ratio of an image region of the target part under examination between neighboring frame images among the plurality of frames of images in the imaging sequence; and said display control unit, when the dynamic image display mode is selected, displays a motion image of the plurality of frames of images indicating dynamic condition on the display screen, and colors the frame image currently being displayed in the motion image according to the area ratio calculated by said calculation unit between the frame image currently being displayed and a frame image imaged immediately prior to it and displays the colored frame image alongside the motion image being displayed.