An object of the present invention is to provide a water dispersion paper having quick water dispersion property and high strength and whose paper surface pH is 6 to 8, and also to provide a water dispersion coated paper designed to ensure quick water dispersion property and prevent discoloration over time. With the DC power source unit of the invention, a microcomputer receives a temperature signal indicative of a temperature of the battery pack and determines that the battery pack is fully charged based on the temperature signal. Minibatteries may be located in one or both cationic and anionic chambers, andor attached to structure of a container outside the chambers. The maximum intensity projection is processed in order to detect the arrival of the contrast enhancing bolus within a volume of interest.