PH CALCULATING APPARATUS, MAGNETIC RESONANCE IMAGING APPARATUS, AND PH CALCULATING METHOD

A pH calculating apparatus according to an embodiment includes an obtaining unit (136) obtaining a Z spectrum generated from a CEST imaging process by using, for a subject, a contrast agent containing types of substances having mutually-different responsiveness to pH and including fall points or local minima of signal values corresponding to the types of substances; and obtaining information related to the subject; a calculating unit (140) calculating a pH dependent value by using MR signal values corresponding to the fall points or the local minima of the signal values; a selecting unit (142) selecting a standard curve indicating a pH value corresponding to the pH dependent value in accordance with the information, from among standard curves prepared in advance in accordance with the information; and a determining unit (144) determining a pH value based on the selected standard curve and the pH dependent value.