A system and method for producing a more accurate ventilation image, as compared to existing lung Fourier decomposition methods, and an image of ventilation dependent blood volume are provided. A time series of images depicting a subject's lungs during free-breathing are acquired and co-registered to a reference image. From the registration process, geometric information indicative proton density changes due to inhalation and exhalation of gas is obtained. This geometric information is used to correct the proton density values in the time series of image frames. These corrected proton density values are Fourier transformed to produce a Fourier spectrum, from which a signal peak occurring at the breathing frequency is extracted and Fourier transformed to produce a more accurate ventilation image. This more accurate ventilation image can be subtracted from a breathing frequency image produced by conventional lung Fourier decomposition methods to produce a ventilation dependent blood volume image.
