1. A computer-implemented method using magnetic resonance imaging to characterize ventilation and perfusion in a lung, comprising: acquiring, using a magnetic resonance imaging (MM) machine under the control of a processing unit, a magnetic resonance (MR) image of the lung that includes MR data in a voxel of the MR image, wherein the acquiring causes the MM machine to measure a breathing frequency value; determining, by the processing unit a water density value and a perfusion value in at least one voxel of the MR image based on the MR data; determining, by the processing unit from the water density value, an air content value in the at least one voxel; determining, by the processing unit, a specific ventilation value in the at least one voxel based on a time delay between an onset of a stimulus to the lung and a response detected in the at least one voxel; determining, by the processing unit a ventilation-perfusion ratio value that is the product of the specific ventilation value, the air content value, the inverse of the perfusion value, and the breathing frequency value; and evaluating, by the processing unit, a spatial distribution of the specific ventilation value, perfusion value, and the ventilation-perfusion ratio by computing a standard deviation of the specific ventilation value and perfusion value; wherein the specific ventilation value is computed by SVI*(1−density)*f B wherein SVI represents quantitative data from the MR image, (1−density) represents the air content value, and f B represents the breathing frequency value, thereby determining when the lung is diseased.