An MRI system , comprising: an MRI scanner comprising a magnet with a magnetic field and a body coil configured to obtain 1 H MRI signal data; a lung coil configured to obtain 19 F MRI signal data and sized and configured to reside proximate a patient; an MRI scanner interface in communication with the scanner and the lung coil, the interface comprising a proton blocking circuit; and a gas delivery system comprising: a gas mixture source comprising a gas mixture of perfluorinated gas in a level that is between about 20-79% and oxygen gas in a level that is at least about 20.5%; a gas flow path in communication with the gas mixture source comprising at least one conduit extending from the gas mixture source to a free-breathing dispensing member residing over, on or in a patient while the patient resides inside the magnetic field to deliver the gas mixture to the patient; and at least one oxygen sensor in communication with the gas mixture; wherein, in operation, the MRI system is configured to obtain 1 H and 19 F MRI signal data of lungs and associated lung airspaces of the patient and generate images showing a temporal and spatial distribution of the perfluorinated gas in the lungs, wherein the system is configured to acquire the 19 F MRI signal data while the patient carries out free-breathing of the gas mixture during equilibrium and wash in and wash out for a plurality of respiratory cycles, wherein the system is configured to generate a cine of free-breathing, three-dimensional images of the lungs of the patient illustrating a temporal and spatial distribution of the perfluorinated gas in the lung space and lungs of the patient to provide ventilation image data. an MRI scanner comprising a magnet with a magnetic field and a body coil configured to obtain 1 H MRI signal data; a lung coil configured to obtain 19 F MRI signal data and sized and configured to reside proximate a patient; an MRI scanner interface in communication with the scanner and the lung coil, the interface comprising a proton blocking circuit; and a gas delivery system comprising: a gas mixture source comprising a gas mixture of perfluorinated gas in a level that is between about 20-79% and oxygen gas in a level that is at least about 20.5%; a gas flow path in communication with the gas mixture source comprising at least one conduit extending from the gas mixture source to a free-breathing dispensing member residing over, on or in a patient while the patient resides inside the magnetic field to deliver the gas mixture to the patient; and at least one oxygen sensor in communication with the gas mixture; a gas mixture source comprising a gas mixture of perfluorinated gas in a level that is between about 20-79% and oxygen gas in a level that is at least about 20.5%; a gas flow path in communication with the gas mixture source comprising at least one conduit extending from the gas mixture source to a free-breathing dispensing member residing over, on or in a patient while the patient resides inside the magnetic field to deliver the gas mixture to the patient; and at least one oxygen sensor in communication with the gas mixture; wherein, in operation, the MRI system is configured to obtain 1 H and 19 F MRI signal data of lungs and associated lung airspaces of the patient and generate images showing a temporal and spatial distribution of the perfluorinated gas in the lungs, wherein the system is configured to acquire the 19 F MRI signal data while the patient carries out free-breathing of the gas mixture during equilibrium and wash in and wash out for a plurality of respiratory cycles, wherein the system is configured to generate a cine of free-breathing, three-dimensional images of the lungs of the patient illustrating a temporal and spatial distribution of the perfluorinated gas in the lung space and lungs of the patient to provide ventilation image data. <EOS>