The existing knowledge on the normal condition of the fine structures of the lung, such as the walls of the pulmonary alveoli in healthy people, is based mainly on a comparatively small number of organs which have been examined under the microscope. Microscopic methods offer a very high resolution. However, the organs for this must be fixed after death and wafer-thin sections produced, which could possibly lead to changes in the structure. 
Magnetic resonance imaging (MRI, also known as magnetic resonance tomography, MRT) is an imaging technique which uses no ionizing radiation and is therefore a particularly gentle process for humans. The resolution of the MRT is, however, limited. What is more, the lung consists mostly of air, which is invisible to the MRT. Xenon gas can, through hyperpolarisation, be made visible in the MRT. In addition, xenon dissolves in the lung tissue, whereby the dynamics of the gas uptake from the pulmonary alveoli in their walls and in the capillaries can be measured. From this, certain models allow conclusions to be drawn with regard to the thickness of the alveolar walls, their surface and the capillary blood flow.
Agilo Kern and his colleagues have now been successful in their examination of the influence of blood pulsation in the lung on the thickness of the walls of the pulmonary alveoli. To do this, healthy test persons underwent high resolution MRT measurement of the gas absorption at various times, which could later be assigned to various phases of heart rate. Thus, the thickness of the walls of the pulmonary alveoli during the peak of the blood pulse wave is slightly greater than during the lowest point. This is consistent with earlier microscopic studies, in which organs were fixed by generating different levels of blood pressure, which however allow only limited conclusions with regard to the situation in living organisms.
The knowledge gained could in future also be interesting for clinical use. The capillary bed of the lung is altered in numerous pulmonary diseases. The type of changes could be diagnosed with a gentle MRT and thus suggest the exact type of disease carried by the person concerned. This exact determination will allow doctors to provide custom-fit treatment.
 

Text: BREATH/ AK

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