Lung imaging with optical coherence tomography
Mechanical ventilation is an essential treatment in modern medicine. Especially in intensive care medicine, ventilation is a life-saving immediate measure and ensures respiration, also for long-term treatment. The choice of the right ventilation strategy is crucial for the recovery of patients with existing lung diseases, who require a long-term artificial ventilation. One of the most severe diseases is ARDS (acute respiratory distress syndrome), which can occur because of lung damages (e.g. by inhalation of salt water, intoxication, traumas) and is mainly characterized by a life-threatening decrease of gas exchange in the lung. ARDS must be obligatorily treated, whereas the ventilation technique has a direct influence on the course of the symptoms of this disease. Though latest techniques are available, mortality is still between 30 and 70 %.
However, nowadays-applied positive pressure ventilation bears also risks. Especially for long-term artificial ventilation of patients with existing lung diseases, the sensitive lung tissue can be damaged additionally by mechanical ventilation (VILI = ventilator induced lung injury). Therefore, it is the aim of physicians and engineers in the scope of the DFG main research project - protective artificial respiration - to develop gentle and more protective ventilation strategies. Basis is the establishment of numeric lung models, to help developing and testing new ventilation strategies without studies on patients. Crucial for this process is the exact understanding of geometric and functional relationships of the lung and their single components. The research group Clinical Sensoring and Monitoring, as a cooperation partner within this research project, concentrates on in vivo imaging of alveolar structures by optical coherence tomography to obtain data on the dynamic processes in the lung during artificial ventilation. One project of our research group deals with the combination of fluorescence microscopy and OCT to get functional and structural information on lung tissue. A further project aims at enhancing the image quality of OCT for structural investigations. Therefore, we develop a liquid ventilation device that helps reducing scattering losses and still allows in vivo imaging. Moreover, liquid ventilation offers interesting medical approaches for therapy and diagnosis, which will be studied in our research group.
Left: Three-dimensional image of an alveolar lumen (gray) with surrounding elastin fibers (red). The image was acquired by combining fluorescence microscopy and OCT. Staining of elastin fibers for fluorescence microscopy is done with the sulforhodamine B dye, so that functional and structural information can be separated. Middle: 3D image of lung tissue of a OCT volume scan. Lung tissue is dyed red. Right: Segmented alveoli. By analyzing such images we can obtain information on structural changes during ventilation.
A detailed description of both research projects can be found on the following pages: