Quantifiable Lung Imaging
Diffuse lung diseases, such as emphysema and pulmonary fibrosis, are very difficult to quantify. Historically, histological sections were used, but unless the entire lung is sliced, quantification can be hampered.
“Improvements in CT devices allow imaging of soft tissues, like the lungs, with fairly good resolution,” explained Lawrence de Garavilla, Ph.D., scientific director and fellow, imaging and PK/PD, immunology research, Janssen Research and Development. “With our micro-CT unit we can get in vivo resolution of 45–50 µm and in ex vivo studies, using a contrast agent, 5 µm. This allows us to look at alveoli, the terminal structures in the lung where gas exchange occurs.
“CT imaging allows us to image the whole lung, create a 3D rendering, and quantify the amount of fibrosis. It is a big change; we now have an objective quantifiable technique. Instead of having a pathologist sit at a microscope and subjectively analyze 50–100 lung slides, the resolution of our assay and the robustness of this imaging technique allow determination of, and differentiation between, 5 and 10% degree of fibrosis.”
Measuring efficacy during pulmonary drug clinical trials is very difficult. Functional tests, such as spirometry, are used but are crude measures of airway inflammation, fibrosis, and emphysema. Imaging techniques could prove to be a valuable clinical tool to quantify the degree of lung disease and improvement with novel therapeutics.
Looking forward, CT imaging may also be applicable as a noninvasive clinical diagnostic tool, especially for airway inflammation. Currently, bronchoscopies are performed but only on a limited basis since they are invasive and provide incomplete diagnostic information.
Dr. de Garavilla envisions using lung imaging to track the number and different types of inflammatory cells, to differentiate which cells are going into the lungs and the therapeutics’ effects on the various cell types.