Lung cancer is typically diagnosed once primary lung tumors are visible through CT scans, and generally becomes more difficult to treat as the tumor growth progresses. This investigation is aimed at using three-dimensional modeling techniques to characterize changes in the vascular tree structures of patients with primary lung tumors, including ratio of parent-child branch radii, vascular area ratio, vessel tortuosity and bifurcation angles. Normalized ranges of a healthy patient will be used as a point of comparison for vascular disorders such as chronic pulmonary arterial hypertension (PAH) and changes in vascular structure around a growing tumor. This research has the potential to identify early markers of vascular injury and further understand the vascular changes and vascular damage that occurs with the growth of primary lung tumors. This investigation will use sequential CT scans of patients who have growing primary lung tumors. Lung CT scans of various sized lung tumors will be gathered from patients enrolled in an on-going IRB approved study and will be compared with a healthy patient CT scan. The chest CT scans will be pre-processed and analyzed using software developed in our lab and built upon the NIH ImageJ platform. Skeletonizing and thresholding will be applied to facilitate traversing and charactering the tree structure, and I will develop code and algorithms to analyze vascular characteristics including parent-child branch radii ratios, bifurcation angles, vessel tortuosity and area ratio.