A less desirable alternative to the LTRC CT Scan for participants enrolled in the LTRC that still fulfills the imaging requirements is a CT scan of the chest previously obtained for clinical reasons. These historical exams must have been obtained less than six months from the time of evaluation at the clinical center and must also be in digital DICOM format for transfer to the RCL. Volumetric high-resolution imaging (slice thickness less than 2mm) with a field of view sufficient to visualize the entire lung volume with non-contrast technique is preferred. The CT portion of a PET/CT, imaging performed with intravenous contrast, image acquisition/reconstruction that is not volumetric (i.e. HRCT with gap) or slice thickness greater than 2mm is not preferred. Subjects who do not have historical imaging with a preferred technique should be strongly encouraged to obtain the LTRC Protocol CT prior to surgery. Radiographs (chest x-ray) and other imaging modalities (MRI, V/Q scans, Ultrasound) are not acceptable. The participant must consent to use of a clinical scan for research purposes, its storage at the Mayo Clinic, or another repository designated by the NHLBI, and the sharing of results and de-identified image data with future researchers as part of the LTRC data repository. If more than one historical exam is available, the most recent examination with optimal acquisition and reconstruction parameters (non-contrast-enhanced, volumetric, high-resolution CT images with (thickness of 2mm or less) will be sent to the RCL for analysis and storage as described in the sections below. In order of preference, non-contrast exam, volumetric high-resolution technique and age of exam are to be considered. For example, if a 1 week old enhanced pulmonary embolism protocol CT, a 1 month old PET/CT and a 3 month old non-contrast volumetric high-resolution CT are available, the 3-month old non-contrast high-resolution CT would be preferred). The LTRC Protocol CT acquired prospectively would be preferred to any of the historical exams, if that can be acquired prior to surgery.