Project Summary (Supplement Project) The micro computed tomography (µCT) Imaging Core (µCTIC) is an integral part of the Penn Center for Musculoskeletal Disorders (PCMD). Since its inception in 2012, the PCMD µCTIC has grown into a thriving resource for the University of Pennsylvania and the region’s MSK research community, serving a vibrant and growing base of 73 active PCMD faculty members and more than 170 trainees from their laboratories to acquire over 55,000 µCT scans, resulting in over 400 terabytes of data. An important recent advance in µCT technology is in vivo imaging of small animals, which enables evaluation of changes in a living animal non- invasively and repeatedly over time. Another exciting advancement is high-resolution peripheral quantitative CT (HR-pQCT), which can assess three-dimensional (3D) bone microarchitecture, geometry, and bone mineral density in the distal peripheral skeleton of clinical patients. Currently, the µCTIC operates 3 in vivo µCT scanners and an HR-pQCT scanner for longitudinal imaging of small rodents and clinical research subjects, respectively. Consequently, individual datasets have grown in size and complexity, along with a growing demand for specialized image analysis for longitudinal image data registration, post-processing, and visualization from our users. To address these needs, the µCTIC has developed a customized software platform called Computed Tomography Processing & Registration - Open Sourced (CTPros) for automated data management, customized image processing, longitudinal image registration and analysis, and two- dimensional (2D) and 3D visualization. This open-source Python software package with a Graphic User Interface (GUI) is compatible with Mac, Linux, and Windows operating systems. Compared to other available commercial and open-source software, CTPros is the only one that is specifically designed and have been validated for quantitative analysis of musculoskeletal tissues based on longitudinal µCT images. Despite the powerful functions of the CTPros software for academic research, the current version of CTPros is still lacking software documentation and a logging system and only supports limited data formats. Through the support of this supplement, we aim to ensure the rigor of CTPros-derived measurements, refine the software documentation and logging system to improve user feedback, and package CTPros into standalone and executable packages with containerized runtime to improve intersystem compatibility. Moreover, by releasing beta versions to obtain user feedback on documentation, features, and usability, we aim to incorporate these feedbacks into a formal release of CTPros to the general research community.