In this study, we focus on validating the accuracy of the previously developed software, which reconstructs thoracic rib cage and thoracic volume in 3D. This software is applied in spine deformity patients to help doctors monitor and follow spine curvature and the thoracic volume variation. Five users were recruited to perform usability testing for the developed software. The usability testing shows that the performance of the thoracic volume reconstruction via our software meets the criterion set by the American Thoracic Society, which recommends an acceptable error of ±3% for the respiratory measurement. In addition, the user operation results were analyzed through a two-way analysis of variance (ANOVA), without replication, statistical method. The outcome indicates the reconstruction accuracy of the software is satisfactory. In the reproducibility study, the result shows that the performance of the developed software is superior to previous literature and the reconstruction is clinically relevant.