Background The size of the intimal tear significantly influences the occurrence, progression, and prognosis of aortic dissection. With the development of endovascular treatment techniques, both domestic and international studies have documented successful clinical cases of aortic tear occlusion using endograft devices. The success of this technique relies heavily on the accurate measurement of the tear size. However, there is currently no standardized method for measuring the tear size. Objective To accurately measure the maximal diameter of the aortic dissection tear by utilizing CTA imaging, so as to provide guidance for the selection of tear occluders.Methods Patients with Stanford type B aortic dissection enrolled in the ROBUST multicenter registry in China from January 2022 to January 2024 were selected. Based on their computed tomography angiography (CTA) imaging data, the tears were three-dimensionally reconstructed using Mimics software with dynamic region growing and Boolean operations. The maximum diameter of the entry tear was measured both on two-dimensional CTA images using Mimics software and the three-dimensional reconstruction using 3-Matic software. The measurements from these two methods were then compared and analyzed.Results A total of 102 patients with Stanford type B aortic dissection were enrolled, comprising 91 males and 11 females, with a mean age of (51.47 ± 12.36) years. Totally 146 entry tears were identified and analyzed. The maximum diameter of the tears measured by three-dimensional reconstruction was significantly larger than that measured in the twodimensional plane (MIQR: 14.02(6.99 - 22.07) mm vs 10.28(4.86 - 15.92) mm, P＜0.001. Stratified analysis based on the Ishimaru aortic zoning system demonstrated that three-dimensional reconstruction measurements consistently yielded larger maximum tear diameters compared to two-dimensional planar quantification across all Zone3-Zone9 anatomical segments (P<0.05). Conclusion 3D reconstruction of tears based on CTA images offers a novel methodological option for measuring the maximum diameter of aortic dissection entry sites, providing critical guidance for endovascular occluder device sizing.