Aortic dissection refers to a pathological condition wherein a local tear occurs in the intima of the aorta, leading to the separation and expansion of the middle layer of the aortic wall due to the impact of blood flow, resulting in the simultaneous formation of true and false lumens within the artery, with or without communication between them [3]. Aortic dissection can trigger complications such as cardiac tamponade and aortic rupture, severely jeopardizing the patient’s physical health and safety [4]. Based on the extent of involvement, aortic dissection originating from the descending aorta without involving the ascending aorta is termed TBAD. TEVAR is currently the preferred clinical treatment for TBAD [5]. In this study, 40 cases of TBAD patients underwent TEVAR procedures smoothly, with no intraoperative deaths reported. Postoperatively, only one case experienced acute complications, confirming the favorable safety profile of TEVAR in treating TBAD.

TEVAR utilizes stent grafts to cover the intimal tear of the aorta, enlarging the true lumen while reducing the false lumen and promoting thrombosis, thereby achieving a restructuring of the aortic morphology [6]. Optimal aortic remodeling is of paramount significance in reducing the risk of complications and extending patient survival [7, 8]. The findings of this study reveal that postoperative diameters of the true lumen at the P1 and P2 planes gradually increased, while those of the false lumen progressively decreased, with this positive remodeling being most significant at 3 months postoperatively, followed by a slowing of progression at 6 months, possibly attributable to the radial supportive force of the stent reaching equilibrium with resistance typically by 6 months postoperatively, and the diameters of the thoracic aortic true and false lumens remained relatively stable [9,10,11]. Additionally, results indicate a gradual increase in the true lumen diameters at the P3 and P4 planes postoperatively, albeit a slight decrease in the P3 true lumen diameter at 6 months postoperatively, possibly due to the gradual attenuation of the radial supportive force of the stent transitioning from the thoracic aorta to the abdominal aorta, and the ongoing blood flow between the true and false lumens of the abdominal aorta. The changes in the area of the P3 false lumen were insignificant, while the area of the P4 false lumen slightly increased at 6 and 12 months postoperatively, likely attributed to hemodynamic disturbances in the abdominal aorta, with some of its branches being supplied by the false lumen. The total areas of P3 and P4 increased postoperatively, primarily due to the enlargement of the true lumen, while the changes in the false lumen were insignificant or mildly increased [12].

Most of the previous studies were on the analysis of the positive remodeling of the aorta after TEVAR, but few studies were on the specific analysis of the distal abdominal aortic segment covered by the stent. In contrast, our study is unique and innovative. For accurate positioning and volume measurement with multiple reviews, only dual-energy post-processing software can be analyzed in our department. We assessed the postoperative remodeling of the distal abdominal aortic segment covered by the stent. By comparing the remodeling of the uncovered dissected segment at 3, 6, and 12 months postoperatively, we found that there were no statistically significant differences in the maximum diameter and maximum area of the true lumen, maximum diameter, and maximum area of the false lumen. However, there were significant changes in the volumes of the true and false lumens. The volume of the true lumen gradually increased while the volume of the false lumen decreased. In some patients, the volume of the false lumen slightly increased at 6 months postoperatively but decreased by 12 months postoperatively. This indicates that relying solely on the maximum diameter and area of the distal dissected segment covered by the stent cannot reflect the overall changes in the vascular lumen. Volume measurement can more accurately and comprehensively reflect the aortic remodeling status [13]. Furthermore, our study employed the calculation of the MARI to assess aortic remodeling. The results showed a continuous increase in MARI in the distal abdominal aortic dissected segment covered by the stent postoperatively.

This study also has limitation. Since this study was a single-center, retrospective study with a small sample size, the robustness of the study was reduced. To sum up, volume measurements can capture subtle changes in the volumes of the true and false lumens of the aorta without stent graft coverage, which may accumulate and lead to different prognoses for patients. This aspect is often overlooked in clinical practice. However, the implementation of volume measurements requires specific post-processing workstations and is time-consuming, thus, its widespread clinical application is still pending. Additionally, in this study, one patient underwent a second scan after the arterial phase, and the comparison revealed a slight enlargement in the enhancement range of the false lumen on the second scan compared to the first. This suggests that the degree of thrombosis in the false lumen and the timing of the scan phase may influence the research results, which is an area for further investigation in our future research endeavors.

In summary, for the dissected segment distal to the stent graft, in addition to conventional diameter and area measurements, advocating for the inclusion of volume measurements is imperative.