Value of multi-slice spiral CT angiography and image fusion technology in preoperative evaluation of laparoscopic radical resection of rectal cancer

Objective To explore the value of computed tomography angiography (CTA) and image fusion technology in preoperative evaluation of laparoscopic radical resection of rectal cancer. Methods The retrospective and descriptive study was conducted. The clinicopathological data of 60 patients who underwent laparoscopic radical resection of rectal cancer in the Affiliated Wuxi Second People′s Hospital of Nanjing Medical University from February 2018 to March 2019 were collected. There were 39 males and 21 females, aged from 45 to 81 years, with an average age of 67 years. All patients underwent abdominal multi-slice spiral computed tomography (CT) plain scan and dual-phase enhanced scan before operation. The original CT images were observed by multiplanar reconstruction and performed three-dimensional (3D) reconstruction of blood vessels by volume rendering. The CT images of arterial vessels with large density difference were abstracted by threshold segmentation and direct abstraction, and the CT images of venous vessels with small density difference were abstracted by region growing method. Then the 3D images of blood vessels were obtained after image fusion with red and blue pseudocolor added. All the 60 patients were performed laparoscopic radical resection of rectal cancer by the same surgical team, and were identified inferior mesenteric artery (IMA) and branches after being bared vessels, including anatomic course of left colonic artery (LCA), sigmoid artery (SA), and superior rectal artery (SRA). Observation indicators: (1) anatomic courses of IMA, LCA, SA, and SRA on the 3D images and their consistency with intraoperative anatomic courses; (2) the first branch of IMA and the distances from the root of IMA to the first branch and from the root of IMA to bifurcation point of the abdominal aorta on 3D images of blood vessels; (3) the spatial relationship between the horizontal level of LCA and the inferior mesenteric vein (IMV) on the 2D CT images and 3D images of blood vessels. Measurement data were represented as Mean±SD, and count data were represented as absolute numbers and percentages. Results (1) Anatomic courses of IMA, LCA, SA and SRA on the 3D images and their consistency with intraoperative anatomic courses: of the 60 patients, 31 (51.7%) had type Ⅰ anatomic course of IMA on the 3D images, with LCA and SA from the common trunk; 9 (15.0%) had type Ⅱ, with LCA and SA from the common trunk; 18 (30.0%) had type Ⅲ, with LCA, SA, and SRA from the common trunk; 2 (3.3%) had type Ⅳ, with no LCA. The consistency of anatomic courses of IMA, LCA, SA, and SRA on the 3D images with intraoperative anatomic courses of bared IMA, LCA, SA, and SRA was 100.0%(60/60). (2) The first branch of IMA and the distances from the root of IMA to its first branch and from the root of IMA to the bifurcation point of abdominal aorta on 3D images of blood vessels: of the 60 patients, 49 (81.7%) had LCA as the first branch of IMA, 11 (18.3%) had SRA or SA as the first branch of IMA. The distances from the root of IMA to its first branch and from the root of IMA to the bifurcation point of abdominal aorta on 3D images of blood vessels were (41±6)cm and (42±7)cm. (3) The spatial relationship between the horizontal level of LCA and the IMV on the 2D CT images and 3D images of blood vessels: two patients of type Ⅳ were excluded from the 60 patients. On the 2D CT images of the rest 58 patients, 39 (67.2%) had LCA adjacent to IMV and 19 (32.8%) had LCA distal to IMV at the horizontal level of IMA root. On the 3D images of blood vessels in the rest 58 patients, 37 (63.8%) had the LCA located at the ventral side of IMV, and 21 (36.2%) had the LCA located at the dorsal side of the IMV. Conclusion Muiti-slice CTA and image fusion technology can visually display the anatomic course and variation of IMA and its branches, which has high clinical application value. Key words: Rectal neoplasms; Rectal cancer; Radical resection of rectal cancer; Vascular reconstruction; Inferior mesenteric artery; Preoperative evaluation; Laparoscopy