An application study of CT perfusion imaging in assessing metastatic involvement of perigastric lymph nodes in patients with T1 gastric cancer

Abstract

Objective: To assess metastatic involvement of perigastric lymph nodes (PLN_s) in patients with T1 gastric cancer by using CT perfusion imaging (CTPI).

Methods: A total of 82 annotated PLN_s of 33 patients with T1 gastric cancer confirmed by endoscopic ultrasonography underwent CTPI and portal phase CT scan before operation. The scan data were post-processed to acquire perfusion maps and calculate perfusion parameters including blood flow (BF) and permeability surface (PS). A radiologist measured the short axis diameters and perfusion parameters of PLN_s. According to the post-operative pathology result, PLN_s were divided into two groups: metastatic and inflammatory LN_s. Perfusion parameters values and the size of PLN_s between two groups were respectively compared statistically by t-test, and a receiver operating characteristic curve analysis was used to determine the optimal diagnostic cut-off value with sensitivity, specificity and area under the curve.

Results: Examined 82 PLN_s were metastatic in 45 (54.9%) and inflammatory in 37 (45.1%). The mean values of perfusion parameters and the short axis diameters in metastatic and inflammatory PLN_s, respectively, were BF of 97.48 vs 81.21 ml/100 mg /min (p < 0.001), PS of 45.11 vs 36.80 ml/100 mg /min (p < 0.001), and the size of 1.51 cm vs 1.29 cm (p = 0.059). The sensitivity of 84.4%, specificity of 67.6% and area under the curve of 0.826 for BF with cut-off value of 88.89 ml/100 mg /min for differentiating metastatic from inflammatory nodes were higher than those of PS or the size of PLN_s (p < 0.001).

Conclusion: CT perfusion parameters values were different between metastatic and inflammatory PLN_s in T1 gastric cancer. BF value may be the most reliable diagnostic marker of metastatic PLNs, and it is helpful for clinicians to choose treatment modality or management plan in T1 gastric cancer patients.

Advances in knowledge: CTPI gives information on vascularization of LN_s.BF value might be a more effective marker than PS or the size of LN_s for differentiating metastatic from inflammatory LN_s in patients with T1 gastric cancer.

Figure 1.

Flow diagram of patient selection. CTPI,CT perfusion imaging; EUS, endoscopic ultrasonography; LN, lymph node.

Figure 2.

The schematic diagram of the numbering of LN stations 1–16 in the perigastric LNs. The figure is from Japanese Gastric Cancer Association. Japanese classification of gastric carcinoma—second English edition. Gastric Cancer (1)(1998) 10–24. LN, lymphnode.

Figure 3.

A portal phase CT image (a) with one metastatic LN (arrow) and T1 gastric cancer (dovetail arrow) shows the annotated LN along the splenic artery (LN #11–1) and the thickened posterior wall of gastric antrum, the short axis diameter of the LN with obvious enhancement after contrast agent injection is about 7 mm; the serosa surface outer the gastric tumor is smooth and is not invaded by cancer tissue. CT perfusion pcolor BF image (b) and PS image (c) demonstrate that the LN and gastric tumor have high blood perfusion and permeability, and the lesions are shown in red and blue. A pathological image of metastatic LN (HE staining,×100) (d) shows the presence of poorly differentiated tubular adenocarcinoma cells with a certain degree of pleomorphism. BF, blood flow; LN, lymphnode; PS, permeability surface.

Figure 4.

A portal phase CT image (a) with two inflammatory LN_s (arrows) and T1 gastric cancer (dovetail arrow) shows the annotated left paracardial LN_s (LN #2-1and #2–2) and the thickened small curvature wall of stomach subcardia, the short axis diameters of the two LN_s with moderate enhancement after contrast agent injection are about 11 and 5 mm, respectively; the serosa surface outer the gastric tumor is smooth and is not invaded by cancer tissue. CT perfusion pcolor BF image (b) and PS image (c) demonstrate that the LN_s and gastric tumor have moderate blood perfusion and permeability, and the lesions are shown in red, yellow and purple. A pathological image of inflammatory LN (HE staining,×100) (d) shows the presence of inflammatory or reactive lymph cells without pleomorphism. BF, blood flow;  LN, lymphnode; PS, permeability surface.

Figure 5.

A graph showing ROC curve for BF, PS and size (the short axis diameters) values of LN_s in predicting metastatic LN. BF, blood flow; LN, lymphnode; PS, permeability surface; ROC, receiver operating characteristic.