ObjectiveTo summarize the application of spectral CT in the diagnosis of common, frequently occurring, and acute severe gastrointestinal diseases. MethodThe literature and guidelines on spectral CT were reviewed, and the main conclusions and opinions were summarized. ResultsThe spectral CT could obtain a variety of tissue parameters through a single scan. Through post-processing, multiple sequence images could be obtained, including virtual single-level images, virtual unenhanced images, iodine density images, effective atomic number images, etc. And multiple quantitative indicators could also be obtained, including iodine concentration, standardized iodine concentration, spectral curve, effective atomic number, etc. It could improve the signal-to-noise ratio of the image, reduce artifacts, increase iodine contrast, and decrease iodine load, then could improve the detection rate of active gastrointestinal bleeding and ischemic bowel diseases, improve the assessment accuracy of inflammatory activity of Crohn disease, and help to identify benign and malignant gastrointestinal tumors, determine the histological origin and evaluate the therapeutic effect. ConclusionFrom the conclusion summarized in this review, spectral CT images and quantitative indicators could provide more valuable information for detection, diagnosis, and prognosis of gastrointestinal diseases.
ObjectiveTo evaluate the value of spectral CT monoenergetic imaging in optimizing the image quality of peripancreatic great vessels in patients with pancreatic malignant tumors. MethodsThe imaging data of 62 patients with pancreatic malignant tumors who underwent contrast-enhanced spectral CT at West China Hospital of Sichuan University from July 2018 to March 2021 were retrospectively analyzed. A total of 21 monoenergetic image sets (from 40 to 140 keV at 5 keV intervals) were reconstructed. The CT value, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the peripancreatic great vessels (including the celiac artery, common hepatic artery, superior mesenteric artery, portal vein, and superior mesenteric vein), as well as the tumor-to-parenchyma ratio (TPR) in the pancreatic parenchymal and portal venous phases, were compared between the mixed-energy images and the monoenergetic images. Additionally, subjective evaluations of vascular involvement in both the mixed-energy and optimal monoenergetic images were performed. ResultsThe overall differences in CT values, SNR, and CNR of the peripancreatic great vessels among mixed-energy and 21 monoenergetic image sets were all statistically significant (all P<0.001). In the monoenergetic images, as the energy level increased, the CT values, SNR, and CNR of the five peripancreatic great vessels showed consistent decreasing trends (all P<0.001). The 40 keV group exhibited the highest values for all indexes, indicating the best visualization. Regarding the TPR, both the pancreatic parenchymal and the portal venous phases showed a decrease as the energy level increased. The intergroup difference in TPR in the pancreatic parenchymal phase was statistically significant (P<0.001), while no significant difference was observed in the portal venous phase (P>0.05). The 40 keV monoenergetic images achieved the highest TPR, providing optimal lesion visualization. The subjective evaluations by two physicians on vascular involvement in 40 keV monoenergetic images and mixed-energy images showed good to excellent interobserver agreement (Kappa=0.775–1.000, all P<0.001). ConclusionThe 40 keV image from spectral CT can significantly optimize the imaging of peripancreatic great vessels, providing better subjective and objective image quality.