Improved Sensitivity and Reader Confidence in CT Colonography Using Dual-Layer Spectral CT: A Phantom Study

Abstract

Background: Limited cathartic preparations for CT colonography with fecal tagging can improve patient comfort but may result in nondiagnostic examinations from poorly tagged stool. Dual-energy CT may overcome this limitation by improving the conspicuity of the contrast agent, but more data are needed.Purpose: To investigate whether dual-energy CT improves polyp detection in CT colonography compared with conventional CT at different fecal tagging levels in vitro. Materials and Methods:In this HIPAA-compliant study, between December 2017 and August 2019, a colon phantom 30 cm in diameter containing 60 polyps of different shapes (spherical, ellipsoid, flat) and size groups (5-9 mm, 11-15 mm) was constructed and serially filled with simulated feces tagged with four different iodine concentrations (1.26, 2.45, 4.88, and 21.00 mg of iodine per milliliter), then it was scanned with dual-energy CT with and without an outer fat ring to simulate large body size (total diameter, 42 cm). Two readers independently reviewed conventional 120-kVp CT and 40-keV monoenergetic dual-energy CT images to record the presence of polyps and confidence (three-point scale.) Generalized estimating equations were used for sensitivity comparisons between conventional CT and dual-energy CT, and a Wilcoxon signed-rank test was used for reader confidence.Results: Dual-energy CT had higher overall sensitivity for polyp detection than conventional CT (58.8%; 95% confidence interval [CI]: 49.7%, 67.3%; 564 of 960 polyps vs 42.1%; 95% CI: 32.1%, 52.8%; 404 of 960 polyps; P , .001), including with the fat ring (48% and 31%, P , .001). Reader confidence improved with dual-energy CT compared with conventional images on all tagging levels (P , .001). Interrater agreement was substantial (k = 0.74; 95% CI: 0.70, 0.77). Conclusion:Compared with conventional 120-kVp CT, dual-energy CT improved polyp detection and reader confidence in a dedicated dual-energy CT colonography phantom, especially with suboptimal fecal tagging.

Metal implants on abdominal CT: does split-filter dual-energy CT provide additional value over iterative metal artifact reduction?

“…Previous studies of DECT have focused on high energy VMI to reduce metal artifact, since low energy VMI increase artifact. However, in abdominal imaging mostly low energy VMIs are employed to investigate clinical questions: Improve vascular contrast and create arterial phase-like images from venous phase images [ 33 ], increase conspicuity of pancreatic or hepatic lesions [ 34 ], bowel wall ischemia [ 35 , 36 ], or sensitivity in CT colonography [ 37 ]. Using iMAR may be a way to enable the use of low keV VMI with metal implants.…”

Principles and Applications of Dual-Layer Spectral CT in Gastrointestinal Imaging

“…A more recent investigation further strengthened these promising results. The authors found that 40-keV monoenergetic images showed higher overall sensitivity in polyp detection compared with conventional 120 kVp PEI (58.8% vs. 42.1%, p < 0.001) and improved reader confidence at different fecal tagging levels (p < 0.001) in a colon phantom [56].…”

Clinical Implementation of Dual-Energy CT for Gastrointestinal Imaging

“…As DECT technology continues to evolve, multiple new technical innovations are anticipated to improve the value of multi-energy CT for evaluation of the gastrointestinal tract. Currently, groups are embracing the high sensitivity and quantitative nature of DECT to define useful thresholds for diagnoses, to expand its clinical applications [e.g., perfusion DECT for tumor characterization and treatment monitoring [76]; liver fibrosis [77]; DECT augmentation of suboptimal stool tagging during CT colonography [78] (Figure 10)], and to further reduce radiation and contrast dose for all CT imaging [63].…”