Abstract
BACKGROUND: Accurate preoperative T staging is essential for determining optimal treatment strategies in colorectal cancer (CRC). Low-keV virtual monoenergetic images (VMIs) have been shown to enhance lesion conspicuity. This study aimed to assess the diagnostic value of dual-layer spectral computed tomography (CT)-derived VMIs, in combination with multiplanar reformation (MPR) and evaluation of peritumoral fat stranding (PFS), for improving the accuracy of T staging in CRC. AIM: To assess the diagnostic performance of dual-layer spectral CT (DLSCT) VMIs, particularly at low energy levels, and their integration with personalized MPR for preoperative T staging of CRC. METHODS: In this retrospective study, 157 patients with pathologically confirmed CRC (mean age: 63.5 ± 12.1 years) underwent DLSCT within 1 week before surgery. VMIs ranging from 40 keV to 70 keV (at 10 keV intervals) and conventional polyenergetic images (PEIs) were reconstructed. Objective image quality parameters, including image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR), were quantified, alongside subjective image quality scores using a 5-point Likert scale. Interobserver agreement was evaluated using κ statistics. Taking histopathology as the reference standard, the diagnostic accuracy of T staging (T1-2 vs T3-4) was compared across PEIs and VMIs, both with and without MPR and PFS. RESULTS: Low-keV VMIs (40-70 keV) demonstrated significantly higher SNR and CNR than PEIs (all P < 0.001). Notably, 40-keV VMIs achieved noise levels comparable to PEIs (8.17 ± 3.63 vs 8.53 ± 2.90; P = 0.673). Subjective image quality peaked at 40-50 keV VMIs (Likert scores 4.85-4.88 vs 3.97 for PEIs; P < 0.001), supported by excellent interobserver agreement (κ = 0.812-0.913). The combination of 40-50 keV VMIs with MPR yielded the highest T staging accuracy (94.27%) compared to axial PEIs (70.7%), with a sensitivity and specificity of 83.87% and 96.83%, respectively (Youden index = 0.81; P < 0.05). While PFS enhanced staging accuracy on PEIs (up to 77.07% with MPR), it provided no significant additional benefit for VMIs. CONCLUSION: DLSCT VMIs at 40-50 keV significantly enhanced image quality and improved preoperative T staging accuracy of CRC when combined with MPR. These findings underscored the clinical value of low-keV spectral imaging in tailoring individualized treatment strategies.