Investigating the potential association between the continuous-time random-walk MR diffusion model and lymph node metastasis and vascular invasion in patients with rectal cancer: A preliminary exploratory study

Objectives To explore, as a preliminary study, the quantitative parameters of single-index and continuous-time random-walk (CTRW) magnetic resonance (MR) diffusion models and their association with lymph node metastasis, vascular invasion, and some prognostic factors in patients with rectal cancer. Methods This retrospective, exploratory study included a total of 43 patients who were pathologically diagnosed with rectal cancer and underwent preoperative MRI between February 2022 and November 2023. The data were fitted using the single-index and CTRW diffusion models to derive ADC, Dm, α, and β parameters. Differences in quantitative diffusion parameters were assessed for lymph node metastasis, vascular invasion, and p53 status using t-tests and rank-sum tests. The associations of quantitative diffusion parameters with lymph node metastasis and vascular invasion were evaluated using receiver operating characteristic (ROC) analysis. Results Lymph node metastasis was positive in 25 patients and negative in 18 patients; vascular invasion was positive in 30 patients and negative in 13 patients. In this initial investigation, the Dm and β values derived from the CTRW model showed a certain association with lymph node metastasis (AUCs of 0.76 and 0.76, respectively). Regarding vascular invasion, only the Dm value showed a certain association (AUC of 0.76), while the β value did not demonstrate a significant association after adjustment.The combination of Dm and β demonstrated stronger associations, with AUCs of 0.83 and 0.83, respectively. Conclusion In this exploratory study, the diffusion parameters derived from the CTRW model may be associated with lymph node metastasis and vascular invasion in rectal cancer, but this requires external validation.