Preoperative spectral computed tomography multi-parameter prediction of postoperative complications in colorectal cancer: A single-center retrospective cohort study

Figure 4 Bootstrap validation of the nomogram model. A: Histogram showing the distribution of C-index values obtained from bootstrap resampling, demonstrating the stability of model performance across different samples; B: C-index trends across bootstrap iterations, where the blue line represents the bootstrap mean C-index, the blue dashed line indicates the original C-index, and the purple dashed line shows the bias-corrected C-index. This analysis validates the model's discriminative ability and internal consistency.