arXiv:2410.05263stat.MLcs.AI2024-10中稿 · ISBI 2026被引 1

医学影像重建中,偏差会破坏置信区间的可靠性,本文提出根据偏差选择对称或非对称校准方法。

Bias-Aware Conformal Prediction for Metric-Based Imaging Pipelines

  • 根据偏差大小选择对称或非对称置信区间,提升校准精度
  • 实验证明对称区间会因偏差扩大两倍,而非对称不受影响
  • 适用于放射治疗规划等关键临床场景的可靠度量

医学影像重建流程中,下游指标的可信置信度可提升临床决策标准。共形预测(Conformal Prediction, CP)能生成校准的预测区间,但其标准形式在影像流程中面临关键挑战:图像重建目标与下游指标常不匹配,导致系统性偏差,即预测值偏离真实值。这种偏差会损害预测区间效率,而该问题在CP文献中尚未被研究。本文形式化分析了常见非一致性评分下对称与非对称区间在偏差存在时的表现,论证偏差必须影响CP形式选择。理论与实证均表明,对称区间受偏差影响,长度扩大两倍;非对称区间不受偏差影响,并给出各自更紧区间的条件。我们在稀疏视角CT重建用于放疗规划的任务上验证了理论分析。本工作使医学影像用户可主动选择最优的CP形式,从而提升关键下游指标的区间效率。

原文摘要 · Abstract (English)

Reliable confidence measures of metrics derived from medical imaging reconstruction pipelines would improve the standard of decision-making in many clinical workflows. Conformal Prediction (CP) provides a robust framework for producing calibrated prediction intervals, but standard CP formulations face a critical challenge in the imaging pipeline: common mismatches between image reconstruction objectives and downstream metrics can introduce systematic prediction deviations from ground truth values, known as bias. These biases in turn compromise the efficiency of prediction intervals, which is a problem that has been unexplored in the CP literature. In this study, we formalize the behavior of symmetric (where bounds expand equally in both directions) and asymmetric (where bounds expand unequally) formulations for common non-conformity scores in CP in the presence of bias, and argue that this measurable bias must inform the choice of CP formulation. We theoretically and empirically demonstrate that symmetric intervals are inflated by a factor of two times the magnitude of bias while asymmetric intervals remain unaffected by bias, and provide conditions under which each formulation produces tighter intervals. We empirically validated our theoretical analyses on sparse-view CT reconstruction for downstream radiotherapy planning. Our work enables users of medical imaging pipelines to proactively select optimal CP formulations, thereby improving interval length efficiency for critical downstream metrics.

共形预测医学影像置信度

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