提出测量几何分析方法,解决生成模型逆问题中的可信重建难题
Measurement Geometry and Design for Trustworthy Generative Inverse Problems

- 从测量几何角度定义局部兼容性度量,判断测量能否捕捉生成先验的关键方向
- 证明该度量控制重建误差的稳定部分,生成先验主导离流形漂移
- 设计测试时自适应测量方案,可避免生成幻觉,适用于医学成像等高风险场景
生成模型被广泛用作逆问题的先验,但其生成逼真图像的能力带来信任问题:重构结果可能是测量支持的,也可能是先验在未观测方向上填补的。这在医疗成像中尤为关键,因采集受扫描时间、剂量和校准约束。本文从测量几何视角研究生成逆问题,核心问题是固定测量算子能否区分生成先验下邻近的合理图像。提出局部测量流形兼容性度量,量化算子对先验相关切向方向的观测能力。在局部正则性假设下,证明该度量控制重建误差的稳定部分,而生成先验控制离流形漂移。该最坏方向证书启发了基于整体局部体积保持的固定与序列采集规则,包括无需训练采样策略的后验云设计。在行采样、断层扫描和磁共振采集设置中,所提评分能预测失败模式、解释测量诱导的幻觉,并指导更优采样。在fastMRI笛卡尔采样中,后验云设计优于强基线,包括变密度和泊松型掩码。
原文摘要 · Abstract (English)
Generative models are increasingly used as priors for inverse problems, but their ability to produce realistic images creates a basic trust problem: a plausible reconstruction may be supported by the measurements, or it may be filled in by the prior along unobserved directions. This distinction is especially important in medical imaging, where acquisition operators are designed under scan-time, dose, and calibration constraints. We study generative inverse problems from a measurement-geometry perspective. The central question is whether a fixed measurement operator can distinguish nearby images that are plausible under the generative prior, and whether this relationship can guide better measurements. We introduce a local measurement-manifold compatibility measure that quantifies how well the operator observes prior-relevant tangent directions. Under local regularity assumptions, we prove that this quantity controls the stable part of the reconstruction error, while the generative prior controls off-manifold drift. This worst-direction certificate motivates practical fixed and sequential acquisition rules based on overall local volume preservation, including a posterior-cloud design that adapts measurements at test time without training a sampling policy. Across row-sampling, tomographic, and MR acquisition settings, the proposed scores predict failure modes, explain measurement-induced hallucinations, and guide better sampling. In fastMRI Cartesian sampling, posterior-cloud measurement design improves over strong non-learned ACS-preserving baselines, including variable-density and Poisson-like masks.
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