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arXiv 2409.08463eess.IV

脑部MRI生成器的质量评估

Evaluating the Quality of Brain MRI Generators

Jiaqi Wu, Wei Peng, Binxu Li, Yu Zhang, Kilian M. Pohl

AI总结:

针对现有脑部MRI生成模型质量评估指标不适配医学图像、结论不可靠的问题,提出含统一处理、标准实现、高可靠分割校验的评估框架,可准确量化解剖合理性,评估结果与定性判断一致。

摘要:

生成结构性脑部MRI的深度学习模型有望显著加速神经科学研究的发现进程,但其应用目前受到限制,部分原因在于质量评估方式存在缺陷。大多数生成模型评估聚焦于原本为自然图像设计的指标(如结构相似性指数、Frechet inception距离)。我们对6个在3000余张MRI上训练和测试的前沿生成模型进行了对比,结果表明这些指标对实验设置敏感,且无法充分评估生成的脑部MRI对脑区宏观结构特性的还原程度(即解剖学合理性)。即便模型输出的定性差异十分明显,这类指标的缺陷仍会导致研究结论不明确。为此,我们提出一套脑部MRI生成模型评估框架,该框架要求对真实MRI进行统一处理、标准化模型实现流程,并对模型生成的MRI进行自动分割。分割结果用于量化MRI中呈现的解剖结构的合理性,而要确保量化结果有意义,分割结果的高可靠性至关重要。我们的框架会严格校验这种可靠性,这一步骤常被既往研究忽略。在6个生成模型中,仅有3个生成的MRI能达到至少95%的样本具备高可靠分割结果。更重要的是,我们的框架对每个模型的评估结果与定性评估一致,印证了该方法的有效性。

英文摘要:

Deep learning models generating structural brain MRIs have the potential to significantly accelerate discovery of neuroscience studies. However, their use has been limited in part by the way their quality is evaluated. Most evaluations of generative models focus on metrics originally designed for natural images (such as structural similarity index and Frechet inception distance). As we show in a comparison of 6 state-of-the-art generative models trained and tested on over 3000 MRIs, these metrics are sensitive to the experimental setup and inadequately assess how well brain MRIs capture macrostructural properties of brain regions (i.e., anatomical plausibility). This shortcoming of the metrics results in inconclusive findings even when qualitative differences between the outputs of models are evident. We therefore propose a framework for evaluating models generating brain MRIs, which requires uniform processing of the real MRIs, standardizing the implementation of the models, and automatically segmenting the MRIs generated by the models. The segmentations are used for quantifying the plausibility of anatomy displayed in the MRIs. To ensure meaningful quantification, it is crucial that the segmentations are highly reliable. Our framework rigorously checks this reliability, a step often overlooked by prior work. Only 3 of the 6 generative models produced MRIs, of which at least 95% had highly reliable segmentations. More importantly, the assessment of each model by our framework is in line with qualitative assessments, reinforcing the validity of our approach.

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