超分辨率会擦除小白质病变,而非凭空生成。
Does FLAIR super-resolution erase or hallucinate small white-matter lesions?

- 用自监督模型从厚层扫描重建高分辨率图像
- 重建后小病灶丢失率随层厚增加而上升
- 最佳模型恢复小病灶信号,但仍有丢失风险
白质高信号(WMH)是脑血管病变和神经退行性变的重要标志,通常在临床中以厚层采集的流体衰减反转恢复(FLAIR)影像获取,导致上下方向分辨率较差。本文使用来自ADNI队列29名受试者的1毫米各向同性高分辨率(HR)FLAIR影像,每例均由专家手动标注WMH。将这些影像降采样为模拟3毫米和5毫米层厚的低分辨率扫描,采用多对比隐式神经表示(INR)、单对比自监督模型ECLARE以及三次插值法进行上采样至原始高分辨率网格。以原始高分辨率和模拟厚层扫描的分割结果作为基准,评估四种分割方法(WMH-SynthSeg、segcsvd、MARS-WMH、TrUE-Net)在检测敏感性、病灶擦除率(高分辨率中存在但在重建后消失的病灶比例)和幻觉率(预测出但未出现在人工标注或高分辨率中的成分比例)。结果显示,超分辨率的主要影响是擦除真实小病灶,而非幻觉;且擦除率随层厚增加而升高,尽管所有重建均优于原始厚层扫描。ECLARE在两种层厚下对小病灶信号恢复最优,而INR表现不优于三次插值。
原文摘要 · Abstract (English)
White matter hyperintensities (WMH), bright regions on Fluid-attenuated Inversion Recovery (FLAIR) scans are associated with cerebrovascular pathology and neurodegeneration. FLAIR is usually acquired with thick slices in clinical settings, giving it poor through-plane resolution. Super-resolution (SR) is a widely used method for recovering an isotropic volume from an anisotropic scan. Yet whether applying it prior to WMH segmentation preserves lesion content remains unknown: a model may erase small real lesions or hallucinate absent ones. We used 1-mm isotropic high-resolution (HR) FLAIR scans from 29 individuals in the ADNI cohort, each manually segmented for WMH by an expert. Then, we degraded each to simulated 3 and 5 mm through-plane acquisitions. Multi-contrast implicit neural representation (INR), a single-contrast self-supervised model (ECLARE), and cubic interpolation were used to upsample them onto the HR grid. WMH segmentation from a simulated thick slice and the original HR FLAIR set the floor and ceiling, respectively, for the per-lesion analysis. Of four WMH segmentation methods (WMH-SynthSeg, segcsvd, MARS-WMH, TrUE-Net), we ran the analysis under the most sensitive one to small lesions on HR (MARS-WMH) with the evaluation metrics of detection sensitivity, erasure rate (HR-detected lesions lost after reconstruction), and hallucination rate (predicted components absent from both the manual and HR segmentation). The dominant effect of SR was erasure of small real lesions, not hallucination, and it increased with slice thickness, though every reconstruction still improved lesion detection over the raw thick slice. ECLARE recovered small lesion signal best at both thicknesses, while the INR was no better than cubic interpolation.
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