ArXiv

Does FLAIR super-resolution erase or hallucinate small white-matter lesions?

2026-08-06 · 17:26 UTC ·Zahra Khodakarami, Yue Li, Pulkit Khandelwal... ·1 min read
Authors
Zahra Khodakarami, Yue Li, Pulkit Khandelwal...
Categories
cs.CV, cs.AI
arXiv
https://arxiv.org/abs/2608.06311v1
PDF
https://arxiv.org/pdf/2608.06311v1

Brief

FLAIR super-resolution for WMH segmentation was evaluated using 29 ADNI subjects with expert 1-mm isotropic FLAIR ground truth, downsampled to simulated 3 mm and 5 mm through-plane scans. Upsampling methods (ECLARE, a multi-contrast INR, and cubic interpolation) were compared under MARS-WMH with metrics for detection sensitivity, erasure, and hallucination. SR mostly erased small true lesions (worse at thicker slices); ECLARE recovered small-lesion signal best, INR matched cubic interpolation. Full text was not available (abstract only); the preprint (arXiv 2026-08-06) was accepted to SASHIMI 2026.

Why it matters

Super-resolution (SR) primarily erased small real white-matter hyperintensity (WMH) lesions rather than hallucinating false ones; erasure increased with through-plane slice thickness (tested on 29 ADNI subjects with 1-mm HR ground truth and simulated 3 mm and 5 mm acquisitions).

Key details

  • ECLARE (single-contrast self-supervised) recovered small-lesion signal best at both 3 mm and 5 mm thicknesses, while the multi-contrast implicit neural representation (INR) performed no better than simple cubic interpolation.
  • Analysis used the most small-lesion-sensitive WMH segmenter (MARS-WMH) and metrics of detection sensitivity, erasure rate (HR-detected lesions lost after reconstruction), and hallucination rate (components absent from both manual and HR); every SR reconstruction still improved detection versus the raw thick slice.
Source evidence

Abstract

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.

Comment: 10 pages, 2 figures, 3 tables. Accepted at the 11th International Workshop on Simulation and Synthesis in Medical Imaging (SASHIMI 2026), held in conjunction with MICCAI 2026. This is the version submitted for review; the final authenticated version will appear in the Springer LNCS proceedings