Purpose

Intraoperative MRI (iMRI) offers the possibility of acquiring intraoperatively real-time images that will guide neurosurgeons when removing brain tumors. The objective of this study was to report the existence of FLAIR abnormalities on iMRI that may occur on the margin of a brain resection and may lead to misdiagnosis of residual tumor.

Methods

We retrospectively analyzed intraoperative MRI (iMRI) in 21 consecutive patients who underwent surgery for a low-grade glioma. Two readers independently reviewed iMRI images to search for the presence of a FLAIR hyperintensity surrounding the surgical cavity. For each patient, they were instructed to characterize FLAIR abnormalities on the margins of the resected area as (1) no FLAIR abnormality; (2) “linear FLAIR hyperintensity (LFH)”, when a < 5 mm linear FLAIR hyperintensity was present; or (3) “nodular FLAIR hyperintensity (NFH)”, in the case of a thick and nodular FLAIR hyperintensity.

Results

LFH were present on at least one surgical margin of one third of the patients analyzed with iMRI, and vanished on follow-up MRI, confirming its transient condition; whereas NFH were linked to persistence of pre-surgical abnormalities, such as residual tumor as confirmed or by histopathological analysis of a second surgery or by its remnant on follow-up MRI.

Conclusion

Linear FLAIR hyperintensities can be present on surgical margins analyzed by iMRI and should not be mistaken for residual tumor.

中文翻译：

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术中 MRI 和 FLAIR 分析：对低级别胶质瘤手术的影响

目的

术中 MRI (iMRI) 提供了获取术中实时图像的可能性，这些图像将在去除脑肿瘤时指导神经外科医生。本研究的目的是报告 iMRI 上 FLAIR 异常的存在，这些异常可能发生在脑切除边缘，并可能导致残留肿瘤的误诊。

方法

我们回顾性分析了 21 名接受低级别胶质瘤手术的连续患者的术中 MRI (iMRI)。两名读者独立审查 iMRI 图像，以寻找手术腔周围是否存在 FLAIR 高信号。对于每位患者，他们被指示将切除区域边缘的 FLAIR 异常表征为 (1) 无 FLAIR 异常；(2) “线性 FLAIR 高信号 (LFH)”，当存在 <  5  mm 的线性 FLAIR 高信号时；或 (3) “结节性 FLAIR 高信号 (NFH)”，在厚且结节的 FLAIR 高信号的情况下。

结果

LFH 出现在 iMRI 分析的三分之一患者的至少一个手术切缘上，并在后续 MRI 中消失，证实其为一过性状态；而 NFH 与术前异常的持续存在有关，例如确认的残留肿瘤或第二次手术的组织病理学分析或其在后续 MRI 中的残留。

结论

线性 FLAIR 高信号可以出现在 iMRI 分析的手术切缘上，不应被误认为是残留肿瘤。