The T2-FLAIR mismatch sign on MR imaging is a highly specific imaging biomarker of isocitrate dehydrogenase (IDH)-mutant astrocytomas, which lack 1p/19q codeletion. However, most studies using the T2-FLAIR mismatch sign have used visual assessment. This study quantified the degree of T2-FLAIR mismatch using digital subtraction of fluid-nulled T2-weighted FLAIR images from non-fluid-nulled T2-weighted images in human nonenhancing diffuse gliomas and then used this information to assess improvements in diagnostic performance and investigate subregion characteristics within these lesions.

Two cohorts of treatment-naïve, nonenhancing gliomas with known IDH and 1p/19q status were studied (n = 71 from The Cancer Imaging Archive (TCIA) and n = 34 in the institutional cohort). 3D volumes of interest corresponding to the tumor were segmented, and digital subtraction maps of T2-weighted MR imaging minus T2-weighted FLAIR MR imaging were used to partition each volume of interest into a T2-FLAIR mismatched subregion (T2-FLAIR mismatch, corresponding to voxels with positive values on the subtraction maps) and nonmismatched subregion (T2-FLAIR nonmismatch corresponding to voxels with negative values on the subtraction maps). Tumor subregion volumes, percentage of T2-FLAIR mismatch volume, and T2-FLAIR nonmismatch subregion thickness were calculated, and 2 radiologists assessed the T2-FLAIR mismatch sign with and without the aid of T2-FLAIR subtraction maps.

Thresholds of ≥42% T2-FLAIR mismatch volume classified IDH-mutant astrocytoma with a specificity/sensitivity of 100%/19.6% (TCIA) and 100%/31.6% (institutional); ≥25% T2-FLAIR mismatch volume showed 92.0%/32.6% and 100%/63.2% specificity/sensitivity, and ≥15% T2-FLAIR mismatch volume showed 88.0%/39.1% and 93.3%/79.0% specificity/sensitivity. In IDH-mutant astrocytomas with ≥15% T2-FLAIR mismatch volume, T2-FLAIR nonmismatch subregion thickness was negatively correlated with the percentage T2-FLAIR mismatch volume (P < .0001) across both cohorts. The percentage T2-FLAIR mismatch volume was higher in grades 3–4 compared with grade 2 IDH-mutant astrocytomas (P < .05), and ≥15% T2-FLAIR mismatch volume IDH-mutant astrocytomas were significantly larger than <15% T2-FLAIR mismatch volume IDH-mutant astrocytoma (P < .05) across both cohorts. When evaluated by 2 radiologists, the additional use of T2-FLAIR subtraction maps did not show a significant difference in interreader agreement, sensitivity, or specificity compared with a separate evaluation of T2-FLAIR and T2-weighted MR imaging alone.

T2-FLAIR digital subtraction maps may be a useful, automated tool to obtain objective segmentations of tumor subregions based on quantitative thresholds for classifying IDH-mutant astrocytomas using the percentage T2 FLAIR mismatch volume with 100% specificity and exploring T2-FLAIR mismatch/T2-FLAIR nonmismatch subregion characteristics. Conversely, the addition of T2-FLAIR subtraction maps did not enhance the sensitivity or specificity of the visual T2-FLAIR mismatch sign assessment by experienced radiologists.

MR 成像上的 T2-FLAIR 不匹配征象是异柠檬酸脱氢酶 ( IDH ) 突变型星形细胞瘤的高度特异性成像生物标志物，缺乏 1p/19q 共缺失。然而，大多数使用 T2-FLAIR 不匹配标志的研究都使用了视觉评估。本研究使用人类非增强弥漫性神经胶质瘤的非流体无效 T2 加权图像中数字减去流体无效 T2 加权 FLAIR 图像来量化 T2-FLAIR 不匹配程度，然后使用此信息来评估诊断性能的改进并进行调查这些病变内的分区特征。

研究了两组未经治疗、已知IDH和 1p/19q 状态的非增强胶质瘤（ n = 71 来自癌症影像档案 (TCIA)，n = 34 来自机构队列）。对与肿瘤相对应的3D感兴趣体积进行分割，并使用T2加权MR成像减去T2加权FLAIR MR成像的数字减影图将每个感兴趣体积划分为T2-FLAIR不匹配的子区域（T2-FLAIR不匹配，对应到减法图上具有正值的体素）和非失配子区域（T2-FLAIR非失配对应于减法图上具有负值的体素）。计算肿瘤分区体积、T2-FLAIR 错配体积百分比和 T2-FLAIR 非错配分区厚度，并由 2 名放射科医生在有或没有 T2-FLAIR 减法图的帮助下评估 T2-FLAIR 错配征。

≥42% T2-FLAIR 错配体积的阈值分类为IDH突变型星形细胞瘤，特异性/敏感性为 100%/19.6% (TCIA) 和 100%/31.6%（机构）； ≥25% T2-FLAIR 错配量显示 92.0%/32.6% 和 100%/63.2% 特异性/敏感性，≥15% T2-FLAIR 错配量显示 88.0%/39.1% 和 93.3%/79.0% 特异性/敏感性。在T2-FLAIR 错配体积≥15% 的IDH突变型星形细胞瘤中，两个队列中 T2-FLAIR 非错配分区厚度与 T2-FLAIR 错配体积百分比呈负相关 ( P < .0001)。与 2 级 IDH 突变型星形细胞瘤相比，3-4 级 T2-FLAIR 错配体积百分比较高( P < .05)，并且 ≥15% T2-FLAIR 错配体积IDH突变型星形细胞瘤显着大于 <15% T2 - 两个队列中的FLAIR 体积不匹配IDH - 突变型星形细胞瘤 ( P < .05)。当由 2 名放射科医生进行评估时，与单独评估 T2-FLAIR 和 T2 加权 MR 成像相比，额外使用 T2-FLAIR 减法图在读者间一致性、敏感性或特异性方面没有显示出显着差异。

T2-FLAIR 数字减影图可能是一种有用的自动化工具，可根据定量阈值获得肿瘤亚区域的客观分割，以使用具有 100% 特异性的 T2 FLAIR 错配体积百分比对IDH突变型星形细胞瘤进行分类，并探索 T2-FLAIR 错配/T2- FLAIR 非失配分区特征。相反，添加 T2-FLAIR 减法图并没有增强经验丰富的放射科医生进行的视觉 T2-FLAIR 不匹配征象评估的敏感性或特异性。