Value of enhanced fluid-attenuated inversion-recovery T1-weighted imaging sequences combined with the three-dimensional modulated flip-angle technique in diagnosing brain metastases.

Background: Accurate identification of brain metastases is critical for radiotherapy planning. The aim of this study was to evaluate the effectiveness of contrast-enhanced T1-weighted fluid-attenuated inversion recovery (CE-T1FLAIR) sequences combined with the three-dimensional modulated flip-angle technique to enhance the visualization of metastatic tumors. Methods: A retrospective study of 326 patients who were pathologically diagnosed with malignant tumors and clinically suspected of brain metastases from October 2023 to February 2024 was conducted. Magnetic resonance images from the modulated flip-angle technique in refocused imaging with extended echo trains (MATRIX) CE-T1FLAIR, three-dimensional magnetization-prepared rapid gradient echo (3D GRE) fast-spin echo (FSE) with modulated flip-angle flow-sensitive preparation (fsp) CE-T1FLAIR, and 2D FSE CE-T1FLAIR sequences were analyzed by three independent radiologists in a double-blind manner. Detection rates were compared with the χ2 test or Fisher exact test, with multiple comparisons conducted via the Bonferroni method. Interrater reliability was assessed with the Kappa consistency test. Results: A total of 176 patients with 887 brain metastases were included based on the linked intelligence brain metastasis artificial intelligence-assisted detection system and clinical follow-up. The MATRIX CE-T1FLAIR sequence had an overall lesion detection rate of 98.9%, significantly higher than the 93.5% for 3D GRE fsp CE-T1FLAIR and 80.6% for 2D FSE CE-T1FLAIR. For lesions <5 mm, the detection rate was 98.8%, with significant differences between the sequences. Lesion distribution analysis indicated that MATRIX CE-T1FLAIR had a higher detection rate in the superficial area of the brain's convexity, gray-white matter junction, and basal ganglia. Conclusions: The MATRIX CE-T1FLAIR sequence demonstrates superior overall and subgroup detection rates, particularly for small brain metastases (<5 mm) in the superficial areas of the brain's convexity as compared to 3D GRE fsp CE-T1FLAIR and 2D FSE CE-T1FLAIR.