Improving small brain metastasis detection with composite and augmented T₁-weighted imaging in contrast-enhanced...

Contrast-enhanced T₁-weighted (T₁W) imaging has limited sensitivity for detecting small brain metastases less than 5 mm in diameter. A recently-developed MULTI-parametric magnetic resonance imaging (MRI) with fLEXible design (MULTIPLEX) has shown promise in the detection of various neurological disorders. In the current study, we compared the performance of MULTIPLEX-derived composite T₁-weighted (cT₁W) and augmented T₁-weighted (aT₁W) imaging with that of magnetization-prepared rapid gradient-echo T₁-weighted (MPRAGE-T₁W) imaging for the detection of small brain metastases.

This prospective study recruited patients with suspected intracranial metastases who underwent contrast-enhanced MRI with both MULTIPLEX and MPRAGE-T₁W imaging. Two radiologists independently assessed the total number of enhanced lesions, visual image quality, and their level of diagnostic confidence. Additionally, sensitivity, the average false-negative rate, the average false- positive rate, and the mean discrepancy were evaluated for small metastases. Image quality was also assessed objectively using signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements. Qualitative and quantitative imaging characteristics were compared using the Friedman test and analysis of variance, respectively. The P values were adjusted for multiple comparison correction using the Bonferroni method. A P value < 0.05 was considered statistically significant.

A total of 47 patients (55±7 years; 22 males) were included in the study, 20 of whom were diagnosed with brain metastases by two radiologists. Compared with MPRAGE-T₁W imaging {2 [interquartile range (IQR), 0-5.25]}, a greater number of small metastases was detected by MULTIPLEX-derived cT₁W [2.5 (IQR, 1-7.5), P=0.002] and aT₁W imaging [2.5 (IQR, 1-7.5), P=0.044], with higher detection sensitivity (94.95% and 84.15% vs. 60.65%). MULTIPLEX-cT₁W imaging had significantly higher SNRs in both metastatic lesions (P=0.027) and grey matter (GM; P<0.001), while MULTIPLEX-aT₁W imaging selectively enhanced lesion-to-GM contrast (P<0.001) compared with MPRAGE-T₁W. Despite comparable subjective image quality (P=0.22), MULTIPLEX-derived imaging yielded higher diagnostic confidence (P=0.031).

MULTIPLEX-derived cT₁W and aT₁W imaging improved the detection of small brain metastases, with enhanced lesion conspicuity and diagnostic confidence, compared with MPRAGE-T₁W imaging.