The Added Value of Double Dose Gadolinium Enhanced 3D T2 Fluid-Attenuated Inversion Recovery for Evaluating Small Brain Metastases

Abstract

PurposeSingle dose gadolinium (Gd) enhanced fluid-attenuated inversion recovery (FLAIR) is helpful for visualizing superficial parenchymal metastases. However, the usefulness of FLAIR with a higher dose of Gd is uncertain. The aim of our study was two-folds: first, to prove that the signal to noise ratio (SNR) of small brain metastases is higher than large brain metastases on double-dose (DD) enhanced FLAIR and, second, to explore the added value of DD Gd enhanced FLAIR in relation to T1 GRE for evaluating small brain metastases.Materials and MethodsFor the first purpose, 50 pairs of small (2 mm<diameter≤5 mm) and large brain metastases (diameter >5 mm) were included. The difference in the SNR and contrast ratio (CR) between small and large metastases on DD Gd-enhanced 3D T2 FLAIR was compared by Wilcoxon signed-rank tests. For the second purpose, a total of 404 small metastases were included. The diagnostic sensitivities between 3D T1 gradient echo (GRE) alone and combined results of 3D T1 GRE and 3D T2 FLAIR were compared with McNemar test.ResultsThe SNR and CR of small brain metastases were significantly higher than those of large brain metastases (p<0.001). In qualitative analysis, the diagnostic sensitivities for small brain metastases were significantly higher for 3D T1 GRE plus 3D T2 FLAIR than 3D T1 GRE alone regardless of scan time (p<0.001).ConclusionSmall brain metastases showed higher signal intensity than large brain metastases on the DD Gd enhanced 3D T2 FLAIR images. DD Gd enhanced 3D T2 FLAIR imaging may have a complementary role to 3D T1 GRE for evaluating small brain metastases.

The detectability of brain metastases using contrast-enhanced spin-echo or gradient-echo images: a systematic review and meta-analysis

“…Accordingly, 3D GRE may be the most common imaging sequences for detecting brain metastases, particularly small lesions, until recently. However, these results probably due to the facts that previous studies compared detectability between 2D SE with a thicker slice thickness and 3D GRE with a thinner slice thickness [8][9][10].…”

“…In the last decade, several original articles have described the detectability of brain metastases using contrastenhanced SE and GRE T1-weighted images [8][9][10][11][12][13][14][15]. Recent studies compared 3D SE and 3D GRE images with 1-mmthick slices for detecting brain metastases [11][12][13][14][15].…”

“…However, there are currently no definitive guidelines state which image should be used to detect brain metastasis, and few the full text (one case report [23], one study with insufficient data [24], and seven studies that were not in the field of interest) [25][26][27][28][29][30][31]. Finally, eight eligible studies, which included a total sample size of 252 patients and 1413 brain metastases, were included in our meta-analysis [8][9][10][11][12][13][14][15].…”

“…Several previous studies compared the contrast-enhanced two-dimensional (2D) spin-echo (SE) and three-dimensional (3D) gradient-echo (GRE) T1-weighted images for detecting small brain metastases [8][9][10]. Although SE T1-weighted images can usually present a higher contrastto-noise ratio (CNR) and signal-to-noise ratio (SNR) in comparison with GRE images, the higher detectability of brain metastases has been reported using GRE with thinner section slices [8][9][10]. Accordingly, 3D GRE may be the most common imaging sequences for detecting brain metastases, particularly small lesions, until recently.…”

“…Six of eight studies were prospective [8,10,[12][13][14][15], and two studies were retrospective [9,11]. In terms of the demographic characteristics of the patients in the included studies, the mean ages of these cases ranged between 57.3 and 66.3 years ( Table 2).…”