Imaging meningiomas: Is there a need for post-contrast FLAIR?
Introduction
Fluid-attenuated inversion recovery (FLAIR) sequence has an inversion time that effectively nulls signals from the cerebrospinal fluid (CSF) with a long echo time (TE) that produces T2 weighting. The FLAIR technique has also a mild T1 weighted contrast, which is responsible for the observation of contrast enhancement on these heavily T2-weighted images.1 Recently, attempts have been made to use the T1 contrast of FLAIR images for gadolinium-enhanced brain magnetic resonance imaging (MRI). FLAIR imaging after contrast medium injection has been shown to be an efficacious method in the detection of various intra and extra-axial brain lesions, but especially in the delineation of meningeal lesions including meningoencephalitis and leptomeningeal metastases.2, 3, 4, 5, 6, 7, 8 The purpose of the present study was to evaluate contrast-enhanced FLAIR imaging in depicting meningiomas and to compare it with post-contrast T1-weighted images (T1WI).
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Materials and methods
Twenty-nine patients (20 women, nine men; mean age 36 years; age range 17–73 years) with 46 meningiomas were included in this prospective study. The distribution of meningiomas per patient ranged between one to nine. Institutional review board approval and informed consent from each patient were obtained. All examinations were performed on a 1.0 T MRI machine. Axial FLAIR and T1-weighted spin-echo images were obtained before and after intravenous administration of 0.1 mmol/kg gadopentetate
Results
Seven of the 46 meningiomas were infratentorial and the remaining 39 were supratentorial in location. The size of meningiomas ranged from 7–50 mm (mean 20.1 mm). Eight meningiomas had an equal, whereas 38 had a lesser degree of contrast enhancement using FLAIR imaging compared with T1WI. None of the meningiomas showed superior contrast enhancement on FLAIR imaging (Table 1). The contrast enhancement degree did not differ in terms of which sequence was performed first or second after
Discussion
Gadopentetate dimeglumine is frequently used as an intravenous contrast agent in order to improve lesion detection and characterization in cranial MRI. Although it shortens both the T1 and T2 relaxation times of the tissues in which it accumulates, the T1 shortening is the prominent effect at commonly used doses. Therefore, T1 weighted spin-echo sequences are routinely used for gadolinium-enhanced MRI, and accepted as the gold standard in the detection and characterization of brain lesions.2, 6
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☆Presented as a scientific poster at the ASNR 2004, Seattle, USA.