T1 contrast versus fluid-attenuated inversion recovery contrast technique for evaluation of cerebral tuberculosis

INTRODUCTION

The fluid-attenuated inversion recovery (FLAIR) approach uses an inversion recovery pulse sequence with an inversion duration that, when used with long-TE T2-weighted (T2W) imaging, effectively nullifies signals from the CSF. The mild T1 effect of the FLAIR sequence is responsible for contrast enhancement on these heavily T2W images. FLAIR imaging of the brain is sensitive for detecting parenchymal lesions and is also promising in evaluating cerebral tubercular pathologies. To diagnose brain diseases, magnetic resonance imaging (MRI) contrast termed FLAIR contrast combines the drawbacks of T2W FLAIR contrast in a single image.^[4,8] Our purpose was to compare post-contrast T1-weighted (T1W) and FLAIR images in evaluating cerebral tubercular pathologies.

MATERIAL AND METHODS

This study was carried out in the Department of Radiodiagnosis, Sri Manakula Vinayagar Medical College and Hospital, Puducherry, India. It is a hospital based prospective study. After obtaining clearance from the Institute’s Ethics Committee, 20 cases who were referred to the department of radiodiagnosis for contrast-enhanced MRI (CE-MRI) brain during the period of August 2021–October 2022 were analyzed. Patients of all ages and both sexes were included in the study. CE-MRI was performed using 1.5 Tesla Intera PHILIPS with intravenous administration of gadolinium at approximately 0.1 mL/kg/body at a rate of 10 mL/15 s. T1 FLAIR contrast sequence was imaged for the patients who had ring enhancing lesions on prior T1 contrast images. Images were obtained in axial and sagittal sections. After acquiring the images, the enhancement pattern and imaging features of T1 contrast and FLAIR contrast technique were compared. The results obtained were calculated and tabulated.

RESULTS

The total number of patients included in the study was 20, which includes 14 males and six females [Figure 1]. The median age of participants is 45 years, with age ranging from 15 to 75 years [Table 1].

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Figure 1:

Gender distribution.

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FLAIR contrast technique for evaluation of cerebral tuberculosis was imaged. In our study, there were no significant differences between T1 and FLAIR contrast images on the basis of number of lesions, lesion extension, and degree of enhancement. There was a significant difference in lesion conspicuity when compared to T1 contrast images. Fifteen out of 20 patients with cerebral tuberculosis showed significant lesion conspicuity on comparison with T1 contrast images.

DISCUSSION

Central nervous system tuberculosis results from either hematogenous spread from distant systemic infection or direct extension from local infection. Its manifestation includes meningitis, pachymeningitis, tuberculoma formation, non-caseating granuloma, caseating granuloma, caseating granuloma with central liquefaction, and calcified granuloma are the various stages of tuberculous granuloma.

T1 post-contrast study showed a significant role in differentiation of various intracranial tuberculoma stages. However, lesion enhancement is occasionally inconspicuous on T1-weighted image (T1WI). Despite being often used, FLAIR sequences also exhibit modest T1W contrast, which causes the contrast amplification.^[9] High contrast for cerebral tuberculosis may be seen in high-isotropic resolution FLAIR images acquired at 1.5T, making it well suited to investigate the relationship between cerebral tuberculosis in a clinical setting.

Contrast-enhanced FLAIR (CE-FLAIR) imaging does not demonstrate enhancement in the normal vascular structures or meninges that can be confused with abnormal meningeal enhancement on CE-T1WI.^[5,6] In addition, due to its extreme sensitivity to minimal modification of the CSF composition, CE-FLAIR is more sensitive to lower gadolinium concentrations.

Our study showed higher percentage of lesion conspicuity when compared to T1 contrast images [Figure 2]. Similar results were exhibited in a study conducted by Sati et al.^[1] stating high-isotropic-resolution FLAIR* images yield high contrast for white matter lesions. There was no significant difference in number of lesions, lesion extension, and degree of enhancement [Figure 3]. Another similar results were exhibited in a study conducted by Mustafa et al.^[2] stating CE-FLAIR imaging should be used as a routine or adjunctive sequence to CE-T1WI to enhance early detection and increase the diagnostic confidence in MRI examination of different brain pathological conditions.^[3,7]

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Figure 2:

66/M with seizures. (a) contrast-enhanced magnetic resonance imaging brain fluid-attenuated inversion recovery contrast images show the increased conspicuity of the lesion when compared to T1 contrast images (b).

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Figure 3:

60/M with seizures. (a) contrast-enhanced magnetic resonance imaging fluid-attenuated inversion recovery contrast images show the lesion conspicuity was increased, however, there was no significant difference in delineation in new lesions, lesion extension, and degree of contrast enhancement when compared to T1 contrast images (b).

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Hence, T1 FLAIR contrast imaging of the brain is sensitive for evaluating cerebral tubercular pathologies and can be used as an adjunctive sequence to contrast-enhanced T1W imaging.

CONCLUSION

CE-FLAIR imaging has many advantages for evaluating cerebral pathologies. CE-FLAIR imaging can be used as an adjunctive sequence to CE-T1WI in equivocal cases to increase the diagnostic confidence and improve patient care. Hence, routine use of FLAIR imaging before and after the administration of contrast is particularly useful for delineating cerebral tuberculosis.