Differentiation of intracranial tuberculomas and high grade gliomas using proton MR spectroscopy and diffusion MR imaging

Abstract

Objective

The purpose of this study was to determine whether proton MR spectroscopy (¹H MRS) and diffusion-weighted (DW) imaging can be used to differentiate intracranial tuberculomas from high grade gliomas (HGGs).

Materials and methods

A total of 41 patients (19 with intracranial tuberculomas and 22 with HGGs) were examined in our study. ¹H MRS and DW imaging were performed at a 1.5T MR scanner before operation or treatment. Concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lipid and lactate (LL) in the contrast-enhancing rim of each lesion were expressed as metabolite ratios and were normalized to the contralateral hemisphere. The apparent diffusion coefficient (ADC) was also calculated. The metabolite ratios and ADC values in the enhancing rim of intracranial tuberculomas and HGGs were compared using the Wilcoxon rank sum test. Diagnostic accuracy was compared using receiver operating characteristic (ROC) analysis.

Results

Significant differences were found in the maximum Cho/Cr (P = 0.015), Cho/NAA (P = 0.001) and Cho/Cho-n ratios (P = 0.002), and minimum ADC value (P < 0.001) between the intracranial tuberculomas and HGGs. Diagnostic accuracy was higher by minimum ADC value than maximum Cho/Cr, Cho/NAA and Cho/Cho-n ratios (93.8% versus 75.7%, 80.8% and 78.1%).

Conclusion

These results suggest a promising role for ¹H MRS and DW imaging in the differentiation between the intracranial tuberculomas and HGGs.

Introduction

In recent years, there has been a resurgence of intracranial tuberculomas in the developing countries as well as in the industrialized nations. The signs and symptoms of tuberculomas usually resemble those of intracranial tumors, and it may be difficult to differentiate tuberculomas from other intracranial tumors such as high grade gliomas (HGGs) on conventional MRI, as both may be seen as low or high signal intensity on T₂-weighted images and nodular or rim enhancement [1].

Accurate differentiation between intracranial tumors and HGGs is extremely important because the therapeutic approach and prognosis of them differ considerably. Intracranial tuberculomas are benign lesions, most of which can be treated by antituberculous chemotherapy, and surgical intervention is restricted to limited cases [1]. Conversely, HGGs have poor prognosis and are often treated aggressively with a combined regimen of chemotherapy and radiation therapy [2]. Prompt diagnosis may result in earlier treatment and better outcome, in some cases, may avoid the necessity of performing a biopsy. Hence, their recognition on imaging is critical for their management.

Some of the studies using either proton MR spectroscopy (¹H MRS) or diffusion-weighted (DW) imaging or a combination of these two techniques have shown improvement in the differential diagnosis of intracranial tuberculomas and other intracranial lesions [3], [4], [5], [6], [7], [8], [9]. Gupta et al. and Pretell et al. [6], [7] reported that DW imaging and ¹H MRS to conventional MR imaging may help in differentiating tuberculous lesions from cysticercus granuloma. Luthra et al. [8] reported that it may be possible to differentiate among the pyogenic, tubercular and fungal abscesses based on the morphologic, apparent diffusion coefficient (ADC), and metabolite information. Recently, Chatterjee et al. [9] reported that perfusion-weighted imaging may enable distinction between tuberculomas and metastases but ADC values for the two conditions were overlapping.

To our knowledge, ¹H MRS and DW imaging have not yet been used to differentiate intracranial tuberculomas from HGGs. We aimed to test the feasibility of ¹H MRS and DW imaging to distinguish between intracranial tuberculomas and HGGs by the evaluation of the contrast-enhancing rim of the lesions. Our hypothesis was that ¹H MRS and DW imaging might help in differentiating between intracranial tuberculomas and HGGs.