Proton MR spectroscopy and diffusion-weighted imaging of intracranial germ cell tumors: Implications for differentiation from other lesions

Abstract

Introduction Intracranial germ cell tumors (GCT) are extremely rare brain neoplasms, with imaging characteristics being often non-specific. Considering such imaging limitation in establishing their exact histology, the aim of this paper is to integrate conventional, physiologic and metabolic magnetic resonance imaging (MRI) with histology of these tumors, with the goal of proposing some new insights that could aid in their diagnosis. Materials and methods We have retrospectively analyzed preoperative imaging findings in 9 patients with histology proven intracranial germ cell tumors. In all patients conventional magnetic resonance imaging in conjunction with diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (MRS) was performed. Results Based on imaging characteristics on conventional sequences germinoma cannot be differentiated from nongerminoma. DWI offered the potential for differentiation of germinomas from non-germinomas since solid part of germinomas demonstrated restricted diffusion with ADC values under 1.0 × 10 −3 mm 2/s, whereas nongerminoma showed elevated diffusion with ADC values above 1.3 × 10 −3 mm 2/s. Short echo MRS demonstrated characteristic spectra in germinomas: increased Cho, decreased NAA and prominent broad lipid resonances. Conclusion DWI and MRS imaging findings provide additional information that can facilitate evaluation of intracranial germ cell tumors.