Objective In diffusely infiltrating gliomas (DIG), positron emission tomography (PET) imaging is a powerful method for detection of anaplastic foci. Recently, ¹H-magnetic resonance spectroscopy chemical shift imaging (CSI) using choline/creatine (Cho/Cr) or choline/N-acetylaspartate (Cho/NAA) ratios has emerged as a new non-invasive, widely available alternative. The authors therefore correlated CSI with ¹¹C-methionine (MET)-PET data in a series of DIG with non-significant contrast-enhancement (CE).

Methods Thirty-two patients with DIG were examined with single-slice CSI on a 3 T MRI and MET-PET. Maximum pathological intratumoural ratios of CSI (=CSI_max) and maximum tumour-to-normal-brain PET ratios (=PET_max; T/N ratio) were determined. Coregistration of MRI with CSI and PET was performed, and the topographic overlap of CSI_max and PET_max was analysed. Histological criteria of anaplasia as well as cell proliferation rate were assessed in tumour samples inside and outside CSI_max.

Results CSI showed a pathological ratio in all patients, whereas PET demonstrated a pathological T/N ratio in 21/32 patients. Topographical correlation of CSI_max and PET_max revealed a ≥50% overlap in 18/21 and <50% overlap in 3/21 patients, respectively. Cho/Cr_max and Cho/NAA_max showed a ≥50% overlap in 24/32 and a <50% overlap in 8/32 patients. Cell proliferation rate was significantly higher inside than outside the CSI_max (13.6% vs 6.9%, p<0.001).

Conclusion The results indicate that CSI is a promising method for detection of anaplastic foci within DIG with non-significant CE. Intraoperative use of CSI by multimodal neuronavigation may increase the reliability of detection of malignant areas in glioma surgery and therefore optimise allocation of patients to adjuvant treatments.