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 (=CSImax) and maximum tumour-to-normal-brain PET ratios (=PETmax; T/N ratio) were determined. Coregistration of MRI with CSI and PET was performed, and the topographic overlap of CSImax and PETmax was analysed. Histological criteria of anaplasia as well as cell proliferation rate were assessed in tumour samples inside and outside CSImax.
Results CSI showed a pathological ratio in all patients, whereas PET demonstrated a pathological T/N ratio in 21/32 patients. Topographical correlation of CSImax and PETmax revealed a ≥50% overlap in 18/21 and <50% overlap in 3/21 patients, respectively. Cho/Crmax and Cho/NAAmax 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 CSImax (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.
- Diffusely infiltrating gliomas
- chemical shift imaging
- methionine positron emission tomography
- correlation of maxima
- proliferation rate
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