Improved tumor contrast and tumor delineation for stereotactic treatment planning of cerebral gliomas and metastases by contrast enhanced FLAIR (fluid attenuated inversion recovery) MR imaging

Background: FLAIR MR imaging has shown to be a valuable imaging modality in pathologic lesions of the brain including intraaxial brain tumors. The aim of the study was to assess the value of a FLAIR technique in the planning process of stereotactic radiotherapy in patients with cerebral gliomas and metastases. Patients and Methods: Thirty-five patients with cerebral gliomas and 12 pat ients with a total of 39 cerebral metastases were examined by T2/PD-weighte d fast spin-echo, fast FLAIR prior and after contrast and contrast enhanced T1-weighted spin-echo using identical slice parameters. The images were ev aluated by using quantitative and qualitative criteria. Quantitative criter ia were tumor-to-background and tumor-to-cerebrospinal fluid contrast and c ontrast-to-noise. The qualitative evaluation was performed as a multireader analysis concerning lesion detection, lesion delineation and image artifac ts. Results: In the qualitative evaluation (Tables 3 and 6), all readers found the fast FLAIR images to be superior to fast spin-echo in the exact delinea tion of cerebral tumors (p < 0.001) and the delineation of enhancing and no n enhancing tumor parts. Fast FLAIR was superior in the delineation of cort ically located and small lesions but was limited in lesions adjacent to the ventricles. Fast FLAIR provided a significantly better tumor-to-CSF contra st and tumor-to-CSF contrast-to-noise (p < 0.001) (Tables 1,2a,2b, 4, 5). T he tumor-to-background contrast and tumor-to-background contrast-to-noise o f the fast FLAIR images were lower than that of T2-weighted spin-echo image s but were significantly increased after the application of contrast media. FLAIR images had more image artifacts, but the image interpretation was no t influenced. Conclusions: FLAIR MR imaging was found to be a valuable sequence in the pl anning protocol of stereotactic radiotherapy. The concurrent presentation o f enhancing and non enhancing tumor tissue on contrast enhanced fast FLAIR imaging enables to use a single imaging sequence in the treatment protocol. This enables to load a reduced image amount into the radiotherapy planning software, is therefore time saving and reduces potential errors.