Comparison of T2 and FLAIR imaging for target delineation in high grade gliomas

Abstract

BackgroundFLAIR and T2 weighted MRIs are used based on institutional preference to delineate high grade gliomas and surrounding edema for radiation treatment planning. Although these sequences have inherent physical differences there is limited data on the clinical and dosimetric impact of using either or both sequences.Methods40 patients with high grade gliomas consecutively treated between 2002 and 2008 of which 32 had pretreatment MRIs with T1, T2 and FLAIR available for review were selected for this study. These MRIs were fused with the treatment planning CT. Normal structures, clinical tumor volume (CTV) and planning tumor volume (PTV) were then defined on the T2 and FLAIR sequences. A Venn diagram analysis was performed for each pair of tumor volumes as well as a fractional component analysis to assess the contribution of each sequence to the union volume. For each patient the tumor volumes were compared in terms of total volume in cubic centimeters as well as anatomic location using a discordance index. The overlap of the tumor volumes with critical structures was calculated as a measure of predicted toxicity. For patients with MRI documented failures, the tumor volumes obtained using the different sequences were compared with the recurrent gross tumor volume (rGTV).ResultsThe FLAIR CTVs and PTVs were significantly larger than the T2 CTVs and PTVs (p < 0.0001 and p = 0.0001 respectively). Based on the discordance index, the abnormality identified using the different sequences also differed in location. Fractional component analysis showed that the intersection of the tumor volumes as defined on both T2 and FLAIR defined the majority of the union volume contributing 63.6% to the CTV union and 82.1% to the PTV union. T2 alone uniquely identified 12.9% and 5.2% of the CTV and PTV unions respectively while FLAIR alone uniquely identified 25.7% and 12% of the CTV and PTV unions respectively. There was no difference in predicted toxicity to normal structures using T2 or FLAIR. At the time of analysis, 26 failures had occurred of which 19 patients had MRIs documenting the recurrence. The rGTV correlated best with the FLAIR CTV but the percentage overlap was not significantly different from that with T2. There was no statistical difference in the percentage overlap with the rGTV and the PTVs generated using either T2 or FLAIR.ConclusionsAlthough both T2 and FLAIR MRI sequences are used to define high grade glial neoplasm and surrounding edema, our results show that the volumes generated using these techniques are different and not interchangeable. These differences have bearing on the use of intensity modulated radiation therapy (IMRT) and highly conformal treatment as well as on future clinical trials where the bias of using one technique over the other may influence the study outcome.

Automated brain tumour detection and segmentation using superpixel-based extremely randomized trees in FLAIR MRI

“…FLAIR images are routinely acquired as part of standard diagnostic clinical MRI of brain tumours. Delineation of the FLAIR hyperintensity is relevant for assessing low-grade glioma growth [34], defining an abnormality region from which imaging features for tumour classification can be extracted [35], aiding with radiation dose planning [36] and assessing treatment response [37]. Different from the methods in [25] and [26], in which image features were calculated based on each individual voxel and a fixed size neighbour-hood was considered for the feature extraction, in this paper, superpixel partition is firstly calculated which provides accurate boundaries between different tissues, and then image features are extracted from each superpixel.…”

Chemoirradiation for Glioblastoma Multiforme: The National Cancer Institute Experience

“…A computerized tomography (CT) scan of the head and upper neck was obtained during simulation using a Philips Brilliant Big Bore CT scanner, and images were transferred to a Varian Eclipse treatment planning system. The MR images, including post-contrast T1 images, T2 images or fluid attenuated inversion recovery (FLAIR) images, were fused (co-registered) to the CT images, as previously described [7]. The majority of patients (91% of patients) received RT at a dose of 2 Gy given once daily, 5 days per week, for a total dose of 60 Gy over the course of 6 weeks.…”

Investigation on the role of integrated PET/MRI for target volume definition and radiotherapy planning in patients with high grade glioma

“…FLAIR provides a better delineation of the lesion once the confounding effect of CSF has been removed. Therefore this sequence allows a more accurate definition of the infiltrating microscopic disease growing outside the enhanced area on T1 MRI [6][7][8].…”

“…FLAIR provides a better delineation of the lesion once the confounding effect of CSF has been removed. Therefore this sequence allows a more accurate definition of the infiltrating microscopic disease growing outside the enhanced area on T1 MRI [6][7][8].More recently, the use of Positron-Emission-Tomography (PET) with different radio-labeled tracers has been investigated for tumor delineation. Particularly, initial reports suggest that Carbon-11-labeled-methionine PET (11C-MET-PET) improves diagnostic accuracy for both diagnosis and treatment planning of brain tumors.…”