Evaluation of low-grade glioma structural changes after chemotherapy using DTI-based histogram analysis and functional diffusion maps.
OBJECTIVES
To explore the role of diffusion tensor imaging (DTI)-based histogram analysis and functional diffusion maps (fDMs) in evaluating structural changes of low-grade gliomas (LGGs) receiving temozolomide (TMZ) chemotherapy.


METHODS
Twenty-one LGG patients underwent 3T-MR examinations before and after three and six cycles of dose-dense TMZ, including 3D-fluid-attenuated inversion recovery (FLAIR) sequences and DTI (b = 1000 s/mm(2), 32 directions). Mean diffusivity (MD), fractional anisotropy (FA), and tensor-decomposition DTI maps (p and q) were obtained. Histogram and fDM analyses were performed on co-registered baseline and post-chemotherapy maps. DTI changes were compared with modifications of tumour area and volume [according to Response Assessment in Neuro-Oncology (RANO) criteria], and seizure response.


RESULTS
After three cycles of TMZ, 20/21 patients were stable according to RANO criteria, but DTI changes were observed in all patients (Wilcoxon test, P ≤ 0.03). After six cycles, DTI changes were more pronounced (P ≤ 0.005). Seventy-five percent of patients had early seizure response with significant improvement of DTI values, maintaining stability on FLAIR. Early changes of the 25th percentiles of p and MD predicted final volume change (R(2) = 0.614 and 0.561, P < 0.0005, respectively). TMZ-related changes were located mainly at tumour borders on p and MD fDMs.


CONCLUSIONS
DTI-based histogram and fDM analyses are useful techniques to evaluate the early effects of TMZ chemotherapy in LGG patients.


KEY POINTS
• DTI helps to assess the efficacy of chemotherapy in low-grade gliomas. • Histogram analysis of DTI metrics quantifies structural changes in tumour tissue. • Functional diffusion maps (fDMs) spatially localize the changes of DTI metrics. • Changes in DTI histograms and fDMs precede changes in conventional MRI. • Early changes in DTI histograms and fDMs correlate with seizure response.
['Castellano|Antonella|A|', 'Donativi|Marina|M|', 'Rudà|Roberta|R|', 'De Nunzio|Giorgio|G|', 'Riva|Marco|M|', 'Iadanza|Antonella|A|', 'Bertero|Luca|L|', 'Rucco|Matteo|M|', 'Bello|Lorenzo|L|', 'Soffietti|Riccardo|R|', 'Falini|Andrea|A|']
D000328:Adult D016880:Anisotropy D000970:Antineoplastic Agents D001921:Brain D001932:Brain Neoplasms D056324:Diffusion Tensor Imaging D005260:Female D005910:Glioma D006801:Humans D008297:Male D008875:Middle Aged
Glioma Chemotherapy Diffusion Tensor Imaging Magnetic Resonance Imaging Response Evaluation Criteria