Diffusion tensor imaging of deep gray matter in children treated for brain malignancies

Abstract

Purpose Previous DTI studies reported microstructural changes in white matter of patients receiving treatment for brain malignancies. The primary aim of this prospective pilot longitudinal study was to examine if DTI can detect microstructural changes in deep gray matter (as evaluated by the apparent diffusion coefficient, ADC) between pediatric patients treated with cranial radiation therapy (CRT) and typically developing healthy children. The relationship between ADC and neurobehavioral performance was also examined. Methods ADC was measured at 1.5T in the caudate, putamen, globus pallidus, thalamus, and hippocampus in 9 patients (mean age 11.8 years) and 9 age-matched healthy controls. The study was designed with 4 visits: baseline, 6-month, 15-month, and 27-month follow-ups. Results Patients had 24% higher overall mean ADC in the hippocampus compared with controls (p=0.003). Post-hoc analyses revealed significantly elevated ADC at baseline (p=0.003) and at the 27-month follow-up (p=0.006). Nevertheless, patients performed normally on a verbal memory test, considered to be a hippocampus-related function. Relative to controls, patients' performance on the tests of the visual-spatial working memory decreased over time (group by visit: p=0.036). Both patients and controls showed a decline in motor speed with increasing ADC in the globus pallidus and putamen. Conclusions Childhood brain malignancies and their treatment may affect gray matter microstructure as measured by water diffusion. Significant findings in the hippocampus but not other regions suggest that differences in tissue sensitivity to disease- and treatment-related injury among gray matter regions may exist. ADC in basal ganglia may be associated with motor performance.

Diffusion MRI monitoring of specific structures in the irradiated rat brain

“…First, this result suggests that there is no radiation-induced brain plasticity in this region, as defined by a transitory state of motricity decline followed by a recovery, but more likely a probable reserve capacity of neurons in M 1 . Second, this result demonstrates that MD alone cannot fully highlight a relationship between mesoscopic and neurofunctional changes, as also demonstrated by Horsk a et al 16 in children who received cranial radiation therapy. Indeed, they studied radiation-induced changes in subcortical mesostructures and showed that elevated MD in the hippocampus was not accompanied by impairment on the visual-spatial working memory performance (bead memory test), whereas performance on the gross motor dexterity and coordination (Purdue pegboard test) declined with increasing MD in the globus pallidus and striatum, suggesting a relationship between motor function and mesostructure of regions of the basal ganglia.…”

“…Our choice of using objective ROIs has the advantage that the procedure is reproducible and unbiased; it may be transferable to clinical application, as performed by Horská et al and Kassubek et al, who kept the same registered ROIs throughout the longitudinal assessment of patients, and it can be reproduced by other research groups. Moreover, the CSF signal intensity in every image were excluded from ROIs to avoid misinterpretation of results because of lesion‐induced ventricles swelling and disruption (Figure ).…”

“…Clearly, a coherent interpretation of the variation of DTI metrics in white matter is not available. Moreover, only sparse reports focused on radiation‐induced grey matter damage, as for example Horská et al, who studied subcortical changes (including the hippocampus and the striatum) after cranial radiation therapy in children.…”

Retrospective study of late radiation-induced damages after focal radiotherapy for childhood brain tumors

“…• assessment of the associations between cognitive and neuropsychological performances and RT doses or DTI values separately in each ROI by means of the Kruskal-Wallis test. The Kruskal-Wallis test results were focused according to the inferred assumption on the direction of the relationships between the dose values and the remaining variables: negative for FA values and test results and positive for AD, RD and MD values [13]. Firstly (first analysis) all ROIs, irrespective to the level of dose, were considered for the analysis.…”

“…These tissue alterations cannot be effectively assessed with morphological Magnetic Resonance Imaging (MRI). Many papers showed that Diffusion Tensor Imaging (DTI) is a reliable tool for evaluating white matter (WM) and grey matter (GM) changes [12][13][14]. DTI can assess alterations in morphologically normal appearing areas and can be used as early indicator of post treatment neurotoxicity [10,[15][16][17][18][19][20][21][22].…”