Partial correlation analyses of global diffusion tensor imaging-derived metrics in glioblastoma multiforme: Pilot study

AIM: To determine existing correlates among diffusion tensor imaging(DTI)-derived metrics in healthy brains and brains with glioblastoma multiforme(GBM). METHODS: Case-control study using DTI data from brain magnetic resonance imaging of 34 controls(mean, 41.47; SD, ± 21.94 years; range, 21-80 years) and 27 patients with GBM(mean, SD; 48.41 ± 15.18 years; range, 18-78 years). Image postprocessing using FSL software calculated eleven tensor metrics: fractional(FA) and relative anisotropy; pure isotropic(p) and anisotropic diffusions(q), total magnitude of diffusion(L); linear(Cl), planar(Cp) and spherical tensors(Cs); mean(MD), axial(AD) and radial diffusivities(RD). Partial correlation analyses(controlling the effect of ageand gender) and multivariate Mancova were performed.RESULTS: There was a normal distribution for all metrics. Comparing healthy brains vs brains with GBM, there were significant very strong bivariate correlations only depicted in GBM: [FA?Cl(+)], [FA?q(+)], [p?AD(+)], [AD?MD(+)], and [MD?RD(+)]. Among 56 pairs of bivariate correlations, only seven were significantly different. The diagnosis variable depicted a main effect [F-value(11, 23) = 11.842, P ≤ 0.001], with partial eta squared = 0.850, meaning a large effect size; age showed a similar result. The age also had a significant influence as a covariate [F(11, 23) = 10.523, P < 0.001], with a large effect size(partial eta squared = 0.834).CONCLUSION: DTI-derived metrics depict significant differences between healthy brains and brains with GBM, with specific magnitudes and correlations. This study provides reference data and makes a contribution to decrease the underlying empiricism in the use of DTI parameters in brain imaging.

Diffusion tensor imaging-derived measures of fractional anisotropy across the pyramidal tract are influenced by the cerebral hemisphere but not by gender in young healthy volunteers： a split-plot factorial analysis of variance

Background Diffusion tensor imaging （DTI） permits quantitative examination within the pyramidal tract （PT） by measuring fractional anisotropy （FA）. To the best of our knowledge, the inter-variability measures of FA along the PT remain unexplained. A clear understanding of these reference values would help radiologists and neuroscientists to understand normality as well as to detect early pathophysiologic changes of brain diseases. The aim of our study was to calculate the variability of the FA at eleven anatomical landmarks along the PT and the influences of gender and cerebral hemisphere in these measurements in a sample of young, healthy volunteers. Methods A retrospective, cross-sectional study was performed in twenty-three right-handed healthy volunteers who underwent magnetic resonance evaluation of the brain. Mean FA values from eleven anatomical landmarks across the PT （at centrum semiovale, corona radiata, posterior limb of internal capsule （PLIC）, mesencephalon, pons, and medulla oblongata） were evaluated using split-plot factorial analysis of variance （ANOVA）. Results We found a significant interaction effect between anatomical landmark and cerebral hemisphere （F （10, 32）=4.516, P=0.001; Wilks＇ Lambda 0.415, with a large effect size （partial η2=0.585））. The influence of gender and age was non-significant. On average, the midbrain and PLIC FA values were higher than pons and medulla oblongata values; centrum semiovale measurements were higher than those of the corona radiata but lower than PLIC. Conclusions There is a normal variability of FA measurements along PT in healthy individuals, which is influenced by regions of interest location （anatomical landmarks） and cerebral hemisphere. FA measurements should be reported for comparing same-side and same-landmark PT to help avoid comparisons with the contralateral PT; ideally, normative values should exist for a clinically significant age group. A standardized package of selected DTI processing tools would allow DTI processing to be routinely performed in clinical settings.