Possible confounding factors on cerebral diffusion tensor imaging measurements

Abstract

BackgroundDiffusion tensor imaging (DTI) is prone to numerous systemic confounding factors that should be acknowledged to avoid false conclusions.PurposeTo investigate the possible effects of age, gender, smoking, alcohol consumption, and education on cerebral DTI parameters in a generally healthy homogenous sample with no neurological or psychiatric diseases.Material and MethodsForty (n = 40) subjects (mean age, 40.3 years; SD, 12.3) underwent brain DTI with 3 T magnetic resonance imaging (MRI). At enrolment, all the subjects were interviewed with respect to general health, education, history of smoking, and alcohol consumption. Studied DTI parameters included: (i) fractional anisotropy (FA); and (ii) apparent diffusion coefficient (ADC). Region-of-interest (ROI)-based measurements were estimated at 13 anatomical locations bilaterally on the axial images, except for the corpus callosum in which the ROIs were placed on the sagittal images. Circular ROI measurements were mainly used. Freehand ROI method was used with the forceps minor, uncinate fasciculus, and thalamus. Intra-observer variability and repeatability were assessed.ResultsThe most consistent finding was that aging decreased FA values in the frontal brain regions. Regarding the other confounding factors, the results were discontinuous and no concrete conclusions could be drawn from these findings. In general, intra-observer repeatability of the DTI measurement was considered relatively good.ConclusionAge should be noted as considerable confounding factors in ROI-based DTI analysis. More research on the effects of gender, smoking, alcohol consumption, and education is needed.

Reliability of the Freehand Region-of-Interest Method in Quantitative Cerebral Diffusion Tensor Imaging

“…In contrast, in our study, the freehand method gave a slightly higher variation in the corpus callosum than the circle method in previous studies (13,41). This may also be due to the fact that in our study, ROIs were plotted on the axial image, whereas in previous studies they were plotted on the sagittal image (13,41). Thus, in this particular region, it would be better to use the circle method for a sagittal image than the freehand method for an axial image.…”

“…Speci cally, in the youngest age group, the FA values were higher and the RD values lower in the frontobasal area in both hemispheres when compared to the other age groups. For FA, this result has already been published in our previous study (41). Other studies have also found changes in the frontal regions of the brain caused by aging (16,17).…”

“…It is noteworthy that the freehand method gives an average of 4% lower variations in the pyramidal regions compared to the circle method (13,41). In contrast, in our study, the freehand method gave a slightly higher variation in the corpus callosum than the circle method in previous studies (13,41). This may also be due to the fact that in our study, ROIs were plotted on the axial image, whereas in previous studies they were plotted on the sagittal image (13,41).…”

“…In addition, the effects of age on changes in white matter are studied with group comparison. Correlation for FA and ADC parameters and age have already been published in our previous study using two ROI method (41). In this study, we also present the AD and RD result with a freehand ROI.…”

“…The Kruskal-Wallis test was used for nonnormally distributed data. Correlation analysis between FA, ADC and age from the same data have been published in our previous study (41). In that study, we mostly used a small circle ROI, including a freehand ROI in three regions for better repeatability.…”