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The purpose of this study was to use diffusion-weighted and diffusion tensor imaging to investigate the status of cerebral white matter (WM) at term gestation and the rate of WM maturation throughout the first year of life in healthy infants.Fifty-three children (35 boys) ranging in age from 1.5 weeks premature to 51.5 weeks (mean age, 22.9 weeks) underwent conventional MRI, diffusion imaging in three directions (b = 1,000 s/mm2), and diffusion tensor imaging with gradient encoding in six directions, all on a 1.5-T MRI system. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in three deep WM structures (posterior limb of internal capsule, genu, and splenium of corpus callosum) and two peripheral WM regions (associational WM underlying prefrontal and posterior parietal cortex) with a standard region of interest (44 +/- 4 cm2). ADC and FA were expressed as a percentage of corresponding values measured in a group of healthy young adults. Mean ADC and FA values for deep and peripheral WM were plotted against gestational age normalized to term. The data were fit best with a broken-line linear regression model with a breakpoint at 100 days. ADC and FA values at term were estimated according to the intercept of the initial linear period (before day 100) with day 0. The slope of the linear fits was used to determine the rate of WM maturation in both the early and the late (after day 100) periods. Multivariate analysis of variance tests were used to compare deep and peripheral WM structures at term and at representative early and late ages (days 30 and 200) and to compare rates of ADC and FA maturation in early and late periods within the first year.At term, peripheral WM was less mature than deep WM according to results of extrapolation of ADC and FA values in the first 100 days of life to day 0 (p0.01). Mean ADC and FA value (percentage of mean adult value) for peripheral WM were 1.32 x 10(-3) mm2/s (163%) and 0.16 (32%), respectively, and 1.09 x 10(-3) mm2/s (143%) and 0.36 (54%), respectively, for deep WM. On day 30 and day 200, estimated mean ADC and FA continued to show greater diffusion (higher ADC) and less anisotropy (lower FA value) in peripheral WM (p0.01). During the first year of postnatal life, both ADC and FA matured at higher rates before postnatal day 100 compared with a later time. Differences were observed in rates of maturation in the first 100 days when rates of decrease in ADC and increase in FA were compared between peripheral WM and deep WM; however, the maturational trends differed whether ADC or FA was examined. The early rate of ADC decrease (maturation) was twice as great for peripheral WM than for deep WM (p0.01) unexpectedly, but the opposite pattern was observed for FA. The early rate of FA increase (maturation) was approximately one half as great for peripheral WM as for deep WM (p = 0.01). Throughout the rest of the first year, no differences were observed in the rates of change in either index between peripheral WM and deep WM.At term, both ADC and FA differ significantly in peripheral WM and deep WM, deep WM structures being more mature. Both deep WM and peripheral WM mature more rapidly during approximately the first 3 months in comparison with the rest of the first year. Unexpected differences in early (first 100 days) rates of maturation assessed with diffusion-weighted (ADC) and diffusion tensor (FA) imaging suggest that these two techniques may be sensitive to different aspects of WM maturation in the early perinatal period.

The first purpose of this study was to compare the degree of anisotropy in compact white matter and noncompact white matter in each of three pediatric age groups using diffusion tensor imaging. We hypothesized that anisotropy would be higher in compact white matter than in noncompact white matter in each age group. The second purpose of our study was to compare the increase in anisotropy over time in compact versus noncompact white matter during early childhood. We hypothesized that increases in anisotropy would be higher in noncompact white matter.We retrospectively analyzed anisotropy maps derived from diffusion tensor imaging studies performed in 66 pediatric patients (age range, 4 days-71 months; mean age, 18.6 months) who underwent clinical MR imaging and were found to have no abnormalities on conventional MR images. Anisotropy was measured in three compact white matter structures (corpus callosum, internal capsule, cerebral peduncle) and two regions of noncompact white matter (corona radiata and peripheral white matter). Patients were assigned to one of the three following groups on the basis of age: group 1, younger than 12 months (n = 40); group 2, 12-35 months (n = 11); and group 3, 36-71 months (n = 15). First, we compared anisotropy values of noncompact white matter with those of compact white matter for each age group. Second, we compared the increase over time in anisotropy of noncompact white matter regions with that seen in compact white matter structures.Among all three age groups, anisotropy measurements in compact white matter structures were higher than those in noncompact white matter (p0.01). The mean anisotropy values in noncompact white matter for groups 1, 2, and 3, respectively, were 0.349, 0.480, and 0.531. The mean anisotropy values in compact white matter for groups 1, 2, and 3, respectively, were 0.494, 0.646, and 0.697. When age groups were compared, a statistically significant increase in anisotropy was seen in both compact white matter and noncompact white matter (p0.01). However, the increase in anisotropy was significantly greater in non-compact white matter regions than in compact white matter structures when comparing group 1 with group 3 (p0.01) as well as group 1 with group 2 (p0.01).Although anisotropy measurements were higher in compact than non-compact white matter in all three age groups, the increase in anisotropy was greater in non-compact white matter across each of the three groups. These data suggest that although myelination is initially greater in compact white matter, the change in myelination may be greater in noncompact white matter during the first few years after infancy.

Our purpose was to evaluate the relationships between the ratio of maximum relative cerebral blood volume (rCBV) (rCBV ratio = rCBV[tumor]/rCBV[contralateral white matter]) and histologic and angiographic vascularities of gliomas using the gradient-echo echoplanar MR imaging technique. We also evaluated the usefulness of rCBV maps for grading gliomas.We examined 30 patients with histologically verified gliomas. Gliomas were classified as glioblastoma, anaplastic glioma with enhancement, anaplastic glioma without enhancement, and low-grade glioma. The maximum rCBV ratio of each glioma was compared with both histologic and angiographic vascularities, and the relationship between the maximum rCBV ratios and each type of glioma was established.The maximum rCBV ratios of the gliomas significantly correlated with both histologic and angiographic vascularities (p.001). Mean values and SDs of maximum rCBV ratios of each type of tumor were 7.32+/-4.39 for glioblastomas, 5.84+/-1.82 for anaplastic gliomas with enhancement, 1.53+/-0.75 for anaplastic gliomas without enhancement, and 1.26+/-0.55 for low-grade gliomas. The maximum rCBV ratios of the glioblastomas were significantly higher than those of the anaplastic gliomas without enhancement (p = .002) and the low-grade gliomas (p.001). The maximum rCBV ratios of the anaplastic gliomas with enhancement were higher than those of the anaplastic gliomas without enhancement and the low-grade gliomas, but the differences were not statistically significant (p = .08 and p = .03, respectively).The results of perfusion-sensitive MR imaging with gradient-echo echoplanar technique correlated with both histologic and angiographic vascularities.