Diffusion-weighted imaging (DWI) provides information about tissue maturation not seen on conventional magnetic resonance imaging. The aim of this study is to analyze the evolution over time of the apparent diffusion coefficient (ADC) of normal fetal brain in utero. DWI was performed on 78 fetuses, ranging from 23 to 37 gestational weeks (GW). All children showed at follow-up a normal neurological evaluation. ADC values were obtained in the deep white matter (DWM) of the centrum semiovale, the frontal, parietal, occipital and temporal lobe, in the cerebellar hemisphere, the brainstem, the basal ganglia (BG) and the thalamus. Mean ADC values in supratentorial DWM areas (1.68 +/- 0.05 mm(2)/s) were higher compared with the cerebellar hemisphere (1.25 +/- 0.06 mm(2)/s) and lowest in the pons (1.11 +/- 0.05 mm(2)/s). Thalamus and BG showed intermediate values (1.25 +/- 0.04 mm(2)/s). Brainstem, cerebellar hemisphere and thalamus showed a linear negative correlation with gestational age. Supratentorial areas revealed an increase in ADC values, followed by a decrease after the 30th GW. This study provides a normative data set that allows insights in the normal fetal brain maturation in utero, which has not yet been observed in previous studies on premature babies.

Responses of GH-secreting adenomas to multimodal management of acromegaly vary widely between patients. Understanding the behavioral patterns of GH-secreting adenomas by identifying factors predictive of their evolution is a research priority. The aim of this study was to clarify the relationship between the T2-weighted adenoma signal on diagnostic magnetic resonance imaging (MRI) in acromegaly and clinical and biological features at diagnosis. An international, multicenter, retrospective analysis was performed using a large population of 297 acromegalic patients recently diagnosed with available diagnostic MRI evaluations. The study was conducted at ten endocrine tertiary referral centers. Clinical and biochemical characteristics, and MRI signal findings were evaluated. T2-hypointense adenomas represented 52.9% of the series, were smaller than their T2-hyperintense and isointense counterparts (P!0.0001), were associated with higher IGF1 levels (PZ0.0001), invaded the cavernous sinus less frequently (PZ0.0002), and rarely caused optic chiasm compression (P!0.0001). Acromegalic men tended to be younger at diagnosis than women (PZ0.067) and presented higher IGF1 values (PZ0.01). Although in total, adenomas had a predominantly inferior extension in 45.8% of cases, in men this was more frequent (P!0.0001), whereas in women optic chiasm compression of macroadenomas occurred more often (PZ0.0067). Most adenomas (45.1%) measured between 11 and 20 mm in maximal diameter and bigger adenomas were diagnosed at younger ages (PZ0.0001). The T2-weighted signal differentiates GH-secreting adenomas into subgroups with

Purpose:To assess the combined value of diffusionweighted imaging (DWI) and proton magnetic resonance spectroscopy ( 1 H-MRS) in differentiating medulloblastoma, ependymoma, pilocytic astrocytoma, and infiltrating glioma in a pediatric population. Materials and Methods:A total of 17 children with untreated posterior fossa tumors (seven medulloblastoma, four infiltrating glioma, two ependymoma, and four pilocytic astrocytoma), were investigated with conventional MRI, DWI, and MRS using a single-voxel technique. Within the nonnecrotic tumor core, apparent diffusion coefficient (ADC) values using a standardized region of interest (ROI) were retrieved. Quantification of water signal and analysis of metabolite signals from MRS measurements in the same tumorous area were reviewed using multivariant linear discriminant analysis.Results: Combination of ADC values and metabolites, which were normalized using water as an internal standard, allowed discrimination between the four tumor groups with a likelihood below 1 ϫ 10 -9 . Positive predictive value was 1 in all cases. Tumors could not be discriminated when using metabolite ratios or ADC values alone, nor could they be differentiated using creatine (Cr) as an internal reference even in combination with ADC values. Conclusion:Linear discriminant analysis using DWI and MRS using water as internal reference, fully discriminates the four most frequent posterior fossa tumors in children.

BACKGROUND AND PURPOSE:Pretherapeutic determination of tumor grade and genotype in grade II and III oligodendroglial tumors is clinically important but is still challenging. Tumor grade and 1p/19q status are currently the 2 most important factors in therapeutic decision making for patients with these tumors. Histopathology and cMRI studies are still limited in some cases. In the present study, we were interested in determining whether the combination of PWI, DWI, and MR spectroscopy could help distinguish oligodendroglial tumors according to their histopathologic grade and genotype.

The indications for fetal brain MRI have increased due to continuous improvements in MRI methods and instruments. As a matter of fact, MRI has become the method of choice to evaluate brain maturation and development (1,2), as well as abnormalities in those processes (1,3,4). The primary indications for fetal brain MRI are evaluations of central nervous system (CNS) malformations, ventricular dilatation, and pregnancies at risk of fetal brain damage (1,3-5). The classic MR protocol includes single-shot T 2 -weighted images and T 1 -weighted images. Diffusion images can also be used routinely to evaluate tissue microstructure. In addition, proton MR spectroscopy ( 1 H MRS) has become an efficient tool for obtaining metabolic information from the human brain. MRS has been used as a powerful diagnostic tool in the pediatric population, especially for detecting hypoxic encephalopathy, leukoencephalopathyies, and inborn errors of metabolism (6 -8).MRS also provides metabolic information on the developing brain (9 -11). However, little is known about metabolic changes that occur in the human brain during in utero development (12)(13)(14)(15). Indeed, many of the available data were obtained ex utero from premature neonates, a situation that does not reflect the physiological conditions of pregnancy. A second bias stems from the differences in acquisition techniques used to collect these data, since for ex utero data a head coil dedicated to brain studies is used, whereas in utero data are obtained with phased-array body and spinal coils (4). Kok et al. (12,13) demonstrated the possibility of investigating in vivo the human fetal brain using 1 H MRS. They also proposed normative values for levels of fetal brain metabolites during the third trimester of pregnancy (gestational age (GA) ϭ 30 -41 weeks), and used two MRS acquisition sequences: stimulated-echo acquisition mode (STEAM) with a short TE of 20 ms, and point-resolved spectroscopy (PRESS) with a long TE of 135 ms. In the present study we attempted to establish normative metabolic values in a wider and earlier range of GAs (22-39 weeks) than that suggested by , and used the PRESS sequence at short and long TEs (30 and 135 ms). MATERIALS AND METHODS SubjectsA total of 69 examinations were performed, and 58 yielded good-quality MR spectra. In the remaining examinations the limited quality of spectra was due to maternal or fetal movements (e.g., a fetal head moving with the mother's breathing) during the MR exploration, especially in cases of breech presentation. The present study thus consisted of 58 MR examinations performed on 58 subjects, since none of the subjects was investigated twice during the pregnancy.MR data on normal fetal brains were obtained from subjects who ultimately displayed normal standard MR images and/or normal brain examination postnatally, and normal neurological outcome at 3 months of age. These