Biomedical subjects

J N Giedd

Publications and source records attributed to J N Giedd.

64 records · Page 4Linked to original sources

PubMed1995

Sydenham's chorea: magnetic resonance imaging of the basal ganglia.

Analysis of cerebral magnetic resonance images of 24 subjects with Sydenham's chorea and 48 age-, height-, weight-, gender-, and handedness-matched controls demonstrated increased sizes of the caudate, putamen, and globus pallidus in the Sydenham's chorea group. In contrast, neither total cerebral, prefrontal, or midfrontal volumes or thalamic area were increased. These results indicate the selective involvement of the basal ganglia in Sydenham's chorea.

Adolescent↗

PubMed1994

Quantitative morphology of the caudate nucleus in attention deficit hyperactivity disorder.

OBJECTIVE: Because the caudate nuclei receive inputs from cortical regions implicated in executive functioning and attentional tasks, caudate and total brain volumes were examined in boys with attention deficit hyperactivity disorder (ADHD) and normal comparison subjects. To gain developmental perspective, a wide age range was sampled for both groups. METHOD: The brains of 50 male ADHD patients (aged 6-19) and 48 matched comparison subjects were scanned by magnetic resonance imaging (MRI). Volumetric measures of the head and body of the caudate nucleus were obtained from T1-weighted coronal images. Interrater reliabilities (intraclass correlations) were 0.89 or greater. RESULTS: The normal pattern of slight but significantly greater right caudate volume across all ages was not seen in ADHD. Mean right caudate volume was slightly but significantly smaller in the ADHD patients than in the comparison subjects, while there was no significant difference for the left. Together these facts accounted for the highly significant lack of normal asymmetry in caudate volume in the ADHD boys. Total brain volume was 5% smaller in the ADHD boys, and this was not accounted for by age, height, weight, or IQ. Smaller brain volume in ADHD did not account for the caudate volume or symmetry differences. For the normal boys, caudate volume decreased substantially (13%) and significantly with age, while in ADHD there was no age-related change. CONCLUSIONS: Along with previous MRI findings of low volumes in corpus callosum regions, these results support developmental abnormalities of frontal-striatal circuits in ADHD.

Adult↗

PubMed1994

Quantitative morphology of the corpus callosum in attention deficit hyperactivity disorder.

OBJECTIVE: By means of quantitative neuroanatomic imaging the authors assessed the hypothesis that there are structural brain abnormalities relevant to frontal lobe circuitry in children with attention deficit hyperactivity disorder (ADHD). METHOD: The midsagittal cross-sectional area of the corpus callosum, divided into seven sections, was measured from magnetic resonance images of 18 boys with ADHD and 18 carefully matched normal boys. RESULTS: Two anterior regions, the rostrum and the rostral body, were found to have significantly smaller areas in the ADHD group. These areas correlated in the expected direction with teacher and parent ratings of hyperactivity/impulsivity. CONCLUSIONS: This finding supports theories of abnormal frontal lobe development and function in ADHD.

Adolescent↗

PubMedDate not supplied

The quantitative relation between T1-weighted and T2-weighted MRI of normal gray matter and iron concentration.

A retrospective analysis of 158 T1-weighted and T2-weighted MRI scans of normal brains at 0.5 and 1.5 Tesla was performed. Signal intensities in the frontal cortex, caudate nucleus, putamen, and globus pallidus were divided by those of frontal white matter; and these gray/white ratios were correlated with iron concentration, estimated from the anatomical region and age of the patient. Intraregional plots were also made of gray/white ratio versus age for the 1.5 Tesla scans. The changes in both T1-weighted and T2-weighted ratios were consistent with the hypothesis that 1/T1 and 1/T2 vary linearly with iron concentration, and the corresponding coefficients, determined separately from the interregional and intraregional plots, were generally in agreement. Furthermore, the variability of the MRI ratios at 1.5 Tesla was consistent with expected iron variability except for the cortex, in which partial volume errors due to sulci and white matter caused increased variations. The MRI results agreed well with in vitro data on T1 and T2 in tissue specimens and with other MRI studies. When compared with T1 and T2 in ferritin solution, a significant "tissue relaxation enhancement" was found, attributable to slower diffusion and clustering of ferritin in tissue.

Adult↗

PubMedDate not supplied

Quantification of white matter and gray matter volumes from three-dimensional magnetic resonance volume studies using fuzzy classifiers.

We accurately measured white matter (WM) and gray matter (GM) from three-dimensional (3D) volume studies, using a fuzzy classification technique. The new segmentation method is a modification of a recently published method developed for T1 parametric images. 3D MR images were transformed into pseudo forms of T1 parametric images and segmented into WM and GM voxel fraction images with a set of standardized fuzzy classifiers. This segmentation method was validated with synthesized 3D MR images as phantoms. These phantoms were developed from cryosectioned human brain images located in the superior, middle, and inferior regions of the cerebrum. Phantom volume measurements revealed that, generally, the difference between measured and actual volumes was less than 3% for 1.5-mm simulated brain slices. The average cerebral GM/WM ratio calculated from 3D MR studies in four subjects was 1.77, which compared favorably with the estimate of 1.67 derived from anatomical data. Results indicate that this is an accurate and rapid method for quantifying WM and GM from Tl-weighted 3D volume studies.

Brain↗

PubMedDate not supplied

Regional MRI measurements of the corpus callosum: a methodological and developmental study.

A technique for quantifying the midsagittal size and shape of the corpus callosum (CC) from magnetic resonance brain scans is presented. The technique utilizes the distances to the ventral and dorsal boundaries of small sectors of the CC from a reference point to compute the size and shape parameters of the CC and its subdivisions. Intrarater and interrater interclass correlation coefficients for the area measurements ranged from 0.88 to 0.99. Correlations between these automated measures and those obtained by pixel counting were equally high. The corpus callosa of 104 (57 male and 47 female) right-handed healthy children and adolescents, ages 4-18, were examined in relation to age and sex. Corpus callosum growth was most striking for the splenium and isthmus with some changes in the midbody regions. The area and perimeter of these regions increased, shapes became more compact, and the boundaries became more regular with age. The length and curvature at the anterior and posterior regions of the CC increased more rapidly in males than in females. These significant and consistent results indicate that the method is reliable and sensitive to developmental changes of the CC.

Adolescent↗

PubMedDate not supplied

Children and adolescents with psychotic disorder not otherwise specified: a 2- to 8-year follow-up study.

Although psychotic phenomena in children with disruptive behavior disorders are more common than expected, their prognostic significance is unknown. To examine the outcome of pediatric patients with atypical psychoses, a group of 26 patients with transient psychotic symptoms were evaluated with clinical and structured interviews at the time of initial contact (mean age, 11.6 +/- 2.7 years) and at follow-up 2 to 8 years later. Measures of functioning and psychopathology were also completed at their initial assessment. Risk factors associated with adult psychotic disorders (familial psychopathology, eyetracking dysfunction in patients and their relatives, obstetrical complications, and premorbid developmental course in the proband) had been obtained at study entry. On follow-up examination (mean age, 15.7 +/- 3.4 years), 13 patients (50%) met diagnostic criteria for a major axis I disorder: three for schizoaffective disorder, four for bipolar disorder, and six for major depressive disorder. The remaining 13 patients again received a diagnosis of psychotic disorder not otherwise specified (NOS), with most being in remission from their psychotic symptoms. Among this group who had not developed a mood or psychotic disorder, disruptive behavior disorders were exceedingly common at follow-up and were the focus of their treatment. Higher initial levels of psychopathology, lower cognitive abilities, and more developmental motor abnormalities were found in patients with a poor outcome. Obstetrical, educational, and family histories did not differ significantly between the groups. Through systematic diagnostic evaluation, children and adolescents with atypical psychotic disorders can be distinguished from those with schizophrenia, a difference with important treatment and prognostic implications. Further research is needed to delineate the course and outcome of childhood-onset atypical psychoses, but preliminary data indicate improvement in psychotic symptoms in the majority of patients and the development of chronic mood disorders in a substantial subgroup.

Adolescent↗

PubMedDate not supplied

Quantitative magnetic resonance imaging of human brain development: ages 4-18.

Brain magnetic resonance images (MRI) of 104 healthy children and adolescents, age 4-18, showed significant effects of age and gender on brain morphometry. Males had larger cerebral (9%) and cerebellar (8%) volumes (P < 0.0001 and P = 0.008, respectively), which remained significant even after correction for height and weight. After adjusting for cerebral size, the putamen and globus pallidus remained larger in males, while relative caudate size was larger in females. Neither cerebral nor cerebellar volume changed significantly across this age range. Lateral ventricular volume increased significantly in males (trend for females), with males showing an increase in slope after age 11. In males only, caudate and putamen decrease with age (P = 0.007 and 0.05, respectively). The left lateral ventricles and putamen were significantly greater than the right (P = 0.01 and 0.001, respectively). In contrast, the cerebral hemispheres and caudate showed a highly consistent right-greater-than-left asymmetry (P < 0.0001 for both). All volumes demonstrated a high degree of variability. These findings highlight gender-specific maturational changes of the developing brain and the need for large gender-matched samples in pediatric neuropsychiatric studies.

Adolescent↗

PubMedDate not supplied

Cerebral magnetic resonance image segmentation using data fusion.

OBJECTIVE: A semiautomated method is described for segmenting dual echo MR head scans into gray and white matter and CSF. The method is applied to brain scans of 80 healthy children and adolescents. MATERIALS AND METHODS: A probabilistic data fusion equation was used to combine simultaneously acquired T2-weighted and proton density head scans for tissue segmentation. The fusion equation optimizes the probability of a voxel being a particular tissue type, given the corresponding probabilities from both images. The algorithm accounts for the intensity inhomogeneities present in the images by fusion of local regions of the images. RESULTS: The method was validated using a phantom (agarose gel with iron oxide particles) and hand-segmented images. Gray and white matter volumes for subjects aged 20-30 years were close to those previously published. White matter and CSF volume increased and gray matter volume decreased significantly across ages 4-18 years. White matter, gray matter, and CSF volumes were larger for males than for females. Males and females showed similar change of gray and white matter volumes with age. CONCLUSION: This simple, reliable, and valid method can be employed in clinical research for quantification of gray and white matter and CSF volumes in MR head scans. Increase in white matter volume may reflect ongoing axonal growth and myelination, and gray matter reductions may reflect synaptic pruning or cell death in the age span of 4-18 years.

Adolescent↗

PubMedDate not supplied

Effects of image orientation on the comparability of pediatric brain volumes using three-dimensional MR data.

PURPOSE: The purpose of this study was to examine the comparability of morphometric measurements made on pediatric data sets collected at five scanner locations, each using variations on a 3D spoiled gradient-recalled echo (SPGR) pulse sequence. METHOD: Archived MR data from 60 typically developing children were collected and separated into seven groups based on the pulse sequence used. A highly automated image-processing procedure was used to segment the brain data into white tissue, gray tissue, and CSF compartments and into various neuroanatomic regions of interest. RESULTS: Volumetric comparisons between groups revealed differences in areas of the temporal and occipital lobes. These differences were observed when comparing data sets with different image orientations and appeared to be due to partial volume averaging (PVA) and susceptibility-induced geometric distortions. CONCLUSION: Our results indicate that slice selection and image resolution should be controlled in volumetric studies using aggregated data from multiple centers to minimize the effects of PVA and susceptibility-induced geometric distortions.

Adolescent↗