Alzheimer病的海马体积测量及脑组织分割分析的初步研究

目的采用ＭＲ体积测量和组织分割分析对Ａｌｚｈｅｉｍｅｒ病（Ａｌｚｈｅｉｍｅｒｄｉｓｅａｓｅ，ＡＤ）患者和正常对照组进行研究，探讨其对ＡＤ的诊断价值。方法对临床诊断为ＡＤ患者和正常老年人各１６例作对照进行ＭＲＩ比较研究。测量两组的海马结构（ＨＦ）体积，脑灰质、脑白质、脑室外脑脊液（ＣＳＦ）和脑室ＣＳＦ体积所占颅内体积百分比，计数两组脑实质Ｔ２ＷＩ上的高信号灶并测量其最大径。结果体积测量显示ＡＤ组左、右侧ＨＦ体积均小于对照组。组织分割分析显示ＡＤ组脑灰质较对照组明显减少，脑室外ＣＳＦ和脑室ＣＳＦ体积所占颅内体积百分比较对照组增加，而脑白质两组间无显著性差异。ＡＤ组和对照组脑实质内高信号灶在大小和分布上无差异。结论ＭＲＨＦ体积测量和脑组织分割分析有助于临床了解ＡＤ的脑部形态结构改变，并能为ＡＤ的进一步诊断提供有价值的影像学评价指标。     

Alteration of white matter MR signal intensity in frontotemporal dementia.

PURPOSETo determine the diagnostic potential of MR imaging to show white matter involvement in frontotemporal dementia.METHODSWe evaluated MR signal intensity in cerebral white matter by visually inspecting and by quantitatively measuring signal intensity on MR images in 22 patients with frontotemporal dementia. The findings were compared with those in 22 age- and sex-matched patients who had had Alzheimer disease for the same length of time and with 16 age- and sex-matched healthy control subjects.RESULTSPatients with frontotemporal dementia had a significant increase in white matter signal intensity in the frontal and/or temporal lobes on T2- and proton density-weighted images. Visual inspection of regular proton density-weighted images and measurements made on the T2- and proton density-weighted images were sensitive to changes in white matter signal.CONCLUSIONIncreased MR signal intensity in the frontotemporal white matter on T2- and proton density-weighted MR images is a useful diagnostic sign of frontotemporal dementia and distinguishes this condition from Alzheimer disease.     

Decreased T1 Contrast between Gray Matter and Normal-Appearing White Matter in CADASIL

BACKGROUND AND PURPOSE:CADASIL is the most frequent hereditary small-vessel disease of the brain. The clinical impact of various MR imaging markers has been repeatedly studied in this disorder, but alterations of contrast between gray matter and normal-appearing white matter remain unknown. The aim of this study was to evaluate the contrast alterations between gray matter and normal-appearing white matter on T1-weighted images in patients with CADASIL compared with healthy subjects.MATERIALS AND METHODS:Contrast between gray matter and normal-appearing white matter was assessed by using histogram analyses of 3D T1 high-resolution MR imaging in 23 patients with CADASIL at the initial stage of the disease (Mini-Mental State Examination score > 24 and modified Rankin scale score ≤ 1; mean age, 53.5 ± 11.1 years) and 30 age- and sex-matched controls.RESULTS:T1 contrast between gray matter and normal-appearing white matter was significantly reduced in patients compared with age- and sex-matched controls (patients: 1.35 ± 0.08 versus controls: 1.43 ± 0.04, P < 10⁻⁵). This reduction was mainly driven by a signal decrease in normal-appearing white matter. Contrast loss was strongly related to the volume of white matter hyperintensities.CONCLUSIONS:Conventional 3D T1 imaging shows significant loss of contrast between gray matter and normal-appearing white matter in CADASIL. This probably reflects tissue changes in normal-appearing white matter outside signal abnormalities on T2 or FLAIR sequences. These contrast alterations should be taken into account for image interpretation and postprocessing.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small-vessel disease of the brain secondary to mutations of the NOTCH3 gene.¹ Conventional MR imaging markers have been repeatedly investigated in this disorder.^2–5 The impact of lacunar lesions detected on T1-weighted sequences seems more important than that of white matter lesions observed on FLAIR sequences.⁶ Recently, various measures of brain and cortical atrophy were shown to be related to clinical worsening.^7,8As reported in the context of Alzheimer disease,⁹ contrast between gray matter and normal-appearing white matter (NAWM) may be altered in CADASIL. This could have important implications for both image interpretation in the clinical setting and postprocessing in research studies. So far however, the alterations of MR imaging T1 contrast between GM and NAWM have not been evaluated in CADASIL. The aim of the present study was to assess potential contrast alterations between GM and NAWM on T1-weighted images in patients with CADASIL at the initial stage of the disease compared with age- and sex-matched individuals.     

Alzheimer disease: measuring loss of cerebral gray matter with MR imaging

The distributions of the cerebral gray matter, the white matter, and the intracranial cerebrospinal fluid (CSF) were measured in 14 patients with Alzheimer disease (AD) and in 14 healthy control subjects. The measurements, derived from two specifically designed magnetic resonance inversion-recovery sequences, compensate for partial signal averaging. The percentage of the gray matter in the brains of AD patients (44.9% +/- 4.4) was significantly lower than in control subjects (50.2% +/- 3.2). The most significant reduction (P less than .001) occurred in the temporal lobes (13.8%) and a central region (12.8); the reduction in frontal lobe (11.2%) and occipital lobe (9.2%) was also statistically significant (P less than .01). There was an increase in the CSF volume in the temporal, occipital, and frontal regions; no region showed a significant difference in the white matter content. The findings of diffuse changes and temporal lobe involvement in AD are consistent with pathologic observations of cortical cell loss.     

Brain MR in chronic fatigue syndrome.

PURPOSETo determine the prevalence of MR white matter abnormalities in patients with chronic fatigue syndrome (CFS).METHODSBrain MR studies of 43 patients (29 women and 14 men, 22 to 78 years old) with a clinical diagnosis of CFS (n = 15), CFS with associated depression (n = 14), and CFS with associated other psychiatric disorders, namely, anxiety and somatization disorder (n = 14), were compared with brain MR studies in 43 age- and sex-matched control subjects.RESULTSMR findings were abnormal in 13 (32%) of the patients in the study group (ages 34 to 78 years) and in 12 (28%) of the control subjects (ages 26 to 73 years). One patient with CFS had multiple areas of demyelination in the supratentorial periventricular white matter. Another patient with CFS and associated depression had a single focus of probable demyelination in the supratentorial periventricular white matter. In four patients with CFS (ages 34 to 48 years) MR abnormalities consisted of one or several punctate hyperintense foci in the corona radiata, centrum ovale, and frontal white matter. The remaining seven patients (ages 50 to 78 years) had frontoparietal subcortical white matter foci of high T2 signal. The prevalence of white matter hyperintensities was not different between the patients and the control subjects.CONCLUSIONSOur findings suggest that no MR pattern of white matter abnormalities is specific to CFS.     

Unsupervised,automated segmentation of the normal brain using a multispectral relaxometric magnetic resonance approach

The purpose of this study was the development and testing of a method for unsupervised, automated brain segmentation. Two spin-echo sequences were used to obtain relaxation rates and proton-density maps from 1.5 T MR studies, with two axial data sets including the entire brain. Fifty normal subjects (age range, 16 to 76 years) were studied. A Three-dimensional (3D) spectrum of the tissue voxels was used for automatic segmentation of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) and for calculation of their volumes. Accuracy and reproducibility were tested with a three-compartment phantom simulating GM, WM, and CSF. In the normal subjects, a significant decrease of GM fractional volume and increased CSF volume with age were observed (P < 0.0001), with no significant changes in WM. This multi-spectral segmentation method permits reproducible, operator-independent volumetric measurements.     

Brain volume in pediatric patients with sickle cell disease: evidence of volumetric growth delay?

BACKGROUND AND PURPOSE: Despite the large body of data available about somatic growth delay in patients with sickle cell disease (SCD), virtually nothing is known about the effect of the disease on volumetric growth of the brain. This study was designed to test a hypothesis that children with SCD have a disease-related delay in brain volumetric growth compared with healthy children. METHODS: A cross-sectional study design was used to evaluate 83 children with SCD and 43 age-similar healthy children, including 27 patient siblings. Brain volume was measured by segmenting and classifying MR imaging data, by using at least three separate image sets (T1-, T2-, and proton density-weighted MR images). A linear model was used to compare the various brain volumes with the covariates of group (patient versus control) and age, with age treated as a continuous variable. RESULTS: With age controlled for, no significant difference was noted in total brain volume between patients and control subjects at age 9.5 years. However, patients showed a deficit specifically in gray matter volume (P=.005), without significant differences in white matter or ventricular volume. The deficit in patient gray matter was greater in central gray matter (P <.005) than in cortical gray matter (P <.02). In healthy control subjects, gray matter volume decreased significantly with age (P <.005), probably due to myelination of white matter tracts. In patients with SCD, gray matter volume did not change with age. CONCLUSION: Volumetric growth of brain gray matter may be delayed in children with SCD, suggesting that there may be neurodevelopmental consequences of this disease.     

White matter MR hyperintensities in adult patients with congenital rubella.

PURPOSETo observe and quantify white matter hyperintensities on MR images in adults with schizophrenialike symptoms who had had congenital rubella, in order to elucidate the neuropathologic sequelae of this perinatal viral infection and to explore the potential relationship of these lesions to schizophrenia.METHODSEleven deaf adult patients with documented prenatal rubella virus infection and schizophrenialike symptoms were compared with 19 age-matched patients with early-onset schizophrenia who did not have congenital rubella and with 18 age-matched control subjects. All MR images (obtained at 1.5 T) were evaluated by a neuroradiologist who was blinded to diagnosis and were rated for white matter lesions on a five-point scale: 0 = no lesions; 1 = 1 lesion less than 1 mm in diameter; 2 = 1 to 4 lesions 1 mm or greater; 3 = 5 to 10 lesions; 4 = more than 10 lesions or a single lesion more than 1 cm in diameter. In addition, the white matter hyperintensities were volumed objectively with a manual threshold technique.RESULTSRatings of white matter lesions were significantly higher in the rubella patients than in the control subjects: 6 of the 11 patients had ratings greater than 1 compared with 1 of the 18 control subjects and none of the 19 schizophrenic patients. Also, MR images in five rubella patients received ratings at the highest end of the scale of abnormality (3 or 4). The white matter hyperintensities were characterized as bilateral T2 signal hyperintensities in periventricular and subcortical regions, punctate or linear in shape; they were observed predominantly in parietal lobes.CONCLUSIONThis quantitative MR study of adult rubella patients disclosed abnormal white matter lesions that may correspond to neurovascular lesions known neuropathologically. They do not appear to be directly related to schizophrenialike symptoms.     

Early assessment of brain maturation by MR imaging segmentation in neonates and premature infants

PURPOSE: We evaluated the impact of premature extrauterine life on brain maturation. PATIENTS AND METHODS: Twelve neonates underwent MR imaging at 40 (39.64 +/- 0.98) weeks (full term). Fifteen premature infants underwent 2 MR imaging examinations, after birth (preterm at birth) and at 40 weeks (41.03 +/- 1.33) (preterm at term). A 3D MR imaging technique was used to measure brain volumes compared with intracranial volume: total brain volume, cortical gray matter, myelinated white matter, unmyelinated white matter, basal ganglia (BG), and CSF. RESULTS: The average absolute volume of intracranial volume (269.8 mL +/- 36.5), total brain volume (246.5 +/- 32.3), cortical gray matter (85.53 mL +/- 22.23), unmyelinated white matter (142.4 mL +/-14.98), and myelinated white matter (6.099 mL +/-1.82) for preterm at birth was significantly lower compared with that for the preterm at term: the average global volume of intracranial volume (431.7 +/- 69.98), total brain volume (391 +/- 66,1), cortical gray matter (179 mL +/- 41.54), unmyelinated white matter (185.3 mL +/- 30.8), and myelinated white matter (10.66 mL +/- 3.05). It was also lower compared with that of full-term infants: intracranial volume (427.4 mL +/- 53.84), total brain volume (394 +/- 49.22), cortical gray matter (181.4 +/- 29.27), unmyelinated white matter (183.4 +/- 27.37), and myelinated white matter (10.72 +/- 4.63). The relative volume of cortical gray matter (30.62 +/- 5.13) and of unmyelinated white matter (53.15 +/- 4.8) for preterm at birth was significantly different compared with the relative volume of cortical gray matter (41.05 +/- 5.44) and of unmyelinated white matter (43.22 +/- 5.11) for the preterm at term. Premature infants had similar brain tissue volumes at 40 weeks to full-term infants. CONCLUSION: MR segmentation techniques demonstrate that cortical neonatal maturation in moderately premature infants at term and term-born infants was similar.     

White matter lesions in panencephalopathic type of Creutzfeldt-Jakob disease: MR imaging and pathologic correlations

BACKGROUND AND PURPOSE: A panencephalopathic type of Creutzfeldt-Jakob disease (pCJD) is characterized by the extensive involvement of the cerebral white matter as well as the cerebral gray matter. It has been a point of controversy, however, whether the white matter changes represent primary or secondary degeneration. The aim of this study was to elucidate, by using MR images and histologic examinations, whether the white matter lesions in pCJD are primary or secondary degeneration. METHODS: Serial changes of T2 hyperintensities and histologic findings of six autopsy-proved cases of pCJD were retrospectively analyzed. RESULTS: Serial MR images of brains affected by pCJD revealed that T2 hyperintensities appeared in the cerebral gray matter 2-5 months after onset and in the cerebral white matter around the lateral ventricles approximately 5 months after onset. They rapidly extended to deep and subcortical white matter during the next several months and then to the entire cerebral white matter 10 months after onset. Histologic examination of the white matter lesions revealed spongy changes or tissue rarefaction associated with gemistocytic astrocytosis, which indicates primary involvement of the white matter. At the terminal stages of cases with a longer clinical course, MR images showed T2 hyperintensities in the corticospinal tracts in the internal capsule and brain stem, which histologically disclosed loss of myelin and axons accompanied by fibrillary gliosis that indicates secondary degeneration. CONCLUSION: Cerebral white matter lesions in pCJD were considered to be primary changes of the disease, but the lesions of the corticospinal tracts were secondary to cortical or cerebral or both white matter lesions.     

Alzheimer病和健康老人的脑容积和脑代谢变化的MRI和MRS分析研究

目的：探讨Ａｌｚｈｅｉｍｅｒ病（ＡＤ）患者与健康对照组脑组织容积和脑组织内Ｎ－乙酰天门冬氨酸（ＮＡＡ）、胆碱（Ｃｈｏ）及肌－肌醇（Ｍｉ）的特征及异同。材料和方法：对临床确诊的１３例ＡＤ患者和１３例健康老人进行ＭＲＩ脑组织分割分析，定量研究两组脑实质容积的变化。对两组各１１例同时进行了磁共振波谱检查，定量分析两组的ＮＡＡ、Ｃｈｏ及Ｍｉ的水平。结果：ＭＲＩ脑组织分割分析显示ＡＤ组较对照组有明显的脑灰质丢失，两组脑白质的容积无明显差异。磁共振波谱分析（ＭＲＳ）显示ＡＤ组ＮＡＡ水平较对照组降低，Ｍｉ水平较对照组升高，两组的Ｃｈｉ水平无显著差异。结论：脑组织分割分析能够准确的反映ＡＤ患者脑灰质萎缩的范围；ＭＲＳ能够准确提供ＡＤ患者脑部ＮＡＡ、Ｃｈｏ和Ｍｉ的代谢情况，两者结合有助于ＡＤ的诊断。     

MR of the brain in mitochondrial myopathy.

PURPOSETo determine the spectrum of MR findings in patients with mitochondrial myopathy and correlate them with central nervous system symptoms and signs.METHODSWe performed a prospective evaluation of the MR findings of eight patients with mitochondrial myopathy (three with Kearns-Sayre syndrome and five with chronic progressive external ophthalmoplegia), six of whom had central nervous system symptoms or signs (ataxia, sensorineural hearing loss, or cognitive dysfunction).RESULTSAll six patients with neurologic symptoms or signs had multiple abnormal MR findings, whereas patients without neurologic symptoms had either normal MR findings (one patient) or the solitary finding of cortical atrophy (one patient). Abnormal MR findings consisted of cerebral cortical atrophy (seven patients), cerebellar atrophy (six patients), and hyperintense signal abnormalities on T2-weighted images within the cerebral white matter (three patients), cerebellar white matter (one patient), basal ganglia (three patients), brain stem (one patient), and thalamus (one patient). In two patients, the cerebral white matter signal abnormalities were primarily peripheral and involved the arcuate fibers. All patients with ataxia had abnormal cerebellar findings on MR imaging, but there was poor correlation between other neurologic features and MR findings.CONCLUSIONSCerebral and cerebellar atrophy are the most common MR findings in Kearns-Sayre syndrome and chronic progressive external ophthalmoplegia. White matter and deep gray nuclei abnormalities, presumed to result from the diffuse spongiform encephalopathy reported in these patients, can also be seen. Patients with abnormal neurologic findings typically have multiple abnormalities on MR imaging, which frequently do not correlate with specific symptoms.     

Cortical hyperintensity on proton density-weighted images: An MR sign of cyclosporine-related encephalopathy.

PURPOSETo describe cortical hyperintensities in proton density-weighted images in six patients with presumed cyclosporine-induced neurotoxicity.METHODSIn six patients with clinical evidence of cyclosporine-related encephalopathy, MR imaging was performed after the onset of symptoms and signs (mean, 24 days after liver transplantation). Five of these patients had serial MR imaging for a period that varied from 2 to 20 months. Along with the imaging studies, the patients'' clinical status was evaluated and various laboratory parameters, including blood pressure and levels of cyclosporine, cholesterol, and magnesium, were monitored.RESULTSIn all six patients, initial MR studies showed hyperintensity of several cerebral gyri that was unequivocal only on proton density-weighted images. Although in five patients these signal abnormalities were limited to the cortex, one patient had increased signal in the subjacent white matter as well. In one patient, the images were also remarkable for areas of cortical hyperintensities on T1-weighted images. In another patient, cortical enhancement occurred after administration of gadopentetate dimeglumine, with a normal cortical signal on the precontrast images. The abnormal cortical signal began to fade after cyclosporine reduction, but in two patients it remained visible for at least 20 months. The neurologic symptomatology associated with cyclosporine-induced neurotoxicity included seizures (three patients), speech disorder (three patients), and disturbance of consciousness (three patients).CONCLUSIONCyclosporine-induced neurotoxicity occurring in patients after liver transplantation appears to affect the cerebral cortex preferentially. Because its MR equivalent resembles changes resulting from hypoxic injury or cortically centered vasculitis, we suspect the underlying mechanism may be a vascular injury that results in cortical hypoperfusion.     

Nipah virus encephalitis: serial MR study of an emerging disease.

PURPOSE: To report the serial magnetic resonance (MR) imaging findings of the Nipah virus. MATERIALS AND METHODS: Twelve patients underwent serial MR imaging. Eight patients were examined at the outbreak; 11, at 1 month; and seven, at 6 months. Contrast material-enhanced MR images, diffusion-weighted images, and single-voxel proton MR spectroscopic images were reviewed. Clinical and neurologic assessment, as well as analysis of the size, location, and appearance of brain lesions on MR images, were performed. RESULTS: During the outbreak, all eight patients had multiple small foci of high signal intensity within the white matter on T2-weighted images. In six patients, cortical and brain stem lesions were also detected, and five patients had diffusion-weighted MR imaging-depicted hyperintensities. One month after the outbreak, five patients had widespread tiny foci of high signal intensity on T1-weighted images, particularly in the cerebral cortex. Diffusion-weighted images showed decreased prominence or disappearance of lesions over time. There was no evidence of progression or relapse of the lesions at 6-month follow-up. MR spectroscopy depicted reduction in N-acetylaspartate-to-creatine ratio and elevation of choline-to-creatine ratios. CONCLUSION: The Nipah virus has findings unlike other viral encephalitides: small lesions that are primarily within the white matter, with transient punctate cortical hyperintensities on T1-weighted images.     

Increased brain water self-diffusion in patients with idiopathic intracranial hypertension.

PURPOSETo investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension.METHODSA motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers.RESULTSA significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter.CONCLUSIONMeasurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.     

Cerebral hemodynamics and cerebral blood volume: MR assessment using gadolinium contrast agents and T1-weighted Turbo-FLASH imaging.

PURPOSE: To assess the degree and regional pattern of first-pass brain enhancement using dynamic MR imaging. MATERIALS AND METHODS: Ultrafast MR imaging (1.06-second acquisition time per image) was performed in 19 healthy subjects following a bolus IV injection of a gadolinium contrast agent; 36 patients with suspected pathology were studied using the same protocol. RESULTS: Calculated percent blood volumes were 4.9% for right cortical gray matter, 4.8% for left cortical gray matter, and 2.6% for white matter. Subtraction images were obtained that depicted the first pass "blood pool" pattern of enhancement (gray and white matter) which was significant. CONCLUSION: Preliminary evidence suggests utility for cerebral "blood pool" imaging, especially if reduced image acquisition times can be achieved.     

Subacute sclerosing panencephalitis: evaluation with CT and MR.

PURPOSETo evaluate the progression of CT and MR changes of the brain in subacute sclerosing panencephalitis (SSPE) as a basis for assessing the effects of different types of therapy.METHODSFifty-two patients with SSPE were examined, 44 with MR imaging and 42 with CT of the brain on one or more occasions. A total of 92 MR and 67 CT studies were performed.RESULTSCorrelation between the clinical status and the MR findings in admission was poor. Of 20 patients with clinically advanced disease, only 8 had marked MR abnormalities; 6 had normal or almost normal findings on MR examinations. Two of 4 patients with clinically mild disease had advanced MR changes. The progression of the MR findings appeared to follow a constant pattern. The earliest pathologic finding was focal, high-T2-intensity white matter changes; later atrophic changes followed. The atrophy lagged behind the white matter changes and was thus mild when white matter changes were moderate or severe. In the most advanced stage, when the patient was in a neurovegetative state, an almost total loss of white matter had usually taken place. At this stage, the corpus callosum was also thin. Basal ganglia changes, usually involving the putamina, were seen in one third of patients and cortical gray matter changes were seen in one fourth of patients examined with MR imaging. In 2 of 20 patients, MR changes regressed in parallel with clinical improvement following therapy, but in 5 patients clinical improvement was accompanied by progression of MR changes.CONCLUSIONThe progress of MR abnormalities seen in patients with SSPE seems to follow a constant pattern, but the severity of MR changes does not always correlate well with the clinical findings. Caution must therefore be used when evaluating the effects of therapy.     

Age-related changes in the pediatric brain: quantitative MR evidence of maturational changes during adolescence.

PURPOSETo determine whether a quantitative MR imaging method to map spin-lattice relaxation time (T1) can be used to characterize maturational changes in the normal human brain.METHODSAn inversion-recovery technique was used to map T1 transversely at the level of the basal ganglia in a study population of 19 healthy children (4 to 10 years old) and 31 healthy adolescents (10 to 20 years old), and in a normative population of 20 healthy adults (20 to 30 years old).RESULTSNonparametric analysis of variance showed that T1 decreases with age in the genu, frontal white matter, caudate, putamen, anterior thalamus, pulvinar nucleus, optic radiation, cortical gray matter (all P < .0001), and occipital white matter. There was a significant reduction in T1 between childhood (mean age, 7.1 +/- 1.4) and adolescence (mean age, 13.5 +/- 2.6) in all brain structures, but there was also a significant reduction in T1 between adolescence (mean age, 13.5 +/- 2.6) and adulthood (mean age, 26.5 +/- 3.4) in all brain structures except occipital white matter. Regression shows that T1 declines to within the range (mean +/- 2 SD) of young adult T1 values by about 2 years in the occipital white matter, by about 4 years in the genu, by 11 years in the cortical gray matter, by 11 years in the frontal white matter, and by 13 years in the thalamus.CONCLUSIONBrain structures mature at strikingly different rates, yet the ratio of gray matter T1 to white matter T1 does not change significantly with age. Thus, conventional MR imaging methods based on inherent contrast are insensitive to these changes. Age-related changes tend to reach completion sooner in white matter than in gray matter tracts. Such normative data are essential for studies of specific pediatric disorders and may be useful for assessing brain maturation in cases of developmental delay.     

Estimating NAA in cortical gray matter with applications for measuring changes due to aging

N-acetylaspartic acid (NAA), a prominent peak in the proton spectrum, is an amino acid thought to be present almost exclusively in neurons and their dendritic and axonal extensions. While ¹H MRS studies are showing promise in identifying NAA deficits in different patient groups, unwanted lipid signal from subcutaneous fat surrounding the skull, and necessarily large voxels have limited investigators' ability to assess NAA in cortical gray matter. Here we report a technique developed to derive estimates of NAA signal from cortical gray matter. This approach uses an inversion recovery imaging pulse sequence with a long TE to suppress lipid signal from the scalp and information from concurrently obtained structural MR images to determine the CSF, white and gray matter composition of each spectroscopic voxel. A regression analysis is then used to estimate what NAA levels would be in “pure” white and gray matter voxels. This technique has been applied to demonstrate reduced NAA gray/white levels in the brains of five healthy older compared with five healthy younger women.     

Brain white matter hyperintensities: relative importance of vascular risk factors in nondemented elderly people

PURPOSE: To prospectively determine whether there is an association between brain white matter signal hyperintensities on magnetic resonance (MR) images and potential risk factors for cerebral ischemia in a well-characterized narrow age cohort of nondemented community-dwelling elderly people. MATERIALS AND METHODS: The study population consisted of surviving members of the Aberdeen 1921 Birth Cohort, a subsample of participants in the 1932 Scottish Mental Survey who were born in 1921. With the permission of the local ethics committee and with informed written consent, 106 nondemented subjects (62 men, 44 women) aged 78-79 years underwent T2-weighted brain MR imaging. Brain MR images were scored semiquantitatively for deep white matter hyperintensities and periventricular hyperintensities. Vascular risk factors and clinical measures potentially associated with cerebral ischemia included hypertension, diabetes, cerebrovascular disease, smoking, body mass index grade, respiratory function levels (forced expiratory volume in 1 second [FEV1], forced vital capacity [FVC], and peak expiratory flow rate [PEFR]) normalized for subject's height, plasma lipid levels (cholesterol, triglycerides, high-density lipoprotein, and low-density lipoprotein), glycated hemoglobin level, and mean fasting blood glucose level. Pearson correlation coefficients were calculated for correlations between potential vascular risk factors and scores for deep white matter and periventricular hyperintensities, and stepwise multiple linear regression analysis was performed for factors with a statistically significant correlation. RESULTS: Significant Pearson correlations with deep white matter hyperintensities were found for glycated hemoglobin level (r = 0.31), hypertension (r = 0.27), normalized FEV1 (r = -0.27), normalized FVC (r = -0.22), normalized PEFR (r = -0.27), low-density lipoprotein (r = 0.24), and cholesterol (r = 0.20), and with periventricular hyperintensities for glycated hemoglobin level (r = 0.28) and normalized PEFR (r = -0.23). Multiple linear regression analysis showed that glycated hemoglobin level and hypertension were predictive of 16.2% of the variance in deep white matter hyperintensities. When subjects with non-insulin-dependent (type 2) diabetes mellitus (n = 11) were excluded, hypertension and decreased normalized PEFR were predictive of 11.7% of the variance. CONCLUSION: White matter hyperintensities are associated with elevated levels of glycated hemoglobin in nondemented community-dwelling elderly subjects. Hypertension and decreased normalized PEFR are the principal predictors of deep white matter hyperintensities in nondiabetic subjects.