Minming Zhang

Age, gender, and hemispheric differences in iron deposition in the human brain: An in vivo MRI study

It is well known that iron accumulates in the brains of patients with various neurodegenerative diseases. To better understand disease-related iron changes, it is necessary to know the physiological distribution and accumulation of iron in the human brain. Studies have shown that brain iron levels increase with aging. However, the effects of gender and hemispheric laterality on iron accumulation and distribution are not well established. In this study, we estimated the brain iron levels in vivo in 78 healthy adults ranging in age 22 to 78 years using magnetic susceptibility-weighted phase imaging. The effects of age, gender, and hemispheric location on brain iron levels were evaluated within the framework of a general linear model. We found that the left hemisphere had higher iron levels than the right in the putamen, globus pallidus, substantia nigra, thalamus, and frontal white matter. We argue that the hemispheric asymmetry of iron content may underlie that of the dopaminergic system and may be related to motor lateralization in humans. In addition, significant age-related iron accumulation occurred in the putamen, red nucleus, and frontal white matter, but no gender-related differences in iron levels were detected. The results of this study extend our knowledge of the physiological distribution and accumulation of iron in the human brain.

Radiation dose of non-enhanced chest CT can be reduced 40% by using iterative reconstruction in image space.

AIM To evaluate the image quality and dose reduction capability of non-enhanced chest computed tomography (CT) examinations using iterative reconstruction in image space (IRIS). MATERIALS AND METHODS A CT water phantom was scanned at 120 kV/150 mAs and 100 kV/270 mAs as the reference, and the tube current was decreased in 10% intervals down to 40% of the reference value. Image noise was evaluated and compared between filtered back-projection (FBP) and IRIS reconstructed data. In the patient study, 90 patients underwent non-enhanced chest CT examinations; the patients were randomly assigned into three groups: group A (n=30) standard dose protocol, 120 kV/110 mAs; group B (n=30) low dose, 100 kV/110 mAs; group C (n=30) low dose, 120 kV/67 mAs. All images were reconstructed by FBP and IRIS algorithm using matched kernels of B30 and I30. The objective image noise (OIN), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the aorta and latissimus dorsi were measured. The subjective image quality and noise were scored using a three-point scale by two experienced radiologists. The results of the subjective and objective image assessment were compared between groups B and C (low dose) IRIS and group A (standard dose) FBP. RESULTS The phantom study showed comparable image noise between the scans using 60% dose with IRIS and 100% dose with FBP for both 120 and 100 kV. In the patient study, groups A, B, and C had effective dose of 3.81 ± 0.43, 2.40 ± 0.19, and 2.41 ± 0.15 mSv. IRIS significantly improved the OIN, SNR, and CNR compared with FBP for the same patient. The OIN, SNR, and CNR using IRIS in group B and C were improved or comparable to those in group A using FBP. No significant difference was found in subjective image quality and noise between groups B and C using IRIS and group A using FBP. CONCLUSION Compared with FBP, IRIS can maintain or improve image quality on unenhanced chest CT image reconstruction while saving 40% radiation dose.

Association of Cerebral Networks in Resting State with Sexual Preference of Homosexual Men: A Study of Regional Homogeneity and Functional Connectivity

Recent imaging studies have shown that brain morphology and neural activity during sexual arousal differ between homosexual and heterosexual men. However, functional differences in neural networks at the resting state is unknown. The study is to characterize the association of homosexual preference with measures of regional homogeneity and functional connectivity in the resting state. Participants were 26 healthy homosexual men and 26 age-matched healthy heterosexual men in whom we collected echo planar magnetic resonance imaging data in the resting state. The sexual orientation was evaluated using the Kinsey Scale. We first assessed group differences in regional homogeneity and then, taking the identified differences as seed regions, we compared groups in measures of functional connectivity from those seeds. The behavioral significances of the differences in regional homogeneity and functional connectivity were assessed by examining their associations with Kinsey Scores. Homosexual participants showed significantly reduced regional homogeneity in the left inferior occipital gyrus, right middle occipital gyrus, right superior occipital gyrus, left cuneus, right precuneus, and increased regional homogeneity in rectal gyrus, bilateral midbrain, and left temporal lobe. Regional homogeneity correlated positively with Kinsey scores in the left inferior occipital gyrus. The homosexual group also showed reduced functional connectivity between left middle temporal gyrus, left supra-marginal gyrus, right cuneus and the seed region, i.e. left inferior occipital gyrus. Additionly, the connection between the left inferior occipital gyrus and right thalamus correlated positively with Kinsey scores. These differences in regional homogeneity and functional connectivity may contribute to a better understanding of the neural basis of male sexual orientation.

Automatic Classification of Early Parkinson's Disease with Multi-Modal MR Imaging

Background In recent years, neuroimaging has been increasingly used as an objective method for the diagnosis of Parkinsons disease (PD). Most previous studies were based on invasive imaging modalities or on a single modality which was not an ideal diagnostic tool. In this study, we developed a non-invasive technology intended for use in the diagnosis of early PD by integrating the advantages of various modals. Materials and Methods Nineteen early PD patients and twenty-seven normal volunteers participated in this study. For each subject, we collected resting-state functional magnetic resonance imaging (rsfMRI) and structural images. For the rsfMRI images, we extracted the characteristics at three different levels: ALFF (amplitude of low-frequency fluctuations), ReHo (regional homogeneity) and RFCS (regional functional connectivity strength). For the structural images, we extracted the volume characteristics from the gray matter (GM), the white matter (WM) and the cerebrospinal fluid (CSF). A two-sample t-test was used for the feature selection, and then the remaining features were fused for classification. Finally a classifier for early PD patients and normal control subjects was identified from support vector machine training. The performance of the classifier was evaluated using the leave-one-out cross-validation method. Results Using the proposed methods to classify the data set, good results (accuracy  = 86.96%, sensitivity  = 78.95%, specificity  = 92.59%) were obtained. Conclusions This method demonstrates a promising diagnosis performance by the integration of information from a variety of imaging modalities, and it shows potential for improving the clinical diagnosis and treatment of PD.

Patterns of Brain Activation during Visually Evoked Sexual Arousal Differ between Homosexual and Heterosexual Men

BACKGROUND AND PURPOSE: Nowadays the mechanism of homosexuality is little known. Few studies have been carried out to explore the brain functional changes of homosexual men during sexual arousal. We used functional MR imaging (fMRI) to determine whether the patterns of brain activation in homosexual and heterosexual men differed during visually evoked sexual arousal. MATERIALS AND METHODS: To all the subjects (10 homosexual and 10 heterosexual), real-time visual stimulation was provided by 3-minute exposure to 3 types of erotic film: heterosexual couples (F-M), male homosexual couples (M-M), and female homosexual couples (F-F) engaged in sexual activity, during which time fMRI was used to determine the patterns of brain activation. Self-reports of level of sexual arousal were collected immediately afterward. RESULTS: Statistical parametric mapping showed that viewing erotic film excerpts that induced sexual arousal was associated, in both groups, with activation of the middle prefrontal gyrus, bilateral temporal lobe and postcentral gyrus, thalamus, insula, vermis, left precuneus, occipital cortex, parietal cortex, and cerebellum. In homosexual men, the left angular gyrus, left caudate nucleus, and right pallidum were activated; in contrast, heterosexual men showed no activation in these regions. However, heterosexual men showed activation in the bilateral lingual gyrus, right hippocampus, and right parahippocampal gyrus, areas not activated in homosexual men. In both groups, region-of-interest analysis revealed no correlation between the magnitude of amygdala or thalamus activation and the reported level of sexual arousal. CONCLUSION: Our findings indicate that different neural circuits are active during sexual arousal in homosexual and heterosexual men and may contribute to a better understanding of the neural basis of male sexual orientation.

Diffusion-weighted imaging in assessing renal pathology of chronic kidney disease: A preliminary clinical study

OBJECTIVE To investigate the clinical potential of diffusion-weighted imaging (DWI) in assessing renal pathology of chronic kidney disease (CKD). METHODS Seventy-one CKD patients and twelve healthy volunteers were examined using DWI with prospective acquisition correction. Renal biopsy specimens from the CKD patients were scored based on the severity of renal pathology and to confirm pathology type. CKD patients were divided into three groups according to pathology scores: mild, moderate, or severe. The association between renal apparent diffusion coefficient (ADC) values and pathology scores was investigated using Pearsons correlation and single factor analysis of variance. Multiple linear regression analysis was performed to explore associations between renal ADC values and pathology score, glomerular filtration rate, serum creatinine, and age. The Kruskal-Wallis H test was conducted to compare ADC values and pathology type. RESULTS Renal ADC values correlated negatively with pathology scores (r=-0.633, P<0.001). The ADC values among the four groups (mild, moderate, severe impairment, and controls) were significantly different (F=19.512, P<0.001). However, when patients were stratified by pathology type, no significant differences were found in ADC values among these groups (χ(2)=9.929, P=0.270). Further multiple linear regression analysis showed that only the pathology score and ADC values were related (t=-4.586, P=0.000). CONCLUSIONS DWI has clinical potential in assessing the severity of renal pathology in CKD and shows promise as a non-invasive and effective technique to guide therapy and follow-up.

Normal Aging in the Basal Ganglia Evaluated by Eigenvalues of Diffusion Tensor Imaging

BACKGROUND AND PURPOSE: The age effect on the diffusion pattern in the basal ganglia differs from that in the white matter. The main purpose of our study was to provide further insight into the change of water diffusion in the basal ganglia during human brain aging by using the eigenvalues of DTI. MATERIALS AND METHODS: We examined 71 healthy subjects (mean age, 41.8 ± 14.5 years; age range, 20–79 years). The values of MD, FA, and the eigenvalues λ1 and λ23 (λ23 = [λ2 + λ3] / 2) were determined in regions of the head of the caudate nucleus, putamen, globus pallidus, and in some regions of white matter. The age-dependence of these measurements was tested for statistical significance by using the Pearson correlation analysis. RESULTS: A significant reduction of MD with aging was found in the head of caudate nucleus (r = −0.319, P = .007) and putamen (r = −0.410, P < .001), and an increase in FA with aging was found in the putamen (r = 0.535, P < .001). Eigenvalue λ23 showed a significant age-related decrease in the putamen (r = −0.451, P < .001) and the head of the caudate nucleus (r = −0.312, P = .008), but no significant changes of λ23 were found in the globus pallidus. The results for eigenvalue λ1 in the head of caudate nucleus (r = −0.299, P = .011) were close to statistical significance. CONCLUSIONS: The eigenvalues provide more insights into the different diffusion patterns in the basal ganglia during human brain aging.

Abnormal amygdala function in Parkinson's disease patients and its relationship to depression.

Depression is a common occurrence in patients with Parkinsons disease (PD). Thus, there may be a common neural mechanism underlying the two diseases. Lewy body accumulation in specific brain areas of PD patients may damage emotion-related functions, leading to depression. Among these areas, the amygdala may present with the earliest to be damaged in PD. However, it is still unclear whether amygdala structural and functional changes are related to depression in PD. We enrolled 19 depressed PD patients, 19 non-depressed PD patients, and 28 normal control subjects. Clinical assessment, including the Unified Parkinsons Disease Rating Scale, the Hamilton Rating Scale for Depression, and the Mini-Mental State Examination, was carried out on all the patients. Structural and resting-state functional brain images were also acquired to assess volumetric and functional changes of the amygdala in the patients. Results showed that although there is no significant volume change, left amygdala activity increased in the PD group compared with the normal control group, and it correlated with Hamilton Rating Scale for Depression scores. Furthermore, functional connectivity between the right amygdala and fronto-parietal areas was found to be decreased in the depressed PD patients compared with non-depressed PD patients. These results suggest that abnormal amygdala function may underlie the occurrence of depression in PD.

Altered Brain Activation and Connectivity in Early Parkinson Disease Tactile Perception

BACKGROUND AND PURPOSE: Deficits in tactile perception are common in patients with PD. However, the neural mechanisms have not been previously reported in the early stages. This study aims to investigate how the brain activity and connectivity changed under tactile perception at early Parkinsonian state by using functional MR imaging. MATERIALS AND METHODS: Twenty-one patients with early PD and 22 age- and sex-matched controls were recruited and scanned under a passive tactile stimulation task. Within-group and between-group activation maps were acquired, and regions of interest were defined according to the group-comparison result. This was followed by a functional connectivity analysis based on the graph theory. RESULTS: We found that in the PD group, bilateral sensorimotor cortex was hypoactive during the task, whereas the hyperactive regions were mainly in bilateral prefrontal cortex, bilateral cerebellum, and contralateral striatum. There was a significant decrease of total connectivity degree in ipsilateral SMA in PD, which was negatively correlated with the Unified Parkinsons Disease Rating Scale score. Furthermore, the connection strengths among the areas of prefrontal cortex, striatum, and cerebellum were increased. CONCLUSIONS: This study illustrated that early PD was associated with not only altered brain activation but also changed functional connectivity in tactile perception. The most significant impairment was in SMA, whereas striato-prefrontal and cerebello-prefrontal loops may play a compensatory role in early PD tactile function.

Disrupted white matter integrity in depressed versus non-depressed Parkinson's disease patients: A tract-based spatial statistics study

Depression is a common occurrence in patients with Parkinsons disease (PD), however, its pathophysiology still remains unclear. With increasing evidence suggesting that depression is a disconnection syndrome, we hypothesized that depression in PD is caused by degenerated fiber connections in the brain. We examined whole brain white matter integrity in 15 depressed PD patients and 15 non-depressed PD patients. All the patients were assessed with the Unified Parkinsons Disease Rating Scale, the Hamilton Rating Scale for Depression, and the Mini-Mental State Examination. White matter difference between the two groups and its correlation with disease severity was calculated. In depressed PD patients, decreased fractional anisotropy was found in the left uncinate fasciculus, superior longitudinal fasciculus, anterior thalamic radiation, forceps minor, and the inferior longitudinal fasciculus. Fractional anisotropy in the left deep temporal cortex was negatively correlated with severity of depression (r = -0.671, p = 0.034). Our results suggest that disrupted fiber connections in the anterior part of the left hemisphere may contribute to depression in PD patients.