T1-weighted Magnetic Resonance Scans Research Articles

Convergent molecular and structural neuroimaging signatures of first-episode depression

BackgroundConvergent studies have demonstrated morphological abnormalities in various brain regions in depression patients. However, the molecular underpinnings of the structural impairments remain largely unknown, despite a pressing need for treatment targets and mechanisms. Here, we investigated the gray matter volume (GMV) alteration in patients with depression and its underlying molecular architecture. MethodsWe recruited 195 first-episode, treatment-naïve depression patients and 78 gender-, age-, and education level-matched healthy controls (HCs) who underwent high-resolution T1-weighted magnetic resonance scans. Voxel-based morphometry (VBM) was adopted to calculate the GMV differences between two groups. Then we analyzed the spatial correlation between depression-induced alteration in GMV and density maps of 10 receptors/transporters deriving from prior molecular imaging in healthy people. ResultsCompared to HCs, the depression group had significantly increased GMV in the left ventral portions of the ventral medial prefrontal cortex, parahippocampal gyrus, amygdala, the right superior parietal lobule and precuneus while decreased GMV in the bilateral hippocampus extending to the thalamus and cerebellum. The GMV alteration introduced by depression was spatially correlated with serotonin receptors (5-HT1a, 5-HT1b, and 5-HT2a), dopamine receptors (D1 and D2) and GABAergic receptor (GABAa) densities. LimitationsThe conclusions drawn in this study were obtained from a single dataset. ConclusionsThis study reveals abnormal GMV alteration and provides a series of neurotransmitters receptors possibly related to GMV alteration in depression, which facilitates an integrative understanding of the molecular mechanism underlying the structural abnormalities in depression and may provide clues to new treatment strategies.

Investigating conditional GAN performance with different generator architectures, an ensemble model, and different MR scanners for MR-sCT conversion

Recent developments in magnetic resonance (MR) to synthetic computed tomography (sCT) conversion have shown that treatment planning is possible without an initial planning CT. Promising conversion results have been demonstrated recently using conditional generative adversarial networks (cGANs). However, the performance is generally only tested on images from one MR scanner, which neglects the potential of neural networks to find general high-level abstract features. In this study, we explored the generalizability of the generator models, trained on a single field strength scanner, to data acquired with higher field strengths. T2-weighted 0.35T MRIs and CTs from 51 patients treated for prostate (40) and cervical cancer (11) were included. 25 of them were used to train four different generators (SE-ResNet, DenseNet, U-Net, and Embedded Net). Further, an ensemble model was created from the four network outputs. The models were validated on 16 patients from a 0.35T MR scanner. Further, the trained models were tested on the Gold Atlas dataset, containing T2-weighted MR scans of different field strengths; 1.5T(7) and 3T(12), and 10 patients from the 0.35T scanner. The sCTs were dosimetrically compared using clinical VMAT plans for all test patients. For the same scanner (0.35T), the results from the different models were comparable on the test set, with only minor differences in the mean absolute error (MAE) (35-51HU body). Similar results were obtained for conversions of 3T GE Signa and the 3T GE Discovery images (40-62HU MAE) for three of the models. However, larger differences were observed for the 1.5T images (48-65HU MAE). The overall best model was found to be the ensemble model. All dose differences were below 1%. This study shows that it is possible to generalize models trained on images of one scanner to other scanners and different field strengths. The best metric results were achieved by the combination of all networks.

Magnetic resonance-based computed tomography metal artifact reduction using Bayesian modelling

Metal artifact reduction (MAR) algorithms reduce the errors caused by metal implants in x-ray computed tomography (CT) images and are an important part of error management in radiotherapy. A promising MAR approach is to leverage the information in magnetic resonance (MR) images that can be acquired for organ or tumor delineation. This is however complicated by the ambiguous relationship between CT values and conventional-sequence MR intensities as well as potential co-registration issues. In order to address these issues, this paper proposes a self-tuning Bayesian model for MR-based MAR that combines knowledge of the MR image intensities in local spatial neighborhoods with the information in an initial, corrupted CT reconstructed using filtered back projection. We demonstrate the potential of the resulting model in three widely-used MAR scenarios: image inpainting, sinogram inpainting and model-based iterative reconstruction. Compared to conventional alternatives in a retrospective study on nine head-and-neck patients with CT and T1-weighted MR scans, we find improvements in terms of image quality and quantitative CT value accuracy within each scenario. We conclude that the proposed model provides a versatile way to use the anatomical information in a co-acquired MR scan to boost the performance of MAR algorithms.

Magnetic Resonance, Vendor-independent, Intensity Histogram Analysis Predicting Pathologic Complete Response After Radiochemotherapy of Rectal Cancer

The objective of this study is finding an intensity based histogram (IBH) signature to predict pathologic complete response (pCR) probability using only pre-treatment magnetic resonance (MR) and validate it externally in order to create a workflow for the external validation of an MR IBH signature and to apply the model out of the environment where it has been tuned. The impact of pCR and the final predictors on the survival outcome were also evaluated. Three centers using different MR scanners were involved in this retrospective study. The first center recruited 162 patients for model training, and the second and third centers provided 34 plus 25 patients for external validation. Patients provided written consent. Accrual period was from May 2008 to December 2014. After surgery pathologic response was defined. T2-weighted MR scans acquired before chemoradiation therapy (CRT) were used for analysis addressed on primary lesions. Images were pre-processed using Laplacian of Gaussian (LoG) filter with multiple σ, and first order intensity histogram-based features (kurtosis, skewness, and entropy) were extracted. Features selection was performed using Mann-Whitney test. Tumor staging (cT, cN) was added to build a logistic regression model and predict pCR. Model performance was evaluated with internal and external validation using area under the curve (AUC) of the receiver operator characteristic (ROC) and calibration with Hosmer-Lemeshow test. The linear cross-correlation matrix (Pearson's coefficient) and the variance inflation factor (VIF) were used to check the correlation and the co-linearity among the final predictors. The amount of the information added through the radiomics features was estimated by using the DeLong's test, and the impact of pCR and the final predictors on survival outcomes were evaluated through the Kaplan-Meier curves by using the log-rank test and the multivariate Cox model. Candidate-to-analysis features were skewness (σ=0.485, P value=.01) and entropy (σ=0.344, P value<.05). Logistic regression analysis showed as significant covariates cT (P value<.01), skewness-σ=0.485 (P value=.01), and entropy-σ=0.344 (P value<.05). Model AUCs were 0.73 (internal) and 0.75 (external). This MR-based, vendor-independent model can be helpful for predicting pCR probability in locally advanced rectal cancer (LARC) patients only using pre-treatment imaging.

Is L5-S1 motion segment different from the rest? A radiographic kinematic assessment of 72 patients with chronic low back pain.

The relationship between biomechanical instability and degenerative changes in the lumbar spine in chronic low back pain (CLBP) patients remains controversial. The main objective of this retrospective radiographical study was to evaluate changes in kinematics at different lumbar levels (in particular the L5-S1 level) with progressive grades of disc degeneration and facet joint osteoarthritis in CLBP patients. Using standing neutral and dynamic flexion/extension (Fx/Ex) radiographs of the lumbar spine, in vivo segmental kinematics at L1-L2 through L5-S1 were evaluated in 72 consecutive CLBP patients. Disc degeneration was quantified using changes in signal intensity and central disc height on mid-sagittal T2-weighted magnetic resonance (MR) scans. Additionally, the presence or absence of facet joint osteoarthritis was noted on T2-weighted axial MR scans. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level (p=0.188), but an association was observed between the two at L4-L5 (p<0.001) and L3-L4 (p<0.05) levels. In the absence of facet joint osteoarthritis, the L5-S1 segment showed a greater range of motion (ROM) in Ex (3.3°±3.6°) and a smaller ROM in Fx (0.6°±4.2°) compared with the upper lumbar levels (p<0.05), but the differences diminished in the presence of it. In the absence of facet joint osteoarthritis, no change in L5-S1 kinematics was observed with progressive disc degeneration, but in its presence, restabilisation of the L5-S1 segment was observed between mild and severe disc degeneration states. The L5-S1 motion segment exhibited unique degenerative and kinematic characteristics compared with the upper lumbar motion segments. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level, but not at the other lumbar levels. Severe disc degeneration in the presence of facet joint osteoarthritis biomechanically restabilised the L5-S1 motion segment.

Connectomics-based structural network alterations in obsessive-compulsive disorder.

Given the strong involvement of affect in obsessive-compulsive disorder (OCD) and recent findings, the current cortico-striato-thalamo-cortical (CSTC) model of pathophysiology has repeatedly been questioned regarding the specific role of regions involved in emotion processing such as limbic areas. Employing a connectomics approach enables us to characterize structural connectivity on a whole-brain level, extending beyond the CSTC circuitry. Whole-brain structural networks of 41 patients and 42 matched healthy controls were analyzed based on 83 × 83 connectivity matrices derived from cortical and subcortical parcellation of structural T1-weighted magnetic resonance scans and deterministic fiber tracking based on diffusion tensor imaging data. To assess group differences in structural connectivity, the framework of network-based statistic (NBS) was applied. Graph theoretical measures were calculated to further assess local and global network characteristics. The NBS analysis revealed a single network consistently displaying decreased structural connectivity in patients comprising orbitofrontal, striatal, insula and temporo-limbic areas. In addition, graph theoretical measures indicated local alterations for amygdala and temporal pole while the overall topology of the network was preserved. To the best of our knowledge, this is the first study combining the NBS with graph theoretical measures in OCD. Along with regions commonly described in the CSTC model of pathophysiology, our results indicate an involvement of mainly temporo-limbic regions typically associated with emotion processing supporting their importance for neurobiological alterations in OCD.

Feasibility of Computed Tomography-Guided Methods for Spatial Normalization of Dopamine Transporter Positron Emission Tomography Image.

BackgroundSpatial normalization is a prerequisite step for analyzing positron emission tomography (PET) images both by using volume-of-interest (VOI) template and voxel-based analysis. Magnetic resonance (MR) or ligand-specific PET templates are currently used for spatial normalization of PET images. We used computed tomography (CT) images acquired with PET/CT scanner for the spatial normalization for [18F]-N-3-fluoropropyl-2-betacarboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) PET images and compared target-to-cerebellar standardized uptake value ratio (SUVR) values with those obtained from MR- or PET-guided spatial normalization method in healthy controls and patients with Parkinson’s disease (PD).MethodsWe included 71 healthy controls and 56 patients with PD who underwent [18F]-FP-CIT PET scans with a PET/CT scanner and T1-weighted MR scans. Spatial normalization of MR images was done with a conventional spatial normalization tool (cvMR) and with DARTEL toolbox (dtMR) in statistical parametric mapping software. The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT). We normalized PET images with cvMR-, dtMR-, ssCT-, itCT-, and PET-guided methods by using specific templates for each modality and measured striatal SUVR with a VOI template. The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison.ResultsThe SUVR values derived from all four structure-guided spatial normalization methods were highly correlated with those measured with FSVOI (P < 0.0001). Putaminal SUVR values were highly effective for discriminating PD patients from controls. However, the PET-guided method excessively overestimated striatal SUVR values in the PD patients by more than 30% in caudate and putamen, and thereby spoiled the linearity between the striatal SUVR values in all subjects and showed lower disease discrimination ability. Two CT-guided methods showed comparable capability with the MR-guided methods in separating PD patients from controls and showed better correlation between putaminal SUVR values and the parkinsonian motor severity than the PET-guided method.ConclusionCT-guided spatial normalization methods provided reliable striatal SUVR values comparable to those obtained with MR-guided methods. CT-guided methods can be useful for analyzing dopamine transporter PET images when MR images are unavailable.

Small vessel stroke and white matter lesions

Damage to small penetrating vessels is an important unifying cause of ischemic and hemorrhagic strokes. Both types of stroke involve tiny arterioles and are often pathologic twins, arteriolosclerosis and lipohyalinosis being the predominant underlying causes.1 Another entity increasingly linked to small vessel damage is extensive leukoaraiosis: white matter lesions frequently seen on T2-weighted magnetic resonance scans of older people. In this issue of Neurology ®, Rost et al.2 report hospital-based findings from 3 stroke registries showing a greater burden of leukoaraiosis in participants with small vessel stroke (including both ischemic and hemorrhagic forms) compared to other ischemic stroke subtypes, supporting a link among these 3 entities. Thought of together, as peas in a pod, ischemic and hemorrhagic small vessel damage accounts for about one-third of all strokes and represents an important cause of morbidity and mortality. Ischemic small vessel stroke, often referred to as “lacunar,” is usually manifested as infarctions less than 1.5 cm in diameter on CT or MRI, and attributed to thrombosis of a penetrating vessel in the basal ganglia, thalamus, deep white matter, or brainstem. Studies suggest that lacunar strokes are associated with lower short-term disability and mortality than other ischemic stroke subtypes, and reported 1-year case-fatality rates are low, near 3%. …

Nurture versus Nature: Long-Term Impact of Forced Right-Handedness on Structure of Pericentral Cortex and Basal Ganglia

Does a conflict between inborn motor preferences and educational standards during childhood impact the structure of the adult human brain? To examine this issue, we acquired high-resolution T1-weighted magnetic resonance scans of the whole brain in adult "converted" left-handers who had been forced as children to become dextral writers. Analysis of sulcal surfaces revealed that consistent right- and left-handers showed an interhemispheric asymmetry in the surface area of the central sulcus with a greater surface contralateral to the dominant hand. This pattern was reversed in the converted group who showed a larger surface of the central sulcus in their left, nondominant hemisphere, indicating plasticity of the primary sensorimotor cortex caused by forced use of the nondominant hand. Voxel-based morphometry showed a reduction of gray matter volume in the middle part of the left putamen in converted left-handers relative to both consistently handed groups. A similar trend was found in the right putamen. Converted subjects with at least one left-handed first-degree relative showed a correlation between the acquired right-hand advantage for writing and the structural changes in putamen and pericentral cortex. Our results show that a specific environmental challenge during childhood can shape the macroscopic structure of the human basal ganglia. The smaller than normal putaminal volume differs markedly from previously reported enlargement of cortical gray matter associated with skill acquisition. This indicates a differential response of the basal ganglia to early environmental challenges, possibly related to processes of pruning during motor development.

Brainstem atrophy on routine MR study in pallidopontonigral degeneration

Sirs, Pallidopontonigral degeneration (PPND) is an autosomal dominant inherited disorder which belongs to the spectrum of frontotemporal dementia linked to chromosome 17 (FTDP-17). It is caused by the N279K mutation in the gene encoding the microtubule-associated protein tau on chromosome 17 [3, 11]. Clinically, PPND is characterized by early and prominent parkinsonism with mild cognitive and behavioral changes, with some differences in clinical presentation between four branches of the PPND kindred [9, 11, 13]. Pathologically, PPND presents with neuronal loss and gliosis, most pronounced in the globus pallidus, pontine and mesencephalic tegmentum and substantia nigra [7, 13]. Immunohistochemistry reveals extensive neuronal and glial tau pathology [7, 8]. Routine magnetic resonance (MR) scanning performed in PPND patients reveals bilateral cortical atrophy, ventricular enlargement, narrowing of the substantia nigra pars compacta and atrophy of the pontine tegmentum [4]. Arvanitakis et al. [1] stressed prominent temporal atrophy in five affected PPND subjects; this was also seen in one asymptomatic N279K mutation carrier who converted to affected status 8 months after the MR study. In some FTDP-17 cases with the MAPT mutation, atrophy of the midbrain and pons was observed at autopsy [14]. Our previous pathological and MR studies confirmed profound brainstem atrophy in progressive supranuclear palsy (PSP) [10, 12]. Because PPND shares some clinical and pathological features with other atypical parkinsonian disorders [1, 8, 9], we decided to examine whether brainstem atrophy is also a feature of PPND and, if so, whether this feature may facilitate the differential diagnosis of PPND. We examined six pathologically confirmed PPND patients [three males, symptom duration 7 ± 3 years, age at death (AAD) 53 ± 5 years] and a historical series [10] of five pathologically confirmed PSP patients [three males, symptom duration 6 ± 2 years, AAD 77 ± 8 years]. The control group consisted of 25 healthy subjects, age and gender-matched to the PPND patients. The time interval between MR imaging and death was 50 ± 13 months in the PPND group and 45 ± 8 months in the PSP group. Six morphometric parameters of the midbrain (MB) and pons were measured on T1-weighted midsagittal and axial MR scans with Image Analyzer software. The technique of MR scanning and image analysis have been described in detail earlier [10]. The Mann–Whitney test was applied. A P value\0.05 was considered to be significant. Results of the study are summarized in Table 1. Midsagittal midbrain (MB) area and the MB area/pons area ratio were significantly smaller in PPND patients than in the controls (Fig. 1a, b), with the PSP cases showing even more pronounced midbrain atrophy. Other measurements did not differ between the PSP and PPND patients. Mean J. L. Slowinski K. J. Schweitzer A. Imamura R. J. Uitti A. J. Strongosky Z. K. Wszolek (&) Department of Neurology, Mayo Clinic Florida, 4500 San Pablo Road, Jacksonville, FL 32224, USA e-mail: wszolek.zbigniew@mayo.edu

Symmetric abnormalities in sulcal patterning in schizophrenia

To compare the morphology of the cerebral cortex and its characteristic pattern of gyri and sulci in individuals with and without schizophrenia, T1-weighted magnetic resonance scans were collected, along with clinical and cognitive information, from 33 individuals with schizophrenia and 30 healthy individuals group-matched for age, gender, race and parental socioeconomic status. Sulcal depth was measured across the entire cerebral cortex by reconstructing surfaces of cortical mid-thickness (layer 4) in each hemisphere and registering them to the human PALS cortical atlas. Group differences in sulcal depth were tested using methods for cluster size analysis and interhemispheric symmetry analysis. A significant group difference was found bilaterally in the parietal operculum, where the average sulcal depth was shallower in individuals with schizophrenia. In addition, group differences in sulcal depth showed significant bilateral symmetry across much of the occipital, parietal, and temporal cortices. In individuals with schizophrenia, sulcal depth in the left hemisphere was correlated with the severity of impaired performance on tests of working memory and executive function.

Thalamic Shape Abnormalities in Individuals with Schizophrenia and Their Nonpsychotic Siblings

Deficits in the volume of the thalamus have been observed in both individuals with schizophrenia and their nonpsychotic relatives. However, no studies to date have examined the underlying pattern of thalamic shape change in relatives of individuals with schizophrenia. This study examined the volume and shape of the thalamus in schizophrenia subjects, their siblings, and healthy control individuals. T1-weighted magnetic resonance scans were collected in a group of young subjects with schizophrenia (mean age, 23 years) and their nonpsychotic siblings (n = 25 pairs), and control subjects and their siblings (n = 40 pairs). Thalamic surfaces were generated using high-dimensional brain mapping. A canonical weighting function was derived from the contrast between schizophrenia and control subjects and then used to generate a canonical shape score for all subjects. Maps of the estimated surface displacement between groups were also created to visualize the thalamic shape differences between groups. The thalamic canonical scores of the siblings of the schizophrenia probands were intermediate between the probands and healthy control subjects. These siblings also displayed an intermediate degree of the inward surface deformation of the anterior and posterior thalamus that was present between schizophrenia probands and controls. There was no main effect of group status on thalamic volume and no significant correlations of the structural measures with measures of psychopathology or cognitive function. Our results indicate that thalamic shape abnormalities are present in relatively young individuals with schizophrenia and their siblings. Inward deformation of the anterior and posterior regions of the thalamus represents a potential neuroanatomical endophenotype of schizophrenia.

Differential Radiation Protection of Salivary Glands versus Tumor by Tempol with Accompanying Tissue Assessment of Tempol by Magnetic Resonance Imaging

The nitroxide free radical, Tempol, was evaluated for potential differential radiation protection of salivary glands and tumor using fractionated radiation. Mechanistic information was explored by monitoring the presence and bioreduction of Tempol in both tissues noninvasively by magnetic resonance imaging (MRI). Female C3H mice were immobilized using custom-made Lucite jigs for localized irradiation (five daily fractions) either to the oral cavity or tumor-bearing leg. Tempol (275 mg/kg) was administered (i.p.) 10 min before each radiation fraction. Salivary gland damage was assessed 8 weeks after radiation by measuring pilocarpine-mediated saliva output. Tumor growth was assessed by standard radiation regrowth methods. Dynamic T1-weighted magnetic resonance scans were acquired before and after Tempol injection using a 4.7T animal MRI instrument. Tempol treatment was found to protect salivary glands significantly against radiation damage (approximately 60% improvement); whereas no tumor protection was observed. Intracellular reduction of Tempol to the nonradioprotective hydroxylamine as assessed by MRI was 2-fold faster in tumor compared with salivary glands or muscle. Tempol provided salivary gland radioprotection and did not protect tumor, consistent with the hypothesis that differential radioprotection by Tempol resides in faster reduction to the nonradioprotective hydroxylamine in tumor compared with normal tissues. The unique paramagnetic properties of Tempol afforded noninvasive MRI monitoring of dynamic changes of Tempol levels in tissue to support the finding. These data support further development and consideration of Tempol for human clinical trials as a selective protector against radiation-induced salivary gland damage.

Abnormalities of cingulate gyrus neuroanatomy in schizophrenia

Objective and methods Abnormalities of the neuroanatomy of the gray matter of the cingulate gyrus, especially its anterior segment, have been suggested to be an important characteristic of schizophrenia. In this study, T1-weighted magnetic resonance scans were collected in 53 individuals with schizophrenia and 68 comparison subjects matched for age, gender, race and parental socioeconomic status. We applied Labeled Cortical Mantle Distance Mapping to assess the volume, surface area and thickness of the cortical mantle within the anterior (AC) and posterior (PC) segments of the cingulate gyrus, excluding the paracingulate gyrus, and related these anatomical measures to measures of psychopathology and illness duration. Results After covarying for total cerebral volume, individuals with schizophrenia showed smaller AC gray matter volume ( p = 0.024), thickness (trend, p = 0.081), but not surface area ( p = 0.16), than comparison subjects. Similar group differences were found for PC gray matter volume ( p = 0.0005) and thickness (trend, p = 0.055), but not surface area ( p = 0.15). Across both groups, there was a significant L > R asymmetry in thickness of the AC, and a significant L > R asymmetry in the surface area of the PC. However, there were no significant group-by-hemisphere interactions. In the individuals with schizophrenia, thinning of the AC, but not the PC, was correlated with a longer duration of illness and a greater severity of psychotic symptoms. Conclusions Individuals with schizophrenia showed smaller gray matter volumes across the entire cingulate gyrus, mostly due to a reduction in cortical mantle thickness. However, structural measures of the AC were more closely related to clinical features of the illness.

Validity of large-deformation high dimensional brain mapping of the basal ganglia in adults with Tourette syndrome

The basal ganglia and thalamus may play a critical role for behavioral inhibition mediated by prefrontal, parietal, temporal, and cingulate cortices. The cortico-basal ganglia-thalamo-cortical loop with projections from frontal cortex to striatum, then to globus pallidus or to substantia nigra pars reticulata, to thalamus and back to cortex, provides the anatomical substrate for this function. In-vivo neuroimaging studies have reported reduced volumes in the thalamus and basal ganglia in individuals with Tourette Syndrome (TS) when compared with healthy controls. However, patterns of neuroanatomical shape that may be associated with these volume differences have not yet been consistently characterized. Tools are being developed at a rapid pace within the emerging field of computational anatomy that allow for the precise analysis of neuroanatomical shape derived from magnetic resonance (MR) images, and give us the ability to characterize subtle abnormalities of brain structures that were previously undetectable. In this study, T1-weighted MR scans were collected in 15 neuroleptic-naïve adults with TS or chronic motor tics and 15 healthy, tic-free adult subjects matched for age, gender and handedness. We demonstrated the validity and reliability of large-deformation high dimensional brain mapping (HDBM-LD) as a tool to characterize the basal ganglia (caudate, globus pallidus and putamen) and thalamus. We found no significant volume or shape differences in any of the structures in this small sample of subjects.

Direct and indirect effects of fetal irradiation on cortical gray and white matter volume in the macaque

Schizophrenia is associated with reductions in thalamic neuronal number and cortical gray matter volume. Exposure of nonhuman primates to x-irradiation in early gestation has previously been shown to decrease thalamic volume and neuronal number. Here we examine whether early gestational irradiation also results in cortical volume reduction. High-resolution, T1-weighted magnetic resonance scans were collected in adult monkeys 1) exposed to irradiation during the early gestational period (E33-E42) corresponding to thalamic neurogenesis, 2) irradiated in midgestation (E70-81) during neocortical neurogenesis, and 3) not exposed to irradiation. Cortical gray matter and white matter volumes were derived via manual segmentation; frontal and nonfrontal volumes were distinguished via sulcal landmarks. Monkeys irradiated in early gestation exhibited a trend reduction in nonfrontal gray matter volume (17%) and significant reductions in white matter volume in frontal (26%) and nonfrontal (36%) lobes. Monkeys irradiated in midgestation had smaller gray (frontal: 28%; nonfrontal: 22%) and white matter (frontal: 29%; nonfrontal: 38%) volumes. The cortical deficits observed in midgestationally irradiated monkeys are consistent with a reduction in cortical neuronal number. Cortical volume reductions following early gestational irradiation may be secondary to reduced thalamic neuronal number and therefore model the thalamocortical pathology of schizophrenia.

Decreased MMP-9 production in primary progressive multiple sclerosis patients.

An increase in MMP-9 levels has been found in relapsing-remitting (RR) multiple sclerosis (MS) showing correlation with magnetic resonance (MR) parameters mainly during relapses. However, data regarding primary progressive (PP) MS is scarce. To determine both the pro and active forms of MMP-9 in PPMS and transitional progressive (TP) MS, RRMS and healthy controls (HC), and to assess the relationship between MMP-9 levels and clinical and radiological variables in PP/TPMS. 73 patients with PP/TPMS, 50 RRMS and 43 HC were studied. Levels of pro and active forms of MMP-9 in serum were measured with ELISA. EDSS and MSFC scores were recorded and T2- and T1-weighted MR scans were obtained at the time of blood sampling and one and two years later for PP/TP MS cases. MMP-9 levels were 202.27 ng/ml for PP/TPMS, 242.20 ng/ml for RRMS and 274.49 ng/ml for HC. MMP-9 levels were significantly lower in PP/TPMS compared to RRMS (P= 0.026) and HC (P= 0.001). No significant correlations were found between MMP-9 levels and clinical scores or radiological parameters. These results point to different regulatory mechanisms of MMP-9 production and/or activity between PP/TPMS and RRMS.

MRI measurements of the cervical spine and their correlation to Pavlov's ratio.

Pavlov's ratio from plain radiographs in patients with neck pain but no radicular symptoms was compared with the areas of the cervical spinal cord and cerebrospinal fluid column on magnetic resonance scans. The area of the cervical canal or cord obviously depends on both the sagittal and transverse diameters. Although the pathology in stenosis of the cervical spine is mainly in the sagittal plane, narrowing only in the sagittal diameter may not indicate significant reduction in the area of the canal. The transverse area of the cord has been shown to correlate well with the pathologic changes of the cord in cervical myelopathy. We correlated Pavlov's ratio on the plain radiographs to the area of the cerebrospinal fluid column and the area of the cord on the magnetic resonance scan. We examined the lateral radiographs and axial and sagittal T2-weighted magnetic resonance scans in the neutral position of the cervical spine (C4-C7) of 87 patients with 332 levels with neck pain but no radicular symptoms and normal magnetic resonance scans. On the magnetic resonance images, the sagittal diameters of the cerebrospinal fluid column and the cord were measured at the midvertebra level on T2 sagittal images from C4 to C7. From the T2 axial images, the area of the cord and the area of the cerebrospinal fluid column were measured at the same levels. The correlation between Pavlov's ratio and the area of cerebrospinal fluid column was moderate, with the highest value of 0.31 at C5. The sagittal diameter of the cerebrospinal fluid column showed variable correlation with the area of the cerebrospinal fluid column. The highest correlation was 0.68 between the sagittal diameter and the area of the cerebrospinal fluid column at C7. The correlation between Pavlov's ratio and the area of the cord is around zero, with the highest correlation of 0.21 at C4. The sagittal diameter of the cord showed a moderate correlation with the area of the cord. This study shows a poor correlation between Pavlov's ratio and the space available for the cord. Therefore, this ratio cannot be solely relied upon to predict the area changes in that plane of the cervical spinal canal.

Topologically controlled segmentation of 3D magnetic resonance images of the head by using morphological operators

This paper proposes a new data-driven segmentation technique of 3D T1-weighted magnetic resonance scans of human head. This technique serves to the construction of individual head models. Several structures of the head are extracted. The morphology-oriented approach combined with an extensive use of topological constraints provides a robust and automatic method requiring minimum user intervention. This new approach is suitable to applications where the topology is one of the main constraints. The originality of the approach lies in the satisfaction of such constraints and in an effort towards robustness.

Can Diffusion- and Perfusion-weighted Magnetic Resonance Imaging Evaluate the Efficacy of Acute Thrombolysis in Patients with Internal Carotid Artery or Middle Cerebral Artery Occlusion?

The value of combined diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) for detecting ischemic lesions of patients with acute ischemic injury was analyzed. Combined pre- and posttreatment DWI and PWI studies were used to assess the efficacy of intra-arterial thrombolysis. Intra-arterial thrombolysis was performed within 6 hours of onset in 10 patients who presented with acute middle cerebral artery or internal carotid artery occlusion. DWI and PWI obtained before and after treatment were studied. The final T2-weighted magnetic resonance scans were obtained 1 month after onset. Thrombolysis resulted in recanalization in seven patients. The mismatch ratio percentage ([initial PWI-initial DWI/initial PWI] x 100) and the rescued ratio percentage ([initial PWI-final T2/initial PWI] x 100) were calculated. The National Institutes of Health Stroke Scale (NIHSS) was used for neurological assessment of stroke severity at admission and at 1 month after onset. In all patients, the mismatch ratio was greater than 60% (mean +/- standard deviation, 81.7 +/- 16.7%) and was significantly correlated with initial NIHSS score (-0.74; P = 0.03), and the rescued ratio was significantly correlated with the NIHSS score 1 month after the insult (r = -0.83; P = 0.01). In patients who exhibited recanalization of the occluded artery (n = 7), the mean rescued ratio was 89.6 +/- 12.8% (range, 63-100%). In addition, the lesion volume on posttreatment DWI scans and final T2-weighted magnetic resonance images was not enlarged; on posttreatment PWI scans, it was significantly decreased. The NHISS score at 1 month after the insult (2.3 +/- 2.1) was markedly improved as compared with the initial NHISS score (10.7 +/- 3.9). In a small number of patients who presented with internal carotid artery or middle cerebral artery occlusion, the DWI/PWI mismatch ratio correlated with the initial neurological severity. The rescued ratio may be an objective indicator of the efficacy of treatment.