Magnetization-prepared Rapid Gradient Echo Research Articles

Evaluation of giant arachnoid granulations with high-resolution 3D-volumetric MR sequences at 3T

PurposeTo evaluate the contribution to the diagnosis of the giant arachnoid granulations (AGs) of three-dimensional (3D) high-resolution magnetic resonance (MR) imaging sequences such as T2-weighted sampling perfection with application optimized contrasts using different flip-angle evolution (SPACE) and post-contrast T1-weighted magnetization prepared rapid gradient echo (MPRAGE). Materials and MethodsPatients with 45 giant AGs were included in this retrospective study. All the patients were performed 3D T2-weighted SPACE and contrast enhanced MR venography sequences, as well as conventional cerebral MR imaging sequences. Post-contrast T1 weighted MPRAGE sequence were performed on 38/45 patients. All cerebral MR examinations were reviewed by the 2 neuroradiologists. Each GA was evaluated carefully to assess location and mean diameter. ResultsThe most common location for giant AGs was at both transverse sinuses. Fluid signal feature within the giant AGs was not isointense to CSF on SE T1 and FLAIR MR imaging in 32 of 45 giant AGs. There were cerebral herniation into AG in 10 (22.2 %) of 45 giant AGs. 33 (73.3 %) of 45 giant AGs had central vein finding into AG in contrast enhanced MR venography. Signal void phenomenon into AG in 3D T2-weighted SPACE MR sequence was identified in 28 (62.2 %) of 45 giant AGs. ConclusionsFluid within giant AGs had no completely CSF-like signal intensity on conventional and 3D high-resolution MR imaging sequences. Majority of CSF-incongruent fluid within giant AGs on conventional sequences is mostly due to intra-AG CSF flow.

Normative hippocampal volumetric measurements using magnetic resonance imaging

Background/aimA wide variety of neurological and psychiatric disorders have been shown to be closely related to changes in hippocampal volume (HV). It appears that hippocampal volumetry will be an indispensable part of clinical practice for a number of neuropsychiatric disorders in the near future. The aim of this study was to establish a normative data set for HV according to age and sex in the general population.Materials and methods Hippocampal magnetic resonance imaging scans of 302 healthy volunteers were obtained using a 1.5 T unit with a 20-channel head coil. The hippocampal volumetric assessment was conducted using the volBrain fully automated segmentation algorithm on coronal oblique T1-weighted magnetization prepared rapid gradient-echo (MP-RAGE) images obtained perpendicular to the long axis of the hippocampus. The mean values of HV of groups according to age and sex were calculated. The associations between HV and age and sex were analyzed.ResultsThe mean HV of the study group was found to be 3.81 ± 0.46 cm3. We found that the mean HV of males (3.94 ± 0.49 cm3) was significantly higher than that of females (3.74 ± 0.42 cm3), and the mean right HV (3.86 ± 0.48 cm3) was significantly higher than that of the left HV (3.78 ± 0.49 cm3) (P = 0.001). Among both females and males, there were statistically significant but poor negative correlations between age and volumetric measurements of both the right and the left hippocampi (P < 0.05).ConclusionThe normative hippocampal volumetric data obtained in this study may be beneficial in clinical applications for many neuropsychiatric diseases, especially for mesial temporal sclerosis and cognitive disorders.

Evaluating the accuracy of geometrical distortion correction of magnetic resonance images for use in intracranial brain tumor radiotherapy.

Determine the 1) effectiveness of correction for gradient-non-linearity and susceptibility effects on both QUASAR GRID3D and CIRS phantoms; and 2) the magnitude and location of regions of residual distortion before and after correction. Using magnetic resonance imaging (MRI) as a primary dataset for radiotherapy planning requires correction for geometrical distortion and non-uniform intensity. Phantom Study: MRI, computed tomography (CT) and cone beam CT images of QUASAR GRID3D and CIRS head phantoms were acquired. Patient Study: Ten patients were MRI-scanned for stereotactic radiosurgery treatment. Correction algorithm: Two magnitude and one phase difference image were acquired to create a field map. A MATLAB program was used to calculate geometrical distortion in the frequency encoding direction, and 3D interpolation was applied to resize it to match 3D T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) images. MPRAGE images were warped according to the interpolated field map in the frequency encoding direction. The corrected and uncorrected MRI images were fused, deformable registered, and a difference distortion map generated. Maximum deviation improvements: GRID3D , 0.27mm y-direction, 0.07mm z-direction, 0.23mm x-direction. CIRS, 0.34mm, 0.1mm and 0.09mm at 20-, 40- and 60-mm diameters from the isocenter. Patient data show corrections from 0.2 to 1.2mm, based on location. The most-distorted areas are around air cavities, e.g. sinuses. The phantom data show the validity of our fast distortion correction algorithm. Patient-specific data are acquired in <2min and analyzed and available for planning in less than a minute.

Combining quantitative susceptibility mapping to the morphometric index in differentiating between progressive supranuclear palsy and Parkinson's disease

PurposeTo determine whether the susceptibility value in the deep gray matter obtained by quantitative susceptibility mapping (QSM) provides additive value to the morphometric index for differentiating progressive supranuclear palsy (PSP) from Parkinson's disease (PD). Materials and methodsPSP- (n = 8) and PD patients (n = 18) and 18 age-matched healthy controls who underwent QSM and 3D magnetization-prepared rapid gradient echo (MPRAGE) sequences. The mean susceptibility values (MSVs) of the deep gray matter structures on QSM- and areas of the midbrain (morphometric index, MI) on 3D MPRAGE images were measured by two neuroradiologists. Analysis of variance, the Scheffe test and receiver operating characteristic (ROC) analysis were conducted to assess differences and discriminate among PSP, PD and controls by the MSVs and the MI. Using the MSV of a structure with the best area under the curve (AUC) and the MI, we created a decision tree to differentiate between PSP and PD. ResultsThe MSVs of the globus pallidus (GP) and substantia nigra (SN) were significantly higher in PSP than PD and the controls (p < .05). By ROC analysis (PSP vs PD), AUC was greatest (0.903) for the GP. The MI was significantly smaller in PSP than PD and the controls (p < .05); AUC (PSP vs PD) was 0.917. The decision tree using cutoff values of 244 parts per billion for MSV of the GP and 74.0 mm2 for MI served to completely differentiate between PSP and PD. ConclusionThe MSV in the GP on QSM images adds value to the MI for differentiating PSP from PD.

Grey matter changes in patients with vestibular migraine

To identify structural changes in the brain regions of patients with vestibular migraine (VM) so as to better understand its pathophysiology. The differences in grey matter (GM) in patients with VM, patients with migraine without aura (MWoA), and healthy controls (HC) were investigated. Using a GE Signa 3 T magnetic resonance imaging (MRI) system, 3D structural images were acquired from 18 VM, 21 MWoA, and 21 age-, gender-, and education level-matched HC using a T1-weighted magnetization-prepared rapid acquisition gradient-echo (MPRAGE) sequence. The volumetric abnormalities of GM were estimated by voxel-based morphometry. Analysis of variance and Bonferroni multiple comparisons were applied. Compared with HC, patients with VM had significantly increased GM volume of the right medial superior frontal gyrus (p=0.008) and the right angular gyrus (p=0.009). Compared to patients with MWoA, patients with VM also had significantly increased volume of the right medial superior frontal gyrus (p=0.001), the right angular gyrus (p=0.008), and the left middle frontal gyrus (p=0.001). The GM volume of some brain regions of patients with VM is significantly larger than the other two groups. The increased GM volume in these brain regions in patients with VM may be related to self-adaptation of the nervous system, leading to an abnormal brain sensitization. Some of the brain regions with increased GM volume identified in this study were involved in assessment, integration, and expectations of pain and were strongly related to mood and anxiety.

Alterations in White Matter Network and Microstructural Integrity Differentiate Parkinson's Disease Patients and Healthy Subjects.

Parkinson’s disease (PD) is a neurodegenerative disease, neuropathologically characterized by progressive loss of neurons in distinct brain areas. We hypothesize that quantifiable network alterations are caused by neurodegeneration. The primary motivation of this study was to assess the specific network alterations in PD patients that are distinct but appear in conjunction with physiological aging. 178 subjects (130 females) stratified into PD patients, young, middle-aged and elderly healthy controls (age- and sex-matched with PD patients), were analyzed using 3D-T1 magnetization-prepared rapid gradient-echo (MPRAGE) and diffusion weighted images acquired in 3T MRI scanner. Diffusion modeling and probabilistic tractography analysis were applied for generating voxel-based connectivity index maps from each seed voxel. The obtained connectivity matrices were analyzed using graph theoretical tools for characterization of involved network. By network-based statistic (NBS) the interregional connectivity differences between the groups were assessed. Measures evaluating local diffusion properties for anisotropy and diffusivity were computed for characterization of white matter microstructural integrity. The graph theoretical analysis showed a significant decrease in distance measures – eccentricity and characteristic path length – in PD patients in comparison to healthy subjects. Both measures as well were lower in PD patients when compared to young and middle-aged healthy controls. NBS analysis demonstrated lowered structural connectivity in PD patients in comparison to young and middle-aged healthy subject groups, mainly in frontal, cingulate, olfactory, insula, thalamus, and parietal regions. These specific network differences were distinct for PD and were not observed between the healthy subject groups. Microstructural analysis revealed diffusivity alterations within the white matter tracts in PD patients, predominantly in the body, splenium and tapetum of corpus callosum, corticospinal tract, and corona radiata, which were absent in normal aging. The identified alterations of network connectivity presumably caused by neurodegeneration indicate the disruption in global network integration in PD patients. The microstructural changes identified within the white matter could endorse network reconfiguration. This study provides a clear distinction between the network changes occurring during aging and PD. This will facilitate a better understanding of PD pathophysiology and the direct link between white matter changes and their role in the restructured network topology.

Improved synthetic T1-weighted images for cerebral tissue segmentation in neurological diseases

Structural cerebral MRI analysis in patients with neurological diseases usually requires T1-weighted datasets for tissue segmentation. For this purpose, synthetic T1-weighted images which are constructed from quantitative maps of the underlying tissue parameters such as the T1 relaxation time and the proton density (PD) may provide advantages over conventional datasets. However, in some cases synthetic images may suffer from specific artifacts, hampering accurate tissue segmentation.The goal was to improve a previously described method for the calculation of synthetic magnetization-prepared rapid gradient-echo (MP-RAGE) datasets from quantitative T1 and PD maps. Improvements comprise a B0-correction for the water-selective excitation pulses employed in T1-mapping and the use of T1-based pseudo-PD maps.Synthetic T1-weighted MP-RAGE datasets were calculated, using the standard and the improved algorithm, for 10 patients with focal epilepsy (caused by focal cortical dysplasia in 9), 10 patients with multiple sclerosis and 10 healthy control subjects and segmented with the Freesurfer toolbox.Visual inspection disclosed that segmentation of the standard synthetic datasets was inaccurate in 6 out of 10 patients with epilepsy, 7 out of 10 patients with multiple sclerosis and 7 out of 10 healthy control subjects, while the improved synthetic datasets resulted in adequate segmentation outcomes in the majority of cases. Only for one patient with multiple sclerosis and one with epilepsy, segmentation in basal temporal regions was not sufficient.Furthermore, data based on the standard algorithm showed strong signal non-uniformities in basal regions. This effect was not present in the improved synthetic datasets.

Synthesizing T1 weighted MPRAGE image from multi echo GRE images via deep neural network

For quantitative neuroimaging studies using multi-echo gradient echo (mGRE) images, additional T1-weighted magnetization prepared rapid gradient echo (MPRAGE) images are often acquired to supplement the insufficient morphometric information of mGRE for tissue segmentation which require lengthened scan time and additional processing such as image registration. This study investigated the feasibility of generating synthetic MPRAGE images from mGRE images using a deep convolutional neural network. Tissue segmentation results derived from the synthetic MPRAGE showed good agreement with those from actual MPRAGE (DSC = 0.882 ± 0.017). There was no statistically significant difference between the mean susceptibility values obtained with the regions of interest from synthetic and actual MPRAGEs and high correlation between the two measurements.

Effect of Off-Target Binding on 18F-Flortaucipir Variability in Healthy Controls Across the Life Span.

Measuring early tau accumulation is important in studying aging and Alzheimer disease and is only as accurate as the signal-to-noise ratio of the tracer. Along with aggregated tau in the form of neurofibrillary tangles, 18F-flortaucipir has been reported to bind to neuromelanin, monoamine oxidase, calcifications, iron, leptomeningeal melanocytes, and microhemorrages. Although 18F-flortaucipir successfully differentiates healthy controls (HCs) from subjects with Alzheimer disease, variability exists in the cortical signal in amyloid-negative HCs. We aimed to explore the relationship between off-target binding signal and variability in the cortical signal in HCs. Methods: Subjects (n = 139) received 11C-Pittsburgh compound B (PIB) and 18F-flortaucipir PET scans and a magnetization-prepared rapid gradient echo MRI scan. PET frames were realigned and coregistered to the MR images, which were segmented using FreeSurfer. In amyloid-negative HCs (n = 90; age range, 21-94 y), 7 nonspecific or off-target binding regions were considered: caudate, pallidum, putamen, thalamus, cerebellar white matter, hemispheric white matter, and choroid plexus. These regions of interest were assigned to 3 similarly behaving groups using principle components analysis, exploratory factor analysis, and Pearson correlations for caudate, putamen, and pallidum (also correlated with age); thalamus and white matter; and choroid plexus. In amyloid-negative HCs with 11C-PIB and 18F-flortaucipir scans, correlations were calculated between white and gray matter before and after partial-volume correction. Results: The correlation between white and gray matter disappeared after partial-volume correction in 11C-PIB (r2 = 0) but persisted for 18F-flortaucipir (r2 = 0.27), demonstrating that the correlation between white and gray matter signal in 18F-flortaucipir is not solely due to partial-volume effects. A linear regression showed that off-target signal from putamen and thalamus together explained 64% of the variability in the cortical signal in amyloid-negative HCs (not seen in amyloid-positive HCs). Variability in amyloid-negative HCs but not amyloid-positive HCs correlated with white matter signal (unrelated to partial-volume effects) and age-related off-target signal (possibly related to iron load). Conclusion: The noise in the 18F-flortaucipir measurement could pose challenges when studying early tau accumulation.

Delineating the topography of amyloid-associated cortical atrophy in Down syndrome

Older adults with Down syndrome (DS) often have Alzheimer's disease (AD) neuropathologies. Although positron emission tomography imaging studies of amyloid deposition (beta amyloid, Aβ) have been associated with worse clinical prognosis and cognitive impairment, their relationships with cortical thickness remain unclear in people with DS. In a sample of 44 DS adults who underwent cognitive assessments, [11C]-PiB positron emission tomography, and T1-weighted magnetization-prepared rapid gradient echo, we used mixed effect models to evaluate the spatial relationships between Aβ binding with patterns of cortical thickness. Partial Spearman correlations were used to delineate the topography of local Aβ-associated cortical thinning. [11C]-PiB nondisplaceable binding potential was negatively associated with decreased cortical thickness. Locally, regional [11C]-PiB retention was negatively correlated with cortical thickness in widespread cortices, predominantly in temporoparietal regions. Contrary to the prevailing evidence in established AD, we propose that our findings implicate Aβ in spatial patterns of atrophy that recapitulated the “cortical signature” of neurodegeneration in AD, conferring support to recent recommendations for earlier disease-interventions.

Automated Generation of Radiologic Descriptions on Brain Volume Changes From T1-Weighted MR Images: Initial Assessment of Feasibility.

Purpose: To examine the feasibility and potential difficulties of automatically generating radiologic reports (RRs) to articulate the clinically important features of brain magnetic resonance (MR) images.Materials and Methods: We focused on examining brain atrophy by using magnetization-prepared rapid gradient-echo (MPRAGE) images. The technology was based on multi-atlas whole-brain segmentation that identified 283 structures, from which larger superstructures were created to represent the anatomic units most frequently used in RRs. Through two layers of data-reduction filters, based on anatomic and clinical knowledge, raw images (~10 MB) were converted to a few kilobytes of human-readable sentences. The tool was applied to images from 92 patients with memory problems, and the results were compared to RRs independently produced by three experienced radiologists. The mechanisms of disagreement were investigated to understand where machine–human interface succeeded or failed.Results: The automatically generated sentences had low sensitivity (mean: 24.5%) and precision (mean: 24.9%) values; these were significantly lower than the inter-rater sensitivity (mean: 32.7%) and precision (mean: 32.2%) of the radiologists. The causes of disagreement were divided into six error categories: mismatch of anatomic definitions (7.2 ± 9.3%), data-reduction errors (11.4 ± 3.9%), translator errors (3.1 ± 3.1%), difference in the spatial extent of used anatomic terms (8.3 ± 6.7%), segmentation quality (9.8 ± 2.0%), and threshold for sentence-triggering (60.2 ± 16.3%).Conclusion: These error mechanisms raise interesting questions about the potential of automated report generation and the quality of image reading by humans. The most significant discrepancy between the human and automatically generated RRs was caused by the sentence-triggering threshold (the degree of abnormality), which was fixed to z-score >2.0 for the automated generation, while the thresholds by radiologists varied among different anatomical structures.

Robotic Radiosurgery for Brain Metastases Diagnosed With Either SPACE or MPRAGE Sequence (CYBER-SPACE)-A Single-Center Prospective Randomized Trial.

Stereotactic radiosurgery (SRS) of brain metastases (BM) is recommended in oligometastatic scenarios as a less toxic treatment alternative to whole-brain radiotherapy. Recent findings support SRS for patients with multiple (>3) BM. Furthermore, advances in MR imaging have facilitated the detection of very small BM, as advances in SRS technology have facilitated the highly conformal and simultaneous treatment of multiple target lesions. To compare efficacy and toxicity of repeated frameless robotic SRS of up to 10 simultaneous BM through a single-center prospective randomized trial. Two hundred patients will be randomized and receive imaging and treatment based on either the highly sensitive SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) or the MPRAGE (magnetization-prepared rapid gradient-echo) magnetic resonance imaging sequence. If during follow-up new metastases are detected, treatment is repeated. The primary endpoint is reached when a patient develops more than 10 simultaneous new BM and is thus deemed unsuitable for further SRS. Overall survival will be assessed as secondary endpoint. Quality of life and neurocognition will be evaluated every 3 mo using CANTAB tests and EORTC (European Organisation for Research and Treatment of Cancer) questionnaires. We expect to show that repeated SRS based on sensitive imaging can delay intracranial dissemination while preserving neurocognitive function and quality of life. The present study is the first to prospectively assess the benefit of sensitive imaging and repeated stereotactic irradiation in the treatment of patients with multiple BM. It represents a novel approach, where in a palliative setting advanced technology in treatment and diagnostics is employed to improve tumor control while also reducing toxicity and preserving quality of life.

Brain Atrophy in Natalizumab-treated Patients with Multiple Sclerosis: A 5-year Retrospective Study.

Studies demonstrated a higher brain volume loss in the first year after initiation of natalizumab treatment than in the second year, but the experiences beyond 24 months are scarce until now. We investigated the evolution of brain volume changes in multiple sclerosis (MS) patients receiving natalizumab for at least 60 months. Using annual 3-dimensional magnetization-prepared rapid acquisition gradient-echo (MPRAGE) sequences acquired on a 3 Tesla magnetic resonance imaging (MRI), we investigated percentage brain volume changes (PBVCs) in 10 MS patients (9 women, mean age at baseline MRI=29±9 years; median Expanded Disability Status Scale=2±1.5; mean disease duration=6±5 years) after 12, 24, 36, 48, and 60 months. PBVCs were statistically higher during the first 12 months (-1.48±1.05%) when compared to 12-24 months (-.6±.61%; P<.05), but not between 12-24 and 24-36 months (-.43±.54%), 24-36 and 36-48 months (-.28±.49%), and 36-48 and 48-60 months (-.33±.49%; P>.05 for all comparisons). Our results contribute to the increasing knowledge of PBVCs in natalizumab-treated MS patients. Our data suggests that after a significant PBVC decrease in the first year, brain atrophy rates show a slowdown during long-term follow-up.

Right hippocampus atrophy is independently associated with Alzheimer's disease with psychosis.

The purpose of this study was to determine whether regionally distributed medial temporal cortex thickness (or hippocampal volume) and frontal lobe volume are independently associated with the onset of Alzheimer's disease (AD) with psychosis. We identified 26 AD patients with psychosis (AD+P) and 48 AD patients without psychosis (AD-P) from the Memory Impairment Clinic at Pusan National University Hospital in South Korea. They were matched for age, gender, duration of AD, and Clinical Dementia Rating sum of box score. All participants met the National Institute of Neurological and Communication Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria for probable AD. Psychosis was diagnosed according to Jeste and Finkel's proposed diagnostic criteria for psychosis of AD. All participants underwent 3-T magnetic resonance imaging, and 3-D magnetization-prepared rapid gradient echo sequence was acquired for each. The FreeSurfer version 5.1 software package was used to analyze cortical thickness and volume on 3-D T1 -weighted images. anova was used to investigate the differences in cortical thickness and the volume of the total frontal cortex, total temporal cortex, and subregions of the medial temporal cortex between groups after age, gender, years of education, Clinical Dementia Rating sum of box score, duration of AD, and total intracranial volume were controlled for. Furthermore, we added the total frontal volume as an additional variable to investigate whether the association between the medial temporal cortex and AD+P is independent of the frontal cortex. We found that both left and right hippocampal volume were smaller in AD+P than in AD-P. In particular, there was a significant difference in right hippocampal volume between the AD+P and AD-P groups after total frontal volume was added as an additional variable. We found that more severe hippocampal atrophy is associated with AD+P than with AD-P. In addition, atrophy of the right hippocampus remained significant among AD+P after adjustment for frontal volume. These findings suggest that right hippocampal atrophy is independently associated with AD+P.

Lateral geniculate nucleus volumetry at 3T and 7T: Four different optimized magnetic-resonance-imaging sequences evaluated against a 7T reference acquisition

PurposeThe lateral geniculate nucleus (LGN) is an essential nucleus of the visual pathway, occupying a small volume (60–160 mm3) among the other thalamic nuclei. The reported LGN volumes vary greatly across studies due to technical limitations and due to methodological differences of volume assessment. Yet, structural and anatomical alterations in ophthalmologic and neurodegenerative pathologies can only be revealed by a precise and reliable LGN representation. To improve LGN volume assessment, we first implemented a reference acquisition for LGN volume determination with optimized Contrast to Noise Ratio (CNR) and high spatial resolution. Next, we compared CNR efficiency and rating reliability of 3D Magnetization Prepared Rapid Gradient Echo (MPRAGE) images using white matter nulled (WMn) and grey matter nulled (GMn) sequences and its subtraction (WMn-GMn) relative to the clinical standard Proton Density Turbo Spin Echo (PD 2D TSE) and the reference acquisition. We hypothesized that 3D MPRAGE should provide a higher CNR and volume determination accuracy than the currently used 2D sequences. Materials and methodsIn 31 healthy subjects, we obtained at 3 and 7 T the following MR sequences: PD-TSE, MPRAGE with white/grey matter signal nulled (WMn/GMn), and a motion-corrected segmented MPRAGE sequence with a resolution of 0.4 × 0.4 × 0.4 mm3 (reference acquisition). To increase CNR, GMn were subtracted from WMn (WMn-GMn). Four investigators manually segmented the LGN independently. ResultsThe reference acquisition provided a very sharp depiction of the LGN and an estimated mean LGN volume of 124 ± 3.3 mm3. WMn-GMn had the highest CNR and gave the most reproducible LGN volume estimations between field strengths. Even with the highest CNR efficiency, PD-TSE gave inconsistent LGN volumes with the weakest reference acquisition correlation. The LGN WM rim induced a significant difference between LGN volumes estimated from WMn and GMn. WMn and GMn LGN volume estimations explained most of the reference acquisition volumes' variance. For all sequences, the volume rating reliability were good. On the other hand, the best CNR rating reliability, LGN volume and CNR correlations with the reference acquisition were obtained with GMn at 7 T. ConclusionWMn and GMn MPRAGE allow reliable LGN volume determination at both field strengths. The precise location and identification of the LGN (volume) can help to optimize neuroanatomical and neurophysiological studies, which involve the LGN structure. Our optimized imaging protocol may be used for clinical applications aiming at small nuclei volumetric and CNR quantification.

Estimating and accounting for the effect of MRI scanner changes on longitudinal whole-brain volume change measurements

ObjectiveLongitudinal MRI studies are often subjected to mid-study scanner changes, which may alter image characteristics such as contrast, signal-to-noise ratio, contrast-to-noise ratio, intensity non-uniformity and geometric distortion. Measuring brain volume loss under these conditions can render the results potentially unreliable across the timepoint of the change. Estimating and accounting for this effect may improve the reliability of estimates of brain atrophy rates. MethodsWe analyzed 237 subjects who were scanned at 1.5 T for the Alzheimer's Disease Neuroimaging Initiative (ADNI) study and were subject to intra-vendor or inter-vendor scanner changes during follow-up (up to 8 years). Sixty-three subjects scanned on GE Signa HDx and HDxt platforms were also subject to a T1-weighted sequence change from Magnetization Prepared Rapid Gradient Echo (MP-RAGE) to Fast Spoiled Gradient Echo with IR Preparation (IR-FSPGR), as part of the transition from ADNI-1 to ADNI-2/GO. Two-timepoint percentage brain volume changes (PBVCs) between the baseline “screening” and the follow-up scans were calculated using SIENA. A linear mixed-effects model with subject-specific random slopes and intercepts was applied to estimate the fixed effects of scanner hardware changes on the PBVC measures. The same model also included a term to estimate the fixed effects of the T1-weighted sequence change. ResultsDifferent hardware upgrade or change combinations led to different offsets in the PBVC (SE; p): Philips Intera to Siemens Avanto, −1.81% (0.30; p < 0.0001); GE Genesis Signa to Philips Intera, 0.99% (0.47, p = 0.042); GE Signa Excite to Signa HDx, 0.33% (0.095, p = 0.0005); GE Signa Excite to Signa HDxt, −0.023% (0.23, p = 0.92); GE Signa Excite to Signa HDx to Signa HDxt, 0.25% (0.095, p = 0.010) and 0.27% (0.16, p = 0.098), respectively; GE Signa HDx to Signa HDxt, −0.24% (0.25, p = 0.34); Siemens Symphony to Symphony TIM, −0.39% (0.16; p = 0.019). The sequence change from MP-RAGE to IR-SPGR was associated with an average −1.63% (0.12; p < 0.0001) change. ConclusionInter-vendor scanner changes generally led to greater effects on PBVC measurements than did intra-vendor scanner upgrades. The effect of T1-weighted sequence change was comparable to that of the inter-vendor scanner changes. Inclusion of the corrective fixed-effects terms for the scanner hardware and T1-weighted sequence changes yielded better model goodness-of-fits, and thus, potentially more reliable estimates of whole-brain atrophy rates.

HIV disease and diabetes interact to affect brain white matter hyperintensities and cognition.

Since the onset of combination antiretroviral therapy use, the incidence of HIV-associated dementia and of HIV encephalitis has fallen dramatically. The present study investigates the extent of white matter hyperintensities (WMHs) among individuals with HIV disease, and factors that predict their presence and their impact on psychomotor speed. A total of 322 men participating in the Multicenter AIDS Cohort Study (185 HIV-infected, age: 57.5 ± 6.0) underwent MRI scans of the brain. T1-weighted magnetization-prepared rapid gradient-echo (MP-RAGE) and T2-weighted Fluid Attenuated Inversion Recovery (FLAIR) images were obtained and processed using an automated method for identifying and measuring WMHs. WMH burden was expressed as the log10 transformed percentage of total white matter. There were no significant associations between WMHs and HIV disease. However, the extent of WMHs was predicted by age more than 60 (β = 0.17), non-white race (β = 0.14), glomerular filtration rate (β = -0.11), and the presence of diabetes (β = 0.12). There were no interactions between HIV status and age (β = -0.03) or between age and diabetes (β = 0.07). However, the interaction between HIV infection and diabetes was significant (β = 0.26). The extent of WMHs was significantly associated with performance on measures of psychomotor speed (β = 0.15). In today's therapeutic environment, in HIV-infected and HIV seronegative individuals, those factors which affect the cerebrovasculature are the best predictors of WMHs. Diabetes has a specific impact among HIV-infected, but not uninfected, men, suggesting the need for more aggressive treatment even in the prediabetes state, especially as WMHs affect cognitive functions.

Corpus Callosum Radiomics-Based Classification Model in Alzheimer's Disease: A Case-Control Study.

Background: Alzheimer's disease (AD) is a progressive neurodegenerative disease that causes the decline of some cognitive impairments. The present study aimed to identify the corpus callosum (CC) radiomic features related to the diagnosis of AD and build and evaluate a classification model.Methods: Radiomics analysis was applied to the three-dimensional T1-weighted magnetization-prepared rapid gradient echo (MPRAGE) images of 78 patients with AD and 44 healthy controls (HC). The CC, in each subject, was segmented manually and 385 features were obtained after calculation. Then, the feature selection were carried out. The logistic regression model was constructed and evaluated according to identified features. Thus, the model can be used for distinguishing the AD from HC subjects.Results: Eleven features were selected from the three-dimensional T1-weighted MPRAGE images using the LASSO model, following which, the logistic regression model was constructed. The area under the receiver operating characteristic curve values (AUC), sensitivity, specificity, accuracy, precision, and positive and negative predictive values were 0.720, 0.792, 0.500, 0.684, 0.731, 0.731, and 0.583, respectively.Conclusion: The results demonstrated the potential of CC texture features as a biomarker for the diagnosis of AD. This is the first study showing that the radiomics model based on machine learning was a valuable method for the diagnosis of AD.

7 Tesla MRI of Balo's concentric sclerosis versus multiple sclerosis lesions.

BackgroundBaló's concentric sclerosis (BCS) is a rare condition characterized by concentrically layered white matter lesions. While its pathogenesis is unknown, hypoxia‐induced tissue injury and chemotactic stimuli have been proposed as potential causes of BCS lesion formation. BCS has been suggested to be a variant of multiple sclerosis (MS). Here, we aimed to elucidate similarities and differences between BCS and MS by describing lesion morphology and localization in high‐resolution 7 Tesla (7 T) magnetic resonance imaging (MRI) scans.MethodsTen patients with Baló‐type lesions underwent 7 T MRI, and 10 relapsing remitting MS patients served as controls. The 7 T MR imaging protocol included 3D T1‐weighted (T1w) magnetization‐prepared rapid gradient echo, 2D high spatial resolution T2*‐weighted (T2*w) fast low‐angle shot and susceptibility‐weighted imaging.ResultsIntralesional veins were visible in the center of all but one Baló‐type lesion. Four Baló‐type lesions displayed inhomogeneous intralesional T2*w signal intensities, which are suggestive of microhemorrhages or small ectatic venules. Eight of 10 BCS patients presented with 97 additional lesions, 36 of which (37%) had a central vein. Lesions involving the cortical gray matter and the U‐fibers were not detected in BCS patients.ConclusionOur findings support the hypothesis that BCS and MS share common pathogenetic mechanisms but patients present with different lesion phenotypes.

Magnetic resonance imaging of tuberous sclerosis complex with or without epilepsy at 7T.

This study was conducted to determine the benefit of magnetic resonance imaging (MRI) at 7T in detecting structural lesions and previously unidentified abnormalities in patients with tuberous sclerosis complex (TSC). Thirteen patients with TSC (8-36years, seven males) previously diagnosed by 3T MRI underwent additional imaging at 7T, which included T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE), T2-weighted turbo spin echo (TSE), SPACE fluid attenuated inversion recovery (FLAIR), susceptibility weighted imaging (SWI), white matter suppressed (WM-suppressed), and gray-white matter tissue border enhancement (GW-TBE) MPRAGE sequences. Subtle lesions, tuberal morphology, and perituberal cortex abnormalities were examined and compared to those observed at 3T MRI using standard sequences. Improved visualization of TSC lesions was achieved in all subjects at 7T compared to 3T imaging, and three subjects received resective surgery. The 7T T1- and T2-weighted images had high spatial resolution and provided a clear delineation of the perituberal cortex. SWI revealed abnormal blood vessel morphology. WM-suppressed and GW-TBE protocols, adjusted specifically for TSC imaging, aided in visualizing lesions and uncovered more extensive subtle lesions and abnormalities beyond the conventionally detected tubers. Due to its high spatial resolution and powerful new imaging protocols, 7T MRI provided a better evaluation of subtle lesions and perituberal details compared with conventional MRI at 3T, with potential implications for diagnosis and operative treatment of TSC and its related epilepsy.