3T MRI Research Articles

Enhancing fine‐tuning efficiency and design optimization of an eight‐channel 3T transmit array via equivalent circuit modeling and Eigenmode analysis

AbstractBackgroundRadiofrequency (RF) transmit arrays play a crucial role in various MRI applications, offering enhanced field control and improved imaging capabilities. Designing and optimizing these arrays, particularly in high‐field MRI settings, poses challenges related to coupling, resonance, and construction imperfections. Numerical electromagnetic simulation methods effectively aid in the initial design, but discrepancies between simulated and fabricated arrays often necessitate fine‐tuning. Fine‐tuning involves iteratively adjusting the array's lumped elements, a complex and time‐consuming process that demands expertise and substantial experience. This process is particularly required for high‐Q‐factor arrays or those with decoupling circuitries, where the impact of construction variations and coupling between elements is more pronounced. In this context, our study introduces and validates an accelerated fine‐tuning approach custom RF transmit arrays, leveraging the arrays equivalent circuit modeling and eigenmode analysis of the scattering (S) parameters.PurposeThis study aims to streamline the fine‐tuning process of lab‐fabricated RF transmit arrays, specifically targeting an eight‐channel degenerate birdcage coil designed for 3T MRI. The objective is to minimize the array's modal reflected power values and address challenges related to coupling and resonance.MethodsAn eight‐channel 3T transmit array is designed and simulated, optimizing capacitor values via the co‐simulation strategy and eigenmode analysis. The resulting values are used in constructing a prototype. Experimental measurements of the fabricated coil's S‐parameters and fitting them into an equivalent circuit model, enabling estimation of self/mutual‐inductances and self/mutual‐resistances of the fabricated coil. Capacitor adjustments in the equivalent circuit model minimize mismatches between experimental and simulated results.ResultsThe simulated eight‐channel array, optimized for minimal normalized reflected power, exhibits excellent tuning and matching and an acceptable level of decoupling (|Snn|≤‐23 dB and |Smn|≤‐11 dB). However, the fabricated array displays deviations, including resonances at different frequencies and increased reflections. The proposed fine‐tuning approach yields an updated set of capacitor values, improving resonance frequencies and reducing reflections. The fine‐tuned array demonstrates comparable performance to the simulation (|Snn|≤‐15 dB and |Smn|≤‐9 dB), mitigating disparities caused by construction imperfections. The maximum error between the calculated and measured S‐parameters is −7 dB.ConclusionThis accelerated fine‐tuning approach, integrating equivalent circuit modeling and eigenmode analysis, effectively optimizes the performance of fabricated transmit arrays. Demonstrated through the design and refinement of an eight‐channel array, the method addresses construction‐related disparities, showcasing its potential to enhance overall array performance. The approach holds promise for streamlining the design and optimization of complex RF coil systems, particularly for high Q‐factor arrays and/or arrays with decoupling circuitry.

MRI-based analysis of the microstructure of the thalamus and hypothalamus and functional connectivity between cortical networks in episodic cluster headache

BackgroundNeuroimaging studies have shown that hypothalamic/thalamic nuclei and other distant brain regions belonging to complex cerebral networks are involved in cluster headache (CH). However, the exact relationship between these areas, which may be dependent or independent, remains to be understood. We investigated differences in resting-state functional connectivity (FC) between brain networks and its relationship with the microstructure of the hypothalamus and thalamus in patients with episodic CH outside attacks and healthy controls (HCs).MethodsWe collected 3T MRI data from 26 patients with CH during the in-bout period outside the attacks and compared them with data from 20 HCs. From resting-state data we derived independent component (IC) networks. We calculated the fractional anisotropy (FA) and mean (MD), axial (AD), and radial (RD) diffusivity values of the hypothalamus and bilateral thalami and correlated them with resting-state IC Z-scores and CH clinical features.ResultsPatients with CH had less FC between the salience network (SN) and left executive control network (ECN) than HCs, but more FC between the default mode network and right ECN. Patients with CH showed lower FA and higher MD microstructural hypothalamic metrics than HCs. Patients with CH had a higher bilateral FA metric in the thalamus than HCs. The AD and RD diffusivity metrics of the hypothalamus were positively correlated with the disease history duration. We found no correlations between the hypothalamic and thalamic diffusivity metrics and the FC of the cortical networks.ConclusionOur findings presented the possibility of a correlation between the FC of the SN and the inability to switch between internalizing and externalizing brain activity during demanding cognitive tasks, such as recurring headaches. Moreover, we found differences in the thalamic and hypothalamic microstructures that may independently contribute to the pathophysiology of CH. These differences may reflect changes in directional organization, cell size, and density.

White Matter Fiber Bundle Alterations Correlate with Gait and Cognitive Impairments in Parkinson’s Disease based on HARDI Data

Background: The neuroanatomical basis of white matter fiber tracts in gait impairments in individuals suffering from Parkinson’s Disease (PD) is unclear. Methods: Twenty-four individuals living with PD and 29 Healthy Controls (HCs) were included. For each participant, two-shell High Angular Resolution Diffusion Imaging (HARDI) and high-resolution 3D structural images were acquired using the 3T MRI. Diffusion-weighted data preprocessing was performed using the orientation distribution function to trace the main fiber tracts in PD individuals. Clinical characteristics between the two groups were compared, and the correlation between the FA value and behavioral data was analyzed. Quantitative gait and clinical parameters were recorded in PD at ON and OFF states, respectively. Results: The mean tract-specific FA values of the right Cingulum Cingulate (rCC) were statistically different between the PD group and the HC group (p =0.047). The FA value of 34-58 equidistant nodes in rCC was positively correlated with Mini-Mental State Examination (MMSE) (r=0.527, p=0.024), Berg Balance Scale (BBS)-OFF (r=0.480, p =0.040), and BBS-ON (r=0.528, p =0.024) scores, while it was negatively correlated with the MDS-UPDRS-III-ON score (r=-0.502, p =0.030). Regarding the gait analysis, the FA value was significantly correlated with velocity, cadence, and stride time of the pace and rhythm domains in both ‘ON’ and ‘OFF’ states, respectively (p<0.05). Conclusion: This study served as an initial exploration to establish that HARDI sequences could be employed as a robust tool for analyzing microstructural alterations in white matter fiber bundles among PD patients, although the sample size was small. We confirmed microstructural integrity impairment of rCC to be significantly associated with both gait and cognitive deficits in patients with PD. Early detection of microstructural changes in rCC and targeted treatment can help improve behavioral disorders. In the future, we intend to further integrate multimodal data with assessments of patient behavior both prior to and following intervention. We will validate our findings within an independent cohort to monitor disease progression and evaluate the efficacy of therapeutic interventions.

Isolated inflammatory involvement of the occipital artery in giant cell arteritis and polymyalgia rheumatica: findings from a retrospective analysis and the critical role of MRI in diagnosis.

Diagnosis of Giant Cell Arteritis (GCA) and Polymyalgia rheumatica (PMR) may be challenging as many patients present with non-specific symptoms. Superficial cranial arteries are predilection sites of inflammatory affection. Ultrasound is typically the diagnostic tool of first choice supplementary to clinical and laboratory examination. Inflammation of temporal arteries can be detected sonographically with high reliability. However, due to the vessel's course and location, occipital arteries evade sonographic detectability. The aim of our study was to evaluate the infestation pattern of superficial cranial arteries in GCA and PMR patients with special focus on the occipital arteries. 90 treatment-naïve patients with clinically and/or histologically proven GCA and/or PMR (51 GCA, 20 PMR, 10 GCA-PMR) were included in the study. All patients underwent contrast-enhanced, fat-suppressed, high-resolution black blood 2D T1-weighted spin echo imaging at 3T MRI. Images were read by three different readers independently. Temporal and occipital arteries were assessed regarding vasculitic affection. Circumferential mural hyperenhancement and thickening of the vessel wall ≥ 600μm was considered positive for vasculitis. 9/90 (10%) of all patients revealed inflammatory changes of the occipital artery only. Prevalence of isolated inflammatory affection of occipital artery was even higher in the GCA subgroup with 7/51 (14%) patients. 14% of GCA patients and 10% of GCA-PMR patients present with signs of inflammation of the occipital artery only. Since the occipital artery is not accessible to routine ultrasound examination, MRI renders incremental value in the diagnosis of GCA and PMR patients.

AI generated synthetic STIR of the lumbar spine from T1 and T2 MRI sequences trained with open-source algorithms.

To train and evaluate an open-source generative adversarial networks (GANs) to create synthetic lumbar spine MRI STIR volumes from T1 and T2 sequences, providing a proof-of-concept that could allow for faster MRI examinations. 1817 MRI examinations with sagittal T1, T2, and STIR sequences were accumulated and randomly divided into training, validation, and test sets. GANs were trained to create synthetic STIR volumes using the T1 and T2 volumes as inputs, optimized using the validation set, then applied to the test set. Acquired and synthetic test set volumes were independently evaluated in a blinded, randomized fashion by three radiologists specializing in musculoskeletal imaging and neuroradiology. Readers assessed image quality, motion artifacts, perceived likelihood of the volume being acquired or synthetic, and presence of 7 pathologies. The optimal model leveraged a customized loss function that accentuated foreground pixels, achieving a structural similarity imaging metric (SSIM) of 0.842, mean absolute error (MAE) of 0.028, and peak signal to noise ratio (PSNR) of 26.367. Radiologists could distinguish synthetic from acquired volumes; however, the synthetic volumes were of equal or better quality in 77% of test patients and demonstrated equivalent or decreased motion artifacts in 78% of test patients. For common pathologies, the synthetic volumes had high positive predictive value (75-100%) but lower sensitivity (0-67%). This work links objective computer vision performance metrics and subject clinical evaluation of synthetic spine MRIs using open-source and reproducible methodologies. High-quality synthetic volumes are generated, reproducing many important pathologies, demonstrating a potential means for expediting imaging protocols. AI = Artificial Intelligence; GANs = general adversarial networks; aqSTIR = acquired STIR volume; sSTIR = synthetically generated STIR volume; SSIM = structural similarity imaging metric; PSNR = peak signal to noise ratio; MAE = mean absolute error.

Hippocampal subfield volume alterations and associations with severity measures in long COVID and ME/CFS: A 7T MRI study.

Long COVID and Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) patients share similar symptoms including post-exertional malaise, neurocognitive impairment, and memory loss. The neurocognitive impairment in both conditions might be linked to alterations in the hippocampal subfields. Therefore, this study compared alterations in hippocampal subfields of 17 long COVID, 29 ME/CFS patients, and 15 healthy controls (HC). Structural MRI data was acquired with sub-millimeter isotropic resolution on a 7 Telsa MRI scanner and hippocampal subfield volumes were then estimated for each participant using FreeSurfer software. Our study found significantly larger volumes in the left hippocampal subfields of both long COVID and ME/CFS patients compared to HC. These included the left subiculum head (long COVID; p = 0.01, ME/CFS; p = 0.002,), presubiculum head (long COVID; p = 0.004, ME/CFS; p = 0.005), molecular layer hippocampus head (long COVID; p = 0.014, ME/CFS; p = 0.011), and whole hippocampal head (long COVID; p = 0.01, ME/CFS; p = 0.01). Notably, hippocampal subfield volumes were similar between long COVID and ME/CFS patients. Additionally, we found significant associations between hippocampal subfield volumes and severity measures of 'Pain', 'Duration of illness', 'Severity of fatigue', 'Impaired concentration', 'Unrefreshing sleep', and 'Physical function' in both conditions. These findings suggest that hippocampal alterations may contribute to the neurocognitive impairment experienced by long COVID and ME/CFS patients. Furthermore, our study highlights similarities between these two conditions.

Impact of Subarachnoid Hemorrhage on Human Glymphatic Function: A Time-Evolution Magnetic Resonance Imaging Study.

Subarachnoid hemorrhage (SAH) is associated with significant mortality and morbidity. The impact of SAH on human glymphatic function remains unknown. This prospective, controlled study investigated whether human glymphatic function is altered after SAH, how it differs over time, and possible underlying mechanisms. Glymphatic enrichment was examined by intrathecal contrast-enhanced magnetic resonance imaging (MRI, glymphatic MRI), utilizing the MRI contrast agent gadobutrol (Gadovist, Bayer AG, GE; 0.50 mmol) as a cerebrospinal fluid (CSF) tracer. The distribution of the tracer in the brain and the subarachnoid and ventricular CSF spaces was assessed using standardized multi-phase MRI T1 sequences, and between-group differences in percentage change of standardized T1 signal unit ratios over time were analyzed by linear mixed models. The study comprised 27 patients with SAH (19 female/8 male; 59.3±10.2 years) who were examined <3 months (n=5), 3 to 6 months (n=10), 6 to 12 months (n=5), or >12 months (n=7) after bleed. A sex- and age-matched control group of 22 individuals (15 female/7 male; 55.5±10.5 years) underwent the same glymphatic MRI protocol but had no neurological or CSF disease. The patients with SAH showed a marked impairment of glymphatic enrichment throughout the brain (particularly addressing the cerebral cortex and subcortical white matter), especially after 24 hours. The glymphatic impairment was accompanied by redistribution of CSF tracer from subarachnoid spaces toward ventricles. These alterations were most pronounced after 3 to 6 months and less after 12 months, though with interindividual variation. CSF tracer transport within perivascular subarachnoid spaces was impaired and coincided with impaired glymphatic enrichment. Human glymphatic function is severely impaired by SAH, particularly shortly after the event. Glymphatic failure is associated with redistribution of CSF from subarachnoid spaces toward ventricles. SAH-related impairment of fluid transport within perivascular subarachnoid spaces may contribute to reduced glymphatic influx. Since patient groups are small, care should be made when concluding about the impact of time on glymphatic function.

Noninvasive blood-brain barrier integrity mapping in patients with high-grade glioma and metastasis by multi-echo time-encoded arterial spin labeling.

In brain tumors, disruption of the blood-brain barrier (BBB) indicates malignancy. Clinical assessment is qualitative; quantitative evaluation is feasible using the K2 leakage parameter from dynamic susceptibility contrast MRI. However, contrast agent-based techniques are limited in patients with renal dysfunction and insensitive to subtle impairments. Assessing water transport times across the BBB (Tex) by multi-echo arterial spin labeling promises to detect BBB impairments noninvasively and potentially more sensitively. We hypothesized that reduced Tex indicates impaired BBB. Furthermore, we assumed higher sensitivity for Tex than dynamic susceptibility contrast-based K2, because arterial spin labeling uses water as a freely diffusible tracer. We acquired 3T MRI data from 28 patients with intraparenchymal brain tumors (World Health Organization Grade 3 & 4 gliomas [n = 17] or metastases [n = 11]) and 17 age-matched healthy controls. The protocol included multi-echo and single-echo Hadamard-encoded arterial spin labeling, dynamic susceptibility contrast, and conventional clinical imaging. Tex was calculated using a T2-dependent multi-compartment model. Areas of contrast-enhancing tissue, edema, and normal-appearing tissue were automatically segmented, and parameter values were compared across volumes of interest and between patients and healthy controls. Tex was significantly reduced (-20.3%) in contrast-enhancing tissue compared with normal-appearing gray matter and correlated well with |K2| (r = -0.347). Compared with healthy controls, Tex was significantly lower in tumor patients' normal-appearing gray matter (Tex,tumor = 0.141 ± 0.032 s vs. Tex,HC = 0.172 ± 0.036 s) and normal-appearing white matter (Tex,tumor = 0.116 ± 0.015 vs. Tex,HC = 0.127 ± 0.017 s), whereas |K2| did not differ significantly. Receiver operating characteristic analysis showed a larger area under the curve for Tex (0.784) than K2 (0.604). Tex is sensitive to pathophysiologically impaired BBB. It agrees with contrast agent-based K2 in contrast-enhancing tissue and indicates sensitivity to subtle leakage.

Cerebral perfusion alterations in healthy young adults due to two genetic risk factors of Alzheimer's disease: APOE and MAPT.

Functional brain changes such as altered cerebral blood flow occur long before the onset of clinical symptoms in Alzheimer's disease (AD) and other neurodegenerative disorders. While cerebral hypoperfusion occurs in established AD, middle-aged carriers of genetic risk factors for AD, including APOE ε4, display regional hyperperfusion due to hypothesised pleiotropic or compensatory effects, representing a possible early biomarker of AD and facilitating earlier AD diagnosis. However, it is not clear whether hyperperfusion already exists even earlier in life. Here, 160 young and cognitively healthy participants from the Chinese PREVENT cohort underwent 3 T arterial spin labelling and T1 MRI and genetic testing for APOE and MAPT rs242557 status. Using FSL, we performed a whole brain voxel-wise analysis and a global mean grey matter analysis comparing for the effects of both risk genes on cerebral perfusion. No significant alterations were seen for APOE genotype, but in MAPT rs242557 A carriers, we observed a significantly hyperperfusion in the left anterior cingulate cortex and left insular cortex. There were no effects of APOE or MAPT status on the global perfusion. These results are novel and may suggest that MAPT genotypes demonstrated a distinct hemodynamic profile in a very young age.

Automatic Characterization of Prostate Suspect Lesions on T2-Weighted Image Acquisitions Using Texture Features and Machine-Learning Methods: A Pilot Study.

Background: Prostate cancer (PCa) is the most frequent neoplasia in the male population. According to the International Society of Urological Pathology (ISUP), PCa can be divided into two major groups, based on their prognosis and treatment options. Multiparametric magnetic resonance imaging (mpMRI) holds a central role in PCa assessment; however, it does not have a one-to-one correspondence with the histopathological grading of tumors. Recently, artificial intelligence (AI)-based algorithms and textural analysis, a subdivision of radiomics, have shown potential in bridging this gap. Objectives: We aimed to develop a machine-learning algorithm that predicts the ISUP grade of manually contoured prostate nodules on T2-weighted images and classifies them into clinically significant and indolent ones. Materials and Methods: We included 55 patients with 76 lesions. All patients were examined on the same 1.5 Tesla mpMRI scanner. Each nodule was manually segmented using the open-source 3D Slicer platform, and textural features were extracted using the PyRadiomics (version 3.0.1) library. The software was based on machine-learning classifiers. The accuracy was calculated based on precision, recall, and F1 scores. Results: The median age of the study group was 64 years (IQR 61-68), and the mean PSA value was 11.14 ng/mL. A total of 85.52% of the nodules were graded PI-RADS 4 or higher. Overall, the algorithm classified indolent and clinically significant PCas with an accuracy of 87.2%. Further, when trained to differentiate each ISUP group, the accuracy was 80.3%. Conclusions: We developed an AI-based decision-support system that accurately differentiates between the two PCa prognostic groups using only T2 MRI acquisitions by employing radiomics with a robust machine-learning architecture.

Association Between Paramagnetic Rim Lesions and Pulvinar Iron Depletion in Persons with Multiple Sclerosis

Background: The deep gray matter (DGM), especially the pulvinar, and the white matter surrounding chronic active lesions have demonstrated depleted iron levels, indicating a possible mechanistic link. However, no studies have investigated the potential relationship between these phenomena. Objectives: The study aimed to determine whether PRLs were associated with pulvinar iron depletion and, if so, whether this relationship was spatially mediated. Methods: This retrospective analysis included 139 people with MS (pwMS) and 43 HCs scanned at 3T MRI at baseline and after 5.4 ± 0.6 years. Pulvinar iron concentrations (cFe) and masses (mFe) were estimated from quantitative susceptibility maps and tested for associations with PRLs. A separate cohort of 96 pwMS with PRLs and propensity-matched HCs was included to evaluate peri-plaque normal-appearing white matter (NAWM) abnormalities. Results: PRL number was associated with greater decline in pulvinar cFe (β = -0.265, p = 0.005) and mFe (β = -0.256, p = 0.006). Peri-plaque NAWM susceptibility was increased 11mm surrounding PRLs, outside which shorter PRL-to-pulvinar distance was associated with greater decline in pulvinar cFe (β = 0.380, p = 0.005) and mFe (β = 0.348, p = 0.022). Conclusions: Our findings support a spatially-related relationship between PRLs and chronic pulvinar iron depletion.

PLB2Tau mice are impaired in novel and temporal object recognition and show corresponding traits in brain MRI

Recent clinical trials targeting tau protein aggregation have heightened interest in tau-based therapies for dementia. Success of such treatments depends crucially on translation from non-clinical animal models. Here, we present the age profile of the PLB2Tau knock-in model of fronto-temporal dementia in terms of cognition, and by utilising a directly translatable magnetic resonance imaging approach. Separate cohorts of mice aged 3, 6 and 12 months were tested in an object recognition protocol interrogating visual, spatial, and temporal discrimination in consecutive tests. Upon completion of their behavioural testing, animals were recorded in a 7T MRI for brain structural integrity and diffusion tensor imaging (DTI) analysis.We report that PLB2Tau mice presented with an age-dependent deficit in novel object discrimination relative to wild-type controls at 6 and 12 months. Spatial and temporal discrimination, though not significantly different from controls, appeared extremely challenging for PLB2Tau subjects, especially at 12 months, since they explored objects less than controls and were devoid of memory. Controls readily recalled all relevant object-related information. At the same time, the T2 weighted voxel-based image analysis revealed a progressive shrinkage of total brain volumes in 6- and 12-month-old PLB2Tau mice as well as relative striatal, but not hippocampal volumes. A regional DTI analysis yielded only reduced mean diffusivity of the fimbria, but not CA1 or dentate gyrus, amygdala, cingulate cortex, or corpus callosum.These data confirm the PLB2Tau mouse as a translationally useful model for dementia research and suggest the importance of the hippocampal input as a determinant for novel object discrimination.

Deconstructing the self and reshaping perceptions: An intensive whole-brain 7T MRI case study of the stages of insight during advanced investigative insight meditation.

The stages of insight (SoI) are a series of psychological realizations experienced through advanced investigative insight meditation (AIIM). SoI provide a powerful structured framework of AIIM for understanding and evaluating insight-based meditative development through changes in perception, experiences of self, cognition, and emotional processing. Yet, the neurophenomenology of SoI remains unstudied due to methodological difficulties, rarity of suitable advanced meditation practitioners, and dominant research emphasis on attention-based meditative practices. We investigated the neurophenomenology of SoI in an intensively sampled adept meditator case study (4 hr 7T fMRI collected in 26 runs with concurrent phenomenology) who performed SoI and rated specific aspects of experience immediately thereafter. Linear mixed models and correlations were used to examine relations among the cortex, subcortex, brainstem, and cerebellum, and SoI phenomenology. We identified distinctive whole-brain activity patterns associated with specific SoI, and that were different from two non-meditative control states. SoI consistently deactivated regions implicated in self-related processing, including the medial prefrontal cortex and temporal poles, while activating regions associated with awareness and perception, including the parietal and visual cortices, caudate, several brainstem nuclei, and cerebellum. Patterns of brain activity related to affective processing and SoI phenomenology were also identified. Our study presents the first neurophenomenological evidence that SoI shifts and deconstructs self-related perception and conceptualization, and increases general awareness and perceptual sensitivity and acuity. Our study provides SoI as a foundation for investigative, and advanced meditation in particular.

Lateralization study of the basal ganglia, thalamus and supplying arteries in healthy individuals based on structure and connectivity analysis using 7.0T MRI.

The human cerebral cortex is known for its hemispheric specialization, which underpins a variety of functions and activities. However, it is not well understood if similar lateralization exists within the deep gray matter nuclei, such as the basal ganglia (BG) and thalamus, and their associated arteries, including the lenticulostriate arteries (LSAs). To explore this, we analyzed images from 7T MRI scans of 40 healthy young individuals. We isolated the LSAs and analyzed their morphological characteristics. Additionally, we segmented the bilateral BG and thalami into 28 subregions based on the Brainnetome atlas and calculated their volumes using single-subject voxel-based morphometry (VBM) analysis. We also obtained four parameters from Diffusion Tensor Imaging (DTI) within these 28 subregions. Bilateral comparisons were conducted using paired t-tests for all measurements. Connectivity-network matrices, based on the number of connecting fibers and fractional anisotropy between subregions, were constructed. The results showed that in the right-handed dominant population, we observed that the total number and length of LSAs in the left hemisphere exceeded those in the right. Among the 28 subregions, several showed leftward volume dominance, including the ventral caudate, globus pallidus, ventromedial putamen, medial pre-frontal thalamus, occipital thalamus, and caudal temporal thalamus. In contrast, the nucleus accumbens, dorsal caudate, dorsolateral putamen, pre-motor thalamus, sensory thalamus, posterior parietal thalamus, and lateral pre-frontal thalamus showed rightward volume dominance. Except for the ventral medial putamen (vmPu), all other subnuclei displayed at least three DTI measures with left-right differences. The connectivity between subregions revealed distinct patterns in the bilateral hemispheres, with a leftward dominance. Collectively, these findings enhance our understanding of lateralization within subcortical structures.

Added value of Dixon MRI in quantification of liver fat in nonalcoholic fatty liver disease

Background The Dixon method for fat/water separation employs a technique for achieving consistent fat suppression by utilizing water-only reconstruction. The fat-only Dixon technique is a tool for identifying microscopic fat and assessing pathological lesions of concern. Aim To investigate the MRI Dixon fat fraction role in assessing fat deposition among nonalcoholic fatty liver disease (NAFLD) cases and correlation with ultrasonography (USG). Patients and methods This study included 30 cases, with an age range falling between 19 and 80 years, both sexes. We included those with one or more risk factors for NAFLD in which diffuse hepatic steatosis or normal liver was identified utilizing USG of the abdomen. Participants were examined using USG examination and MRI. Results Good agreement (k=0.615) between two imagining methods (MRI T1 Dixon and USG) in detecting fatty liver with significant difference between diagnostic confidence (accuracy) of MRI T1 Dixon and USG in detection of fatty liver (P=0.005). A significant variance was observed among the grading of fatty liver by MRI T1 Dixon and the presence of METs criteria and alanine aminotransferase level (P&lt;0.05). By USG, a moderate agreement between fatty liver grading utilizing MRI T1 Dixon and fatty liver grading utilizing USG (k=0.526). Conclusions Dixon MRI was a noninvasive method for quantifying fat fraction in NAFLD. When comparing the fatty liver grading on USG with the assessment of liver fat with MRI T1 Dixon of the liver, there was a significant overlap in the fat percentage within each grade.

Change in transverse relaxation rates (R2) and change in cognition for older African Americans

AbstractDespite transverse relaxation rate (R2) being one of the fundamental contrasts in MRI, most investigations of brain R2 and cognition have been cross‐sectional and conducted in predominantly non‐Latino White adults. We investigated the profile of R2 as related to cognition in 212 older African Americans (~75 years of age) with longitudinal 3T MRI scans and cognitive test data to determine how changes in R2 are associated with changes in cognition. For each participant, the slopes of global cognitive and five cognitive domain scores were each separately combined with voxel‐specific slopes of R2 in whole brain voxelwise analyses. Participants with less negative rates of R2 change within left basal ganglia and centrum semiovale, bilateral hippocampal complex and temporal gyri, parietooccipital white matter, as well as posterior cingulate displayed less negative slopes in global cognition. Similar associations were seen for regional R2 change and episodic memory (most robustly within bilateral hippocampi) as well as semantic memory (left greater than right hemisphere involvement). Results suggest a relatively wide distribution of regional associations between rates of changes in R2 and changes in global cognition for older African Americans; a profile that became more regionally specific when considering individual cognitive domains. Relative preservation of tissue integrity across grey and white matter, and in key regions associated with specific cognitive domains, is associated with slower cognitive decline for older African Americans. These results may lay the foundation for more directed work to support healthy brain aging in older African Americans.

SWI brush sign of cerebral parenchymal veins in central nervous system diseases.

Brush sign (BS) was first reported as prominent hypointensity of deep medullary veins and subependymal veins on T2*-weighted images at 3T MRI in patients with acute stroke in the territory of the middle cerebral artery. Subsequently, BS in central nervous system (CNS) diseases such as moyamoya disease, cerebral venous thrombosis, and Sturge-Weber syndrome was also described on susceptibility-weighted imaging (SWI), and the clinical implications of BS were discussed. The purpose of this review is to demonstrate BS on SWI in various CNS diseases and its mechanisms in the above-mentioned diseases. We also explain the clinical implications of this finding in each disease.

Cine-MRI of Deglutition: A Systematic Review.

Videofluoroscopy, recognized as the gold standard for dysphagia exploration, has inherent limitations, including poor soft tissue discrimination, radiation exposure, and aspiration risk. In response to these challenges, cine-MRI of swallowing has evolved over the past three decades, yielding diverse methodologies and results across various studies.This systematic review, conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, meticulously outlines cine-MRI protocols, applications, advantages, and limitations. Our qualitative analysis encompasses 36 studies involving 715 subjects from 2001 to 2023. Cine-MRI, a promising alternative, provides safe application for dysphagic patients, offering insights into the intricacies of deglutition mechanisms and eliminating the necessity for oral contrast material. Notably, this approach is adaptable to both 1.5 and 3T MRI scanners with specific image acceleration protocols.Despite these merits, a crucial gap remains, as no non-inferiority prospective study has yet been conducted to compare cine-MRI with the gold standard. Additionally, the lack of uniform swallowing assessment criteria and the uncertain impact of the supine position underscore the need for further investigation. In conclusion, while cine-MRI of deglutition emerges as a compelling tool for dysphagia exploration, its precise indications and role in the diagnostic approach to swallowing disorders necessitate comprehensive evaluation in future studies.

ORACLE: An analytical approach for T1, T2, proton density, and off-resonance mapping with phase-cycled balanced steady-state free precession.

To develop and validate a novel analytical approach simplifying , , proton density (PD), and off-resonance quantifications from phase-cycled balanced steady-state free precession (bSSFP) data. Additionally, to introduce a method to correct aliasing effects in undersampled bSSFP profiles. Off-resonant-encoded analytical parameter quantification using complex linearized equations (ORACLE) provides analytical solutions for bSSFP profiles. which instantaneously quantify , , proton density (PD), and . An aliasing correction formalism was derived to allow undersampling of bSSFP profiles. ORACLE was used to quantify , , PD, / , and based on fully sampled ( ) bSSFP profiles from numerical simulations and 3T MRI experiments in phantom and 10 healthy subjects' brains. Obtained values were compared with reference scans in the same scan session. Aliasing correction was validated in subsampled ( ) bSSFP profiles in numerical simulations and human brains. ORACLE quantifications agreed well with input values from simulations and phantom reference values (R2 = 0.99). In human brains, and quantifications when compared with reference methods showed coefficients of variation below 2.9% and 3.9%, biases of 182 and 16.6 ms, and mean white-matter values of 642 and 51 ms using ORACLE. The quantification differed less than 3 Hz between both methods. PD and maps had comparable histograms. The maps effectively identified cerebrospinal fluid. Aliasing correction removed aliasing-related quantification errors in undersampled bSSFP profiles, significantly reducing scan time. ORACLE enables simplified and rapid quantification of , , PD, and from phase-cycled bSSFP profiles, reducing acquisition time and eliminating biomarker maps' coregistration issues.

Radiomic Consensus Clustering in Glioblastoma and Association with Gene Expression Profiles.

Glioblastoma (GBM) is the most common malignant primary central nervous system tumor with extremely poor prognosis and survival outcomes. Non-invasive methods like radiomic feature extraction, which assess sub-visual imaging features, provide a potentially powerful tool for distinguishing molecular profiles across groups of patients with GBM. Using consensus clustering of MRI-based radiomic features, this study aims to investigate differential gene expression profiles based on radiomic clusters. Patients from the TCGA and CPTAC datasets (n = 114) were included in this study. Radiomic features including T1, T1 with contrast, T2, and FLAIR MRI sequences were extracted using PyRadiomics. Selected radiomic features were then clustered using ConsensusClusterPlus (k-means base algorithm and Euclidean distance), which iteratively subsamples and clusters 80% of the data to identify stable clusters by calculating the frequency in which each patient is a member of a cluster across iterations. Gene expression data (available for n = 69 patients) was analyzed using differential gene expression (DEG) and gene set enrichment (GSEA) approaches, after batch correction using ComBat-seq. Three distinct clusters were identified based on the relative consensus matrix and cumulative distribution plots (Cluster 1, n = 25; Cluster 2, n = 46; Cluster 3, n = 43). No significant differences in patient demographic characteristics, MGMT methylation status, tumor location, or overall survival were identified across clusters. Differentially expressed genes were identified in Cluster 1, which have been previously associated with GBM prognosis, recurrence, and treatment sensitivity. GSEA of Cluster 1 showed an enrichment of genes upregulated for immune-related and DNA metabolism pathways and genes downregulated in pathways associated with protein and histone deacetylation. Clusters 2 and 3 exhibited fewer DEGs which failed to reach significance after multiple testing corrections. Consensus clustering of radiomic features revealed unique gene expression profiles in the GBM cohort which likely represent subtle differences in tumor biology and radiosensitivity that are not visually discernible, underscoring the potential of radiomics to serve as a non-invasive alternative for identifying GBM molecular heterogeneity. Further investigation is still required to validate these findings and their clinical implications.