Gradient-echo Echo-planar Imaging Research Articles

Identification of peroneal artery perforators using non-contrast-enhanced T2prep multi-shot gradient echo planar imaging MRA.

The purpose of this study was to investigate the spatial resolution of non-contrast-enhanced (CE) T2prep multi-shot gradient echo planar imaging (MSG-EPI) magnetic resonance angiography (MRA) required to identify peroneal artery perforators and demonstrate its effectiveness in preoperative simulation. Twenty-six legs of 13 volunteers were scanned using non-CE T2prep MSG-EPI-MRA at three spatial resolutions: 1.0-, 0.8-, and 0.6-mm isotropic voxels. The location and number of peroneal artery perforators that could be candidates for free fibula flaps were identified by consensus among three plastic surgeons. Surgeons distinguished between septocutaneous and musculocutaneous perforators using MRA, and confirmed the accuracy of their presence and identification using ultrasonography (US). The ability to detect hypoplasia or stenosis of the anterior tibial, posterior tibial, and peroneal arteries was evaluated by confirming the consistency between the MRA and US results. The number of cutaneous perforators identified using MRA and confirmed using US was 39, 51, and 52 at each respective resolution. The discrimination accuracies between septocutaneous and musculocutaneous perforators were 92.3%, 96.1%, and 96.2%. The number of identified septocutaneous perforators was 1.3 ± 0.6, 1.6 ± 0.8, and 1.7 ± 0.8 at 1.0-, 0.8-, and 0.6-mm data, respectively. All the MRA results, including hypoplasia and stenosis, were consistent with the US results. Non-CE T2prep MSG-EPI-MRA with a spatial resolution of 0.8mm or less shows promise for identifying septocutaneous perforators of the peroneal artery, suggesting its potential as an alternative to conventional imaging methods for the preoperative planning of free fibula osteocutaneous flap transfers.

Pseudo-resting-state functional MRI derived from dynamic susceptibility contrast perfusion MRI can predict cognitive impairment in glioma.

Resting-state functional MRI (rs-fMRI) can be used to estimate functional connectivity (FC) between different brain regions, which may be of value for identifying cognitive impairment in patients with brain tumors. Unfortunately, neither rs-fMRI nor neurocognitive assessments are routinely assessed clinically, mostly due to limitations in exam time and cost. Since DSC perfusion MRI is often used clinically to assess tumor vascularity and similarly uses a gradient echo-EPI sequence for T2*sensitivity, we theorized a "pseudo-rs-fMRI" signal could be derived from DSC perfusion to simultaneously quantify FC and perfusion metrics, and these metrics can be used to estimate cognitive impairment in patients with brain tumors. N=24 consecutive patients with gliomas were enrolled in a prospective study that included DSC perfusion MRI, rs-fMRI, and neurocognitive assessment. Voxel-wise modeling of contrast bolus dynamics during DSC acquisition was performed and then subtracted from the original signal to generate a residual "pseudo-rs-fMRI" signal. Following the pre-processing of pseudo-rs-fMRI, full rs-fMRI, and a truncated version of the full rs-fMRI (first 100 timepoints) data, the default mode, motor, and language network maps were generated with atlas-based ROIs. Dice scores were calculated for the resting-state network maps from pseudo-rs-fMRI and truncated rs-fMRI using the full rs-fMRI maps as reference. Seed-to-voxel and ROI-to-ROI analyses were performed to assess FC differences between cognitively impaired and non-impaired patients. Dice scores for the group-level and patient-level (mean±SD) default mode, motor, and language network maps using pseudo-rs-fMRI were 0.905/0.689±0.118 (group/patient), 0.973/0.730±0.124, and 0.935/0.665±0.142, respectively. There was no significant difference in Dice scores between pseudo-rs-fMRI and the truncated rs-fMRI default mode (P=0.97) or language networks (P=0.30), but there was a difference in motor networks (P=0.02). A multiple logistic regression classifier applied to ROI-to-ROI FC networks using pseudo-rs-fMRI could identify cognitively impaired patients (Sensitivity=84.6%, Specificity=63.6%, ROC AUC=0.7762±0.0954 (SE), P=0.0221) and performance was not significantly different than full rs-fMRI predictions (AUC=0.8881±0.0733 (SE), P=0.0013, P=0.29 compared to pseudo-rs-fMRI). DSC perfusion MRI-derived pseudo-rs-fMRI data can be used to perform typical rs-fMRI FC analyses that may identify cognitive decline in patients with brain tumors while still simultaneously performing perfusion analyses.ABBREVIATIONS: AUC = Area under curve; BOLD = Blood oxygenation level dependent; FC = Functional connectivity; MNI = Montreal Neurological Institute; ROC = Receiver operating characteristic; Rs-fMRI = Resting-state functional MRI.

Resting-state functional magnetic resonance imaging: features of statistical processing of ROI-analysis data

BACKGROUND: In many works, to study intra- and inter-network connections, a method for constructing networks is used — ROI-analysis (region of interest analysis). The conflicting results obtained when assessing brain connectivity using ROI-analysis can be explained by methodological differences associated with the statistical processing of fMRI data. In this regard, it is relevant to conduct a study with a comparative assessment of various statistical methods of ROI-analysis in processing resting state fMRI data.
 AIM: to assess the functional connectivity of the main resting state networks of the brain using ROI-analysis using various statistical approaches.
 MATERIALS AND METHODS: We analyzed data from 15 resting-state fMRI studies of the brain of patients without neurological and mental pathology. fMRI scanning was performed on a Phillips Ingenia 1.5 T scanner using a gradient echo-planar imaging (EPI-BOLD) sequence. ROI-analysis was used to build networks. Statistical data processing was performed using methods: functional network connectivity, randomization/permutation spatial pairwise clustering statistics, and threshold-free cluster enhancement.
 RESULTS: The number of connections between the structures of brain networks recorded using the method of functional network connectivity is 280, spatial pairwise clustering — 186, threshold-free cluster enhancement — 182. An interesting fact is that negative connections were identified only when using parametric statistics.
 CONCLUSION: A comparative assessment of methods for statistical processing of fMRI data during ROI-analysis was carried out. The functional network connectivity method based on multivariate parametric statistics turned out to be more informative than randomization/permutation spatial pairwise clustering statistics and the method based on threshold-free cluster enhancement. Despite the growing popularity in recent years of resting-state fMRI in the study of functional activity and connectivity of the brain, there are no standardized algorithms for constructing networks of the brain.

Altered Dynamics of Brain Spontaneous Activity and Functional Networks Associated With Cognitive Impairment in Patients With Type 2 Diabetes.

Cognitive impairment is increasingly recognized as an important comorbidity and complication of type 2 diabetes (T2D), affecting patients' quality of life and diabetes management. Dynamic brain activity indicators can reflect changes in key neural activity patterns of cognition and behavior. To investigate dynamic functional connectivity (DFC) changes and spontaneous brain activity based on resting-state functional magnetic resonance imaging (rs-fMRI) in patients with T2D, exploring their correlations with clinical features. Retrospective. Forty-five healthy controls (HCs) (22 males and 23 females) and 102 patients with T2D (57 males and 45 females). 3.0 T/T1-weighted imaging and rs-fMRI with gradient-echo planar imaging sequence. Functional networks were created using independent component analysis. DFC states were determined using sliding window approach and k-means clustering. Spontaneous brain activity was assessed using dynamic regional homogeneity (dReHo) variability. One-way analysis of variance and post hoc analysis were used to compare the essential information including demographics, clinical data, and features of DFC and dReHo among groups. Diagnostic performance was assessed using receiver operating characteristic (ROC) curve. P-values <0.05 were taken to indicate statistical significance. T2D group had significantly decreased mean dwell time and fractional windows in state 4 compared to HC. T2D with mild cognitive impairment showed significantly increased dReHo variability in left superior occipital gyrus compared to T2D with normal cognition. Mean dwell time and number of fractional windows of state 4 both showed significant positive correlations with the Montreal cognitive assessment scores (r = 0.309; r = 0.308, respectively) and the coefficient of variation of dReHo was significantly positively correlated with high-density lipoprotein cholesterol (r = 0.266). The integrated index had an area under the curve of 0.693 (95% confidence interval = 0.592-0.794). Differences in DFC and dynamic characteristic of spontaneous brain activity associated with T2D-related functional impairment may serve as indicators for predicting symptom progression and assessing cognitive dysfunction. 2 TECHNICAL EFFICACY: Stage 2.

Automated Quality Evaluation Index for Arterial Spin Labeling Derived Cerebral Blood Flow Maps.

Arterial spin labeling (ASL) derived cerebral blood flow (CBF) maps are prone to artifacts and noise that can degrade image quality. To develop an automated and objective quality evaluation index (QEI) for ASL CBF maps. Retrospective. Data from N = 221 adults, including patients with Alzheimer's disease (AD), Parkinson's disease, and traumatic brain injury. Pulsed or pseudocontinuous ASL acquired at 3 T using non-background suppressed 2D gradient-echo echoplanar imaging or background suppressed 3D spiral spin-echo readouts. The QEI was developed using N = 101 2D CBF maps rated as unacceptable, poor, average, or excellent by two neuroradiologists and validated by 1) leave-one-out cross validation, 2) assessing if CBF reproducibility in N = 53 cognitively normal adults correlates inversely with QEI, 3) if iterative discarding of low QEI data improves the Cohen's d effect size for CBF differences between preclinical AD (N = 27) and controls (N = 53), 4) comparing the QEI with manual ratings for N = 50 3D CBF maps, and 5) comparing the QEI with another automated quality metric. Inter-rater reliability and manual vs. automated QEI were quantified using Pearson's correlation. P < 0.05 was considered significant. The correlation between QEI and manual ratings (R = 0.83, CI: 0.76-0.88) was similar (P = 0.56) to inter-rater correlation (R = 0.81, CI: 0.73-0.87) for the 2D data. CBF reproducibility correlated negatively (R = -0.74, CI: -0.84 to -0.59) with QEI. The effect size comparing patients and controls improved (R = 0.72, CI: 0.59-0.82) as low QEI data was discarded iteratively. The correlation between QEI and manual ratings (R = 0.86, CI: 0.77-0.92) of 3D ASL was similar (P = 0.09) to inter-rater correlation (R = 0.78, CI: 0.64-0.87). The QEI correlated (R = 0.87, CI: 0.77-0.92) significantly better with manual ratings than did an existing approach (R = 0.54, CI: 0.30-0.72). Automated QEI performed similarly to manual ratings and can provide scalable ASL quality control. 2 TECHNICAL EFFICACY: Stage 1.

Development and Validation of Interpretable Machine Learning Models for Clinically Significant Prostate Cancer Diagnosis in Patients With Lesions of PI-RADS v2.1 Score ≥3.

For patients with PI-RADS v2.1 ≥ 3, prostate biopsy is strongly recommended. Due to the unsatisfactory positive rate of biopsy, improvements in clinically significant prostate cancer (csPCa) risk assessments are required. To develop and validate machine learning (ML) models based on clinical and imaging parameters for csPCa detection in patients with PI-RADS v2.1 ≥ 3. Retrospective. One thousand eighty-three patients with PI-RADS v2.1 ≥ 3, randomly split into training (70%, N = 759) and validation (30%, N = 324) datasets, and 147 patients enrolled prospectively for testing. 3.0 T scanners/T2-weighted fast spin echo sequence and DWI with diffusion-weighted single-shot gradient echo planar imaging sequence. The factors evaluated for csPCa detection were age, prostate specific antigen, prostate volume, and the diameter and location of the index lesion, PI-RADSv2.1. Five ML models for csPCa detection were developed: logistic regression (LR), extreme gradient boosting, random forest (RF), decision tree, and support vector machines. The csPCa was defined as Gleason grade ≥2. Univariable and multivariable LR analyses to identify parameters associated with csPCa. Area under the receiver operating characteristic curve (AUC), Brier score, and DeLong test were used to assess and compare the csPCa diagnostic performance with the LR model. The significance level was defined as 0.05. The RF model exhibited the highest AUC (0.880-0.904) and lowest Brier score (0.125-0.133) among the ML models in the validation and testing cohorts, however, there was no difference when compared to the LR model (P = 0.453 and 0.548). The sensitivity and negative predictive values in the validation and testing cohorts were 93.8%-97.6% and 82.7%-95.1%, respectively, at a threshold of 0.450 (99% sensitivity of the RF model). The RF model might help for assessing the risk of csPCa and preventing overdiagnosis and unnecessary biopsy for men with PI-RADSv2.1 ≥ 3. 3 TECHNICAL EFFICACY: Stage 2.

Investigating amplitude of low-frequency fluctuation and possible links with cognitive impairment in childhood and adolescence onset schizophrenia: a correlation study.

Cognitive impairment (CI) is a distinctive characteristic of schizophrenia, with evidence suggesting that childhood and adolescence onset schizophrenia (CAOS), representing severe but rare forms of schizophrenia, share continuity with adult-onset conditions. While relationships between altered brain function and CI have been identified in adults with schizophrenia, the extent of brain function abnormalities in CAOS remains largely unknown. In this study, we employed resting-state functional magnetic resonance imaging (rs-fMRI) to investigate functional alterations in brain areas among patients with CAOS. To assess CI across multiple cognitive domains, we utilized the Stroop Color and Word Tests (SCWT) and MATRICS Consensus Cognitive Battery (MCCB) tests. Our objective was to explore the associations between functional CI and the amplitude of low-frequency fluctuation (ALFF) levels in these patients. We enrolled 50 patients diagnosed with CAOS and 33 healthy controls (HCs) matched for sex and age. Cognitive functions were assessed using the MCCB and SCWT methods. Rs-fMRI data were acquired using gradient-echo echo-planar imaging sequences. Voxel-based ALFF group maps were compared through two-sample t-tests in SPM8. Subsequently, correlation analyses were conducted to identify associations between ALFF levels and cognitive scores. In comparison to HCs, patients exhibited significantly increased ALFF levels in the right fusiform gyrus, frontal lobe, and caudate, as well as the left frontal lobe and caudate. Conversely, reduced ALFF levels were observed in the temporal and left medial frontal lobes. Significant differences were identified between HCs and patients in terms of total cognitive scores, ALFF levels, and domain scores. All test scores were decreased, except for TMA. Correlation analyses between ALFF levels and cognitive functions in patients with CAOS differed from those in HCs. Pearson correlation analyses revealed positive associations between Brief Visuospatial Memory Test - Revised (BVMT-R) scores and ALFF levels in the left medial frontal gyrus. Digital Span Test (DST) scores were negatively correlated with ALFF levels in the right caudate, and Maze Test values were negatively correlated with levels in the left caudate. However, Pearson correlation analyses in HCs indicated that color and Hopkins Verbal Learning Test (HVLT-R) scores positively correlated with ALFF levels in the left frontal lobe, while color-word and symbol coding scores negatively correlated with levels in the right caudate. Altered ALFF levels in the brain may be linked to cognitive impairment (CI) in patients with CAOS. We highlighted the pathophysiology of schizophrenia and provide imaging evidence that could potentially aid in the diagnosis of CAOS.

Rich Club Reorganization in Nurses Before and After the Onset of Occupational Burnout: A Longitudinal MRI Study.

Studies on potential disruptions in rich club structure in nursing staff with occupational burnout are lacking. Moreover, existing studies on nurses with burnout are limited by their cross-sectional design. To investigate rich club reorganization in nursing staff before and after the onset of burnout and the underlying impact of anatomical distance on such reconfiguration. Prospective, longitudinal. Thirty-nine hospital nurses ( years old at baseline, years old at a follow-up within 1.5 years, 38 female). Magnetization-prepared rapid gradient-echo and gradient-echo echo-planar imaging sequences at 3.0 T. The Maslach Burnout Inventory and Symptom Check-List 90 testing were acquired at each MRI scan. Rich club structure was assessed at baseline and follow-up to determine whether longitudinal changes were related to burnout and to changes in connectivities with different anatomical distances (short-, mid-, and long range). Chi-square, paired-samples t, two-sample t, Mann-Whitney U tests, network-based statistic, Spearman correlation analysis, and partial least squares regression analysis. Significance level: Bonferroni-corrected . In nurses who developed burnout: 1) Strengths of rich club, feeder, local, short-, mid-, and long-range connectivities were significantly decreased at follow-up compared with baseline. 2) At follow-up, strengths of above connectivities and that between A5m.R and dlPu.L were significantly correlated with emotional exhaustion (r ranges from -0.57 to -0.73) and anxiety scores (r = -0.56), respectively. 3) Longitudinal change (follow-up minus baseline) in connectivity strength between A5m.R and dlPu.L reflected change in emotional exhaustion score (r = 0.87). Longitudinal changes in strength of connectivities mainly involving parietal lobe were significantly decreased in nurses who developed burnout compared with those who did not. In nurses after the onset of burnout, rich club reorganization corresponded to significant reductions in strength of connectivities with different anatomical distances. 1 TECHNICAL EFFICACY: Stage 2.

Simultaneous fMRI and metabolic MRS of hyperpolarized [1-13C]pyruvate during nicotine stimulus in rat.

Functional MRI (fMRI) and MRS (fMRS) can be used to noninvasively map cerebral activation and metabolism. Recently, hyperpolarized 13C spectroscopy and metabolic imaging have provided an alternative approach to assess metabolism. In this study, we combined 1H fMRI and hyperpolarized [1-13C]pyruvate MRS to compare cerebral blood oxygenation level-dependent (BOLD) response and real-time cerebral metabolism, as assessed with lactate and bicarbonate labelling, during nicotine stimulation. Simultaneous 1H fMRI (multislice gradient echo echo-planar imaging) and 13C spectroscopic (single slice pulse-acquire) data were collected in urethane-anaesthetized female Sprague-Dawley rats (n= 12) at 9.4 T. Animals received an intravenous (i.v.) injection of either nicotine (stimulus; 88 μg/kg, n= 7, or 300 μg/kg, n= 5) or 0.9% saline (matching volume), followed by hyperpolarized [1-13C]pyruvate injection 60 s later. Three hours later, a second injection was administered: the animals that had previously received saline were injected with nicotine and vice versa, both followed by another hyperpolarized [1-13C]pyruvate i.v. injection 60 s later. The low-dose (88 μg/kg) nicotine injection led to a 12% ± 4% (n= 7, t-test, p~ 0.0006 (t-value -5.8, degrees of freedom 6), Wilcoxon p~ 0.0078 (test statistic 0)) increase in BOLD signal. At the same time, an increase in 13C-bicarbonate signal was seen in four out of six animals. Bicarbonate-to-total carbon ratios were 0.010 ± 0.004 and 0.018 ± 0.010 (n= 6, t-test, p~ 0.03 (t-value -2.3, degrees of freedom 5), Wilcoxon p~ 0.08 (test statistic 3)) for saline and nicotine experiments, respectively. No increase in the lactate signal was seen; lactate-to-total carbon was 0.16 ± 0.02 after both injections. The high (300 μg/kg) nicotine dose (n= 5) caused highly variable BOLD and metabolic responses, possibly due to the apparent respiratory distress. Simultaneous detection of 1H fMRI and hyperpolarized 13C-MRS is feasible. A comparison of metabolic response between control and stimulated states showed differences in bicarbonate signal, implying that the hyperpolarization technique could offer complimentary information on brain activation.

P346 Assessing Brain Morphology in Functional Gastrointestinal and Inflammatory Bowel Disorders Using Functional Magnetic Resonance Imaging (fMRI)

Abstract Background Functional gastrointestinal disorders (FGIDs) and non-specific inflammatory bowel diseases (IBD) are increasingly common in young adults. Studies have shown abnormal interhemispheric interactions in FGIDs and altered Default Mode Network (DMN) connectivity in brain regions linked to gastric sensations and emotional regulation. This study explores these neural mechanisms in FGIDs and IBDs, focusing on chronic visceral pain and its association with DMN reorganization. Methods The study included patients with functional dyspepsia (FD), N=18; irritable bowel syndrome (IBS), N=20 and IBD, N=18 alongside a control group of 18 healthy volunteers. Selection criteria included the Rome III Criteria for FGIDs and various diagnostic tests for IBDs. MRI scans were conducted using a 3T Achieva TX Scanner, applying standard T1 and T2 sequences without contrast agents. Functional imaging utilized T2 Gradient Echo-Planar Imaging. Results DMN analysis showed no anterior-posterior split. Significant differences were observed in the IBD group compared to controls, particularly in the left superior frontal gyrus. When comparing all patient groups with controls, increased DMN connectivity was noted in the left cingulum and supplementary motor area. These areas were also significant when comparing only FGIDs patients with controls, indicating altered DMN connectivity in these disorders. Please see: Figure 1 and Table 1. Conclusion The study highlights differences in DMNs between patient and control groups, especially in the left superior frontal gyrus, left cingulum, and left supplementary motor area. All disease groups showed variations from controls in the DMN pattern within the left cingulum. Significant differences in the DMN of the supplementary motor area were observed in functional gastric disease groups compared to controls. These findings suggest a link between brain areas involved in sensorimotor processes and symptoms of FD and IBS, providing insights into the neural basis of these conditions. Despite varied changes, common features differentiating the entire study group from healthy controls were identified. This condensed version focuses on the key aspects of your original text, ensuring that the main findings and methodology are clearly presented within the character limit.

Abnormal Local Brain Activity and Cognitive Impairments in Young Non-Disabled Patients With Intracerebral Hemorrhage: A Resting-State Functional MRI Study.

Resting-state functional MRI (rs-fMRI) has identified static changes of local brain activity among patients with intracerebral hemorrhage (ICH). However, the dynamic and concordance-related characteristics of brain activity remain unclear. To investigate static, dynamic, and concordance-related features of the regional brain activity of young non-disabled ICH patients. Prospective. Thirty-three ICH patients (modified Rankin Scale score ≤2, 21% female, 46.36 ± 6.53) and 33 matched healthy controls (HCs) (21% female, 47.64 ± 6.16). 3-T, rs-fMRI using gradient echo-planar imaging, T1-weighted imaging. Neuropsychological and rs-fMRI data were acquired from all participants. Amplitude of low-frequency fluctuations (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), voxel-mirrored homotopic connectivity, global signal correlation (GSCorr) and degree centrality (DC), and their dynamic and concordance-related changes with sliding window analysis were calculated based on rs-fMRI data at a whole-brain level. The burden of cerebral small vascular diseases (cSVD) was assessed by cSVD scores. All hemorrhage lesions were delineated on normalized T1 images. Multiple regression models, a voxel-level uncorrected P < 0.001, a cluster-level false discovery rate (FDR) corrected q < 0.05, a re-corrected qFDR <0.05 were considered significant. Pearson or Spearman correlation analyses between fMRI data and neurocognitive performance were performed. Compared to HCs, ICH patients showed significant abnormal changes of ALFF, dynamic ALFF, fALFF, ReHo, dynamic ReHo, GSCorr, DC, and voxel-wise concordance in multiple brain regions mainly including the bilateral cerebellar hemispheres, ipsilesional thalamus, and bilateral middle cingulum gyrus. The ALFF in the cerebellar posterior lobe and thalamus were significantly associated with attention (r = -0.481) and executive function (rho = -0.521) in ICH patients. Young non-disabled ICH patients exhibit static, dynamic, and concordance-related alterations of local brain activity, part of which shows associations with cognitive functions.These findings may help comprehensively understand the mechanism of cognitive impairment after ICH. 2 TECHNICAL EFFICACY: Stage 3.

MRI compatibility study of a prototype radiofrequency penetrable oval PET insert at 3T.

To perform an MRI compatibility study of an RF field-penetrable oval-shaped PET insert that implements an MRI built-in body RF coil both as a transmitter and a receiver. Twelve electrically floating RF shielded PET detector modules were used to construct the prototype oval PET insert with a major axis of 440mm, a minor axis of 350mm, and an axial length of 225mm. The electric floating of the PET detector modules was accomplished by isolating the cable shield from the detector shield using plastic tape. Studies were conducted on the transmit (B1) RF field, the image signal-to-noise ratio (SNR), and the RF pulse amplitude for a homogeneous cylindrical (diameter: 160mm and length: 260mm) phantom (NaCl + NiSO4 solution) in a 3T clinical MRI system (Verio, Siemens, Erlangen, Germany). The B1 maps for the oval insert were similar to the MRI-only field responses. Compared to the MRI-only values, SNR reductions of 51%, 45%, and 59% were seen, respectively, for the spin echo (SE), gradient echo (GE), and echo planar (EPI) images for the case of oval PET insert. Moreover, the required RF pulse amplitudes for the SE, GE, and EPI sequences were, respectively, 1.93, 1.85, and 1.36 times larger. However, a 30% reduction in the average RF reception sensitivity was observed for the oval insert. The prototype floating PET insert was a safety concern for the clinical MRI system, and this compatibility study provided clearance for developing a large body size floating PET insert for the existing MRI system. Because of the RF shield of the insert, relatively large RF powers compared to the MRI-only case were required. Because of this and also due to low RF sensitivity of the body coil, the SNRs reduced largely.

Feasibility study of the multishot gradient-echo planar imaging sequence in non-enhanced and free-breathing whole-heart magnetic resonance coronary angiography

To investigate the feasibility of non-enhanced and free-breathing whole-heart magnetic resonance coronary angiography (MRCA) using multishot gradient-echo planar imaging (MSG-EPI). In total, 29 healthy volunteers were recruited for free-breathing whole-heart MRCA acquisition using the MSG-EPI sequence and fast gradient echo (GRE) sequence. After the examination, the actual scanning times, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the left main (LM) coronary artery, subjective quality scores for each segment, and evaluable length of the coronary artery were recorded and statistically analysed. There was no significant difference between the SNRLM of the MSG-EPI sequence and fast GRE sequence (p=0.130), but the CNRLM of the MSG-EPI sequence was higher (p=0.001). The subjective quality score of the mid- and distal left anterior descending branch as well as the distal circumflex branch of the coronary artery in the MSG-EPI sequence was higher than that in the fast GRE sequence (p=0.003, 0.001, and 0.003, respectively). The evaluable length of the left anterior descending branch and the circumflex branch was better using the MSG-EPI sequence than that of the fast GRE sequence (p=0.015 and<0.001, respectively). Moreover, the scanning time of the MSG-EPI sequence was 54.5% less than that of the fast GRE sequence (p<0.001). The MSG-EPI sequence improves the subjective and objective image quality of MRCA as well as reduces the scanning time.

Simultaneous T1, T2 and T2⁎ mapping of the liver with multi-shot MI-SAGE

PurposeTo apply multi-shot high-resolution multi inversion spin and gradient echo (MI-SAGE) acquisition for simultaneous liver T1, T2 and T2* mapping. MethodsInversion prepared spin- and gradient-echo EPI was developed with ascending slice order across measurements for efficient acquisition with T1, T2, and T2⁎ weighting. Multi-shot EPI was also implemented to minimize distortion and blurring while enabling high in-plane resolution. A dictionary-matching approach was used to fit the images to quantitative parameter maps, which were compared to T1 measured by modified Look-Locker (MOLLI), T1 measured by variable flip angle (VFA), T2 measured by multiple echo time-based Half Fourier Single-shot Turbo spin-Echo (HASTE), T2 measured by radial turbo-spin-echo (rTSE) and T2⁎ measured by multiple gradient echo (MGRE) sequences. ResultsThe multi-shot variant of the sequence achieved higher in-plane resolution of 1.7 × 1.7 mm2 with good image quality in 28 s. Derived quantitative maps showed comparable values to conventional mapping methods. As measured in phantom and in vivo, MOLLI, MESE and MGRE give closest values to MISAGE. VFA, HASTE and rTSE show obvious overestimation. ConclusionsThe proposed multi-shot inversion prepared spin- and gradient-echo EPI sequence allows for high-resolution quantitative T1, T2 and T2 liver tissue characterization in a single breath-hold scan.

4 Resting State Functional Connectivity Impairments Implicate CNS Mechanisms Underlying Chronic Pain and Depression in Gulf War Veterans’ Illness

Objective:Around 200,000 veterans (up to 32% of those deployed) of the 1991 Gulf War (GW) suffer from GW veterans’ illness (GWVI). GWVI is a poorly understood chronic medical condition, characterized by symptoms indicative of brain function deficits in multiple domains. Among the symptoms of brain impairment GWVI-related chronic headaches and body muscle and joint pain conditions (GWVI-HAP) are the most debilitating, affecting around 64% of the GWVI veterans. Further, depression carries a very high co-morbid rate (&gt;50%) in patients with chronic pain, including GWVI-HAP. In this preliminary study, we examined the integrity of brain function networks in a group of GWI-HAP veterans, with resting state fMRI (rsfMRI).Participants and Methods:Data from the first twenty-two GWVI-HAP veterans from two ongoing parallel clinical trials was examined. Of these 14 subjects (GWVI-HAP-DM) had mild depression (Hamilton Rating Scale for Depression (HSRD &lt; 13); and 8 subjects (GWVI-HAP-DS) had moderate to severe depression (HSRD &gt; 14). Written informed consent was obtained from all participants in the protocol approved by the local Institutional Review Board. RsfMRI data was acquired on a Siemens 3T Prisma-Fit MRI scanner using a 10-minute whole-brain high resolution simultaneous multi-slice (SMS) gradient echo echo-planar imaging (EPI) sequence: TR/TE/FA = 2.2 sec/ 27 msec/80°, and analyzed with well-established image processing pipelines. Functional connectivity (FC) to different regions implicated in depression and chronic pain was assessed with seed-based correlation analysis. Between group differences in FC were obtained with 2-sample t-tests.Results:GWVI-HAP-DS group exhibited significantly (p &lt; 0.05) reduced FC compared to GWVI-HAP-DM between frontal lobe (medial (mPFC), and dorsolateral (dlPFC) prefrontal cortex) and the striatum. This indicates that malfunction of fronto-striatal circuits could be a source of the increased chronic pain and depression seen in veterans with GWVI- HAP-DS. Dysregulation of fronto-striatal networks has been implicated in major depressive disorder as well as many chronic pain conditions. In addition, FC between mPFC, and salience network (SN; anterior insula and dorsal anterior cingulate) and limbic (subgenual and ventral anterior cingulate) regions were also reduced in GWVI-HAP-DS. Similarly, mPFC and SN also exhibited reduced FC to pain processing regions (posterior insula, centromedian thalamus and cerebellum). These FC impairments could reflect greater deficits in regulation of and salience attribution to emotions and nociception in the GWVI-HAP-DS group. Finally, GWVI-HAP-DS also exhibited reduced FC between nodes of the default mode network. DMN impairments also have been observed in many depressive and chronic pain conditions.Conclusions:The results of this preliminary analysis implicate impairments in cognitive control of emotion and nociception as a mechanism underlying the enhanced chronic pain and depression observed in GWVI-HAP veterans, especially those with moderate to severe depression. A fuller picture of deficits in FC in brain function networks is expected to emerge as more GWI-HAP subjects of both groups along with age matched healthy controls are examined in this ongoing project. Better understanding of impairments in these networks in GWI-HAP will benefit the rehabilitation of veterans with GWI-HAP.

Optimization of Gradient-Echo Echo-Planar Imaging for T2* Contrast in the Brain at 0.5 T.

Gradient-recalled echo (GRE) echo-planar imaging (EPI) is an efficient MRI pulse sequence that is commonly used for several enticing applications, including functional MRI (fMRI), susceptibility-weighted imaging (SWI), and proton resonance frequency (PRF) thermometry. These applications are typically not performed in the mid-field (<1 T) as longer T2* and lower polarization present significant challenges. However, recent developments of mid-field scanners equipped with high-performance gradient sets offer the possibility to re-evaluate the feasibility of these applications. The paper introduces a metric "T2* contrast efficiency" for this evaluation, which minimizes dead time in the EPI sequence while maximizing T2* contrast so that the temporal and pseudo signal-to-noise ratios (SNRs) can be attained, which could be used to quantify experimental parameters for future fMRI experiments in the mid-field. To guide the optimization, T2* measurements of the cortical gray matter are conducted, focusing on specific regions of interest (ROIs). Temporal and pseudo SNR are calculated with the measured time-series EPI data to observe the echo times at which the maximum T2* contrast efficiency is achieved. T2* for a specific cortical ROI is reported at 0.5 T. The results suggest the optimized echo time for the EPI protocols is shorter than the effective T2* of that region. The effective reduction of dead time prior to the echo train is feasible with an optimized EPI protocol, which will increase the overall scan efficiency for several EPI-based applications at 0.5 T.

A cross-sectional study to test equivalence of low- versus intermediate-flip angle dynamic susceptibility contrast MRI measures of relative cerebral blood volume in patients with high-grade gliomas at 1.5 Tesla field strength.

1.5 Tesla (1.5T) remain a significant field strength for brain imaging worldwide. Recent computer simulations and clinical studies at 3T MRI have suggested that dynamic susceptibility contrast (DSC) MRI using a 30° flip angle ("low-FA") with model-based leakage correction and no gadolinium-based contrast agent (GBCA) preload provides equivalent relative cerebral blood volume (rCBV) measurements to the reference-standard acquisition using a single-dose GBCA preload with a 60° flip angle ("intermediate-FA") and model-based leakage correction. However, it remains unclear whether this holds true at 1.5T. The purpose of this study was to test this at 1.5T in human high-grade glioma (HGG) patients. This was a single-institution cross-sectional study of patients who had undergone 1.5T MRI for HGG. DSC-MRI consisted of gradient-echo echo-planar imaging (GRE-EPI) with a low-FA without preload (30°/P-); this then subsequently served as a preload for the standard intermediate-FA acquisition (60°/P+). Both normalized (nrCBV) and standardized relative cerebral blood volumes (srCBV) were calculated using model-based leakage correction (C+) with IBNeuro™ software. Whole-enhancing lesion mean and median nrCBV and srCBV from the low- and intermediate-FA methods were compared using the Pearson's, Spearman's and intraclass correlation coefficients (ICC). Twenty-three HGG patients composing a total of 31 scans were analyzed. The Pearson and Spearman correlations and ICCs between the 30°/P-/C+ and 60°/P+/C+ acquisitions demonstrated high correlations for both mean and median nrCBV and srCBV. Our study provides preliminary evidence that for HGG patients at 1.5T MRI, a low FA, no preload DSC-MRI acquisition can be an appealing alternative to the reference standard higher FA acquisition that utilizes a preload.

Functional Connectome Hierarchy Distortions in Female Nurses With Occupational Burnout and Its Gene Expression Signatures.

Burnout has become a serious public health issue worldwide, particularly during the COVID-19 pandemic. Functional connectome impairments associated with occupational burnout were widely distributed, involving both low-level sensorimotor cortices and high-level association cortices. To investigate whether there are hierarchical perturbations in the functional connectomes and if these perturbations are potentially influenced by genetic factors in nurses who feel "burned out." Prospective, case control. Thirty-three female nurses with occupational burnout (aged 27-40, 32.42 ± 3.37) and 32 matched nurses who were not feeling burned out (aged 27-42, 32.50 ± 4.21). 3.0 T, gradient-echo echo-planar imaging sequence (GE-EPI). Gradient-based techniques were used to depict the perturbations in the multi-dimensional hierarchical structure of the macroscale connectome. Gene expression data were acquired from the Allen Human Brain Atlas. Cortex-wide multivariate analyses were used for between-group differences in gradients as well as association analyses between the hierarchy distortions and the MBI score (FDR corrected). Partial least squares, spin test and bootstrapping were utilized together to select the gene sets (FDR corrected). Gene enrichment analyses (GO, KEGG and cell-type) were further performed. Significance level: P < 0.05. There were significant gradient distortions, with strong between-group effects in the somatosensory network and moderate effects in the higher-order default-mode network, which were significantly correlated with the gene expression profiles (r = 0.3171). The most related genes were broadly involved in the cellular response to minerals, neuronal plasticity, and the circadian rhythm pathway (q value < 0.01). Significant enrichments were found in excitatory (r = 0.2588), inhibitory neurons (r = 0.2610), and astrocytes cells (r = 0.2633). Regions affected by burnout severity were mainly distributed in the association and visual cortices. By connecting in vivo imaging to genes, cell classes, and clinical data, this study provides a framework to understand functional impairments in occupational burnout and how the microscopic genetic architecture drive macroscopic distortions. 1 TECHNICAL EFFICACY: Stage 2.

Altered Callosal Morphology and Connectivity in Asymptomatic Carotid Stenosis.

Carotid stenosis, even in the clinically asymptomatic stage, causes cognitive impairment, silent lesions, and hemispheric changes. The corpus callosum (CC) is crucial for hemispheric cortical integration and specialization. To examine if CC morphology and connectivity relate to cognitive decline and lesion burden in asymptomatic carotid stenosis (ACS). Retrospective, cross-sectional. 33 patients with unilaterally severe (70%) ACS and 28 demographically and comorbidity-matched controls. A publicly available healthy adult lifespan (ages between 18 and 80; n = 483) MRI dataset was also included. A 3.0 T; T1 MPRAGE and diffusion weighted gradient echo-planar imaging sequences. Structural MRI and multidomain cognitive data were obtained. Midsagittal CC area, circularity, thickness, integrity, and probabilistic tractography were calculated and correlated with cognitive tests and white matter hyperintensity. Fractional anisotropy, mean diffusivity (MD), and radial diffusivity were determined from DTI. Independent two-sample t-tests, χ2 tests, Mann-Whitney U, locally weighted scatterplot smoothing (LOWESS) curve fit, and Pearson correlation. A P value < 0.05 was considered statistically significant. Patients with ACS demonstrated significant reductions in callosal area, circularity, and thickness compared to controls. The callosal atrophy was significantly correlated with white matter hyperintensity size (r = -0.629, P < 0.001). Voxel-wise analysis of diffusion measures in the volumetric CC showed that ACS patients exhibited significantly lower fractional anisotropy and higher MD and radial diffusivity in the genu and splenium of the CC than controls. Further lifespan trajectory analysis showed that although the midsagittal callosal area, circularity, and thickness exhibited age-related decreases, the values in the ACS patients were significantly lower in all age groups. Midsagittal callosal atrophy and connectivity reflect the load of silent lesions and the severity of cognitive decline, respectively, suggesting that CC degeneration has potential to serve as an early marker in ACS. 3 TECHNICAL EFFICACY STAGE: 2.

MRI Assessment of Intrinsic Neural Timescale and Gray Matter Volume in Parkinson's Disease.

Numerous studies have indicated altered temporal features of the brain function in Parkinson's disease (PD), and the autocorrelation magnitude of intrinsic neural signals, called intrinsic neural timescales, were often applied to estimate how long neural information stored in local brain areas. However, it is unclear whether PD patients at different disease stages exhibit abnormal timescales accompanied with abnormal gray matter volume (GMV). To assess the intrinsic timescale and GMV in PD. Prospective. 74 idiopathic PD patients (44 early stage (PD-ES) and 30 late stage (PD-LS), as determined by the Hoehn and Yahr (HY) severity classification scale), and 73 healthy controls (HC). 3.0 T MRI scanner; magnetization prepared rapid acquisition gradient echo and echo planar imaging sequences. The timescales were estimated by using the autocorrelation magnitude of neural signals. Voxel-based morphometry was performed to calculate GMV in the whole brain. Severity of motor symptoms and cognitive impairments were assessed using the unified PD rating scale, the HY scale, the Montreal cognitive assessment, and the mini-mental state examination. Analysis of variance; two-sample t-test; Spearman rank correlation analysis; Mann-Whitney U test; Kruskal-Wallis' H test. A P value <0.05 was considered statistically significant. The PD group had significantly abnormal intrinsic timescales in the sensorimotor, visual, and cognitive-related areas, which correlated with the symptom severity (ρ = -0.265, P = 0.022) and GMV (ρ = 0.254, P = 0.029). Compared to the HC group, the PD-ES group had significantly longer timescales in anterior cortical regions, whereas the PD-LS group had significantly shorter timescales in posterior cortical regions. This study suggested that PD patients have abnormal timescales in multisystem and distinct patterns of timescales and GMV in cerebral cortex at different disease stages. This may provide new insights for the neural substrate of PD. 2 TECHNICAL EFFICACY STAGE: 1.