Echo-planar Magnetic Resonance Imaging Research Articles

Multi-contrast echo-planar imaging sequence (Echo-planar imaging mix) in clinical situations demanding faster MRI-brain scans.

The excellent resolution offered by magnetic resonance imaging (MRI) has a trade-off in the form of scan duration. The purpose of the present study was to assess the clinical utility of echo-planar imaging mix (EPIMix), an echo-planar imaging-based MRI sequence for the brain with a short acquisition time. This was a retrospective observational study of 50 patients, who could benefit from faster MRI brain scans. The T1, T2, fluid attenuated inversion recovery, diffusion-weighted imaging (DWI), and T2*/susceptibility-weighted imaging sequences were acquired, conventionally and with EPIMix. Conventional and EPIMix images were assessed by two radiologists for overall quality, motion, and susceptibility artifacts and scored on a Likert scale. The scores given for conventional and EPIMix images were compared. The diagnostic performance of EPIMix was also assessed by the ability to detect clinically relevant findings. The acquisition time for conventional MRI was 11 min and 45 s and for EPIMix 1 min and 15 s. All EPIMix images were sufficient for diagnostic use. On assessment of the diagnostic performance, it was excellent for ischemic and hemorrhagic strokes. Smaller lesions, lesions adjacent to bone, and post-operative tumors were difficult to identify. Moderate to perfect agreement (Kappa values 0.41-1) was seen between radiologists for all categories except skull base, calvarial, and orbital lesions. Image quality, artifact assessment showed excellent interobserver agreement (>90%) for the scores. All EPIMix images showed reduced motion artifacts. The EPIMix-DWI was comparable to conventional-DWI in terms of quality and artifacts. The remaining sequences showed reduced quality and increased susceptibility. The EPIMix has a significantly reduced acquisition time than conventional MRI and could be used instead of conventional MRI in situations demanding faster scans such as suspected acute ischemic or hemorrhagic stroke. In other clinical scenarios, it could help tailor the MRI examination for each patient.

Model-based iterative reconstruction for direct imaging with point spread function encoded echo planar MRI

BackgroundEcho planar imaging (EPI) is a fast measurement technique commonly used in magnetic resonance imaging (MRI), but is highly sensitive to measurement non-idealities in reconstruction. Point spread function (PSF)-encoded EPI is a multi-shot strategy which alleviates distortion, but acquisition of encodings suitable for direct distortion-free imaging prolongs scan time. In this work, a model-based iterative reconstruction (MBIR) framework is introduced for direct imaging with PSF-EPI to improve image quality and acceleration potential. MethodsAn MBIR platform was developed for accelerated PSF-EPI. The reconstruction utilizes a subspace representation, is regularized to promote local low-rankedness (LLR), and uses variable splitting for efficient iteration. Comparisons were made against standard reconstructions from prospectively accelerated PSF-EPI data and with retrospective subsampling. Exploring aggressive partial Fourier acceleration of the PSF-encoding dimension, additional comparisons were made against an extension of Homodyne to direct PSF-EPI in numerical experiments. A neuroradiologists' assessment was completed comparing images reconstructed with MBIR from retrospectively truncated data directly against images obtained with standard reconstructions from non-truncated datasets. ResultsImage quality results were consistently superior for MBIR relative to standard and Homodyne reconstructions. As the MBIR signal model and reconstruction allow for arbitrary sampling of the PSF space, random sampling of the PSF-encoding dimension was also demonstrated, with quantitative assessments indicating best performance achieved through nonuniform PSF sampling combined with partial Fourier. With retrospective subsampling, MBIR reconstructs high-quality images from sub-minute scan datasets. MBIR was shown to be superior in a neuroradiologists' assessment with respect to three of five performance criteria, with equivalence for the remaining two. ConclusionsA novel image reconstruction framework is introduced for direct imaging with PSF-EPI, enabling arbitrary PSF space sampling and reconstruction of diagnostic-quality images from highly accelerated PSF-encoded EPI data.

Simultaneous quantification of perfusion, permeability, and leakage effects in brain gliomas using dynamic spin-and-gradient-echo echoplanar imaging MRI

ObjectiveTo determine the feasibility and biologic correlations of dynamic susceptibility contrast (DSC), dynamic contrast enhanced (DCE), and quantitative maps derived from contrast leakage effects obtained simultaneously in gliomas using dynamic spin-and-gradient-echo echoplanar imaging (dynamic SAGE-EPI) during a single contrast injection.Materials and methodsThirty-eight patients with enhancing brain gliomas were prospectively imaged with dynamic SAGE-EPI, which was processed to compute traditional DSC metrics (normalized relative cerebral blood flow [nrCBV], percentage of signal recovery [PSR]), DCE metrics (volume transfer constant [Ktrans], extravascular compartment [ve]), and leakage effect metrics: ΔR2,ss* (reflecting T2*-leakage effects), ΔR1,ss (reflecting T1-leakage effects), and the transverse relaxivity at tracer equilibrium (TRATE, reflecting the balance between ΔR2,ss* and ΔR1,ss). These metrics were compared between patient subgroups (treatment-naïve [TN] vs recurrent [R]) and biological features (IDH status, Ki67 expression).ResultsIn IDH wild-type gliomas (IDHwt—i.e., glioblastomas), previous exposure to treatment determined lower TRATE (p = 0.002), as well as higher PSR (p = 0.006), Ktrans (p = 0.17), ΔR1,ss (p = 0.035), ve (p = 0.006), and ADC (p = 0.016). In IDH-mutant gliomas (IDHm), previous treatment determined higher Ktrans and ΔR1,ss (p = 0.026). In TN-gliomas, dynamic SAGE-EPI metrics tended to be influenced by IDH status (p ranging 0.09–0.14). TRATE values above 142 mM−1s−1 were exclusively seen in TN-IDHwt, and, in TN-gliomas, this cutoff had 89% sensitivity and 80% specificity as a predictor of Ki67 > 10%.ConclusionsDynamic SAGE-EPI enables simultaneous quantification of brain tumor perfusion and permeability, as well as mapping of novel metrics related to cytoarchitecture (TRATE) and blood–brain barrier disruption (ΔR1,ss), with a single contrast injection.Clinical relevance statementSimultaneous DSC and DCE analysis with dynamic SAGE-EPI reduces scanning time and contrast dose, respectively alleviating concerns about imaging protocol length and gadolinium adverse effects and accumulation, while providing novel leakage effect metrics reflecting blood–brain barrier disruption and tumor tissue cytoarchitecture.Key Points• Traditionally, perfusion and permeability imaging for brain tumors requires two separate contrast injections and acquisitions.• Dynamic spin-and-gradient-echo echoplanar imaging enables simultaneous perfusion and permeability imaging.• Dynamic spin-and-gradient-echo echoplanar imaging provides new image contrasts reflecting blood–brain barrier disruption and cytoarchitecture characteristics.Graphical

Measurement of changes in cerebrospinal fluid pulsation after traumatic brain injury using echo-planar imaging-based functional MRI.

Traumatic brain injury (TBI) is a major public health concern worldwide, with a high incidence and a significant impact on morbidity and mortality. The alteration of cerebrospinal fluid (CSF) dynamics after TBI is a well-known phenomenon; however, the underlying mechanisms and their implications for cognitive function are not fully understood. In this study, we propose a new approach to studying the alteration of CSF dynamics in TBI patients. Our approach involves using conventional echo-planar imaging-based functional MRI with no additional scan, allowing for simultaneous assessment of functional CSF dynamics and blood oxygen level-dependent-based functional brain activities. We utilized two previously suggested indices of (i) CSFpulse, and (ii) correlation between global brain activity and CSF inflow. Using CSFpulse, we demonstrated a significant decrease in CSF pulsation following TBI (p< 0.05), which was consistent with previous studies. Furthermore, we confirmed that the decrease in CSF pulsation was most prominent in the early months after TBI, which could be explained by ependymal ciliary loss, intracranial pressure increment, or aquaporin-4 dysregulation. We also observed a decreasing trend in the correlation between global brain activity and CSF inflow in TBI patients (p< 0.05). Our findings suggest that the decreased CSF pulsation after TBI could lead to the accumulation of toxic substances in the brain and an adverse effect on brain function. Further longitudinal studies with larger sample sizes, TBI biomarker data, and various demographic information are needed to investigate the association between cognitive decline and CSF dynamics after TBI. Overall, this study sheds light on the potential role of altered CSF dynamics in TBI-induced neurologic symptoms and may contribute to the development of novel therapeutic interventions.

Femur development in fetal growth restriction as observed on prenatal magnetic resonance imaging.

To investigate human femur development in fetal growth restriction (FGR) by analyzing femur morphometrics and distal epimetaphyseal features on prenatal magnetic resonance imaging (MRI). This was a retrospective study of 111 fetuses (mean gestational age (GA), 27 + 2 weeks (range, 19-35 weeks)) with FGR associated with placental insufficiency without other major abnormalities and 111 GA-matched normal controls. On 1.5-Tesla echoplanar MRI, femur morphometrics, including diaphyseal length, epiphyseal length and epiphyseal width, were assessed. Using a previously reported grading system, epimetaphyseal features, including cartilaginous epiphyseal shape, metaphyseal shape and epiphyseal ossification, were analyzed qualitatively. To compare FGR cases and controls, the paired t-test was used to assess morphometrics, generalized estimating equations were used for epimetaphyseal features and time-to-event analysis was used to assess the visibility of epiphyseal ossification. There were significant differences in femur morphometrics between FGR cases and controls (all parameters, P < 0.001), with bone shortening observed in FGR. No significant differences were found in the distribution of epimetaphyseal features between FGR cases and controls (epiphyseal shape, P = 0.341; metaphyseal shape, P = 0.782; epiphyseal ossification, P = 0.85). Epiphyseal ossification was visible at a median of 33.6 weeks in FGR cases and at 32.1 weeks in controls (P = 0.008). On prenatal MRI, cases with FGR associated with placental insufficiency exhibit diaphyseal and epiphyseal shortening of the femur. However, FGR cases and normal controls share similarly graded distal epimetaphyseal features. Consequently, these features may not be appropriate MRI characteristics for the identification of FGR. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Resting-State fMRI Study of Vigilance Under Circadian and Homeostatic Modulation Based on Fractional Amplitude of Low-Frequency Fluctuation and Regional Homogeneity in Humans Under Normal Entrained Conditions.

How brain neural activity changes at multiple time points throughout the day and the neural mechanisms underlying time-dependent modulation of vigilance are less clear. To explore the effect of circadian rhythms and homeostasis on brain neural activity and the potential neural basis of time-dependent modulation of vigilance. Prospective. A total of 30 healthy participants (22-27 years old). A 3.0 T, T1-weighted imaging, echo-planar functional MRI (fMRI). Six resting-state fMRI (rs-fMRI) scanning sessions were performed at fixed times (9:00 h, 13:00 h, 17:00 h, 21:00 h, 1:00 h, and 5:00 h) to investigate fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) diurnal variation. The fALFF/ReHo and the result of the psychomotor vigilance task were used to assess local neural activity and vigilance. One-way repeated measures analysis of variance (ANOVA) was used to assess changes in vigilance (P < 0.05) and neural activity in the whole brain (P < 0.001 at the voxel level and P < 0.01 at the cluster level, Gaussian random field [GRF] corrected). Correlation analysis was used to examine the relationship between neural activity and vigilance at all-time points of the day. The fALFF/ReHo in the thalamus and some perceptual cortices tended to increase from 9:00 h to 13:00 h and from 21:00 h to 5:00 h, whereas the key nodes of the default mode network (DMN) tended to decrease from 21:00 h to 5:00 h. The vigilance tended to decrease from 21:00 h to 5:00 h. The fALFF/ReHo in the thalamus and some perceptual cortices was negatively correlated with vigilance at all-time points of the day, whereas the fALFF/ReHo in the key nodes of the DMN was positively correlated with vigilance. Neural activities in the thalamus and some perceptual cortices show similar trends throughout the day, whereas the key nodes of the DMN show roughly opposite trends. Notably, diurnal variation of the neural activity in these brain regions may be an adaptive or compensatory response to changes in vigilance. 1. 1.

Real-time phase contrast MRI versus conventional phase contrast MRI at different spatial resolutions and velocity encodings

PurposesTo compare the accuracy of real-time phase-contrast echo-planar MRI (EPI-PC) and conventional cine phase-contrast MRI (Conv-PC) and to assess the influence of spatial resolutions (pixel size) and velocity encoding on flow measurements obtained with the two sequences. MethodsFlow quantification was assessed using a pulsatile flow phantom (diameter: 9.5 mm; mean flow rate: 1150 mm3/s; mean flow velocity: 1.6 cm/s). Firstly, the accuracy of the EPI-PC was checked by comparing it with the flow rate in the calibrated phantom and the pulsation index from Conv-PC. Secondly, flow data from the two sequences were compared quantitatively as a function of the pixel size and the velocity encoding. ResultsThe mean percentage difference between the EPI-PC flow rate and calibrated phantom flow rate was −2.9 ± 2.1% (Mean ± SD). The pulsatility indices for EPI-PC and Conv-PC were respectively 0.64 and 0.59. In order to keep the flow rate measurement error within 10%, the ROI in Conv-PC had to contain at least 13 pixels, while the ROI in EPI-PC had to contain at least 9 pixels. Furthermore, Conv-PC had a higher velocity-to-noise ratio and could use a higher velocity encoding than EPI-PC (20 cm/s and 15 cm/s, respectively). ConclusionsThe result of this in vitro study confirmed the accuracy of EPI-PC, and found that EPI-PC can adapt to lower spatial resolutions, but is more sensitive to velocity encoding than Conv-PC.

Abstract 479: The role of diffusion in molecular networks: Diffusion coefficients in describing the development of cancer

Abstract To study and forecast the developments of cancers, the molecular networks, compositional fluctuations, diffusion in networks and altogether the biological processes resulting at cellular and intracellular levels, are highly important. Focusing on diffusion coefficients as the translational biomarkers to quantify the nucleation and growth of tumors and cancers has potential advantages. Because, diffusion coefficients act as guiding tools in preventing or treating the cancers and associated adversities. Collectively the biological, pharmacological and toxicological indicators during and prior to the course of cancer are taken as measures for the data over specific distances of the molecules to determine diffusion coefficients. Because, multiple mechanisms are simultaneously responsible in altering the compositions. In this work, the mass transportation in both healthy individuals and cancer patients are taken into account to compare and contrast the initiation and spread of cancers in the light of immunology and immunotherapy. Measurements through incoherent motion diffusion-weighted imaging (IVIM-DWI) and echo planar magnetic resonance (MR) imaging are applied in determining the diffusion parameters. Diffusion coefficients were within the ranges of 0.1 to 5 X 10-3 mm2/sec. Perfusion played important role in quantifications. Magnitudes of diffusion coefficients are used to forecast biological prevalence and to develop prevention and treatment therapeutics. Citation Format: Narayana Garimella. The role of diffusion in molecular networks: Diffusion coefficients in describing the development of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 479.

RESTING STATE FUNCTIONAL CONNECTIVITY CHANGES IN NATURALISTIC STIMULATION STUDY

Naturalistic stimulation has had increasing influence on cognitive neuroscience in the last decade. Several studies have used naturalistic stimulation to investigate the connectivity dynamics under pathological condition or in healthy children for studying the developing brain. However, little is known about the connectivity changes during watching a movie in healthy, adult population. Our aim is to delineate the potential dynamic connectivity pattern of the healthy, mature brain during naturalistic movie watching compared to complete rest. In an observational case series, e leven healthy adult volunteers with no history of psychiatric or neurological illness underwent two magnetic resonance echo-planar imaging acquisitions. During the first acquisition they were asked to rest with their eyes closed and during the subsequent acquisition they watched a movie clip with slow human body movements. The Independent Component Analysis provided neural components which were further submitted to intra- and inter-network analyses. We found significantly increased intra-network connectivity during movie watching for the extrastriate visual and for the posterior visual networks. The inter-network analysis showed that for the extravisual and primary visual pair, the connectivity was lower during movie watching compared to rest condition. We also found significant uncoupling between the anterior Default Mode Network and the secondary somatosensory network during movie watching. These findings suggest greater visual network segregation during movie watching in order to support processing of complex stimuli. The decoupling of the secondary somatosensory network from the anterior Default Mode Network during movie watching suggest a somatosensory function segregation and its important role in processing information from observing the naturalistic movements of others. Brain imaging measures of major brain networks can contribute to early identification of risk for common psychiatric disorders hence facilitating preventive therapy. Keywords: naturalistic stimulation , rest, conectivity Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0cm; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi; mso-ansi-language:EN-US; mso-fareast-language:EN-US;}

Exposure to Repetitive Head Impacts Is Associated With Corpus Callosum Microstructure and Plasma Total Tau in Former Professional American Football Players.

Exposure to repetitive head impacts (RHI) is associated with an increased risk of later-life neurobehavioral dysregulation and neurodegenerative disease. The underlying pathomechanisms are largely unknown. To investigate whether RHI exposure is associated with later-life corpus callosum (CC) microstructure and whether CC microstructure is associated with plasma total tau and neuropsychological/neuropsychiatric functioning. Retrospective cohort study. Seventy-five former professional American football players (age 55.2 ± 8.0 years) with cognitive, behavioral, and mood symptoms. Diffusion-weighted echo-planar MRI at 3 T. Subjects underwent diffusion MRI, venous puncture, neuropsychological testing, and completed self-report measures of neurobehavioral dysregulation. RHI exposure was assessed using the Cumulative Head Impact Index (CHII). Diffusion MRI measures of CC microstructure (i.e., free-water corrected fractional anisotropy (FA), trace, radial diffusivity (RD), and axial diffusivity (AD)) were extracted from seven segments of the CC (CC1-7), using a tractography clustering algorithm. Neuropsychological tests were selected: Trail Making Test Part A (TMT-A) and Part B (TMT-B), Controlled Oral Word Association Test (COWAT), Stroop Interference Test, and the Behavioral Regulation Index (BRI) from the Behavior Rating Inventory of Executive Function, Adult version (BRIEF-A). Diffusion MRI metrics were tested for associations with RHI exposure, plasma total tau, neuropsychological performance, and neurobehavioral dysregulation using generalized linear models for repeated measures. RHI exposure was associated with increased AD of CC1 (correlation coefficient (r)=0.32, P< 0.05) and with increased plasma total tau (r= 0.34, P< 0.05). AD of the anterior CC1 was associated with increased plasma total tau (CC1: r= 0.30, P< 0.05; CC2: r= 0.29, P< 0.05). Higher trace, AD, and RD of CC1 were associated with better performance (P< 0.05) in TMT-A (trace, r= 0.33; AD, r= 0.31; and RD, r= 0.28) and TMT-B (trace, r= 0.31; RD, r= 0.34). Higher FA and AD of CC2 were associated with better performance (P< 0.05) in TMT-A (FA, r= 0.36; AD, r= 0.28), TMT-B (FA, r= 0.36; AD, r= 0.27), COWAT (FA, r= 0.36; AD, r= 0.32), and BRI (AD, r= 0.29). These results suggest an association among RHI exposure, CC microstructure, plasma total tau, and clinical functioning in former professional American football players. 3 Technical Efficacy Stage: 1.

One-Minute Multi-contrast Echo Planar Brain MRI in Ischemic Stroke: A Retrospective Observational Study of Diagnostic Performance.

Fast multi-contrast echo planar MRI (EPIMix) has comparable diagnostic performance to standard MRI for detecting brain pathology but its performance in detecting acute cerebral infarctions has not been determined. To assess the diagnostic performance of EPIMix for the detection of acute cerebral infarctions. Retrospective observational cohort. One hundred and seventy-two consecutive patients with a clinical suspicion of non-hyperacute ischemic stroke (January 2018 to December 2019). 1.5 T or 3 T. EPIMix ((echo-planar based: diffusion weighted (DWI), T2*-weighted, T2-weighted, T2- and T1-fluid attenuated inversion recovery (FLAIR) images) vs. standard MRI: echo-planar DWI, echo-planar T2*-weighted or susceptibility weighted, turbo spin-echo T2-weighted, T2- and T1-FLAIR turbo spin-echo sequences. Three neuroradiologists rated EPIMix and standard MRI on two separate occasions. Incongruent assessments were resolved in consensus with the fourth reader. The ratings included the diagnostic category (acute infarct, normal, and other pathology). Congruent diagnoses together with consensus diagnoses served as the reference standard. The diagnostic performance of EPIMix and standard MRI against the reference standard was calculated by the area under the receiver operating characteristic curve (AUC) and compared by DeLong's test. Sensitivity and specificity were determined. Inter-rater agreements were evaluated by Fleiss's kappa. Of 172 patients (61 ± 16 years, 103 men), acute infarcts were present in 80/172 (47%), normal findings in 60/172 (35%), and other pathology in 32/172 (19%). Across readers, the AUCs were .94-.95 for EPIMix and .95-.99 for standard MRI, with overlapping 95% CI (P = .02-.18). Inter-rater agreement for EPIMix was 0.90 and for standard MRI was 0.93. The sensitivity for EPIMix and standard MRI was 88-91% and 91-98%, respectively, while the specificity was 98-100% and 98-99%, both with overlapping 95% CI. Multi-contrast echo planar MRI showed a high but marginally lower diagnostic performance compared to standard MRI for the detection and characterization of acute brain infarct. 3 TECHNICAL EFFICACY: Stage 2.

Using Deep Learning to Emulate the Use of an External Contrast Agent in Cardiovascular 4D Flow MRI.

Although contrast agents would be beneficial, they are seldom used in four-dimensional (4D) flow magnetic resonance imaging (MRI) due to potential side effects and contraindications. To develop and evaluate a deep learning architecture to generate high blood-tissue contrast in noncontrast 4D flow MRI by emulating the use of an external contrast agent. Retrospective. Of 222 data sets, 141 were used for neural network (NN) training (69 with and 72 without contrast agent). Evaluation was performed on the remaining 81 noncontrast data sets. Gradient echo or echo-planar 4D flow MRI at 1.5 T and 3 T. A cyclic generative adversarial NN was trained to perform image translation between noncontrast and contrast data. Evaluation was performed quantitatively using contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), structural similarity index (SSIM), mean squared error (MSE) of edges, and Dice coefficient of segmentations. Three observers performed a qualitative assessment of blood-tissue contrast, noise, presence of artifacts, and image structure visualization. The Wilcoxon rank-sum test evaluated statistical significance. Kendall's concordance coefficient assessed interobserver agreement. Contrast in the regions of interest (ROIs) in the NN enhanced images increased by 88%, CNR increased by 63%, and SNR improved by 48% (all P < 0.001). The SSIM was 0.82± 0.01, and the MSE of edges was 0.09± 0.01 (range [0,1]). Segmentations based on the generated images resulted in a Dice similarity increase of 15.25%. The observers managed to differentiate between contrast MR images and our results; however, they preferred the NN enhanced images in 76.7% of cases. This percentage increased to 93.3% for phase-contrast MR angiograms created from the NN enhanced data. Visual grading scores were blood-tissue contrast=4.30± 0.74, noise=3.12± 0.98, and presence of artifacts=3.63± 0.76. Image structures within and without the ROIs resulted in scores of 3.42± 0.59 and 3.07± 0.71, respectively (P < 0.001). The proposed approach improves blood-tissue contrast in MR images and could be used to improve data quality, visualization, and postprocessing of cardiovascular 4D flow data. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 1.

Texture analysis of apparent diffusion coefficient (ADC) map for glioma grading: Analysis of whole tumoral and peri-tumoral tissue

PurposeTo prospectively investigate the capabilities of texture analysis (TA) based on apparent diffusion coefficient (ADC) map of the entire tumor volume and the whole volume of peri-tumoral edema, in discriminating between high-grade glioma (HGG) and low-grade glioma (LGG). Materials and methodsA total of 33 patients with histopathological proven glioma were prospectively included. There were 20 men and 13 women with a mean age of 54.5±14.7 (standard deviation [SD]) years (range: 34–75years). TA parameters of whole tumor and peri-tumoral edema were extracted from the ADC map obtained with diffusion-weighted spin-echo echo-planar magnetic resonance imaging at 1.5–T. TA variables of HGG were compared to those of LGG. The optimum cut-off values of TA variables and their corresponding sensitivity, specificity and accuracy for differentiating between LGG and HGG were calculated using receiver operating characteristic curve analysis. ResultsMean and median tumoral ADC of HGG were significantly lower than those of LGG, at 1.23×10−3 mm2/s and 1.21×10−3 mm2/s cut-off values, yielding 70% sensitivity each (95% CI: 59–82% and 61–80%, respectively), 80% (95% CI: 79–98%) and 90% (95% CI: 82–97%) specificity, and 73% (95% CI: 66–91%) and 76% (95% CI: 72–90%) accuracy, respectively. Significant differences in tumoral and peri-tumoral kurtosis were found between HGG and LGG at 1.60 and 0.314 cut-off values yielding sensitivities of 74% (95% CI: 58–83%) and 70% (95% CI: 59–84%), specificities of 90% (95% CI: 80–95%) and 70% (95% CI: 64–83%) and accuracies of 79% (95% CI: 69–89%) and 70% (95% CI: 64–77%), respectively. ConclusionMeasurements of whole tumoral and peri-tumoral TA, based on ADC maps, provide useful information that helps distinguish between HGG and LGG.

Central vein sign: A diagnostic biomarker in multiple sclerosis (CAVS-MS) study protocol for a prospective multicenter trial

The specificity and implementation of current MRI-based diagnostic criteria for multiple sclerosis (MS) are imperfect. Approximately 1 in 5 of individuals diagnosed with MS are eventually determined not to have the disease, with overreliance on MRI findings a major cause of MS misdiagnosis. The central vein sign (CVS), a proposed MRI biomarker for MS lesions, has been extensively studied in numerous cross sectional studies and may increase diagnostic specificity for MS. CVS has desirable analytical, measurement, and scalability properties. “Central Vein Sign: A Diagnostic Biomarker in Multiple Sclerosis (CAVS-MS)” is an NIH-supported, 2-year, prospective, international, multicenter study conducted by the North American Imaging in MS Cooperative (NAIMS) to evaluate CVS as a diagnostic biomarker for immediate translation into clinical care. Study objectives include determining the concordance of CVS and McDonald Criteria to diagnose MS, the sensitivity of CVS to detect MS in those with typical presentations, and the specificity of CVS among those with atypical presentations. The study will recruit a total of 400 participants (200 with typical and 200 with atypical presentations) across 11 sites. T2*-weighted, high-isotropic-resolution, segmented echo-planar MRI will be acquired at baseline and 24 months on 3-tesla scanners, and FLAIR* images (combination of FLAIR and T2*) will be generated for evaluating CVS. Data will be processed on a cloud-based platform that contains clinical and CVS rating modules. Imaging quality control will be conducted by automated methods and neuroradiologist review. CVS will be determined by Select6* and Select3* lesion methods following published criteria at each site and by central readers, including neurologists and neuroradiologists. Automated CVS detection and algorithms for incorporation of CVS into McDonald Criteria will be tested. Diagnosis will be adjudicated by three neurologists who served on the 2017 International Panel on the Diagnosis of MS. The CAVS-MS study aims to definitively establish CVS as a diagnostic biomarker that can be applied broadly to individuals presenting for evaluation of the diagnosis of MS.

A field-monitoring-based approach for correcting eddy-current-induced artifacts of up to the 2nd spatial order in human-connectome-project-style multiband diffusion MRI experiment at 7T: A pilot study

Over the recent years, significant advances in Spin-Echo (SE) Echo-Planar (EP) Diffusion MRI (dMRI) have enabled improved fiber tracking conspicuity in the human brain. At the same time, pushing the spatial resolution and using higher b-values inherently expose the acquired images to further eddy-current-induced distortion and blurring. Recently developed data-driven correction techniques, capable of significantly mitigating these defects, are included in the reconstruction pipelines developed for the Human Connectome Project (HCP) driven by the NIH BRAIN initiative. In this case, however, corrections are derived from the original diffusion-weighted (DW) magnitude images affected by distortion and blurring. Considering the complexity of k-space deviations in the presence of time varying high spatial order eddy currents, distortion and blurring may not be fully reversed when relying on magnitude DW images only. An alternative approach, consisting of iteratively reconstructing DW images based on the actual magnetic field spatiotemporal evolution measured with a magnetic field monitoring camera, has been successfully implemented at 3T in single band dMRI (Wilm et al., 2017, 2015). In this study, we aim to demonstrate the efficacy of this eddy current correction method in the challenging context of HCP-style multiband (MB ​= ​2) dMRI protocol.The magnetic field evolution was measured during the EP-dMRI readout echo train with a field monitoring camera equipped with 16 19F NMR probes. The time variation of 0th, 1st and 2nd order spherical field harmonics were used to reconstruct DW images. Individual DW images reconstructed with and without field correction were compared. The impact of eddy current correction was evaluated by comparing the corresponding direction-averaged DW images and fractional anisotropy (FA) maps.19F field monitoring data confirmed the existence of significant field deviations induced by the diffusion-encoding gradients, with variations depending on diffusion gradient amplitude and direction. In DW images reconstructed with the field correction, residual aliasing artifacts were reduced or eliminated, and when high b-values were applied, better gray/white matter delineation and sharper gyri contours were observed, indicating reduced signal blurring. The improvement in image quality further contributed to sharper contours and better gray/white matter delineation in mean DW images and FA maps.In conclusion, we demonstrate that up-to-2nd-order-eddy-current-induced field perturbation in multiband, in-plane accelerated HCP-style dMRI acquisition at 7T can be corrected by integrating the measured field evolution in image reconstruction.

Is diffusion-weighted magnetic resonance imaging (DW-MRI) a requirement for suspected cholesteatoma in patients to undergo primary surgery?

Aim: In this study, the aim was to investigate the correlation of preoperative diffusion-weighted magnetic resonance imaging (DW-MRI) with postoperative pathology findings in patients undergoing tympanomastoidectomy with suspicion of primary cholesteatoma. Materials and Methods: The study consisted of the retrospective evaluation of preoperative MRIs, surgical findings and pathology results of patients who underwent tympanomastoidectomy and had preoperative DW-MRI at the Department of Otorhinolaryngology between the years 2017 and 2019. Results: The study was conducted with 199 patients who underwent tympanomastoidectomy surgery. A retrospective examination of patient files revealed that 80 (40.2%) of the patients underwent echoplanar diffusion-weighted magnetic resonance imaging (DW-MRI) because of suspected cholesteatoma in the preoperative period. Of these 80 patients, cholesteatoma was detected in 22 (27.5%) as a result of pathological analysis and/or surgery, but no diffusion restriction was found in MRI interpretation; in 44 (55%) of them, both cholesteatoma in pathological analysis and/or surgery and diffusion restriction in MRI interpretation were detected. In 10 (12.5%) of these 80 patients, cholesteatoma was not detected either in the MRI interpretation or in the pathological analysis and/or surgery. In the remaining 4 (5%) patients, there was a cholesteatoma suspicion in MRI, but it was not detected as a result of pathological analysis or surgery. In this study, the sensitivity of MRI for the diagnosis of cholesteatoma was 66.6%, and its specificity was 71.4%. Conclusion: MRI provides moderately (66.6%) reliable information in the diagnosis of cholesteatoma patients. However, it is more reliable (71.4%) when it comes to exclusion of the disease. Therefore, it should not be used as the sole determining factor in patients who will undergo primary surgery with suspected cholesteatoma. As much as our study results provide guidance for a more accurate use of imaging methods, series with higher numbers of patients are needed.

MoDL-MUSSELS: Model-Based Deep Learning for Multishot Sensitivity-Encoded Diffusion MRI.

We introduce a model-based deep learning architecture termed MoDL-MUSSELS for the correction of phase errors in multishot diffusion-weighted echo-planar MR images. The proposed algorithm is a generalization of the existing MUSSELS algorithm with similar performance but significantly reduced computational complexity. In this work, we show that an iterative re-weighted least-squares implementation of MUSSELS alternates between a multichannel filter bank and the enforcement of data consistency. The multichannel filter bank projects the data to the signal subspace, thus exploiting the annihilation relations between shots. Due to the high computational complexity of the self-learned filter bank, we propose replacing it with a convolutional neural network (CNN) whose parameters are learned from exemplary data. The proposed CNN is a hybrid model involving a multichannel CNN in the k-space and another CNN in the image space. The k-space CNN exploits the annihilation relations between the shot images, while the image domain network is used to project the data to an image manifold. The experiments show that the proposed scheme can yield reconstructions that are comparable to state-of-the-art methods while offering several orders of magnitude reduction in run-time.

Intrinsic Brain Pulsatile Motion Analysis Using Velocity Mapping with Echo-Planar Cine Imaging - Implications for Intracranial Radiosurgery

Brain pulsatile motion during the cardiac cycle was measured with echo-planar magnetic resonance (MR) imaging. The major cerebral lobes, diencephalon, brain stem, cerebellum, cerebellar tonsils, and spinal cord were studied. The authors measured the intrinsic pulsatile motion of normal brain parenchyma in 10 healthy volunteers using Phase-sensitive, electrocardiography-gated, two-dimensional cine images acquired throughout the cardiac cycle by using a spin-echo, blipped echo-planar MR pulse sequence acquired in Transverse and coronal planes. Corrections were made for gross head motion. Brain motion consisted of a rapid displacement in systole, with a slow diastolic recovery. The overall pattern of brain motion showed caudal motion of the central structures (diencephalon, brain stem, and cerebellar tonsils) shortly after carotid systole, with concurrent cephalic motion of the major cerebral lobes and posterior cerebellar hemisphere. Peak brain displacement was in the range of 0.1-0.5 mm for all the structures except the cerebellar tonsils, which had greater displacement (0.4 mm +/- 0.16 [mean +/- SE]). The motion occurred chiefly in the cephalocaudal and lateral directions; the anteroposterior motions were relatively small. Cephalocaudal velocities increase with proximity to the foramen magnum. Brain parenchymal velocities were as high as 2 mm/sec caudally in the brain stem and 1.5 mm/sec medially in the thalami. The lateral motion is mainly a compressive motion of the thalami. Velocity mapping with Cine echo-planar imaging offers a rapid and flexible method of assessing the pulsation velocities of the human brain.The subtle brain motion captured through cine imaging quantified the physiologic oscillatory motion, albeit minor, would have particular relevance in the intracranial Radiosurgery.

Reduced field of view echo-planar imaging diffusion tensor MRI for pediatric spinal tumors.

Spine MRI is a diagnostic modality for evaluating pediatric CNS tumors. Applying diffusion-weighted MRI (DWI) or diffusion tensor imaging (DTI) to the spine poses challenges due to intrinsic spinal anatomy that exacerbates various image-related artifacts, such as signal dropouts or pileups, geometrical distortions, and incomplete fat suppression. The zonal oblique multislice (ZOOM)-echo-planar imaging (EPI) technique reduces geometric distortion and image blurring by reducing the field of view (FOV) without signal aliasing into the FOV. The authors hypothesized that the ZOOM-EPI method for spine DTI in concert with conventional spinal MRI is an efficient method for augmenting the evaluation of pediatric spinal tumors. Thirty-eight consecutive patients (mean age 8 years) who underwent ZOOM-EPI spine DTI for CNS tumor workup were retrospectively identified. Patients underwent conventional spine MRI and ZOOM-EPI DTI spine MRI. Two blinded radiologists independently reviewed two sets of randomized images: conventional spine MRI without ZOOM-EPI DTI, and conventional spine MRI with ZOOM-EPI DTI. For both image sets, the reviewers scored the findings based on lesion conspicuity and diagnostic confidence using a 5-point Likert scale. The reviewers also recorded presence of tumors. Quantitative apparent diffusion coefficient (ADC) measurements of various spinal tumors were extracted. Tractography was performed in a subset of patients undergoing presurgical evaluation. Sixteen patients demonstrated spinal tumor lesions. The readers were in moderate agreement (kappa = 0.61, 95% CI 0.30-0.91). The mean scores for conventional MRI and combined conventional MRI and DTI were as follows, respectively: 3.0 and 4.0 for lesion conspicuity (p = 0.0039), and 2.8 and 3.9 for diagnostic confidence (p < 0.001). ZOOM-EPI DTI identified new lesions in 3 patients. In 3 patients, tractography used for neurosurgical planning showed characteristic fiber tract projections. The mean weighted ADCs of low- and high-grade tumors were 1201 × 10-6 and 865 × 10-6 mm2/sec (p = 0.002), respectively; the mean minimum weighted ADCs were 823 × 10-6 and 474 × 10-6 mm2/sec (p = 0.0003), respectively. Diffusion MRI with ZOOM-EPI can improve the detection of spinal lesions while providing quantitative diffusion information that helps distinguish low- from high-grade tumors. By adding a 2-minute DTI scan, quantitative diffusion information and tract profiles can reliably be obtained and serve as a useful adjunct to presurgical planning for pediatric spinal tumors.

Diagnostic Accuracy of Echo-planar Diffusion-weighted Imaging in the Diagnosis of Intra-cerebral Abscess by Taking Histopathological Findings as the Gold Standard.

ObjectiveTo determine the diagnostic accuracy of echo-planar diffusion-weighted imaging (DWI) in the diagnosis of intra-cerebral abscesses by taking histopathological findings as the gold standard.Subject and methodsA retrospective cross-sectional study was performed from July 2014 to June 2015 at a tertiary care hospital in Karachi. A total of 462 patients, who were referred for magnetic resonance imaging (MRI) brain, presenting with clinical suspicion of an intra-cerebral abscess on the basis of clinical signs and symptoms, were included in this study. MR imaging was performed. All patients subsequently underwent surgery. The histopathological findings of these patients were collected and compared with echo-planar diffusion-weighted MRI findings. A proforma was used to record the findings.ResultsThe mean age of the patients was 47.39±13.54 years. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of echo-planar diffusion-weighted MRI in the diagnosis of intra-cerebral abscesses was 85.64%, 95.88%, 93.82%, 90.14%, and 91.56%, respectively.ConclusionBrain abscesses and necrotic tumors are, most of the time, difficult to differentiate on routine conventional imaging, and prompt diagnosis is important, as an untreated brain abscess could be lethal. Diffusion imaging can aid in the diagnosis and further management plan so as to help in improved patient care. Although this sequence has high sensitivity and specificity, it should be used in addition to conventional imaging and not as a replacement of histopathology.