Gradient-recalled Echo Images Research Articles

Precision and Test-Retest Repeatability of Stiffness Measurement with MR Elastography: A Multicenter Phantom Study.

Background MR elastography (MRE) has been shown to have excellent performance for noninvasive liver fibrosis staging. However, there is limited knowledge regarding the precision and test-retest repeatability of stiffness measurement with MRE in the multicenter setting. Purpose To determine the precision and test-retest repeatability of stiffness measurement with MRE across multiple centers using the same phantoms. Materials and Methods In this study, three cylindrical phantoms made of polyvinyl chloride gel mimicking different degrees of liver stiffness in humans (phantoms 1-3: soft, medium, and hard stiffness, respectively) were evaluated. Between January 2021 and January 2022, phantoms were circulated between five different centers and scanned with 10 MRE-equipped clinical 1.5-T and 3-T systems from three major vendors, using two-dimensional (2D) gradient-recalled echo (GRE) imaging and/or 2D spin-echo (SE) echo-planar imaging (EPI). Similar MRE acquisition parameters, hardware, and reconstruction algorithms were used at each center. Mean stiffness was measured by a single observer for each phantom and acquisition on a single section. Stiffness measurement precision and same-session test-retest repeatability were assessed using the coefficient of variation (CV) and the repeatability coefficient (RC), respectively. Results The mean precision represented by the CV was 5.8% (95% CI: 3.8, 7.7) for all phantoms and both sequences combined. For all phantoms, 2D GRE achieved a CV of 4.5% (95% CI: 3.3, 5.7) whereas 2D SE EPI achieved a CV of 7.8% (95% CI: 3.1, 12.6). The mean RC of stiffness measurement was 5.8% (95% CI: 3.7, 7.8) for all phantoms and both sequences combined, 4.9% (95% CI: 2.7, 7.0) for 2D GRE, and 7.0% (95% CI: 2.9, 11.2) for 2D SE EPI (all phantoms). Conclusion MRE had excellent in vitro precision and same-session test-retest repeatability in the multicenter setting when similar imaging protocols, hardware, and reconstruction algorithms were used. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Tang in this issue.

Magnetic resonance imaging subtraction vs. pre- and post-contrast 3D gradient recalled echo fat suppressed imaging for evaluation of the canine and feline brain.

Subtraction magnetic resonance imaging (MRI) has been reported to increase accuracy in the diagnosis of meningeal and inflammatory brain diseases in small animals. 3D T1W gradient recalled echo (GRE) techniques have been proposed as a suitable alternative to conventional spin echo sequences in imaging the canine brain. The aim of this study was to compare subtraction images and paired pre- and post-contrast 3D T1W GRE fat suppressed (FS) images in canine and feline MRI studies using clinical diagnosis as the gold standard. Paired pre- and post-contrast T1W 3D FS GRE images and individual subtraction images of 100 small animal patients were randomized and independently evaluated by 2 blinded observers. Diagnosis categories were "normal," "inflammatory," "neoplastic," and "other." Clinical diagnosis was made in the same categories and served as the gold standard. Image interpretation results were compared to the clinical diagnosis. Interobserver agreement was determined. Clinically, 41 studies were categorized as "normal," 18 as "inflammatory," 28 as "neoplastic," and 13 as "other." The agreement of the pre- and post-contrast GRE images with the gold standard was significantly higher than that of the subtraction images (k = 0.7491 vs. k = 0.5924; p = 0.0075). The largest sources of error were misinterpretation of "other" as "normal" and "normal" as "inflammatory." There was no significant difference between the two observers (p = 0.8820). Based on this study, subtraction images do not provide an advantage to paired pre- and post-contrast FS GRE images when evaluating the canine and feline brain.

Enhancing the brain MRI at ultra-high field systems using a meta-array structure.

The main advantage of ultra-high field (UHF) magnetic resonance neuroimaging is theincreased signal-to-noise ratio (SNR) compared with lower field strength imaging. However, the wavelength effect associated with UHF MRI results in radiofrequency (RF) inhomogeneity, compromising whole brain coverage for many commercial coils. Approaches to resolving this issue of transmit field inhomogeneity include the design of parallel transmit systems (PTx), RF pulse design, and applying passive RF shimming such as high dielectric materials. However, these methods have some drawbacks such as unstable material parameters of dielectric pads, high-cost, and complexity of PTx systems. Metasurfaces are artificial structures with a unique platform that can control the propagation of the electromagnetic (EM) waves, and they are very promising for engineering EM device. Implementation of meta-arrays enhancing MRI has been explored previously in several studies. The aim of this study was to assess the effect of new meta-array technology on enhancing the brain MRI at 7T. A meta-array based on a hybrid structure consisting of an array of broadside-coupled split-ring resonators and high-permittivity materials was designed to work at the Larmor frequency of a 7 Tesla (7T) MRI scanner. When placed behind the head and neck, this construct improves the SNR in the region of the cerebellum,brainstem and the inferior aspect of the temporal lobes. Numerical electromagnetic simulations were performed to optimize the meta-array design parameters and determine the RF circuit configuration. The resultant transmit-efficiency and signal sensitivity improvements were experimentally analyzed in phantoms followed by healthy volunteers using a 7T whole-body MRI scanner equipped with a standard one-channel transmit, 32-channel receive head coil. Efficacy was evaluated through acquisition with and without the meta-array using two basic sequences: gradient-recalled-echo (GRE) and turbo-spin-echo (TSE). Experimental phantom analysis confirmed two-fold improvement in the transmit efficiency and 1.4-fold improvement in the signal sensitivity in the target region. In vivo GRE and TSE images with the meta-array in place showed enhanced visualization in inferior regions of the brain, especially of the cerebellum, brainstem, and cervical spinal cord. Addition of the meta-array to commonly used MRI coils can enhance SNR to extend the anatomical coverage of the coil and improve overall MRI coil performance. This enhancement in SNR can be leveraged to obtain a higher resolution image over the same time slot or faster acquisition can be achieved with same resolution. Using this technique could improve the performance of existing commercial coils at 7T for whole brain and other applications.

MRI-based quantification of whole-organ renal metabolic rate of oxygen.

During the early stages of diabetes, kidney oxygen utilization increases. The mismatch between oxygen demand and supply contributes to tissue hypoxia, a key driver of chronic kidney disease. Thus, whole-organ renal metabolic rate of oxygen (rMRO2 ) is a potentially valuable biomarkerof kidney function. The key parameters required to determine rMRO2 include the renal blood flow rate (RBF) in the feeding artery and oxygen saturation in the draining renal vein (SvO2 ). However, there is currently no noninvasive method to quantify rMRO2 in absolute physiologic units. Here, a new MRI pulse sequence, Kidney Metabolism of Oxygen via T2 and Interleaved Velocity Encoding (K-MOTIVE), is described, along with evaluation of its performance in the human kidney in vivo. K-MOTIVE interleaves a phase-contrast module before a background-suppressed T2 -prepared balanced steady-state-free-precession (bSSFP) readout to measure RBF and SvO2 in a single breath-hold period of 22 s, yielding rMRO2 via Fick's principle. Variants of K-MOTIVE to evaluate alternative bSSFP readout strategies were studied. Kidney mass was manually determined from multislice gradient recalled echo images. Healthy subjects were recruited to quantify rMRO2 of the left kidney at 3-T field strength (N= 15). Assessments of repeat reproducibility and comparisons with individual measurements of RBF and SvO2 were performed, and the method's sensitivity was evaluated with a high-protein meal challenge (N= 8). K-MOTIVE yielded the following metabolic parameters: T2 = 157 ± 19 ms; SvO2 = 92% ± 6%; RBF = 400 ± 110 mL/min; and rMRO2 = 114 ± 117(μmol O2 /min)/100 g tissue. Reproducibility studies of T2 and RBF (parameters directly measured by K-MOTIVE) resulted in coefficients of variation less than 10% and intraclass correlation coefficients more than 0.75. The high-protein meal elicited an increase in rMRO2 , which was corroborated by serum biomarkers. The K-MOTIVE sequence measures SvO2 and RBF, the parameters necessary to quantify whole-organ rMRO2 , in a single breath-hold. The present work demonstrates that rMRO2 quantification is feasible with good reproducibility. rMRO2 is a potentially valuable physiological biomarker.

Functional and Morphological Brain Alterations in Dysthyroid Optic Neuropathy: A Combined Resting-State fMRI and Voxel-Based Morphometry Study.

Increasing evidence has indicated that the entire visual pathway from retina to visual cortex may be involved in dysthyroid optic neuropathy (DON) pathological mechanisms. To explore the functional and morphological brain characteristics in DON and their relationship with ophthalmologic performance. Retrospective. A total of 30 DON patients, 40 thyroid-associated ophthalmopathy (TAO) without DON patients and 21 healthy-controls (HCs). A 3.0 T, 3D T1-weighted spoiled gradient-recalled echo and gradient-recalled echo-planar imaging. Functional and structural alterations in brain regions were evaluated with fractional amplitude of low-frequency fluctuations, degree centrality (DC), and gray matter volume (GMV). Clinical activity score (CAS) is assessed across patients. One-way analysis of variance with post hoc two sample t-tests (GRF-corrected, voxel level: P< 0.005, cluster level: P< 0.05) and correlation analysis (significance level: P< 0.05). Compared to HCs, DON patients had significantly decreased DC values in the bilateral BA17 and BA18 regions. Compared to the TAO group, DON patients had decreased GMV in the left anterior cingulate cortex, left middle frontal gyrus, left lingual gyrus, left parietal gyrus, right Rolandic operculum, left supplementary motor area, and right middle temporal gyrus. In addition, GMV in the right Rolandic operculum was significantly positively correlated with CAS (correlation coefficient: r= 0.448). This study showed significant morphological and functional alterations in visual cortex and morphological alterations in partial default mode network regions of DON patients, which may provide insights into the mechanism of vision loss and may facilitate the diagnosis and treatment of DON. 3. Stage 3.

Quantitative Susceptibility Mapping of Brain Iron Deposition in Patients With Recurrent Depression.

Objective Recurrence is the most significant feature of depression and the relationship between iron and recurrent depression is still lack of direct evidence in vivo. Methods Twenty-one patients with depression and twenty control subjects were included. Gradient-recalled echo, T1 and T2 images were acquired using a 3.0T MRI system. After quantitative susceptibility mapping were reconstructed and standardized, a whole-brain and the regions of interest were respectively analyzed. Results Significant increases in susceptibility were found in multiple recurrent depression patients, which involved several brain regions (frontal lobes, temporal lobe structures, occipital lobes hippocampal regions, putamen, thalamus, cingulum, and cerebellum). Interestingly, no susceptibility changes after treatment compared to pre-treatment (all p>0.05) and no significant correlation between susceptibility and Hamilton Depression Rating Scale were found. Besides, it was close to significance that those with a higher relapse frequency or a longer mean duration of single episode had a higher susceptibility in the putamen, thalamus, and hippocampus. Further studies showed susceptibility across the putamen (ρ2=0.27, p<0.001), thalamus (ρ2=0.21, p<0.001), and hippocampus (ρ2=0.19, p<0.001) were strongly correlated with total course of disease onset. Conclusion Brain iron deposition is related to the total course of disease onset, but not the severity of depression, which suggest that brain iron deposition may be a sign of brain damage in multiple recurrent depression.

Multi-echo quantitative susceptibility mapping: how to combine echoes for accuracy and precision at 3 Tesla.

PurposeTo compare different multi‐echo combination methods for MRI QSM. Given the current lack of consensus, we aimed to elucidate how to optimally combine multi‐echo gradient‐recalled echo signal phase information, either before or after applying Laplacian‐base methods (LBMs) for phase unwrapping or background field removal.MethodsMulti‐echo gradient‐recalled echo data were simulated in a numerical head phantom, and multi‐echo gradient‐recalled echo images were acquired at 3 Tesla in 10 healthy volunteers. To enable image‐based estimation of gradient‐recalled echo signal noise, 5 volunteers were scanned twice in the same session without repositioning. Five QSM processing pipelines were designed: 1 applied nonlinear phase fitting over TEs before LBMs; 2 applied LBMs to the TE‐dependent phase and then combined multiple TEs via either TE‐weighted or SNR‐weighted averaging; and 2 calculated TE‐dependent susceptibility maps via either multi‐step or single‐step QSM and then combined multiple TEs via magnitude‐weighted averaging. Results from different pipelines were compared using visual inspection; summary statistics of susceptibility in deep gray matter, white matter, and venous regions; phase noise maps (error propagation theory); and, in the healthy volunteers, regional fixed bias analysis (Bland–Altman) and regional differences between the means (nonparametric tests).ResultsNonlinearly fitting the multi‐echo phase over TEs before applying LBMs provided the highest regional accuracy of χ and the lowest phase noise propagation compared to averaging the LBM‐processed TE‐dependent phase. This result was especially pertinent in high‐susceptibility venous regions.ConclusionFor multi‐echo QSM, we recommend combining the signal phase by nonlinear fitting before applying LBMs.

A Multifunctional Contrast Agent for 19F-Based Magnetic Resonance Imaging.

Magnetic resonance imaging, MRI, relying on 19F nuclei has attracted much attention, because the isotopes exhibit a high gyromagnetic ratio (comparable to that of protons) and have 100% natural abundance. Furthermore, due to the very low traces of intrinsic fluorine in biological tissues, fluorine labeling allows easy visualization in vivo using 19F-based MRI. However, one of the drawbacks of the available fluorine tracers is their very limited solubility in water. Here, we detail the design and preparation of a set of water-compatible fluorine-rich polymers as contrast agents that can enhance the effectiveness of 19F-based MRI. The agents are synthesized using the nucleophilic addition reaction between poly(isobutylene-alt-maleic anhydride) copolymer and a mixture of amine-appended fluorine groups and polyethylene glycol (PEG) blocks. This allows control over the polymer architecture and stoichiometry, resulting in good affinity to water solutions. We further investigate the effects of introducing additional segmental mobility to the fluorine moieties in the polymer, by inserting a PEG linker between the moieties and the polymer backbone. We find that controlling the polymer stoichiometry and introducing additional segmental mobility enhance the NMR signals and narrow the peak profile. In particular, we assess the impact of the PEG linker on T2* and T1 relaxation times, using a series of gradient-recalled echo images with varying echo times, TE, or recovery time, TR, respectively. We find that for equivalent concentrations, the PEG linker greatly increases T2*, while maintaining high T1 values, as compared to polymers without this linker. Phantom images collected from these compounds show bright signals over a background with high intensities.

T1 mapping as a surrogate marker of chemotherapy response evaluation in patients with osteosarcoma

ObjectivesTo characterize baseline T1 values of tumors, measure changes after the course of chemotherapy, and evaluate its potential as a marker of response assessment in patients with osteosarcoma. Materials and MethodsA total of 35 patients (male:female = 27:8; age = 17.9 ± 6 years; metastatic:localized = 11:24) with biopsy-proven osteosarcoma were analyzed prospectively. All patients underwent magnetic resonance imaging before neoadjuvant chemotherapy (NACT) (baseline) and after NACT completion (follow-up), followed by surgery and histopathological evaluation. Histopathological necrosis served as the gold standard for assessing chemotherapy response (responder: ≥50% necrosis and non-responder: <50% necrosis). Three-dimensional spoiled gradient recalled echo images were acquired with varying flip angles (50, 100, 200, and 300) using a 1.5 Tesla scanner. T1 values were estimated in healthy muscle tissue and tumors at baseline and follow-up, and the relative percentage changes after NACT (ΔT1) were evaluated, and histogram analysis was performed to characterize the T1 value of the tumor and predict the NACT response using the Pearson correlation coefficient (r) and receiver operating characteristic curve analysis. ResultsAt baseline, a significantly higher T1-mean (830.96 ± 193.88 msec versus 683.29 ± 210.00 msec; p = 0.003) and lower T1-skewness (0.86 ± 1.66 versus 1.60 ± 1.55; p = 0.02) were observed in osteosarcoma than healthy tissue. Responder:non-responder ratio was 13:22. At baseline, a significantly higher T1-mean (936.14 ± 193.17 msec versus 768.82 ± 169.25 msec; p = 0.018) and lower T1-skewness (-0.17 ± 0.85 versus 1.47 ± 1.73; p = 0.003) were observed among responders, than non-responders. After NACT, ΔT1 in tumor was significantly higher among responders than non-responders (-27.22 ± 12.17% versus −15.70 ± 18.99%; p = 0.034). ΔT1-mean and ΔT1-skewness after NACT were moderately correlated (r = − 0.4, p = 0.030; r = 0.4, p = 0.011) with histopathological necrosis. For predicting NACT response, T1-mean and T1-skewness jointly produced an area under the curve (AUC) = 0.80 at baseline, and ΔT1-mean and ΔT1-skewness jointly produced AUC = 0.76 after NACT. ConclusionThe mean and skewness of T1 values in osteosarcoma are potential non-invasive imaging markers for chemotherapy response assessment.

Quantitative analysis of the ACL and PCL using T1rho and T2 relaxation time mapping: an exploratory, cross-sectional comparison between OA and healthy control knees

BackgroundQuantitative magnetic resonance imaging (MRI) methods such as T1rho and T2 mapping are sensitive to changes in tissue composition, however their use in cruciate ligament assessment has been limited to studies of asymptomatic populations or patients with posterior cruciate ligament tears only. The aim of this preliminary study was to compare T1rho and T2 relaxation times of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) between subjects with mild-to-moderate knee osteoarthritis (OA) and healthy controls.MethodsA single knee of 15 patients with mild-to-moderate knee OA (Kellgren-Lawrence grades 2–3) and of 6 age-matched controls was imaged using a 3.0 T MRI. Three-dimensional (3D) fat-saturated spoiled gradient recalled-echo images were acquired for morphological assessment and T1ρ- and T2-prepared pseudo-steady-state 3D fast spin echo images for compositional assessment of the cruciate ligaments. Manual segmentation of whole ACL and PCL, as well as proximal / middle / distal thirds of both ligaments was carried out by two readers using ITK-SNAP and mean relaxation times were recorded. Variation between thirds of the ligament were assessed using repeated measures ANOVAs and differences in these variations between groups using a Kruskal-Wallis test. Inter- and intra-rater reliability were assessed using intraclass correlation coefficients (ICCs).ResultsIn OA knees, both T1rho and T2 values were significantly higher in the distal ACL when compared to the rest of the ligament with the greatest differences in T1rho (e.g. distal mean = 54.5 ms, proximal = 47.0 ms, p < 0.001). The variation of T2 values within the PCL was lower in OA knees (OA: distal vs middle vs proximal mean = 28.5 ms vs 29.1 ms vs 28.7 ms, p = 0.748; Control: distal vs middle vs proximal mean = 26.4 ms vs 32.7 ms vs 33.3 ms, p = 0.009). ICCs were excellent for the majority of variables.ConclusionT1rho and T2 mapping of the cruciate ligaments is feasible and reliable. Changes within ligaments associated with OA may not be homogeneous. This study is an important step forward in developing a non-invasive, radiological biomarker to assess the ligaments in diseased human populations in-vivo.

MR elastography in patients with suspected diffuse liver disease at 1.5T: Intraindividual comparison of gradient-recalled echo versus spin-echo echo-planar imaging sequences and investigation of potential confounding factors

PurposeTo compare liver stiffness (LS) in patients with suspected diffuse liver disease between gradient-recalled-echo magnetic resonance elastography (GRE-MRE) and different spin-echo echo-planar imaging (SE-EPI-MRE) sequences and to investigate confounding factors including fat, iron, age, and sex. MethodLS was measured at 1.5T using GRE-MRE, SE-EPI-MRE and short-TE-SE-EPI-MRE (hiSE-EPI-MRE) sequences and compared using Bland-Altman-plots together with concordance correlation coefficients (CCC). Success gradings were evaluated considering possible confounding factors. Results305 patients (225 male, 80 females, mean age 51.12 years) were included. 109/305 showed hepatic iron overload, 183 hepatic steatosis. The mean difference (bias) in stiffness values between GRE-MRE and SE-EPI-MRE/hiSE-EPI-MRE was 0.15/0.2 kPa (LOA: −0.72,0.41 kPa/-0.94,0.55 kPa), between SE-EPI-MRE and hiSE-EPI-MRE 0.04 kPa (LOA: −0.62,0.53 kPa). The CCC for agreement between stiffness values for GRE-MRE and SE-EPI-MRE was 0.94 (0.92–0.95), 0.89 (0.86–0.91) for hiSE-EPI-MRE and GRE-MRE and 0.94 (0.92–0.95) for SE-EPI-MRE and hiSE-EPI-MRE. Using GRE-MRE, 72/305 showed unusable results whereby all these patients had high iron levels (mean R2*=209.7 1/s). For SE-EPI-MRE and hiSE-EPI-MRE only 10/305 and 8/305 were inconclusive respectively, corresponding to a significantly higher iron load (mean R2*= 549.2 1/s for SE-EPI-MRE and 570.7 1/s for hiSE-EPI-MRE). Concerning fat, age or sex no significant influence on success was observed for all sequences. ConclusionsGood agreement of LS values was observed between GRE-MRE and SE-EPI-MRE sequences. The number of successful exams, however, was considerably lower for GRE-MRE, mainly due to iron content.Study reference number: AN5093.

Reader Response: Critical Illness-Associated Cerebral Microbleeds in COVID-19 Acute Respiratory Distress Syndrome.

We read with great interest the report by Cannac et al.,1 which adds to a rapidly growing body of evidence that severe COVID-19 is associated with cerebral microvascular lesions.2 However, we caution against the assumption that the observed lesions solely represent microhemorrhages. Although lesions showing a susceptibility effect on T2*-weighted gradient-recalled echo imaging often indicate microhemorrhages,3 the differential diagnosis for these lesions also includes microthrombi and air emboli, the latter being common in patients treated with extracorporeal membrane oxygenation (ECMO), as in the patient reported here. Indeed, in a patient with similar susceptibility lesions in the setting of H1N1 influenza treated with ECMO, postmortem histopathologic analysis revealed that many lesions corresponded to microinfarcts, not microhemorrhages.4

Frequency, Determinants, and Outcomes of Emboli to Distal and New Territories Related to Mechanical Thrombectomy for Acute Ischemic Stroke.

Clot fragmentation and distal embolization during endovascular thrombectomy for acute ischemic stroke may produce emboli downstream of the target occlusion or in previously uninvolved territories. Susceptibility-weighted magnetic resonance imaging can identify both emboli to distal territories (EDT) and new territories (ENT) as new susceptibility vessel signs (SVS). Diffusion-weighted imaging (DWI) can identify infarcts in new territories (INT). We studied consecutive acute ischemic stroke patients undergoing magnetic resonance imaging before and after thrombectomy. Frequency, predictors, and outcomes of EDT and ENT detected on gradient-recalled echo imaging (EDT-SVS and ENT-SVS) and INT detected on DWI (INT-DWI) were analyzed. Among 50 thrombectomy-treated acute ischemic stroke patients meeting study criteria, mean age was 70 (±16) years, 44% were women, and presenting National Institutes of Health Stroke Scale score 15 (interquartile range, 8–19). Overall, 21 of 50 (42%) patients showed periprocedural embolic events, including 10 of 50 (20%) with new EDT-SVS, 10 of 50 (20%) with INT-DWI, and 1 of 50 (2%) with both. No patient showed ENT-SVS. On multivariate analysis, model-selected predictors of EDT-SVS were lower initial diastolic blood pressure (odds ratio, 1.09 [95% CI, 1.02–1.16]), alteplase pretreatment (odds ratio, 5.54 [95% CI, 0.94–32.49]), and atrial fibrillation (odds ratio, 7.38 [95% CI, 1.02–53.32]). Classification tree analysis identified pretreatment target occlusion SVS as an additional predictor. On univariate analysis, INT-DWI was less common with internal carotid artery (5%), intermediate with middle cerebral artery (25%), and highest with vertebrobasilar (57%) target occlusions (P=0.02). EDT-SVS was not associated with imaging/functional outcomes, but INT-DWI was associated with reduced radiological hemorrhagic transformation (0% versus 54%; P<0.01). Among acute ischemic stroke patients treated with thrombectomy, imaging evidence of distal emboli, including EDT-SVS beyond the target occlusion and INT-DWI in novel territories, occur in about 2 in every 5 cases. Predictors of EDT-SVS are pretreatment intravenous fibrinolysis, potentially disrupting thrombus structural integrity; atrial fibrillation, possibly reflecting larger target thrombus burden; lower diastolic blood pressure, suggestive of impaired embolic washout; and pretreatment target occlusion SVS sign, indicating erythrocyte-rich, friable target thrombus.

Intracerebral Hemorrhage in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy: Prevalence, Clinical and Neuroimaging Features and Risk Factors.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a monogenic cerebral small vessel disease. The role of intracerebral hemorrhage (ICH) in CADASIL remains elusive. The present study aims to investigate the prevalence, characteristics, and risk factors for ICH in CADASIL. This retrospective cross-sectional study investigated ICH and cerebral microbleeds (CMBs) in brain susceptibility-weighted imaging or T2*-weighted gradient-recalled echo images of 127 Taiwanese patients with genetically confirmed CADASIL. We analyzed CMBs, lacunes, white matter hyperintensity, and perivascular space. The total small vessel disease score (range, 0-4) was calculated to estimate the overall magnetic resonance imaging burden of small vessel disease. Multivariate regression analysis was performed to identify factors related to ICH lesions in CADASIL. Thirty-seven ICH lesions, including 15 symptomatic and 22 asymptomatic lesions, were found in 27 (21.3% [95% CI, 14.0%-30.9%]) of the 127 patients with CADASIL. The thalamus and lobar regions were the most common ICH locations, and 72.7% of the lobar hemorrhages occurred silently. Patients with CADASIL with ICH lesions more often had hypertension and a higher total small vessel disease score than those without ICH (odds ratio [95% CI]: 3.22 [1.25-8.30] and 3.79 [1.51-9.51]). The presence of CMBs in the brain stem and a total CMB count >10 were independently associated with ICH lesions in patients with CADASIL, with odds ratio (95% CI) of 5.82 (1.80-18.80) and 3.83 (1.08-13.67), respectively. ICH is an underestimated but important manifestation of CADASIL. The location and number of CMBs are associated with the presence of ICH lesions in patients with CADASIL.

MRI-based R2* mapping in patients with suspected or known iron overload.

R2* relaxometry is a quantitative method for assessment of iron overload. The purpose is to analyze the cross-sectional relationships between R2* in organs across patients with primary and secondary iron overload. Secondary analyses were conducted to analyze R2* according to treatment regimen. This is a retrospective, cross-sectional, institutional review board-approved study of eighty-one adult patients with known or suspected iron overload. R2* was measured by segmenting the liver, spleen, bone marrow, pancreas, renal cortex, renal medulla, and myocardium using breath-hold multi-echo gradient-recalled echo imaging at 1.5T. Phlebotomy, transfusion, and chelation therapy were documented. Analyses included correlation, Kruskal-Wallis, and post hoc Dunn tests. p < 0.01 was considered significant. Correlations between liver R2* and that of the spleen, bone marrow, pancreas, and heart were respectively 0.49, 0.33, 0.27, and 0.34. R2* differed between patients with primary and secondary overload in the liver (p < 0.001), spleen (p < 0.001), bone marrow (p < 0.01), renal cortex (p < 0.001), and renal medulla (p < 0.001). Liver, spleen, and bone marrow R2* were higher in thalassemia than in hereditary hemochromatosis (all p < 0.01). Renal cortex R2* was higher in sickle cell disease than in hereditary hemochromatosis (p < 0.001) and in thalassemia (p < 0.001). Overall, there was a trend toward lower liver R2* in patients assigned to phlebotomy and higher liver R2* in patients assigned to transfusion and chelation therapy. R2* relaxometry revealed differences in degree or distribution of iron overload between organs, underlying etiologies, and treatment.

English

A 53 year old man presented with right sided neck swelling which was tender on palpation along with symptoms such as high grade fever and sweating since 4 days. No significant and relevant personal and family history was present. Patient had a successful operative history for a benign neurogenic tumour in right infratemporal fossa 1.5 months back. Patient was relatively asymptomatic before 10 days. He then gradually developed a swelling at the operative site which sooner became tender and was accompanied with high grade fever 4 days back. Patient also complained of mild restriction of neck movements as well. He then came for detailed examination and then was referred for MRI examination as a part of protocol. Radiological Features Routine MRI examination showed a well-defined circumscribed lesion at operative site in right infra temporal fossa which appeared to be peripherally thick walled hypo intense in T1W images (green arrow Fig. 1) and hyper intense in T2W images (green arrow Fig. 2). On further sequences it was noted that a diffuse hypo intense central part is noted in all sequences which was prominent in GRE (Gradient Recalled Echo) images showing again hyper intense thick wall (pink arrow in Fig 3) and central hypo intensity (blue arrow in Fig. 3) suggesting multiple air foci. Haemorrhage was excluded in view of lack of T1W hyper intensity. On STIR (Short Tau Inversion Recovery) images no significant other information was gained about the lesion (green arrow in Fig. 4). Observing the whole examination at first it looked like an abscess but due to lack of diffusion restriction and surrounding soft tissue swelling, this differential is ruled out

Associations of quantitative susceptibility mapping with Alzheimer's disease clinical and imaging markers

Altered iron metabolism has been hypothesized to be associated with Alzheimer's disease pathology, and prior work has shown associations between iron load and beta amyloid plaques. Quantitative susceptibility mapping (QSM) is a recently popularized MR technique to infer local tissue susceptibility secondary to the presence of iron as well as other minerals. Greater QSM values imply greater iron concentration in tissue. QSM has been used to study relationships between cerebral iron load and established markers of Alzheimer's disease, however relationships remain unclear. In this work we study QSM signal characteristics and associations between susceptibility measured on QSM and established clinical and imaging markers of Alzheimer's disease. The study included 421 participants (234 male, median age 70 years, range 34–97 years) from the Mayo Clinic Study of Aging and Alzheimer's Disease Research Center; 296 (70%) had a diagnosis of cognitively unimpaired, 69 (16%) mild cognitive impairment, and 56 (13%) amnestic dementia. All participants had multi-echo gradient recalled echo imaging, PiB amyloid PET, and Tauvid tau PET. Variance components analysis showed that variation in cortical susceptibility across participants was low. Linear regression models were fit to assess associations with regional susceptibility. Expected increases in susceptibility were found with older age and cognitive impairment in the deep and inferior gray nuclei (pallidum, putamen, substantia nigra, subthalamic nucleus) (betas: 0.0017 to 0.0053 ppm for a 10 year increase in age, p = 0.03 to <0.001; betas: 0.0021 to 0.0058 ppm for a 5 point decrease in Short Test of Mental Status, p = 0.003 to p<0.001). Effect sizes in cortical regions were smaller, and the age associations were generally negative. Higher susceptibility was significantly associated with higher amyloid PET SUVR in the pallidum and putamen (betas: 0.0029 and 0.0012 ppm for a 20% increase in amyloid PET, p = 0.05 and 0.02, respectively), higher tau PET in the basal ganglia with the largest effect size in the pallidum (0.0082 ppm for a 20% increase in tau PET, p<0.001), and with lower cortical gray matter volume in the medial temporal lobe (0.0006 ppm for a 20% decrease in volume, p = 0.03). Overall, these findings suggest that susceptibility in the deep and inferior gray nuclei, particularly the pallidum and putamen, may be a marker of cognitive decline, amyloid deposition, and off-target binding of the tau ligand. Although iron has been demonstrated in amyloid plaques and in association with neurodegeneration, it is of insufficient quantity to be reliably detected in the cortex using this implementation of QSM.

Rapid single scan ramped hybrid-encoding for bicomponent T2* mapping in a human knee joint: A feasibility study.

The purpose of this study is to determine the feasibility of using a single scan ramped hybrid-encoding (RHE) method for rapid bicomponent T2* analysis of the human knee joint. The proposed method utilizes RHE to acquire ultrashort echo time (UTE) and subsequent gradient echo images at 16 different echo times ranging between 40 μs and 30 ms in a single scan. In the proposed RHE technique, UTE imaging was followed by acquisition of 14 gradient recalled echo images, where an additional UTE image was obtained within the first readout by oversampling single point imaging (SPI) encoding. The single scan RHE method with a 9-minute scan time was performed on human cadaveric knee joints from six donors and in vivo knee joints from four healthy volunteers at 3 T. A bicomponent signal model was used to characterize the short T2* and long T2* water components. Mean bicomponent T2* parameters for patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) and meniscus were calculated. In the experimental results, the RHE technique provided bicomponent T2* parameter estimations of tendon, ACL, PCL and meniscus, which were similar to previously reported values in the literature. In conclusion, the proposed single scan RHE technique provides rapid bicomponent T2* analysis of the human knee joint with a total scan time of less than 9 minutes.

Application of 3D-FS-SPGR imaging combined synovial fluid GGCX detection in the evaluation of knee osteoarthritis.

Osteoarthritis represents a kind of chronic and degenerative joint disease characterized by articular cartilage injury and osteoproliferation. Osteoarthritis especially poses a serious threat to the elderly patients. At present, the diagnosis of osteoarthritis mainly consists of clinical examination, X-ray examination, magnetic resonance imaging (MRI), and arthroscopy. However, limitations and misdiagnosis are found within the single method. This article intends to investigate the feasibility of assessing the condition of knee osteoarthritis through quantitative analysis of cartilage using nuclear magnetic resonance 3D fast-spin spoiled gradient-recalled echo (NMR 3D-FS-SPGR) imaging and γ-glutamic acid carboxylase (GGCX) detection in synovial fluid. A total of 60 patients with primary knee osteoarthritis were enrolled. All the patients were staged and received 3D-FS-SPGR sequence MRI scan for grading based on scan results and cartilage injury. Cartilage tissues were collected for immunohistochemistry (IHC). The GGCX in cartilage was detected using western blotting to analyze the correlation with arthritis. The condition of articular cartilage injury in arthritis patients was clearly observed using 3D-FS-SPGR sequence. The expression of GGCX was decreased in 46 patients (p < 0.05). The expression of GGCX in synovial fluid was significantly reduced following upstaging (p < 0.05). The sensitivity measured using combined 3D-FS-SPGR imaging and synovial fluid GGCX detection for the evaluation of arthritis condition was significantly higher than that of the single detection method (p < 0.05). Our data showed that the sensitivity of combined detection was obviously higher than single detection for the evaluation of arthritis. The 3D-FS-SPGR combined with synovial fluid GGCX detection could be treated as a promising strategy for arthritis evaluation.

Validation of threshold values for pancreas thickness and T1-weighted signal intensity ratio in the pediatric pancreas.

Pancreas atrophy and the loss of T1-weighted signal intensity by magnetic resonance imaging (MRI) are findings of chronic pancreatitis. The purpose of this study was to test published normal values and cutoffs for pancreas thickness and the pancreas:spleen T1-weighted signal intensity ratio in children without pancreatic disease. This was a secondary analysis of prospectively collected MRI data for 50 children (range: 6.3-15.9years; 27 female) with no history of pancreatic disease. Two observers (R1, R2) measured linear pancreas thickness on axial T1-weighted, fat-saturated gradient recalled echo images and placed regions of interest in the pancreas and spleen to calculate the T1-weighted signal intensity ratio. Measurements were compared to published pediatric normal values (computed tomography [CT], ultrasound [US]) and adult cutoffs (CT, MRI). Compared to published pediatric values for CT, 68% (R1: 34/50) or 40% (R2: 22/50) of participants had ≥1 pancreas segment with thickness below the normal range. No participant had a thickness value below the normal range published for US. Compared to cutoff values in adults, 84% (R1: 42/50) or 80% (R2: 40/50) of participants met the criteria for pancreas atrophy. Mean T1-weighted signal intensity ratio was 1.33±0.15 (R1) and 1.32±0.16 (R2). Twelve (R1: 24.5% of 49) or 11/49 (R2: 22.4%) participants had a T1-weighted signal intensity ratio below the threshold associated with exocrine insufficiency in adults. Previously defined thresholds for pancreas thickness and pancreas:spleen T1-weighted signal intensity ratio appear too restrictive for a pediatric population. Further study is needed to define optimal quantitative metrics for findings of chronic pancreatitis in children.