Synthetic MRI is not yet ready for morphologic and functional assessment of patellar cartilage at 1.5 Tesla

PurposeThe purpose of this study was to compare morphologic assessment and relaxometry of patellar hyaline cartilage between conventional sequences (fast spin-echo [FSE] T2-weighted fat-saturated and T2-mapping) and synthetic T2 short-TI inversion recovery (STIR) and T2 maps at 1.5 T magnetic resonance imaging (MRI).MethodThe MRI examinations of the knee obtained at 1.5 T in 49 consecutive patients were retrospectively studied. There were 21 men and 28 women with a mean age of 45 ± 17.7 (SD) years (range: 18–88 years). Conventional and synthetic acquisitions were performed, including T2-weighted fat-saturated and T2-mapping sequences. Two radiologists independently compared patellar cartilage T2-relaxation time on conventional T2-mapping and synthetic T2-mapping images. A third radiologist evaluated the patellar cartilage morphology on conventional and synthetic T2-weighted images. The presence of artifacts was also assessed. Interobserver agreement for quantitative variables was assessed using intraclass correlation coefficient (ICC).ResultsIn vitro, conventional and synthetic T2 maps yielded similar mean T2 values 58.5 ± 2.3 (SD) ms and 58.8 ± 2.6 (SD) ms, respectively (P = 0.414) and 6% lower than the expected experimental values (P = 0.038). Synthetic images allowed for a 15% reduction in examination time compared to conventional images. On conventional sequences, patellar chondropathy was identified in 35 patients (35/49; 71%) with a mean chondropathy grade of 4.8 ± 4.8 (SD). On synthetic images, 28 patients (28/49; 57%) were diagnosed with patellar chondropathy, with a significant 14% difference (P = 0.009) and lower chondropathy scores (3.7 ± 4.9 [SD]) compared to conventional images. Motion artifacts were more frequently observed on synthetic images (18%) than on conventional ones (6%). The interobserver agreement was excellent for both conventional and synthetic T2 maps (ICC > 0.83). Mean cartilage T2 values were significantly greater on synthetic images (36.2 ± 3.8 [SD] ms; range: 29-46 ms) relative to conventional T2 maps (31.8 ± 4.1 [SD] ms; range: 26-49 ms) (P < 0.0001).ConclusionDespite a decrease in examination duration, synthetic images convey lower diagnostic performance for chondropathy, greater prevalence of motion artifacts, and an overestimation of T2 values compared to conventional MRI sequences.     

Position paper on stress cardiac MRI in chronic coronary syndrome: Endorsed by the Société Française de Radiologie (SFR) the Société Française d’Imagerie CardioVasculaire (SFICV) and the Société Française de Cardiologie (SFC)

This position paper was intended to update the former consensus between the French Societies of Radiology and Cardiology about the use of stress cardiac magnetic resonance imaging (MRI) in chronic coronary syndrome published in 2009. The Delphi method was used to build the present consensus. This expert panel consensus includes recommendations for indications, procedure with patient preparation, stress inducing drugs, acquisition protocol, interpretation and risk stratification by stress MRI.     

Comparison of quantitative susceptibility mapping methods on evaluating radiation-induced cerebral microbleeds and basal ganglia at 3T and 7T

Quantitative susceptibility mapping (QSM) has the potential for being a biomarker for various diseases because of its ability to measure tissue susceptibility related to iron deposition, myelin, and hemorrhage from the phase signal of a T₂*-weighted MRI. Despite its promise as a quantitative marker, QSM is faced with many challenges, including its dependence on preprocessing of the raw phase data, the relatively weak tissue signal, and the inherently ill posed relationship between the magnetic dipole and measured phase. The goal of this study was to evaluate the effects of background field removal and dipole inversion algorithms on noise characteristics, image uniformity, and structural contrast for cerebral microbleed (CMB) quantification at both 3T and 7T. We selected four widely used background phase removal and five dipole field inversion algorithms for QSM and applied them to volunteers and patients with CMBs, who were scanned at two different field strengths, with ground truth QSM reference calculated using multiple orientation scans. 7T MRI provided QSM images with lower noise than did 3T MRI. QSIP and VSHARP + iLSQR achieved the highest white matter homogeneity and vein contrast, with QSIP also providing the highest CMB contrast. Compared with ground truth COSMOS QSM images, overall good correlations between susceptibility values of dipole inversion algorithms and the COSMOS reference were observed in basal ganglia regions, with VSHARP + iLSQR achieving the susceptibility values most similar to COSMOS across all regions. This study can provide guidance for selecting the most appropriate QSM processing pipeline based on the application of interest and scanner field strength.     

Correlation between magnetic resonance imaging characteristics and BRAF alteration status in individuals with optic pathway/hypothalamic pilocytic astrocytomas

Background and purposeMost individuals with optic pathway/hypothalamic pilocytic astrocytoma (OPHPA) harbor either the BRAF V600E mutation or KIAA1549-BRAF fusion (K-B). This study aimed to investigate the imaging characteristics of OPHPA in relation to BRAF alteration status.Materials and methodsSeven cases of OPHPA harboring either the BRAF V600E mutation or K-B fusion were included in the study. Preoperative magnetic resonance imaging (MRI) was assessed for degree of T2 hyperintensity on T2-weighted images (T2WI) and the ratio of nonenhancing T2 or fluid-attenuated inversion recovery (FLAIR) hyperintense area to the contrast enhanced area (CE) on gadolinium-enhanced-T1 weighted images (T2/FLAIR-CE mismatch). The T2 signal intensity was normalized to cerebrospinal fluid (T2/CSF) for both the V600E and K-B group and compared. T2/FLAIR-CE mismatch was assessed by calculating the proportion of the tumor volume of nonenhancing high T2 signal intensity to the whole lesion (nonenhancing and enhancing components).ResultsFour and three cases of OPHPA harboring the BRAF V600E mutation and K-B, respectively, were analyzed. The T2/CSF value was higher in the K-B group than in the V600E group. Moreover, the V600E group had a larger T2/FLAIR-CE mismatch than the K-B group.ConclusionsThe BRAF alteration status in individuals with OPHPA was associated with preoperative MRI by focusing on T2 signal intensity and T2/FLAIR-CE mismatch. The BRAF V600E mutation was associated with a lower T2/CSF value and larger T2/FLAIR-CE mismatch, whereas K-B fusion was associated with a higher T2/CSF value and smaller T2/FLAIR-CE mismatch.     

Single-source dual energy CT to assess myocardial extracellular volume fraction in aortic stenosis before transcatheter aortic valve implantation (TAVI)

PurposeTo assess myocardial extracellular volume fraction (ECV) measurement provided by a single-source dual-energy computed tomography (SSDE-CT) acquisition added at the end of a routine CT examination before transcatether aortic valve implantation (TAVI) compared to cardiac magnetic resonance imaging (MRI).Materials and methodsTwenty-one patients (10 men, 11 women; mean age, 86 ± 4.9 years [SD]; age range: 71–92 years) with severe aortic stenosis underwent standard pre-TAVI CT with additional cardiac SSDE-CT acquisition 7 minutes after intravenous administration of iodinated contrast material and myocardial MRI including pre- and post-contrast T1-maps. Myocardial ECV and standard deviation (σECV) were calculated in the 16-segments model. ECV provided by SSDE-CT was compared to ECV provided by MRI, which served as the reference. Analyses were performed on a per-segment basis and on a per-patient involving the mean value of the 16-segments.ResultsECV was slightly overestimated by SSDE-CT (29.9 ± 4.6 [SD] %; range: 20.9%–48.3%) compared to MRI (29.1 ± 3.9 [SD] %; range: 22.0%–50.7%) (P < 0.0001) with a bias and limits of agreement of +2.3% (95%CI: −16.1%– + 20.6%) and +2.5% (95%CI: −2.1%– + 7.1%) for per-segment and per-patient-analyses, respectively. Good (r = 0.81 for per-segment-analysis) to excellent (r = 0.97 for per-patient-analysis) linear relationships (both P < 0.0001) were obtained. The σECV was significantly higher at SSDE-CT (P < 0.0001). Additional radiation dose from CT was 1.89 ± 0.38 (SD) mSv (range: 1.48–2.47 mSv).ConclusionA single additional SSDE-CT acquisition added at the end of a standard pre-TAVI CT protocol can provide ECV measurement with good to excellent linear relationship with MRI.     

Interval Estimations for Variance Components: A Review and Implementations

Abstract

Statistical methods are often required in the pharmaceutical industry to ensure that precision parameters of interest are kept within acceptable levels. For example, analytical methods are validated to determine whether the method is fit for its intended purpose before used in a decision process. In these cases, analytical methods are evaluated on the basis of precision parameters of interest. An analysis of variance approach based on a random effect model is commonly used for describing precision parameters. Bounds on precision parameters are needed to quantify the uncertainty present in the data. Several frequentist, fiducial, and Bayesian approaches have been used for constructing bounds on precision parameters. However, in some cases, there is no clear guidance on how to effectively apply some of these methods. Other recently proposed (and less known) methods have been reported to have very good statistical properties and are rarely, or to the best of our knowledge, never used in precision studies. We survey and compare methods for constructing confidence intervals of linear combinations of variance components in a balanced random effect model. We consider not only widely used traditional methods, but also those that are less well known. We further elucidate potential issues and provide general guidance on the construction of the confidence intervals. Finally, the methods are demonstrated with two examples from applications with similar kinds of data.     

Morphological,Functional, and Tissue Characterization of Silent Myocardial Involvement in Patients With Primary Biliary Cholangitis

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Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis

PurposeTo evaluate the efficacy and safety of embolization of hyperemic synovial tissue for the treatment of knee pain secondary to osteoarthritis (OA).Materials and MethodsTwenty patients with radiographic knee OA and moderate-to-severe pain refractory to conservative therapy were enrolled in a prospective, 2-site pilot study. Genicular artery embolization (GAE) was performed with 75- or 100-μm spherical particles. Patients were assessed with magnetic resonance imaging at baseline and at 1 month and with the Visual Analogue Scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at baseline and at 1, 3, and 6 months. Adverse events were recorded at all timepoints.ResultsEmbolization of at least 1 genicular artery was achieved in 20/20 (100%) patients. Mean VAS improved from 76 mm ± 14 at baseline to 29 mm ± 27 at 6-month follow-up (P < .01). Mean WOMAC score improved from 61 ± 12 at baseline to 29 ± 27 at 6-month follow-up (P < .01). Self-limiting skin discoloration occurred in 13/20 (65%) patients. Two of 20 (10%) patients developed plantar sensory paresthesia that resolved within 14 days.ConclusionsGAE to treat knee pain secondary to OA can be performed safely and demonstrates potential efficacy. Further randomized comparative studies are needed to determine true treatment effect versus placebo effect.     

Multi-Frequency Contrast Source Inversion for Reflection Seismic Data

In the contrast source inversion (CSI) method, the contrast sources (equivalent scattering sources) and the contrast (parameter perturbation) are iteratively reconstructed by an alternating optimization scheme. Traditionally integral equation CSI method is formulated for transmission tomography using analytic Green's function in homogeneous background. To extend the method to the case of reflection seismology, in this paper, we use WKBJ method to compute the Green's function of depth dependent background media and the solving method of equations to initialize the contrast source of different frequencies, resulting in an efficient method to invert multi-frequency reflection seismic data – multi-frequency contrast source inversion method (MFCSI). Numerical results for the Marmousi model show that MFCSI method can obtain good results even when low frequency data are missing, in which case the conventional FWI fails.     

Artificial Intelligence–Enabled Electrocardiogram for Atrial Fibrillation Identifies Cognitive Decline Risk and Cerebral Infarcts

ObjectiveTo investigate whether artificial intelligence–enabled electrocardiogram (AI-ECG) assessment of atrial fibrillation (AF) risk predicts cognitive decline and cerebral infarcts.Patients and MethodsThis population-based study included sinus-rhythm ECG participants seen from November 29, 2004 through July 13, 2020, and a subset with brain magnetic resonance imaging (MRI) (October 10, 2011, through November 2, 2017). The AI-ECG score of AF risk calculated for participants was 0-1. To determine the AI-ECG-AF relationship with baseline cognitive dysfunction, we compared linear mixed-effects models with global and domain-specific cognitive z-scores from longitudinal neuropsychological assessments. The AI-ECG-AF score was logit transformed and modeled with cubic splines. For the brain-MRI subset, logistic regression evaluated correlation of the AI-ECG-AF score and the high-threshold, dichotomized AI-ECG-AF score with infarcts.ResultsParticipants (N=3729; median age, 74.1 years) underwent cognitive analysis. Adjusting for age, sex, education, and APOE ?4-carrier status, the AI-ECG-AF score correlated with lower baseline and faster decline in global-cognitive z-scores (P=.009 and P=.01, respectively, non–linear-based spline-models tests) and attention z-scores (P<.001 and P=.01, respectively). Sinus-rhythm-ECG participants (n=1373) underwent MRI. As a continuous measure, the AI-ECG-AF score correlated with infarcts but not after age and sex adjustment (P=.52). For dichotomized analysis, an AI-ECG-AF score greater than 0.5 correlated with infarcts (OR, 4.61; 95% CI, 2.45-8.55; P<.001); even after age and sex adjustment (OR, 2.09; 95% CI, 1.06-4.07; P=.03).ConclusionThe AI-ECG-AF score correlated with worse baseline cognition and gradual global cognition and attention decline. High AF probability by AI-ECG-AF score correlated with MRI cerebral infarcts. However, most infarcts observed in our cohort were subcortical, suggesting that AI-ECG not only predicts AF but also detects other non-AF cardiac disease markers and correlates with small vessel cerebrovascular disease and cognitive decline.