Keywords: YIA, White Matter

Motivation: The mechanisms underlying age-related structural neurodegeneration are not well understood, limiting our knowledge of atypical versus typical aging. 

Goal(s): Our goal was to use data involving advanced hemodynamic and structural MRI techniques tailored to white matter to characterize the aging process.

Approach: We used data from a large cohort of the Human Connectome Project in Aging to investigate the relationship between brain blood flow and white matter tract microstructural integrity.

Results: We found strong relationships between white matter hemodynamics and tract integrity that were affected by both age and sex.

Impact: These findings could reveal potential underlying physiological mechanisms behind structural changes during typical aging. This could help us understand healthy brain aging and encourage future research to target hemodynamic biomarkers to understand neurodegeneration.

Keywords: Flow, Blood vessels, 4D Flow MRI

Motivation: The motivation of this work is to understand the hemodynamics parameters in subjects with carotid web (CaW), atherosclerosis subjects with similar luminal narrowing, and normal subjects using 4D Flow MRI.

Goal(s): The main goal of this work is to quantify parameters related to vascular dysfunction including wall shear stress (WSS) and oscillatory shear index (OSI). 

Approach: 4D Flow MRI was utilized to prospectively scan subjects with CaW and hemodynamic parameters were compared to subjects with mild atherosclerosis and healthy volunteers.

Results: The results show that subjects with CaW have larger regions of complex blood flow represented by low WSS and high OSI. 

Impact: This study improves our understanding of disturbed hemodynamics caused by CaWs in comparison to atherosclerosis, which may explain the mechanism of thrombus formation and lay the groundwork for stroke risk assessment in patients with CaW.

Keywords: YIA, Neuro

Motivation: To address the unmet need for a cross-vendor, multiparametric technique to facilitate data pooling across sites.

Goal(s): To evaluate a vendor-standardized multiparametric mapping scheme based on 3D-QALAS for whole-brain T1, T2, and proton density (PD) mapping.

Approach: Intra-scanner repeatability and inter-vendor reproducibility were evaluated in vivo on five different 3T systems from four vendors (GE, Philips, Siemens, and Canon). Patients with multiple sclerosis were scanned on systems from different vendors to assess the feasibility of the scheme in real-world clinical settings.

Results: 3D-QALAS provided T1, T2, and PD with coefficient of variations <4.0% using 3T scanners from different manufacturers.

Impact: The four major vendors used in this study constitute a considerable portion of the global installation base, demonstrating the value of cross-vendor quantitative technique 3D-QALAS for imaging in clinical sites with multiple vendors, as well as in multicenter research settings.

Keywords: Non-Array RF Coils, Antennas & Waveguides, Non-Proton, Multinuclear, RF coil, X-nuclei

Motivation: There are 118 elements. Nearly all elements have NMR active isotopes and 39 different nuclei have been shown to have biological relevance. Despite this, most of today’s MRI is based on only one nucleus – ¹H.

Goal(s): To significantly reduce the cost and complexity of imaging all potential nuclei.

Approach: We present the Any-nucleus Distributed Active Programmable Transmit Coil (ADAPT Coil), with fast switches integrated into the coil itself which allows it to selectively excite any nucleus using digital controls.

Results: Using the ADAPT Coil, we acquired ¹H, ²³Na, ²H, and ¹³C phantom images and ¹H and ²³Na ex vivo images at 3T.

Impact: The ADAPT Coil enables arbitrary nucleus excitation in high field MRI, significantly reducing the cost and technological barriers of clinical translation of X-nuclei research. X-nuclei benefits include improved early diagnosis and treatment evaluation for cancer, osteoarthritis, Alzheimer’s, and many more.

Keywords: YIA, Diffusion/other diffusion imaging techniques, Diffusion-weighted MR spectroscopy, rodent brain, high field, SPECIAL, glutamine, J-coupled metabolites

Motivation: Diffusion-weighted MR spectroscopy (dMRS) uniquely probes cell-specific tissue microstructure in vivo but most sequences suffer from long TE leading to signal loss by J-evolution and T₂ relaxation.

Goal(s): To propose an alternative dMRS sequence (DW-SPECIAL) with a shorter TE while preserving the benefits of the current gold-standard rodent sequence at high field (STE-LASER).

Approach: DW-SPECIAL was tested in vivo in the rat brain and compared to STE-LASER.

Results: DW-SPECIAL halved the minimum TE while reducing specific absorption rate compared to STE-LASER, thereby 1) improving the J-coupled metabolites’ diffusion properties estimation and 2) offering a new candidate sequence for human dMRS.

Impact: With its shorter TE, our newly proposed DW-SPECIAL can serve as an alternative to STE-LASER when strongly J-coupled metabolites like glutamine are investigated, thereby extending the range of accessible metabolites in the context of diffusion-weighted MRS acquisitions at high field.

Keywords: YIA, Fetus

Motivation: Small for gestational age (SGA) fetuses are undernourished and at higher risk for adverse outcomes; however, conventional assessment methods exhibit limited sensitivity.

Goal(s): To stratify perinatal risk using MRI-based body composition metrics.

Approach: TruFISP and 2-points Dixon images were used to compute the total fetal volume (TFV), fat-to-body volume ratio (FBVR) and adipose tissue fat signal fraction (FSF) using deep-learning segmentation.

Results: SGA fetuses (N=40) with lower FBVR were more likely to require obstetric interventions because of non-reassuring status, while those with reduced TFV were prone to adverse neonatal outcomes. The model’s sensitivity/specificity rates are 85.7%/87.5% and 82.35%/86.4%, respectively.

Impact: Quantifying fetal body composition through MRI can offer additional insights into the severity of small for gestational age complicated pregnancies and may help in stratifying perinatal risk.

Keywords: YIA, Data Acquisition, Acquisition & Analysis, Body, Lung, Lung water, Heart failure, Translational Studies

Motivation: Quantification of lung water during exercise is of interest for early diagnosis of heart failure.

Goal(s): To develop a time-resolved 3D MRI method to quantify lung water in transitions between rest and exercise.

Approach: We derive quantitative time-resolved lung water density (LWD) maps using a motion corrected sliding-window image reconstruction. We included 12 healthy controls and 2 patients with heart failure, and a porcine model of mitral regurgitation (n=5).

Results: We measured a peak exercise ΔLWD=16±6.8% in controls, but detected no changes during rest (ΔLWD=-1.4±3.5%, p=0.18). Accumulation rates were slower in patients (2.0±0.1%/min) vs controls (2.6±0.9%/min). Animals developed ΔLWD=3.3±1.5%.

Impact: Exercise-induced changes in lung water can be dynamically quantified using a continuous 3D MRI acquisition with a sliding-window and motion corrected image reconstruction, which may have clinical utility in unmasking latent heart failure at early stages of disease.

Keywords: YIA, Hybrid & Novel Systems Technology, Physics & Engineering, Acquisition & Reconstruction, New Trajectories & Spatial Encoding Methods, Acquisition Methods, nonlinear gradient

Motivation: The inherently slow MRI scans can be accelerated through rapid modulation of nonlinear gradient fields; however, its fundamental mechanisms and limits remain incompletely understood and validated.

Goal(s): We investigate accelerated MRI with flexible modulations of nonlinear B₀ fields using a custom-built local B₀ array.

Approach: The sampling theory is extended to rigorously compare nonlinear field modulation schemes in a quantitative k-space. A novel field calibration technique is proposed to enhance reconstruction. With safety evaluations, we perform in-vivo accelerated scans.

Results: Our in-vivo 2D FLASH scans make significant steps to speed up MRI with local B₀ array, achieving eight-fold joint acceleration with parallel imaging.

Impact: For the first time, the sampling efficiency of nonlinear gradients in the entire k-space is quantitatively visualized, allowing rigorous comparison of distinct B₀ modulations. Furthermore, the field estimation technique enables fast and robust in-vivo scans accelerated by flexible nonlinear fields.