Keywords: Lung, Lung, Mid-field

Motivation: Pulmonary perfusion imaging requires ionizing radiation (CT) or gadolinium-based contrast agents (MR) and therefore cannot be used on all patients.

Goal(s): We propose an easy-to-prescribe non-contrast pulmonary perfusion imaging method to improve the diagnosis and monitoring of pulmonary hypertension.

Approach: We designed a free-breathing arterial spin labeling imaging sequence that is compatible with whole-lung coverage at 0.55T. We demonstrate this method in healthy volunteers and a swine model. 

Results: We measured 11.55±4.09% and 7.76±2.62% ASL signals using inversion and saturation labeling which was comparable between breath-held and free-breathing scans. Perfusion defects were clearly visualized in the swine model. 

Impact: Our method should enable qualitative assessment of non-contrast pulmonary perfusion in patients who are contraindicated for gadolinium-based contrasts or who need frequent monitoring of pulmonary perfusion. Our method would contribute to enabling contrast-free comprehensive pulmonary exams at 0.55T.

Keywords: Lung, Lung

Motivation: Vascular stiffness and secondary pulmonary hypertension in COPD are common. Noninvasive measurement of pulse wave velocity as a marker of arterial stiffness by PREFUL MRI is feasible. The effect of bronchodilators on PWV is unclear.

Goal(s): To determine the effect of bronchodilators on pulmonary artery stiffness as measured by PWV derived using PREFUL MRI.

Approach: PREFUL MRI in 52 patients before and after placebo-controlled bronchodilator treatment.  

Results: In patients with elevated PWV, a significant decrease in PWV was measured after treatment. In the placebo control period and in the patients with normal baseline PWV, no significant changes were observed. 

Impact: Pulmonary artery stiffness can be measured by PREFUL MRI-based pulse wave velocity (PWV) calculation.  PREFUL MRI is a promising tool to monitor PWV changes after bronchodilator treatment.

Keywords: Lung, Quantitative Imaging

Motivation: The optimum flip angle which provides a trade-off between ventilation and perfusion signal in free-breathing proton MRI (3 T) of the lung is unknown. 

Goal(s): To optimise the acquisition of free-breathing pulmonary proton MRI to maximise both ventilation and perfusion signals.

Approach: Assessment of the flip angle in a 2D fast field echo (FFE) sequence in healthy volunteers utilising voxel-wise lung ventilation (VOLVE) analysis.

Results: Increasing the flip angle tends to reduce the ventilation signal but increase the perfusion signal. A flip angle higher than the Ernst angle for lung parenchyma is recommended when assessing both perfusion and ventilation.

Impact: Demonstration of the dependence of 2D FFE proton MRI ventilation and perfusion signal on flip angle to inform future studies. A flip angle greater than the parenchyma Ernst angle maintains a strong ventilation signal without supressing the perfusion signal.

Keywords: Lung, Lung, DCE-MRI

Motivation:  DCE-MRI were used to valuate the vascular construction of solid solitary nodules (SPN) to help the qualitative clinical diagnosis.

Goal(s):  To evaluate the value of DCE-MRI in the vascular architecture of solid SPN.

Approach: 32 patients with SPN underwent chest DCE-MRI. Pathological specimens and vascular structural parameter MVD and MPI were evaluated by immunohistochemical markers CD31, VEGF, and SMA.

Results: Ktrans and Ve from DCE-MRI had significant differences between benign and malignant SPN, and high diagnostic efficacy with AUC of 0.893 and 0.880. Ktrans and Kep were significantly positively correlated with CD31-MVD and VEGF, while negatively correlated with MPI. 

Impact: Dynamic enhancement Magnetic resonance imaging can be used as an effective auxiliary means to distinguish benign and malignant pulmonary nodules.

Keywords: Lung, DSC & DCE Perfusion, Lung

Motivation: Dynamic Contrast Enhancement-CT (DCE-CT) and Dynamic Contrast Enhancement-MRI (DCE-MRI) are among the most valuable imaging techniques for the noninvasive assessment of tumor vascular perfusion and trophoblast angiogenesis in lung cancer.

Goal(s): To evaluate the image quality value of free-breathing GRASP in MRI of lung cancer.

Approach: All patients underwent free-breathing DCE-MRI with breath-holding VIBE sequence before and after contrast injections. Two experienced thoracic radiologists independently evaluated the overall image quality, lesion contour, artifact level, and diagnostic confidence using the patient's simultaneous CT images as a reference.

Results: Free-breathing GRASP DCE-MRI technique is a reliable method for the high-resolution imaging of pulmonary lesions.

Impact: The study showcases GRASP's superiority over BH-VIBE in lung cancer imaging, offering clearer results with patient comfort. This breakthrough prompts investigation into GRASP's broader clinical applications and sets a new standard in patient-friendly MRI diagnostics.

Keywords: Lung, Cancer, ultrashort echo time (UTE)；oxygen-enhanced MRI (OE-MRI)

Motivation: People pay more and more attention to the high incidence and mortality of lung cancer. 

Goal(s): To develop a non-invasive, radiation-free imaging scheme to distinguish between benign and malignant solid pulmonary nodules and to improve the management of patients with pulmonary nodules.

Approach: Two three-dimensional ultrashort echo time series scans of pulmonary nodules were performed on 3.0T MRI under the condition of 21% and 100% oxygen, respectively, and the percent signal enhancement was used as the evaluation index of benign and malignant nodules.

Results: The increase of the percent signal enhancement in benign pulmonary nodules was higher than that in malignant pulmonary nodules.

Impact: This imaging tool will reduce or eliminate the radiation damage caused by computed tomography, reduce clinicians' over-dependence on high resolution computed tomography, and bring new gospel for personalized and accurate diagnosis and treatment of patients.

Keywords: Lung, COVID-19, Lung

Motivation: COVID-19's persistent respiratory effects are well-documented, but the long-term pulmonary consequences, particularly after severe illness, remain inadequately understood.

Goal(s): To identify enduring perfusion deficits in the lungs of individuals previously hospitalized with COVID-19, using dynamic contrast-enhanced (DCE) MRI.

Approach: The study recruited adults post-COVID-19 for a comprehensive pulmonary assessment. Dynamic contrast enhanced MRI was used to quantify lung perfusion and relating them to COVID-related hospitalization.

Results: The study found a significant correlation between MRI perfusion parameters and previous hospitalization for COVID-19. It indicated that patients with a history of hospitalization due to COVID-19 might experience persistent alterations in lung perfusion.

Impact: Our research, through dynamic contrast-enhanced MRI, reveals persisting lung perfusion deficits in post-hospitalized COVID-19 patients, notably related to severity of initial disease. This aids in understanding post-COVID pulmonary sequelae, guiding future patient management and research on long-term COVID-19 impact.

Keywords: Digestive, Digestive, PC-MRI, Intestine

Motivation: Measuring the reproducibility of 2D PC-MRI measures of intestinal blood flow is important for its clinical application.

Goal(s): The aim is to examine the precision of 2D PC-MR measures of resting intestinal blood flow and postprandial blood flow changes.

Approach: Ten healthy men were scanned on eight different days collecting at least three repeated 2D PC-MRI measures each day. Participants were also given an oral glucose tolerance test. 

Results: A CoV of 6%-9% was obtained for consecutive flow measures and 13%-15% for between day measurements. Flow increased 75% in the arteria mesenterica superior and 60% in the vena portae after glucose consumption.

Impact: The low variability of repeated flow measures in the arteria mesenterica superior  and vena portae compared to the high change in flow after glucose consumption makes 2D PC-MRI measures of flow changes in these vessels a feasible diagnostic test.

Keywords: Vessels, Vessels

Motivation: The blood flow of carotid artory can be assessed by the standard 2D PC MRI, as well as the advanced 4D Flow MRI.

Goal(s): The aim of this study is to test the potential of 4D flow for accuracy of quantification of carotid flow parameters compared to the reference standards 2D PC MRI in patients.

Approach: 4D Flow MRI and 2D PC MRI were performed in patients with carotid artery stenosis. Quantitative hemodynamics of carotid arteries were measured in 2D PC and 4D Flow MRI. 

Results: 4D Flow MRI and 2D PC MRI had a good consistency in the evaluation of carotid hemodynamics.
 

Impact: This study found that 4D Flow MRI and 2D PC MRI had a good consistency in the evaluation of carotid hemodynamics in patients with mild to moderate carotid artery stenosis.

Keywords: Vessels, Heart, NMR spectroscopy

Motivation: Heart valve disease (HVD) is a complex condition with a poorly known pathogenesis. 

Goal(s): NMR-based serum metabolomics of HVD patients (aortic, mitral valve, and double valve replacement) and healthy controls to identify potential biomarkers for HVD.

Approach: Proton NMR spectroscopy 

Results: The results obtained from PLS-DA and VIP score plots of metabolites in serum showed a separation between patients with HVD and HC. 

Impact: To understanding the potential metabolic alteration such as BCAA, and fatty acids, amino acids, and carbohydrate metabolism associated with inflammation, oxidative stress, and tissue degradation of HVD.

Keywords: Vessels, Low-Field MRI, Magnetic Resonance Angiography

Motivation: The recent resurgence of ultra-low-field MRI (i.e., below 0.1 T) is showing great promise for future clinical applications due to its low cost, portability, and accessibility, potentially advancing neck MRA for evaluating and diagnosing carotid diseases in point-of-care scenarios and low/mid-income countries.

Goal(s): To explore the neck MRA using TOF technique at 0.05 Tesla.

Approach: Flow-compensated 2D GRE sequences with and without flow saturation for multi-slice neck scans.

Results: Carotid arteries/bifurcations and jugular veins can be visualized with strong vessel-to-background contrast. We envision that usable and quality neck MRA can be potentially achieved at ULF with further sequence and/or post-processing optimization.

Impact: Ultra-low-field (ULF) neck MRA can potentially advance the evaluation of carotid stenosis and occlusion, as well as the diagnosis of stroke and aneurysms, in point-of-care scenarios and low/mid-income countries.

Keywords: Kidney, Perfusion

Motivation: Noninvasive assessment of renal function is necessary in transplanted renal artery stenosis (TRAS), which significantly impacts graft function and prognosis.

Goal(s): The purpose was to evaluate renal function in patients with TRAS using ASL-MRI and IVIM-MRI.

Approach: We used ASL-MRI and IVIM-MRI to evaluate renal blood flow (RBF), D, D^*, and f in TRAS, and analyzed their correlation with eGFR.

Results: Renal allograft in the stenosis group displayed notably lower RBF and f, both of which were positively associated with eGFR. This research highlights the importance of noninvasive techniques like ASL-MRI and IVIM-MRI in the clinical management of TRAS.

Impact: This study demonstrates that TRAS reduces renal perfusion, thereby affecting transplanted kidney function. ASL-MRI and IVIM-MRI can indirectly and noninvasive reflect renal function impacted by TRAS, providing valuable information for treatment decisions and active monitoring.

Keywords: Vessels, Blood vessels

Motivation: The introduction of ultra-high field  5 tesla (T) system provides brand-new opportunities in whole-body MR that can potentially be applied in peripheral MR angiography (MRA).

Goal(s): This study performed two-dimensional (2D) time-of-flight (TOF) MRA of the lower body in ten healthy volunteers for both 3T  and 5T systems. 

Approach: MRA with high spatial resolutions (true voxel sizes, 1$$$\times$$$1.25$$$\times$$$2) from different field strengths were evaluated quantitively and qualitatively.

Results:  2D TOF MRA at 5 T is capable of providing superior vessel delineation and image quality (in both quantitative and subjective assessment) to 3 T.

Impact: This comparative study demonstrated the superiority of  5T to 3T in TOF MRA for pelvis and lower extremities. 5T TOF MRA provides a possible alternative for the clinical assessment of peripheral  arteries.

Keywords: Vessels, Vessels, velocity; high-field MR

Motivation: Unenhanced MRA on feet has always been challenging due to slow blood flow. The ultra-high field strength MR systems have been proved to offer improved visualization of distal small vessels.

Goal(s): We aim to assess the visualization of foot vessels using three-dimensional phase contrast MRA (3D-PC-MRA) at 5T field-strength. 

Approach: Participants were prospectively recruited and underwent 5T 3D-PC-MRA on feet with and without warm water immersion. 

Results: Immersion of feet in warm water significantly improves visualization of distal small branches, and increases the average velocity of blood flow by 40%, resulting in the visualized enhancement in blood signal.

Impact: 5T 3D phase-contrast MRA is effective in visualizing lower-extremity vasculatures and small branches, and its visualization can be significantly improved by immersing feet in warm water.

Keywords: Vessels, Blood vessels

Motivation: Inflow-based NCE MRA techniques have limited capability of background and venous suppression at the high field strength.

Goal(s): This study described a new arterial spin labeling (ASL)-based method for lower limb MR angiography (MRA) called FINE (Flow-Inversion Non-Enhanced).

Approach: The performance of FINE was evaluated on ten healthy volunteers and compared with 2D TOF MRA on 3T. 

Results: 2D FINE technique provides superior suppression of background and venous signal with reduced acquisition time than that of 2D TOF.

Impact: The results of this study demonstrate the feasibility of FINE MRA of the lower limbs at 3T.

Keywords: Vessels, Velocity & Flow, iliac venous compression

Motivation: Hemodynamic changes are important for evaluating Iliac venous compression syndrome.  CFD simulation can obtain individualized and quantitative hemodynamic information that traditional imaging methods cannot obtain.

Goal(s): Qbtain hemodynamic parameters through the establishment of patient individualized vascular model and CFD simulation. By observing hemodynamic parameters, the changes in blood flow caused by iliac venous compression can be more accurately evaluated.

Approach: The 3D model is constructed based on the MRA images.  After CFD simulation,  changes of flow dynamics parameters observed due to the influence of iliac venous compression.
 

Results: The CFD simulation shows that iliac venous compression can cause significant changes in hemodynamics

Impact: Hemodynamic changes are the pathological basis of iliac venous compression. Accurate diagnosis of blood flow changes is helpful to guide the surgical treatment of iliac venous compression and provide powerful help for clinical decision-making.