Keywords: Pancreas, Thermometry, pancreas graft, MR spectroscopy, hypothermic storage, temperature

Motivation: Phosphorus (³¹P) and proton (¹H) MRS are methods of choice in assessment of pancreas graft quality before transplantation. Since MR scanning can increase the temperature of the pancreas graft, measurement of the graft temperature is desirable. 

Goal(s): The aim of this study was to investigate if it is possible to measure pancreas graft temperature in MR scanner using ¹H-MRS.

Approach: Single-voxel ¹H-MRS. Temperature constants were obtained by calibration experiments with the water-vegetable oil phantom.

Results: The present study has shown that ¹H-MRS is able to measure the graft temperature during MR scanning.

Impact: ¹H-MRS is able to measure the pancreas graft temperature during MR scanning. The temperature is computed from the chemical shift difference between water spectral line and methylene (CH₂)n line originating from the pancreatic adipocytes.

Keywords: Liver, Liver, Liver Diffusion Acquisition & Reconstruction

Motivation: Diffusion-weighted PROPELLER-EPI (periodically rotated overlapping parallel lines with enhanced reconstruction using EPI as signal readout) can enable high-fidelity free-breathing liver DWI. 

Goal(s): It is challenging to acquire liver DW-PROPELLER-EPI with breath hold for improving the acquisition efficiency.

Approach: In this study, we proposed a self-referenced and collaborative PROPELLER-EPI reconstruction based on POCSMUSE (SCOPUSE) framework that can 1) correct the Nyquist ghost phase errors, 2) minimize the streaking artifacts, and 3) enable breath hold for liver DWI. 

Results: This method can accelerate the acquisition of DW-PROPELLER-EPI data and provide improved image quality compared with conventional PROPELLER-EPI reconstruction pipeline.

Impact: Breath-hold acquisition can reduce the respiratory artifact in liver DWI with high scan efficiency, however, the attainable image quality is often limited by the breath-hold time. The proposed SCOPUSE can enable breath-hold liver DW-PROPELLER-EPI acquisition for achieving high-fidelity liver DWI.

Keywords: Liver, Liver

Motivation: Sarcopenia has been associated with a higher risk of adverse outcomes in patients with chronic diseases.

Goal(s): To evaluate sarcopenia as a prognostic biomarker in patients with primary sclerosing cholangitis (PSC).

Approach: Muscle mass was measured in 231 PSC patients at the level of L3 and correlated with patient demographics, clinical scores and clinical endpoints.

Results: Sarcopenia was more prevalent in women and in patients without concomitant inflammatory bowel disease. Muscle mass significantly correlated negatively with the MELD score, but not with solid clinical endpoints.

Impact: While sarcopenia is highly prevalent in PSC patients, imaging-based quantification of muscle mass seems to be of limited prognostic value.

Keywords: Liver, Velocity & Flow

Motivation: To evaluate the potential of portal flow as a biomarker of metabolic-dysfunction associated steatohepatitis (MASH) in obese patients undergoing weight loss surgery (WLS).

Goal(s): Determine feasibility of portal non-contrast 4D Flow in obese patients, to assess whether flow is impacted by BMI and the presence of MASH.

Approach: Portal flow was quantified at 5 timepoints before and after WLS. Mass conservation and inter-observer agreement assessed validation. Results were correlated with BMI and presence/absence of biopsy-proven MASH.

Results: Non-contrast 4D Flow was successful in 339/382 exams (87%); BMI correlated with portal flow (p=0.010); flow was significantly higher in MASH (p=0.013, AUC=0.706)

Impact: Our work demonstrates the feasibility of non-contrast 4D flow in individuals with obesity. Further, it indicates possible effects of obesity on portal venous flow and demonstrates its potential as a treatment monitoring tool in MASH.  
 
 


 
 
 

Keywords: Liver, Liver, Free-Breathing, Pseudo-Spiral, 7T, Phase-Shimming

Motivation: Ultra-high field (B₀ ≥ 7T) MRI potentially offers high spatial resolution. However, 7T abdominal MRI is challenging due to B₁⁺-inhomogeneities and patients’ breath-holding limits, especially for high-resolution scans.

Goal(s): To develop a high-quality, free-breathing liver scan at 7T.

Approach: We implemented a 3D-GRE with golden-angle pseudo-spiral sampling pattern at 7T, that allowed respiratory binning in a free-breathing acquisition followed by Compressed Sensing reconstruction. Phase-shimming was used to achieve a homogeneous signal intensity over the liver.

Results: We successfully achieved 1.35x1.35x1.35mm³-resolution liver images with high image quality, including signal homogeneity over the entire liver, demonstrating the potential of free-breathing 7T liver MRI.

Impact: This study addresses breath-holding and B₁⁺-inhomogeneity challenges associated with 7T abdominal MRI. It could further the development of non-invasive and detailed liver visualization. Ultimately, this would alter clinical pathways and offer patients a more comfortable imaging experience.

Keywords: Pancreas, Pancreas

Motivation: Single-shot technique such as HASTE with one breath-hold and thin section images reconstructed by DL may allow detection and detailed characterization of pancreas cystic lesions. 

Goal(s): This study was aimed to assess the feasibility of single breath-hold HASTE using DLR with additional denoising effect for the evaluation of pancreas cystic lesions.

Approach: Four HASTE sequences with/without DLR were obtained. Two radiologists independently reviewed four image sets for qualitative and quantitative analyses of image quality.

Results: HASTE using DL with additional denoising showed higher image quality than conventional HASTE in both qualitative and quantitative analyses. It also showed lower variability in cyst size measurement.

Impact: DL-accelerated HASTE sequence with denoising effect may be useful for reducing acquisition time with one-breath hold without compromising image quality in the evaluation of pancreatic cystic lesions. It may be applied to abbreviated MRI for follow-up of pancreatic cystic lesions.

Keywords: Liver, DSC & DCE Perfusion, DISCO-Star, DL Stack-of-stars, Double Wash-in phase

Motivation: Free breathing DCE imaging is beneficial for patients who have difficulty holding their breath, but can be susceptible to artifacts and suboptimal contrast bolus timing, which may compromise diagnostic accuracy. 

Goal(s): Our goal was to validate application of deep learning to 3D DISCO-Star imaging in the abdomen after doubling the number of wash-in phases via spoke reordering.

Approach: 8 and 16 wash-in phase images were assessed by two radiologists across different IQ attributes. Noise characteristics were evaluated and AUC was calculated.

Results: The radiologists preferred DL enhanced 16 wash-in phase across many of the IQ attributes, with higher SNR and decreased streaks. 

Impact: The ability to double the wash-in phases in DISCO-Star DCE imaging without compromising image quality via deep learning will provide enhanced diagnostic quality, and has the potential to improve patient care.

Keywords: Liver, Liver, function

Motivation: Interaction of drugs via inhibition of liver function affects their toxicity and efficacy, but this is currently difficult to assess clinically.

Goal(s): To determine if a DCE-MRI measurement of liver function is sufficiently sensitive to detect drug-induced inhibition of liver function in humans.

Approach: 10 healthy volunteers underwent a DCE-MRI measurement of their baseline liver function. The measurement was repeated on a second day after administration of rifampicin, a powerful inhibitor of liver function.

Results: Rifampicin reduced the hepatocellular uptake rate by 93%, and the effect was consistent between volunteers. The biliary excretion rate reduced by 48% and the effect was more variable.

Impact: Early clinical assessment of drug-drug interactions can significantly reduce the risk of expensive late-stage failures in drug development, potentially increasing the rate at which new drugs can enter the market, and reducing the risk to trial subjects and patients.

Keywords: Liver, Body

Motivation: T2 mapping is an effective way to classify benign and malignant lesions within the liver, but existing methods that do not account for partial volume systematically underestimate lesion T2, leading to false positives.

Goal(s): To develop a signal model that accounts for partial volume effects to more accurately quantify T2 of liver lesions.

Approach: Use a two-compartment signal model tailored for turbo spin-echo acquisitions taking into account the varying lesion fraction across the imaging slice.

Results: The proposed method leads to more accurate T2 estimation in the presence of partial volume as demonstrated in simulations, physical phantoms, and subjects with focal liver lesions.

Impact: This work presents a turbo spin-echo signal model that accounts for partial volume effects to estimate T2 values of focal liver lesions more accurately. The proposed method improves the accuracy of classifying benign and malignant liver lesions.

Keywords: Pancreas, Diffusion/other diffusion imaging techniques, Pancreas, Deep-learning, Phase Correction, DWI, rFOV, multishot, SNR

Motivation: Diffusion weighted imaging (DWI) is valuable in pancreatic imaging but suffers from artifacts and low SNR. The combination of reduced FOV imaging with a multishot data sampling strategy (rFOV-msDWI) improves artifacts from susceptibility and allows higher achievable resolution but still suffers from low SNR. 

Goal(s): Here we report early findings from an ongoing pilot study 

Approach: Evaluate a DL-based phase correction algorithm for improved SNR in patients undergoing rFOV-msDWI of the pancreas.

Results: DL-based phase correction subjectively improves image quality.

Impact: DL-based phase correction may improve rFOV-msDWI of the pancreas. Further evaluation is warranted.

Keywords: Liver, Liver

Motivation: It is important to identify patients with cirrhosis at high risk of decompensation or death using noninvasive methods to stabilize disease progression and reduce patient mortality

Goal(s): To investigate whether the functional parameters from gadoxetic acid–enhanced MRI can predict decompensation in cirrhosis.

Approach: To compare MRI parameters and clinical parameters between CACLD and DACLD groups. Associations between MRI parameters and clinical parameters were investigated. To differentiate the diagnostic performance of MRI parameters and clinical parameters between CACLD and DACLD groups.

Results: The functional parameters from gadoxetic acid–enhanced MRI can predict decompensation in cirrhosis.

Impact: This study confirms that non-invasive imaging parameters can predict the decompensation of cirrhosis and provides a new method for clinicians to evaluate the condition of patients with cirrhosis.

Keywords: Liver, Liver

Motivation: Hepatobiliary Phase (HBP) of Gd-EOB-DTPA-enhanced MRI is helpful for the detection and diagnosis of liver lesions but requires waiting 20 minutes after injection of contrast agent to obtain it.

Goal(s): Therefore, we aimed to use deep learning to synthesize HBP to obtain HBP images more conveniently and efficiently.

Approach: We used generative adversarial network to synthesize HBP from multi-phase dynamic contrast-enhanced images. 

Results: The results showed that the synthetic HBP images closely mimicked the real HBP images in quantitative and qualitative image analysis, which illustrated that the model could be used to synthesize HBP in clinic to shorten the acquisition time.

Impact: This study proposed a more conveniently and efficiently method to obtain hepatobiliary phase images based on generative adversarial network, which can reduce the clinical burden.

Keywords: Hepatobiliary, Metabolism, Exercise

Motivation: The menstrual cycle (MC) has been shown to effect muscle glycogen utilisation during exercise but little is known about the full metabolic or glycogenic effects at varying phases. 

Goal(s): To explore MC effects on exercise-induced changes in metabolites and glycogen stores.

Approach: ¹³C MRS and bloods were acquired from the liver and leg before and after 45 minutes of moderate exercise in healthy females. Test day was repeated 4 times 1 week apart throughout the MC.

Results: Previous findings of hormonal effects on muscle glycogen utilization were confirmed. Also, liver glycogen stores appear reduced in later MC days and correlated negatively with progesterone.

Impact: This study provides pilot data for future research. ¹³C MRS allows for the repeated monitoring of glycogen storage and turnover in an ethically viable way. This work has implications in understanding metabolic disorders, medical research and sports science.

Keywords: Liver, Liver

Motivation: Gadoxetic acid-enhanced MRI is a promising tool for assessing liver function, especially in the context of liver transplants.

Goal(s): This study aims to examine the relationship between functional T1 mapping from gadoxetic acid-enhanced MRI and transplanted liver function.

Approach: Liver transplant recipients underwent liver MRI, including T1 mapping and gadoxetic acid-enhanced MRI, to evaluate the relationship between MRI parameters and MELD.

Results: Liver transplant recipients at low or moderate risk had significantly higher ΔT1% values compared to high-risk recipients.

Impact: Gadoxetic acid-enhanced MRI offers dynamic and hepatocyte-specific imaging, making it a comprehensive "one-stop" method for post-transplant complication and liver injury evaluation.

Keywords: Liver, Liver, Motion Correction

Motivation: Respiratory motion disturbs the stability of the primary magnetic field (B0), leading to potential image artifacts. Despite the significant influence of respiratory motion on B0, understanding these variations in the liver remains understudied in quantitative MRI.

Goal(s): To provide a comprehensive analysis of respiration-induced B0 variations in the liver.

Approach: The study used direct simulations, acquisition simulations followed by reconstruction, and in vivo scans to quantify B0 variations in the liver.

Results: Maximal temporal fieldmap variations were subject dependent and showed a mean variation in the order of 24.9 Hz across the respiratory cycle in the region close to the liver-diaphram interface.

Impact: This research provides a clearer understanding of respiratory motion effects on MRI, particularly in the liver. These insights could lead to improved image clarity for quantitative imaging.

Keywords: Liver, Low-Field MRI

Motivation: Improve accessibility of MRI by measuring quantitative liver biomarkers at 0.55T.

Goal(s): Perform and validate free-breathing radial stack-of-stars for simultaneous measurement of liver fat fraction, R2*, and T1 on a 0.55T system in patients with chronic liver disease.

Approach: 11 subjects undergoing 3T MRI were offered a 0.55T examination. Fat fraction and R2* were compared at both field strengths. Composite T1 was compared to water-only T1.

Results: Fat fraction at 0.55T was highly correlated to 3T, with minimal bias and variance. R2* correlation did not achieve statistical significance. Composite T1 was linearly related to water-only T1.

Impact: Free-breathing simultaneous measurement of important liver biomarkers is achievable in a low-cost commercially available MRI system, which promises to help make the benefits of MRI more accessible to patients who need it.