Ruvini Navaratna^1,2, Daiki Tamada², Diego Hernando^1,2, and Scott B Reeder^1,2,3,4,5
1Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ²Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁴Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁵Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States

There is an unmet need for non-invasive methods that provide rapid and accurate quantification of liver iron concentration (LIC) over a wide range of iron overload severity. Current R2 mapping techniques suffer from long acquisition times and limited spatial coverage. Recently, a phase-based R2 mapping technique for rapid whole-liver R2 quantification within a single breath-hold has been introduced. However, the feasibility of this method to quantify liver iron overload has not been demonstrated. In this work, we optimize and validate phase-based R2 mapping to quantify R2 in phantom experiments, healthy volunteers, and demonstrate feasibility in patients with iron overload.

Ziwei Zhao¹, Nam G. Lee², Sophia X. Cui³, and Krishna S. Nayak^1,2
1Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, ²Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, ³Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States

Lung perfusion is challenging because of the complex anatomy and pulsatile blood flow. At 1.5T and 3T, a major challenge is the low signal from parenchyma due to the short T2*. Here, we demonstrate feasibility of lung ASL perfusion imaging on a high-performance 0.55T system. Experiments were performed using FAIR labeling with snapshot bSSFP imaging and quantified using Buxton’s GKM. In four healthy volunteers, pulmonary blood flow (PBF) ranges from 0.62 to 0.99 ml-blood/ml-tissue/min, which are within the expected range (0.51 to 1.52 ml/ml/min) and agree with the total average PBF estimated by a phase contrast method.

Andrew Duffy¹, Andreu Costa², Sharon Clarke^2,3, Ashley Stueck⁴, Magnus McLeod⁵, and James Rioux^2,3
1Faculty of Medicine, Dalhousie University, Halifax, NS, Canada, ²Diagnostic Radiology, Dalhousie University, Halifax, NS, Canada, ³Biomedical Translational Imaging Centre, Nova Scotia Health Authority, Halifax, NS, Canada, ⁴Pathology, Dalhousie University, Halifax, NS, Canada, ⁵General Internal Medicine, Dalhousie University, Halifax, NS, Canada

Fat is a confounding factor in the use of T₁ measurements as a non-invasive method of assessing non-alcoholic fatty liver disease. A Dixon-based water/fat separation was used to produce T₁ maps based on the separated water signal in MPRAGE and MP2RAGE sequences. A correlation inconsistent with biophysical processes was observed between uncorrected MP2RAGE T₁ values and fibrosis stage, but using the fat compensated T₁ values corrects the correlation. The same effect was seen to a lesser extent with MPRAGE T₁ values. Further investigation and validation with a larger cohort may provide a more reliable biomarker of liver fibrosis within NAFLD.

Zihan Wang^1,2, Scott B Reeder, MD, PhD^1,2,3,4,5, and Diego Hernando, PhD^2,3
1Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, United States, ²Radiology, University of Wisconsin-Madison, Madison, WI, United States, ³Medical Physics, University of Wisconsin-Madison, Madison, WI, United States, ⁴Medicine, University of Wisconsin-Madison, Madison, WI, United States, ⁵Emergency Medicine, University of Wisconsin-Madison, Madison, WI, United States

The purpose of this study is to assess the reproducibility of CSE-MRI methods to measure proton density fat fraction (PDFF) in liver in patients with iron overload. The PDFF measurements of 31 patients with known or suspected iron overload and 10 healthy volunteers were imaged at both 1.5T and 3.0T. Patients were separated into four groups with increasing liver iron concentration (LIC). The reproducibility across field strengths was quantified within each group and reported below.

Zheng Zhu¹, Jiahui Li¹, Usman Yaqoob², Alina M Allen², Terry Therneau³, Kevin J Glaser¹, Safa Hoodeshenas¹, Sudhakar K Venkatesh¹, Armando Manduca¹, Vijay H Shah², Richard L Ehman¹, and Meng Yin^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, United States, ³Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, United States

We measured the longitudinal change of MRE-assessed liver stiffness (LS), loss modulus (LM) and MRI-assessed proton density fat fraction (PDFF) in a preclinical NASH model of 25 rats and 52 patients with NAFLD to assess disease severity, as well as the direction of progression/regression. Our pilot studies suggest that ΔLM and ΔPDFF are promising for monitoring treatment effects in a short-term period, while ΔLS is recommended for stratifying significant fibrosis that needs treatment in long-term follow-ups. 

Daeun Kim¹, Brian P Lee², Junzhou Chen^1,3, Kevin King¹, Justin P Haldar^4,5, Norah A Terrault², and Zhaoyang Fan^1,5,6
1Department of Radiology, University of Southern California, Los Angeles, CA, United States, ²Department of Medicine, Division of Gastroenterology and Liver Diseases, University of Southern California, Los Angeles, CA, United States, ³Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, ⁴Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, ⁵Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, ⁶Department of Radiation Oncology, University of Southern California, Los Angeles, CA, United States

Diffusion-relaxation correlation spectroscopic imaging (DR-CSI) is an advanced microstructure imaging approach that can resolve sub-voxel tissue compartments and quantify their fractions. In this work, we investigated the feasibility of DR-CSI with an optimized experiment design for in-vivo liver imaging. Our study showed that DR-CSI can measure multiple sub-voxel compartments in the liver and provide consistent component fraction maps in healthy livers. An initial test on a subject with chronic hepatitis B also demonstrated the potential of DR-CSI to identify and characterize pathological changes in liver parenchyma. Further studies on variable liver diseases are underway.

Enamul Bhuiyan^1,2, Octavia Bane^1,2, Paul Kennedy^1,2, Sema Yildiz², Muhammed Shareef², M. Isabel Fiel³, Stephen Ward³, Myron Schwartz⁴, Thomas Marron⁵, Miriam Merad⁶, and Bachir Taouli^1,2
1BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Department of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ³Department of Pathology, Molecular and Cell Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁴Recanati/Miller Transplantation Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁵The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁶Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States

The reported rate of intrahepatic recurrence of hepatocellular carcinoma (HCC) after resection is high (up to 50%), even with negative surgical margins, which is postulated to be due to micrometastases. Immunotherapy present new possibilities in cancer treatment with encouraging results in HCC. Selection of patients for immunotherapy may be based on background immune features, thus imaging features associated with immunophenotype may aid in patient selection. Specifically, radiomics features exhibited a fair to excellent diagnostic performance for differentiating tumors with high vs. low/moderate tumor infiltrating lymphocytes (TILs) and presence vs absence of tertiary lymphoid structure (TLS) with AUC range of 0.70-0.95.

Enamul Bhuiyan^1,2, Paul Kennedy^1,2, Octavia Bane^1,2, Muhammed Shareef², Stefanie Hectors³, Hung Kam Cheung ³, Elizabeth Miller³, M. Isabel Fiel⁴, Myron Schwartz⁵, Stephen Ward⁴, Thomas Marron⁶, Miriam Merad⁷, and Bachir Taouli^1,2
1BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Department of Diagnostic, Molecular and Interventional Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ³Regeneron Pharmaceuticals Inc. Tarrytown, New York, NY, United States, ⁴Department of Pathology, Molecular and Cell Based Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁵Recanati/Miller Transplantation Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁶The Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ⁷Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States

Neoadjuvant immunotherapy has the potential to decrease the risk of hepatocellular carcinoma (HCC) recurrence post resection. The objectives of this study were to assess the value of pre-treatment MRI parameters for prediction of HCC immunophenotype and response in a cohort of patients undergoing neoadjuvant immunotherapy prior to liver resection. We hypothesize that diffusion and perfusion MRI can predict HCC response to neoadjuvant immunotherapy. It was observed that abundant of TILs decreases ADC in tumors. Moreover, uptake rate is higher in highly necrotic tumors.

Bochao Li¹, Nam Gyun Lee¹, and Krishna Shrinivas Nayak^1,2
1Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, ²Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States

Lung MRI with excellent image quality has been demonstrated at 0.55T, largely due to reduced susceptibility effects. Here, we present joint estimation of lung parenchyma transverse relaxation rates $$$R_{2}$$$, $$$R_{2}^{\prime}$$$, and off-resonance $$$\Delta f$$$. A custom echo-shifted turbo spin echo (TSE) pulse sequence with ECG triggering and breath hold was performed in 4 healthy volunteers, resulting in the mean  $$$R_{2}$$$ of 23.4s^-1, $$$R_{2}^{\prime}$$$ of 53.9s^-1, and $$$\Delta f$$$ of 45.7Hz. This work demonstrates the feasibility of echo-shifted TSE for the estimation of three parameters of interest in lung MRI, and confirms prior measurements made with separate pulse sequences. 

Can Wu¹, Guruprasad Krishnamoorthy², Ergys Subashi¹, Victoria Yu¹, and Ricardo Otazo^1,3
1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Philips Healthcare, MR R&D, Rochester, MN, United States, ³Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States

This work aims to develop high-resolution 4D lung MRI with golden-angle 3D radial (kooshball) acquisition and motion-resolved sparse reconstruction. The golden-angle radial k-space lines were continuously acquired during free-breathing and retrospectively binned to multiple respiratory phases with respect to the respiratory signal obtained from a built-in motion-sensing camera. The sparsity along the respiratory motion dimension was exploited using compressed sensing reconstruction to suppress artifacts and improve SNR. The feasibility of half-spoke ultrashort echo time (UTE) and full-spoke 4D lung MRI was demonstrated on healthy volunteers on a clinical 3T MRI scanner.

Yijing Yang¹, Ziwei Zhao¹, Ye Tian¹, Roberta M. Kato², Sophia X. Cui³, C.-C. Jay Kuo¹, and Krishna S. Nayak^1
1Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, ²Children's Hospital of Los Angeles, Los Angeles, CA, United States, ³Siemens Medical Solutions USA, Inc., Los Angeles, CA, United States

Assessment of regional lung ventilation has significant clinical value for the diagnosis and follow-up of pulmonary diseases. High-performance 0.55T systems have provided new opportunities for pulmonary imaging due to prolonged T2* and reduced susceptibility. Here, we describe an image-based regional lung ventilation assessment method based on real-time bSSFP imaging with 0.3s temporal and 1.64x1.64 mm² spatial resolution, and feature tracking. In healthy adult volunteers, we demonstrate the ability to detect posture-related left-right differences in ventilation, and test-retest repeatability. We detected -5% to 64% regional volume changes throughout the respiratory cycle from end of exhalation to total lung capacity.

Sang Hun Chung¹, Khoi Minh Huynh¹, Yong Chen², Pew-Thian Yap³, Jennifer L. Goralski^4,5,6, Scott H. Donaldson^4,5, and Yueh Z. Lee^3,4
1Biomedical Engineering, University of North Carolina, Chapel hill, NC, United States, ²Department of Radiology, Case Western Reserve University, Cleveland, OH, United States, ³Department of Radiology and Biomedical Research Imaging Center, University of North Carolina, Chapel hill, NC, United States, ⁴Division of Pulmonary and Critical Care Medicine, University of North Carolina, Chapel hill, NC, United States, ⁵Marsico Lung Institute/UNC Cystic Fibrosis Center, University of North Carolina, Chapel hill, NC, United States, ⁶Division of Pediatric Pulmonology, University of North Carolina, Chapel hill, NC, United States

¹⁹F lung ventilation MRI is usually acquired with extended breath holds that limit the acquisition to relatively healthy patients. New denoising methods have the potential to decrease the scan time significantly while achieving comparable SNRs. We compare ¹⁹F breath held scans to spiral acquisition based scans performed while free breathing combined with post-acquisition denoising in human subjects at 3T. VDP and SNR were evaluated. The denoised spiral scans yield higher SNRs (29.3 average increase) but overestimated VDPs (8.5% average increase). The differences in VDP were correlated (R-squared 0.74). The approach shows the potential for free-breathing 19F MRI ventilation imaging.

Fei Tan¹, Xucheng Zhu², and Peder Larson^1
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, ²GE Healthcare, Menlo Park, CA, United States

In this abstract, we introduce motion-compensated low-rank constrained reconstruction with iterative registration. This method jointly improves the motion field estimation and the reconstruction, providing both functional and structural images. In addition, we test the effect of the regularization parameter on structural images and ventilation maps. We conclude that the motion-compensated low-rank constrained with iterative registration method is suitable for regional ventilation quantification.

Anupama Ramachandran¹, Kathleen Ropella-Panagis¹, Nancy Dudek¹, Joel Morehouse¹, Vikas Gulani¹, Mishal Mendiratta-Lala¹, and Nicole Seiberlich^1
1Department of Radiology, University of Michigan, Ann Arbor, MI, United States

MRCP exams were performed in three volunteers on 0.55T and 1.5T MRI systems. Images were rated on overall image quality and visualization of ducts by two board certified abdominal radiologists. All images on both systems were rated as excellent diagnostic quality. A paired sample t-test did not show significant differences in acquisition time between the two field strengths. The advantages of performing an MRCP exam on a 0.55T MRI system may include reduced susceptibility artifacts, reduced artifacts from cholecystectomy clips, improved patient comfort due to larger bore sizes, and potentially lower overhead costs.

Yan Wu¹, Yongwook Kee¹, Marc Alley¹, John Pauly², Lei Xing¹, and Shreyas Vasanawala^1
1Stanford University, Stanford, CA, United States, ²Stanford University, Stanford University, CA, United States

Quantitative R2* map is an important liver disease indicator. However, the availability of R2* map is limited by the long scan time. In this study, we present a new paradigm to predict R2* and B0 maps from dual echo images. A self-attention deep convolutional neural network is trained and validated, where promising accuracy has been obtained. The proposed quantitative parametric mapping approach has a potential to eliminate the necessity for additional data acquisition other than clinical routine.

Orso Pusterla^1,2,3, Rahel Heule^4,5, Francesco Santini^1,3,6, Thomas Weikert⁶, Corin Willers², Simon Andermatt³, Robin Sandkühler³, Sylvia Nyilas⁷, Philipp Latzin², Oliver Bieri^1,3, and Grzegorz Bauman^1,3
1Division of Radiological Physics, Department of Radiology, University Hospital Basel, University of Basel, Basel, Switzerland, ²Division of Pediatric Respiratory Medicine and Allergology, Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland, ³Department of Biomedical Engineering, University of Basel, Basel, Switzerland, ⁴High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübinge, Germany, ⁵Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany, ⁶Department of Radiology, University Hospital Basel, University of Basel, Basel, Switzerland, ⁷Department of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland

Pulmonary biomarkers quantifications on a lobar level provide improved specificity against whole-lung analyses. However, lobar quantifications of pulmonary MR data are hardly accessible due to the complex work required for the manual segmentations. Supervised neural networks have shown the premise for automatic segmentation, but it is challenging to gather labelled data for the training. To overcome these limitations, in this work, we “translate” publicly accessible chest CT datasets and lobe segmentations to pseudo-MR data, and we then train a network able to segment consistently lung lobes of acquired MRI data. The cross-modality approach has excellent prospects to automatize MRI analyses.