Yuanyuan Liu¹, Zhuo-Xu Cui¹, Xin Liu¹, Dong Liang¹, and Yanjie Zhu^1
1Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China

T_1ρ mapping requires the acquisition of multiple T_1ρ-weighted images with different spin lock times to obtain the T_1ρ  maps, resulting in a long scan time. Compressed sensing has shown good performance in fast quantitative T_1ρ mapping. In this study, we used a patch-based low-rank tensor imaging method to reconstruct the T_1ρ-weighted images from highly undersampled data. Preliminary results show that the proposed method achieves a 6-fold acceleration and obtains more accurate T_1ρ maps than the existing methods.

Huimin Zhang¹, Baiyan Jiang¹, Jian Hou¹, Queenie Chan², and Weitian Chen^1
1Imaging and Interventional Radiology, The Chinese University of Hong Kong, Sha Tin, Hong Kong, ²Philips Healthcare, Hong Kong, Hong Kong

T1rho is a valuable biomarker to probe macromolecular components in tissue. However, conventional T1rho quantification techniques are susceptible to B1 RF and B0 field inhomogeneities, which cause failure of spin-lock and signal oscillation. Adiabatic pulses have been used before and after spin-lock for simultaneous B1 RF and B0 field inhomogeneities compensation and have achieved robust spin-lock, but it does not remove the effect of field inhomogeneities to the actual T1rho value. Therefore, robust T1rho quantification still remains a problem. In this work, we utilized AC-iTIP and combined it with a proposed correction method to address this problem.  

Fatemeh Adelnia¹, Zhongliang Zu^1,2, Feng Wang^1,2, Kevin D Harkins³, and John C Gore^1,2,3,4,5
1Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ²Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, United States, ³Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ⁴Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, United States, ⁵Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN, United States

R_1ρ dispersion over a range of weak locking fields has the potential to reveal information on microvascular geometry and density such as microvascular spacing. This work presents in-vivo results supporting the application of R_1ρ dispersion at low locking fields to the measurement of microvascular sizes and spacings in skeletal muscle. We present model fit parameters from measurements of  R_1ρ dispersion of human skeletal muscle that is close to ex-vivo data.

Jeehun Kim^1,2, Chaoyi Zhang³, Mingrui Yang¹, Hongyu Li³, Mei Li¹, Richard Lartey¹, Leslie Ying^3,4, and Xiaojuan Li^1
1Department of Biomedical Engineering, Program of Advanced Musculoskeletal Imaging (PAMI), Cleveland Clinic, Cleveland, OH, United States, ²Department of Electrical Engineering, Case Western Reserve University, Cleveland, OH, United States, ³Electrical Engineering, University at Buffalo, State University of New York, Buffalo, NY, United States, ⁴Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, NY, United States

The T_1ρ imaging is a promising biomarker for early diagnosis of osteoarthritis, but the application of the method is hindered by its long scan time. In this work, a novel compressed sensing algorithm based on kernel-based low-rank was proposed. The algorithm was evaluated with numerical simulation and volunteer scans, where the volunteers with and without osteoarthritis was scanned with prospective downsampling to evaluate the algorithm performance regarding the presence of pathology.

Gabriele Bonanno^1,2,3, Tom Hilbert^4,5,6, Patrick Leibig⁷, and Tobias Kober^4,5,6
1Advanced Clinical Imaging Technology,Siemens Healthcare AG, Bern, Switzerland, ²Translational Imaging Center, sitem-insel AG, Bern, Switzerland, ³Departments of Radiology and Biomedical Research, University of Bern, Bern, Switzerland, ⁴Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland, ⁵Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland, ⁶LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ⁷Siemens Healthcare GmbH, Erlangen, Germany

Relaxometry in the rotating frame can give unique insights into low frequency biological processes, and therefore may be a valuable quantitative MRI method for clinical research of neurodegenerative diseases. However, T_1ρ maps require long scan times for whole-brain coverage with high isotropic resolution. We present a T_1ρ mapping method based on an accelerated spiral-phyllotaxis 3D Cartesian gradient echo scan with compressed sensing reconstruction that allows for <7-min acquisition time and provides maps directly at the scanner to facilitate a fast workflow for clinical applications. Our method also demonstrated excellent repeatability and reproducibility.

Zhongliang Zu¹, Fatemeh Adelnia¹, Kevin Harkins¹, Feng Wang¹, and John Gore^1
1Vanderbilt University Medical Center, Nashville, TN, United States

Spin-lock imaging at low locking amplitudes are sensitive to the effects of water diffusion in intrinsic gradients and may provide information on tissue microvasculature. However, although composite pulse preparations have been used to reduce artifacts due to B₀ and B₁ inhomogeneities, there are still residual errors. Here, we analyze the source of these errors and developed an approximate theoretical analysis to correct these errors. Simulations and experiments on a healthy human subject show that these errors are mainly due to B₀ shifts, and can be reduced by this correction approach when the B₀ shift is relatively small compared with w₁.

Can Wu^1,2 and Qi Peng^3
1Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Philips Healthcare, Andover, MA, United States, ³Department of Radiology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, United States

The 3D MAPSS T1ρ sequence provides fast and accurate T1ρ quantification with high spatial fidelity using RF phase cycling and variable flip angle in a MP-GRE sequence. However, the conventional 3D MAPSS sequence uses continuous-wave RF pulses for spin locking and is thus sensitive to B₀ and B₁ field inhomogeneities. In this study, a 3D MAPSS T1ρ sequence with adiabatic RF pulses was implemented and was shown to be less sensitive to B₀ frequency offset on phantom compared to conventional 3D MAPSS T1ρ mapping. It was also successfully applied to high-resolution 3D T1ρ mapping of knee cartilage and brain tissue.

Zhao Wei^1,2,3, Alecio F. Lombardi¹, Zubiad Ibrahim¹, Mohammadamin Cheraghi¹, Koihi Masuda⁴, Jiang Du¹, Eric Y. Chang^1,5, Graeme M. Bydder¹, Wenhui Yang^2,3, and Ya-Jun Ma^1
1Department of Radiology, UC San Diego, San Diego, CA, United States, ²Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China, ³University of Chinese Academy of Sciences, Beijing, China, ⁴Department of Orthopedic Surgery, UC San Diego, San Diego, CA, United States, ⁵Radiology Service, Veterans Affairs, San Diego Healthcare System, San Diego, CA, United States

To assess the feasibility of using a 3D ultrashort echo time sequence with adiabatic T_1ρ preparation (UTE-Adiab-T_1ρ) to map the T_1ρ of entire lumbar intervertebral discs (IVDs), 17 human subjects’ lumbar spines were scanned. Correlations between T_1ρ values of all of the components of the IVD and disc degeneration grades and subjects' ages were calculated. T_1ρ differences between subjects with and without low back pain were also assessed. The study showed that the UTE-Adiab-T_1ρ sequence can measure T_1ρ values of the whole IVD. These may be useful for assessment of IVD degeneration.

Gopal Varma¹, Aaron K Grant¹, Olivier M Girard², Guillaume Duhamel², and David C Alsop^1
1Radiology, Division of MR Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, ²CNRS, CRMBM, Aix-Marseille Univ, Marseille, France

Inhomogeneous magnetization transfer (ihMT) is predominantly associated with myelin imaging and shows promise in detection and monitoring myelin related disorders, including multiple sclerosis (MS). Extraction of quantitative parameters from ihMT data (qihMT) would ideally provide information independent of the ihMT sequence. We used Cramer Rao lower bound analysis to develop an optimized acquisition protocol for qihMT and simulations to test the fidelity of the protocol. Preliminary application to central nervous system samples showed differences in free pool longitudinal relaxation rate R_1a, bound pool transverse relaxation time T_2b, and dipolar relaxation time T_1d between specimens from donors with and without MS.

Masanori Ozaki¹ and Masao Yui^1
1Research and Development Center, Canon Medical Systems Corporation, Kawasaki, Japan

Inhomogeneous magnetization transfer is a promising technique to provide high sensitivity and specificity of detecting myelinated content in tissue. 3D steady-state ihMT imaging with 3D segmented Spoiled Gradient Echo (SPGR) sequence can provide myelin information of the whole brain within 5-10min of acquisition time. In this work, we demonstrate 3D steady-state ihMT imaging with a 3D segmented Spoiled Gradient Echo - Echo Planar Imaging (SPGR-EPI) sequence instead of 3D segmented SPGR to reduce acquisition time. We successfully reduced approximately 30% of the acquisition time for 3D steady-state ihMT imaging by applying 3D Segmented SPGR-EPI compared to 3D segmented SPGR.

Matt Hemsley^1,2, Rachel W Chan², Liam Lawrence^1,2, Sten Myrehaug^3,4, Arjun Sahgal^2,3,4, and Angus Z Lau^1,2
1Medical Biophysics, University of Toronto, Toronto, ON, Canada, ²Department of Physical Sciences, Sunnybrook Research Institute, Toronto, ON, Canada, ³Department of Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, ON, Canada, ⁴Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada

qMT has been suggested as a biomarker in Glioblastoma patients. However, reconstruction involves a computationally expensive fitting procedure involving the Bloch-McConnell equations. In this work, the use of neural networks was investigated to perform the fit and to compute uncertainty heatmaps to identify regions of potential error. The dataset consisted of 164 scans from N=41 glioblastoma patients (33=training, 8=testing). Models were evaluated using MAE and correlation in the whole-head volumes and specific ROIs. The model output agreed with a conventional curve-fitting algorithm (r=0.93, and <1% error) with speed up factors of 240000x. Uncertainty predictions were correlated with prediction error (r=0.59).

Scott D. Swanson^1
1Department of Radiology, University of Michigan, Ann Arbor, MI, United States

MT studies of model systems disentangle effects of MT asymmetry and dipolar oder. Choice of lipid materials controls amplitude of ihMT. These studies help outline the physical mechanisms of MT and provide guidance for design of MT, MTA, and ihMT phantoms.

Nabeelah Jinnah¹, Olivier Mougin¹, Penny Gowland¹, Caroline Hoad¹, Gordon Moran¹, Andrew Carradus¹, and Hannah Williams^1
1University of Nottingham, Nottingham, United Kingdom

We have characterized the z-spectrum of collagen at 3T and 7T. We found two peaks +1.9 ppm and at +3.5 ppm and fitting to the Bloch McConnell equations yielded pool sizes that increased monotonically with concentration.

Anliang Chen¹, Ailian Liu¹, Jiazheng Wang², Zhiwei Shen², Deshuo Dong¹, Wan Dong¹, Yuhui Liu¹, Qingwei Song¹, and Renwang Pu^1
1Radiology, The First Affiliated Hospital of Dalian Medical University, Dalian, China, ²Philips Healthcare, Beijing, China

Amide proton transfer-weighted (APTw) imaging can be used to assess changes of intracellular protein concentration and the pH value. Non-invasive visualization and quantification of tissue composition could be detected by T1 map. In this study, we aim to explore the value in difference of rectal cancer with and without lymph node metastasis using APTw imaging combined with T1 map. High diagnostic efficacy (AUC: 0.891; sensitivity: 81.8%; specificity: 100.0%) was achieved with combination of APT and T1 values.

Ying-Hua Chu¹, Yi-Cheng Hsu¹, and Patrick Alexander Liebig^2
1MR Collaboration, Siemens Healthcare Ltd., Shanghai, China, ²Siemens Healthcare GmbH, Erlangen, Germany

We propose a new simultaneous B₀ and B₁ correction for Chemical Exchange Saturation Transfer imaging. This method undersamples the number of offsets on the B₁ and B₀ plane. The CEST map's mean error almost halved at the upper brain region compared with the conventional method and the minimal sampled B₀/B₁ correction method. The proposed method provides an efficient B₀ and B₁ correction and may improve the diagnostic accuracy using CEST imaging at 3T.

Ouri Cohen¹ and Ricardo Otazo^1
1Memorial Sloan Kettering Cancer Center, New York, NY, United States

Chemical Exchange Saturation Transfer (CEST) is a novel imaging technique that is sensitive to metabolite concentrations at imaging resolutions in clinically relevant scan times. These features have generated much interest and applications of CEST in assessing disease pathologies, progression and therapeutic response are currently being explored. A quantitative framework for CEST based on MR Fingerprinting (MRF) was recently proposed using an EPI readout. Here we describe preliminary work to leverage the inherent B0 and motion robustness of radial imaging to develop a clinical golden-angle radial CEST-MRF that doesn't suffer from the classic EPI drawbacks.

Julius Chung¹ and Tao Jin^1
1University of Pittsburgh, Pittsburgh, PA, United States

Low duty cycle π-pulsed CEST is an easy to implement method for exchange rate insensitive CE-MRI measurement that is dependent on labile proton concentration. In creatine phantoms with varying pH, decreasing duty cycle of π-pulse trains decreased pH dependence.  In creatine phantoms of varying concentration and varied pH, exchange dependent relaxation asymmetry of π-pulsed CEST shows stronger linear dependence on concentration at lower duty cycles than continuous wave. Low duty cycle π-pulsed CEST may be useful in studies in which a change of chemical exchange rate (e.g., pH, catalyst concentration, and temperature changes) can interfere with accurate assessment of pathology.

Ravi Prakash Reddy Nanga¹, Mohammad Haris², Hari Hariharan¹, and Ravinder Reddy^1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, ²Research Branch, Sidra Medical and Research Center, Doha, Qatar

Glutamate chemical exchange saturation transfer (GluCEST) is an emerging imaging technique and in the recent years has shown promising applications in Alzheimer’s, Parkinson’s, Epilepsy, Brain tumors and Schizophrenia. Due to structural similarity of glutamine with glutamate, often there is a misconception of glutamine contribution to CEST effect of glutamate. In this study, we investigated the glutamine contribution to glutamate CEST at 3ppm offset.

Botao Zhao¹, Ying Liu¹, and Xiao-Yong Zhang^1
1Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China

The motion in chemical exchange saturation transfer (CEST) image was overlooked in many published studies. Fortunately, several works have been reported to do motion correction for CEST processing. However, the performance of these methods has not been evaluated. The main purpose of this study is to compare the performance of  these methods on motion correction for CEST imaging. We used NMSE, MCC, and UI to evaluate the performance of these methods. Our simulation and preliminary in-vivo data showed that the method of Reg2mean works the best.

Ruibin Liu¹, Zihua Qian², Zhe Wu³, Yi-Cheng Hsu⁴, Caixia Fu⁵, Yi Sun⁴, Dan Wu¹, and Yi Zhang^1
1Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China, ²Department of Radiology, The Children’s Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China, ³Techna Institute, University Health Network, Toronto, ON, Canada, ⁴MR Collaboration, Siemens Healthcare Ltd., Shanghai, China, ⁵MR Application Development, Siemens Shenzhen Magnetic Resonance Ltd., Shenzhen, China

CEST imaging benefits from longer saturation duration and a higher saturation duty cycle. Dielectric shading effects occur when the RF wavelength approaches the object size. Here, we proposed a parallel-transmission-based CEST (pTx-CEST) sequence to extend the maximum saturation duration at 100% duty-cycle and mitigate shading effects. The maximum saturation duration in pTx-CEST was lengthened to 2170, 3150, and 4130ms compared to 1050ms in non-pTx-CEST at TR of 3s, 4s, and 5s, respectively, leading to a significant sensitivity enhancement. Besides, the optimal amplitude ratio and phase difference between RF channels, manifesting circular or elliptical polarization, help reduce the dielectric shading effects.