Showing papers by "Kyunghyun Sung published in 2016"

Rapid quantitative T2 mapping of the prostate using three-dimensional dual echo steady state MRI at 3T

Abstract: Purpose To develop and evaluate a rapid three-dimensional (3D) quantitative T2 mapping method for prostate cancer imaging using dual echo steady state (DESS) MRI at 3T. Methods In simulations, DESS-T2 mapping in the presence of T1 and B1+ variations was evaluated. In a phantom and in healthy volunteers (n = 4), 3D DESS-T2 mapping was compared with a two-dimensional turbo spin echo (TSE) approach. In volunteers and a pilot patient study (n = 29), quantitative T2 in normal prostate anatomical zones and in suspected cancerous lesions was evaluated. Results The simulated bias for DESS-T2 was < 2% (5%) for typically observed T1 ( B1+) variations. In phantoms and in vivo, high correlation of DESS-T2 and TSE-T2 (r2 = 0.98 and 0.88, P < 0.001) was found. DESS-T2 in the normal peripheral zone and transition zone was 115 ± 26 ms and 64 ± 7 ms, respectively, in healthy volunteers and 129 ± 39 ms and 83 ± 12 ms, respectively, in patients. In suspected cancerous lesions, DESS-T2 was 72 ± 14 ms, which was significantly decreased from the normal peripheral zone (P < 0.001) but not from the transition zone. Conclusion Rapid 3D T2 mapping in the entire prostate can be performed in 1 min using DESS MRI. Magn Reson Med 76:1720–1729, 2016. © 2016 International Society for Magnetic Resonance in Medicine

Quantification of liver perfusion using multidelay pseudocontinuous arterial spin labeling

Abstract: ORIGINAL RESEARCH Quantification of Liver Perfusion Using Multidelay Pseudocontinuous Arterial Spin Labeling Xinlei Pan, BS, 1 Tianyi Qian, PhD, 2 Maria A. Fernandez-Seara, PhD, 3 Robert X. Smith, PhD, 4 Kuncheng Li, MD, PhD, 5 Kui Ying, PhD, 6 Kyunghyun Sung, PhD, 7 and Danny J.J. Wang, PhD, MSCE 4,7 * Purpose: To develop a free-breathing multidelay pseudocontinuous arterial spin labeling (pCASL) technique for quanti- tative measurement of liver perfusion of the hepatic artery and portal vein, respectively. Materials and Methods: A navigator-gated pCASL sequence with balanced steady-state free precession (bSSFP) read- out was developed and applied on five healthy young volunteers at 3T. Two labeling schemes were performed with the labeling plane applied on the descending aorta above the liver, and perpendicular to the portal vein before its entry to liver to label the hepatic artery and portal vein, respectively. For each labeling scheme, pCASL scans were performed at five or six postlabeling delays between 200 and 2000 msec or 2500 msec with an interval of 400 or 500 msec. Multide- lay pCASL images were processed offline with nonrigid motion correction, outlier removal, and fitted for estimation of liver perfusion and transit time. Results: Estimated liver perfusion of the hepatic artery and hepatic portal vein were 21.8 6 1.9 and 95.1 6 8.9 mL/100g/ min, with the corresponding transit time of 1227.3 6 355.5 and 667.2 6 85.0 msec, respectively. The estimated liver per- fusion and transit time without motion correction were less reliable with greater residual variance compared to those processed with motion correction (P < 0.05). Conclusion: The liver perfusion measurement using multidelay pCASL showed good correspondence with values noted in the literature. The capability to noninvasively and selectively label the hepatic artery and portal vein is a unique strength of pCASL as compared to other liver perfusion imaging techniques, such as computed tomography perfusion and dynamic contrast-enhanced MRI. J. MAGN. RESON. IMAGING 2015;00:000–000. L iver diseases afflict more than 30 million people in the US, or 1 in 10 Americans. 1 The number of people diag- nosed with liver diseases such as hepatitis C, nonalcoholic fatty liver disease, and liver cancer are on the rise both in the US and worldwide. 2 Liver ultrasonography and magnetic res- onance imaging (MRI) are the two main imaging modalities for detecting, characterizing, and monitoring treatment responses of focal and diffuse liver diseases. 3–5 Ultrasonogra- phy remains the first-line imaging modality for examining liver morphology and blood flow; these are accentuated through the recent development of elastography. MRI offers multiparametric examinations of the morphology, perfusion, and diffusion of the liver. Dynamic contrast-enhanced (DCE) MRI and MR elastography (MRE) are two emerging tech- nologies capable of quantitative assessments of liver perfu- sion/permeability and viscoelasticity, respectively. Liver perfusion imaging is useful in detecting regional and global alterations in liver blood flow caused by a range View this article online at wileyonlinelibrary.com. DOI: 10.1002/jmri.25070 Received Jul 4, 2015, Accepted for publication Sep 24, 2015. *Address reprint requests to: D.J.J.W., Laboratory of Functional MRI Technology (LOFT), Department of Neurology, UCLA, 660 Charles E Young Dr. South, Los Angeles, CA 90095. E-mail: jwang71@gmail.com From the 1 Department of Biomedical Engineering, Tsinghua University, Beijing, China; 2 Siemens Healthcare, MR Collaboration NE Asia, Beijing, China; Neuroimaging Laboratory, Division of Neuroscience, Center for Applied Medical Research, University of Navarra, Spain; 4 Laboratory of Functional MRI Technology (LOFT), Department of Neurology, University of California Los Angeles, Los Angeles, California, USA; 5 Department of Radiology, Xuanwu Hospital of Capital Medical University, Beijing, China; 6 Department of Engineering Physics, Tsinghua University, Beijing, China; and 7 Department of Radiology, University of California Los Angeles, Los Angeles, California, USA. Additional Supporting Information may be found in the online version of this article. C 2015 Wiley Periodicals, Inc. V