Tissue Characterization
Yuheng Huang, MS
Visiting Graduate Student
Indiana University School of Medicine, Indiana, United States
Yuheng Huang, MS
Visiting Graduate Student
Indiana University School of Medicine, Indiana, United States
Xingmin Guan, PhD
Postdoctoral Fellow
Indiana University School of Medicine
San Diego, California, United States
.jpg "Xinheng Zhang, MSc photo")
Xinheng Zhang, MSc
Ph.D. Candidate
Indiana University School of Medicine
Indianapolis, Indiana, United States
Richard LQ. Tang, MD
Faculty
Indiana University School of Medicine, California, United States
Xiaoming Bi
Director
Siemens Healthineers, California, United States
Fei Han, Ph.D.
Senior Scientist
Siemens Medical Solutions USA, Inc.
LOS ANGELES, California, United States
HsuLei Lee
MR Physicist
Cedars-Sinai Medical Center, United States
Anthony G. Christodoulou, PhD
Assistant Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Debiao Li, PhD
Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Hui Han, PhD
Associate professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Rohan Dharmakumar, PhD
Professor of Medicine, Radiology & Imaging Sciences, Anatomy, Cell Biology & Physiology
Krannert Cardiovascular Research Center, Indiana University School of Medicine
Indianapolis, Indiana, United States
Hsin-Jung Yang, PhD
Assistant Professor
Cedars-Sinai Medical Center
Los Angeles, California, United States
Accurate detection and characterization of intramyocardial hemorrhage(IMH) following reperfused myocardial infarction(MI) are important for the advancement of understanding and therapies to limit its detrimental effects of IMH on the heart. Quantitative susceptibility mapping(QSM) has evolved into the standard method for iron imaging in the brain. However, its application in the heart has been limited by major technical shortcomings. Confounders, such as the involuntary cardiac and respiratory motion, the large B0 inhomogeneity at the heart-lung interfaces, and the susceptibility streaking artifacts in cases of IMH with high iron concentration, all make cardiac QSM challenging. In this study, we developed a free-breathing, motion-mitigated, whole-heart QSM technique with a High Dynamic Range phase reconstruction algorithm(HDR-QSM). HDR-QSM overcomes key confounders for imaging IMH on the basis of iron and provides highly reliable QSM measurements across a wide range of field disturbances and iron concentrations.
Methods:
A 3D, non-ECG gated, free-breathing 8-echo mGRE sequence was prescribed and reconstructed using an LRT framework(TE1/ΔTE = 1.42/ 2.01ms)1. An HDR-QSM reconstruction pipeline was developed to eliminate common confounders in cardiac QSM images(Fig.1). In brief, phase images of the mGRE sequence were derived with an Auto-HDR phase unwrapping algorithm2, and an SNR-guided fitting algorithm3 to avoid off-resonance and wrapping induces phase map errors. Subsequently, a two-step QSM was adopted to minimize streaking artifacts associated with a high iron concentration in IMH lesions. Canines subjected to hemorrhagic MIs(n=10) were studied 7 days post-MI. Animals were images in a clinical 3T scanner. For validation purposes, ex-vivo mGRE images with similar parameters were acquired post-euthanization(n=5). Results from HDR-QSM were compared with conventional iron-sensitive images(R2* maps (1/T2*) and standard QSM4) derived from the same datasets.
Results: Representative findings in a canine with IMH are shown in Fig.2. In the conventional iron-sensitive images, strong off-resonance artifacts were present at the heart-lung interfaces(red boxes) but were eliminated by HDR-QSM processing. In addition, HDR-QSM corrected the strong streaking artifacts around the IMH zone evident in the standard QSM images(green boxes) and demonstrated a more homogeneous susceptibility measure in the lesions. In Fig.3, ROC analysis was performed using ex-vivo R2* maps as the ground truth. The AUC of HDR-QSM was significantly higher than other approaches, which reflects the successful elimination of the susceptibility-induced error in the conventional modalities(AUC: R2*=0.83; standard QSM=0.69; HDR-QSM=0.94).
Conclusion: We have developed an HDR-QSM technique that mitigates the persistent susceptibility-induced imaging artifacts in iron-sensitive CMR. HDR-QSM opens the door for robust iron quantification in the heart. Additional studies are needed to establish its utility in clinical settings.