Xiaoliang Zhang, Ph.D. xzhang@radiology.ucsf.edu Associate Professor Dept of Radiology, UCSF UCSF/UC Berkeley Bioengineering, and California Institute for Quantitative Biosciences (QB3) PI, Parallel Imaging and High Field MR Technology Laboratory

Research Program
Magnetic resonance (MR) has been proven to be a robust noninvasive, nonionic imaging modality in biomedical investigations and clinical diagnosis. The major problem of MRI is its long acquisition time and low sensitivity, consequently resulting in limited temporal resolution and spatial resolution. Parallel imaging and ultrahigh field MR (7T and above) are two promising MR methodologies emerged recently which are capable of improving conventional MR performance in temporal resolution and spatial resolution in vivo. My research focuses on development of the parallel imaging technique, ultrahigh field MR, and also integration of the two promising techniques, providing a fast, highly sensitive MR for in vivo biomedical research. The research endeavor involves parallel imaging algorithm, transmit SENSE, parallel excitation, new strategies for high frequency RF coils and coil arrays, electromagnetic problems and computational electromagnetism in in-vivo MR at high fields by using FDTD method and other finite element methods, and applications of the developed techniques to in vivo MR Imaging and spectroscopy. One of such applications is related to the use of the hyperpolarized C-13 MR spectroscopic imaging to study metabolism and pathology in normal and cancerous conditions in humans and experimental animals. With increased capability of temporal resolution and spatial resolution, exploration of DTI with SENSE technique at 7T is also an important research field in our group. Another research component in our group is MRI compatibility and safety of implanted medical devices, making MRI examinations possible to numerous patients with implanted medical devices, such as the pacemaker.


Current Research Grants

RF Coils for Parallel MRI/MRS in vivo at High Fields
NIH R01 EB004453

Abstract
High and ultra-high field (3-9.4 Tesla) magnetic resonance imaging and spectroscopy (MRI/MRS) has been proven to be fundamentally advantageous due to their intrinsically high sensitivity. Recently, with the advent of new reconstruction algorithms such as SENSE and SMASH, parallel imaging, a fast imaging technique introduced some 20 years ago has been revived and has become practical and robust. This technique with utilization of RF coil arrays can dramatically reduce the minimum data acquisition time. A technique combining parallel imaging with high-field MR is desired and will be ideal because it possesses both the advantages of fast acquisition time and high sensitivity. However, due to high operating frequencies at high fields, both parallel imaging and high-field MR confront RF coil design challenges such as increased radiation losses, difficult to achieve coil decoupling among resonant elements, increased coil/subject interactions, and complicated design and operation. These challenges have become a major obstacle for further development of parallel imaging at high fields. Therefore, we propose a comprehensive project in this application for developing high frequency RF coil arrays based on the newly developed microstrip transmission line (MTL) coil design technique. The major goals of this project will be focused on (i) development of a wide variety of efficient high-frequency RF coil arrays for in-vivo high-field parallel imaging using the MTL concept; and (ii) establishment of a simulation, modeling a wide variety of parallel MTL coil arrays for the analysis of resonant frequencies, decoupling and EM fields, numerically. The proposed coil arrays are characterized by unmatched advantages of (i) a high Q factor and better sensitivity, (ii) unique and efficient decoupling mechanisms, (iii) a completely distributed circuit design, and (iv) simple and compact coil design, with easy fabrication and low cost. Successful outcomes from this research will provide a robust solution to RF coil array designs for parallel imaging at high fields and result in significant technological advances in high-field RF coil array engineering. They will be important to the future success of in vivo high-field parallel MRI/MRS.

Related Articles

Zhang X, Ugurbil K and Chen W. Microstrip RF surface coil design for extremely high-field MRI and spectroscopy. Magn Reson Med, 46, 443-50. (2001).

Zhang X, Ugurbil K and Chen W. A Novel RF volume coil using microstrip transmission line for MR imaging and spectroscopy at 4 Tesla. J Magn Reson, 161: 242-251 (2003).

Zhang X, Zhu X and Chen W. RF coil design using the high-order harmonic resonance for MR imaging. Magn Reson Med, 53:1234-1239 (2005).

Collins C, Yang Q, Wang J, Zhang X, Liu H, Michaeli S, Zhu X, Adriany G, Vaughan T, Anderson P, Merkle H, Ugurbil K, Smith M and Chen W. Different excitation and reception distributions with a single-loop transmit-receive surface coil near a head-sized spherical phantom at 300 MHz. Magn Reson Med, 47, 1026-8 (2002).

Wang J, Yang Q, Zhang X, Collins M, Smith M, Zhu X, Adriany G, Ugurbil K and Chen W. Polarization of the RF field in a human head at high field: a study with a quadrature surface coil at 7.0 T. Magn Reson Med, 48, 362-9 (2002).

Yang Q, Wang J, Zhang X, Collins C, Smith M, Liu H, Zhu X, Vaughan T, Ugurbil K and Chen W. Analysis of wave behavior in lossy dielectric samples at high field. Magn Reson Med, 47, 982-9 (2002).

Zhu X, Zhang Y, Tian R, Lei H, Zhang N, Zhang X, Merkle H, Ugurbil K and Chen W. Development of 17O NMR approach for fast imaging of cerebral metabolic rate of oxygen in rat brain at high field. Proc Natl Acad Sci U S A, 99, 13194-9 (2002).

Zhang X, Ugurbil K, Chen W. A 300-MHz Volume RF Coil Using Inverted Microstrip Transmission Line (iMTL) for Human Head Imaging at 7T. IEEE Trans Biomed Eng, 52(3): 495-504 (2005).

Wu B, Zhang X, Shen G, An Optimized Four-channel Microstrip Loop Array at 7T. ISMRM 2006, p2569.

Wu B, Zhang X, Shen G, Inductively Decoupled Microstrip Array at 9.4T. ISMRM 2006, p528

Wu B, Zhang X, Qu P, Shen G. Design of an Inductively Decoupled Microstrip Array at 9.4T. J Magn Reson. 182: 126-132 (2006).

Wu B, Zhang X, Qu P, Shen G. Capacitively Decoupled Tunable Loop Microstrip Array at 7T. Magn Reson Imaging. 25(3): 418-424 (2007)

Xie Z, Xu D, Kelley D, Vigneron D, Zhang X. Dual-frequency volume coil with quadrature capability for 13C/1H MRI/MRS at 7T, ISMRM workshop on Advances in high field MR (2007).

Zhang X. Sample Self-resonance Excitation and Reception, ENC (2007).

Zhang X, Ogawa S, Chen W. An inverted microstrip transmission line (iMTL) surface coil for 3T and 4T MR imaging, ENC (2007).

Xie Z, Zhang X. An 8-channel microstrip array coil for mouse parallel MR imaging at 7T by using magnetic wall decoupling technique. ISMRM 2008.

Xie Z, Zhang X. An 8-channel non-overlapped spinal cord array coil for 7T MR imaging. ISMRM 2008.

Xie Z, Xu D, Kelley D, Vigneron D, Zhang X. A Dual-tuned quadrature microstrip volume coil for 13C/1H MRI/S at 7T. ISMRM 2008.

Xie Z, Zhang X. A dual-frequency, common mode and differential mode (CMDM) microstrip surface coil for 13C/1H MRI/S at 7T. ISMRM 2008.

Xie Z, Zhang X. A novel dual-frequency volume coil using common mode/differential mode (CMDM) resonators at 7T. ISMRM 2008.

Xie Z, Xu D, Zhang X. A novel common mode, quadrature drive birdcage coil for 7T Proton MRI. ISMRM 2008.

Xie Z, Zhang X. An eigenvalue/eigenvector analysis of decoupling methods and its application at 7T MR imaging. ISMRM 2008

Xie Z, Zhang X. A novel decoupling technique for non-overlapped microstrip array coil at 7T MR imaging. ISMRM 2008

Zhang X. NMR Experiments using no RF coil: RF-Coilless NMR. ISMRM 2008

Zhang X, Wang C, Xie Z, Wu B. Non-resonant microstrip (NORM) RF coils: an unconventional RF solution to MR imaging and spectroscopy. ISMRM 2008
Wang C, Wu B, Zhang X. A Practical Double-tuned 1H/13C Birdcage Resonator for MRI/MRS at 7T. ISMRM 2008.

Wang C, Zhang X. B1 field optimization for microstrip transmission line volume coil at high field. ISMRM 2008.

Wang C, Wu B, Xu D, Zhang X. A Novel double-tuned head coil with 16 double-tuned elements for 7T MRI/S. ISMRM 2008.

Wang C, Zhang X. B1 Shimming by Pre-emphasis at High Field. ISMRM 2008.

Wang C, Wu B, Zhang X. A Practical Double-tuned 1H/13C Birdcage Resonator for MRI/MRS at 7T. ISMRM 2008

Wu B, Wang C, Xie Z, Zhang X. 16-channel microstrip array using 1st and 2nd harmonics for parallel imaging at 7T. ISMRM 2008.

Wu B, Qu P, Wang C, Zhang X. Channel Scalable Coil Array with Extended GRAPPA. ISMRM 2008.

Wu B, Gao J, Yao J, Zhang C, Zhang X. Design of a Strip Transmit Coil/Array for Low Field Open MR. ISMRM 2008.


Parallel Excitation and Multiple Transceiver Channels for Enhanced Parallel Imaging Capability at 7T
QB3 R1 Research Award

Abstract
With quantitative capability, magnetic resonance imaging and spectroscopy (MRI/MRS) have become a promising non-invasive imaging modality for biomedical research. This project aims to upgrade our 7T whole body MR system housed in the QB3 with multiple transmit/receive channels. This upgrade will enable the parallel imaging technique for both signal transmit and receive on the 7T system. The multi-channel transceiver is capable of independent amplitude and phase control of RF excitation power. With the multiple channels, parallel imaging techniques can be used to dramatically accelerate the acquisitions (thus increase temporal resolution), improve image SNR, or increase the spatial resolution, performance of transmit SENSE, and RF shimming at the ultrahigh field. The successful outcome of this upgrade will significantly improve the 7T imaging capability in basic and clinical research. The improvement will provide a much powerful, highly sensitive and fast imaging tool and significantly benefits a wide range of biomedical research in a qualitative fashion within the QB3. This research effort could give our 7T MR, a multi-million dollars project, a quantum leap and move imaging capability of QB3 to the forefront of the field. This is not about a local competition or a simple improvement of QB3, but rather about making QB3 a world leader in in-vivo MRI/MRS methodology and its medical, biological and pharmaceutical research applications.

Related Articles

Xie Z, Zhang X. An 8-channel microstrip array coil for mouse parallel MR imaging at 7T by using magnetic wall decoupling technique. ISMRM 2008.

Xie Z, Zhang X. An 8-channel non-overlapped spinal cord array coil for 7T MR imaging. ISMRM 2008.

Xie Z, Xu D, Kelley D, Vigneron D, Zhang X. A Dual-tuned quadrature microstrip volume coil for 13C/1H MRI/S at 7T. ISMRM 2008.

Xie Z, Zhang X. A dual-frequency, common mode and differential mode (CMDM) microstrip surface coil for 13C/1H MRI/S at 7T. ISMRM 2008.

Xie Z, Zhang X. A novel dual-frequency volume coil using common mode/differential mode (CMDM) resonators at 7T. ISMRM 2008.

Xie Z, Xu D, Zhang X. A novel common mode, quadrature drive birdcage coil for 7T Proton MRI. ISMRM 2008.

Xie Z, Zhang X. An eigenvalue/eigenvector analysis of decoupling methods and its application at 7T MR imaging. ISMRM 2008

Xie Z, Zhang X. A novel decoupling technique for non-overlapped microstrip array coil at 7T MR imaging. ISMRM 2008