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REAL-TIME FLOW QUANTIFICATION TECHNIQUES IN CARDIOVASCULAR MRI APPLICATIONS

Lin, Hung-Yu
http://rave.ohiolink.edu/etdc/view?acc_num=osu1238594589

Abstract Details

2009, Doctor of Philosophy, Ohio State University, Biomedical Engineering.
Velocity measurement based on phase-contrast magnetic resonance imaging (PC-MRI) is firmly recognized as a valuable and accurate technique to assess hemodynamics in a variety of clinical applications. However, conventional PC-MRI requires the acquisition of two separate and complete k-space dataset with different flow sensitivities. Real-time MR velocity measurement experiences limited success due to the insufficient temporal sampling rate to depict hemodynamic prosperities within each cardiac cycle. Accelerated data acquisition strategies described by this dissertation were developed to reduce the reference data requirements. Time-efficient PC-MRI methods accelerate the acquisition of phase-reference data in the spatial and temporal domain with minimum loss of velocity accuracy. Root-Mean-Square error estimation demonstrates the accuracy of the proposed accelerated velocity measurement methods as compared to the conventional PC-MRI reconstruction. As an alternative accelerated PC-MRI, shared velocity encoding (SVE) method was developed to achieve the same temporal sampling rate comparing to standard MR cine scans. In SVE method, phase-difference images from alternative polarity pairs (+ -), (- +), (+ -), etc. can be reconstructed and resulted in a factor of 2 increase in the effective temporal resolution. With the SVE method implementation, the local pulse wave velocity (PWV) measurement becomes practical and useful in the common carotid arteries in current clinical 1.5T MRI scanners. Echo-planar imaging (EPI) is an ultra-high-speed MRI method that is capable of producing snap-shot MR images in the ranges of 10-100 msec. Recently, EPI sequence has been used in attempts to acquire real-time cardiac cine images in a standard MR scan. Consequently, we propose to utilize the advantage of high acquisition speed of EPI combining with PC-MRI to achieve real-time velocity measurement in the major vessels. However, chemical shift artifacts resulting from the off-resonance effect of fat spins limit the use of long echo train length, which compromises acquisition speed of the EPI method. This work investigated the problem of off-resonance artifacts and developed a fat-suppression method not only applicable to the EPI but also to the SSFP cine sequence. With the fat-suppression EPI sequence, we demonstrate the potential capability of using the SVE technique for real-time velocity mapping in both in-vitro pulsatile flow phantom and in-vivo volunteer studies. Long scan time of multiple-directional velocity measurement is the common difficulties to perform in clinical routines. With an echo-planar readout sequence combined with SVE reconstruction, we conduct a feasibility study that shows the 2D multiple-directional and 3D single-directional velocity measurement become feasible in standard MRI scanners.
Orlando Simonetti, PhD (Committee Chair)
Subha Raman, MD (Committee Member)
Petra Schmalbrock, PhD (Committee Member)
Yiucho Chung, PhD (Committee Member)
240 p.
Biomedical Research
Phase-Contrast; Flow Quantification; Velocity Measurement; Fat Suppression; Real-Time MRI

Recommended Citations

Citations

  • Lin, H.-Y. (2009). REAL-TIME FLOW QUANTIFICATION TECHNIQUES IN CARDIOVASCULAR MRI APPLICATIONS [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238594589

    APA Style (7th edition)

  • Lin, Hung-Yu. REAL-TIME FLOW QUANTIFICATION TECHNIQUES IN CARDIOVASCULAR MRI APPLICATIONS. 2009. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1238594589.

    MLA Style (8th edition)

  • Lin, Hung-Yu. "REAL-TIME FLOW QUANTIFICATION TECHNIQUES IN CARDIOVASCULAR MRI APPLICATIONS." Doctoral dissertation, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1238594589

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.