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High resolution three-dimensional time-of-flight magnetic resonance angiography and flow quantification

Lin, Weili
http://rave.ohiolink.edu/etdc/view?acc_num=case1057241590

Abstract Details

1993, Doctor of Philosophy, Case Western Reserve University, Biomedical Engineering.
While gaining clinical acceptance, magnetic resonance angiography (MRA) continues to suffer difficulties associated with spin dephasing in regions of complex flow and spin saturation in regions of slow flow. The objectives of this research are to reduce these two artifacts in three-dimensional (3D) time-of-flight (TOF) MRA and clinically evaluate them for sickle cell anemia, arteriovenous malformation, stenosis and aneurysm patients. In this research, a very short echo time (TE) is used to reduce the difficulties associated with spin dephasing. Magnetization transfer saturation (MTS) and fat saturation (FS) pulses are used to suppress the enhanced signal from brain parenchyma and fatty tissue with short TEs. Saturation effects are reduced with a dual-slab MTS acquisition allowing a large region of interest to be covered. Alternatively, a variable TE sequence maintains good flow compensation while suppressing fat signal. A variable repetition time (TR) scheme reduces spin saturation and can be used to enhance vessel contrast or reduce acquisition time. In addition, the contrast agent, Gd-DTPA is used to reduce T1 and enhance vessel signal. As this enhances all vessels, a vessel tracking is used as a post-processing step to separate arteries from veins and to reduce artifacts associated with the MIP. Phase contrast (PC) flow measurement methods are also used to obtain flow information for the primary feeding vessels on the AVM patients prior to and after embolization. In all cases, the artifacts associated with spin dephasing in regions of complex flow are minimized with short TEs. The brain parenchyma is suppressed by 25% by applying the MTS pulse with short TEs. The FS pulse reduces the signal intensity of fatty tissue so that it will not obscure vascular structures. The variable TE acquisition method successfully suppresses fat signal uniformly throughout the entire imaging volume while maintaining good flow compensation. Dual-slab acquisition with MTS overcomes spin saturation making it possible to cover the entire brain. Variable TR is equivalent to constant TR MRA when acquired in a shorter time and gives better contrast in the same acquisition time. Gd-DTPA improves vascular contrast by a factor of 2. Using PC flow quantification for AVM studies, the velocity in the primary feeding vessel is seen to reduce and the velocity for the same vessel in the contralateral side is seen to increase after embolization.
George Robinson (Advisor)
304 p.
Engineering, Biomedical
High resolution three-dimensional; time-of-flight; magnetic resonance; angiography; flow quantification

Recommended Citations

Citations

  • Lin, W. (1993). High resolution three-dimensional time-of-flight magnetic resonance angiography and flow quantification [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1057241590

    APA Style (7th edition)

  • Lin, Weili. High resolution three-dimensional time-of-flight magnetic resonance angiography and flow quantification. 1993. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1057241590.

    MLA Style (8th edition)

  • Lin, Weili. "High resolution three-dimensional time-of-flight magnetic resonance angiography and flow quantification." Doctoral dissertation, Case Western Reserve University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057241590

    Chicago Manual of Style (17th edition)

case1057241590
405
© 1993, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.
Release 3.2.12