کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1807239 1025250 2009 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Improved SNR in linear reordered 2D bSSFP imaging using variable flip angles
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه فیزیک و نجوم فیزیک ماده چگال
پیش نمایش صفحه اول مقاله
Improved SNR in linear reordered 2D bSSFP imaging using variable flip angles
چکیده انگلیسی

This article presents a variable flip-angle approach for balanced steady-state free precession (bSSFP) imaging, which allows increases in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) while keeping specific absorption rate (SAR) constant or reduces SAR for given CNR and SNR. The gain in SNR is achieved by utilizing the higher signal in the transient phase. Flip-angle variation during the echo train is realized using a trigonometric function with M steps (ramp length). Variation is combined with a linear k-space reordering such that outer parts of k-space are sampled using a lower flip angle αmin, while the central part of k-space is acquired with a higher flip angle αmax. No additional preparation or dummy cycles are applied prior to data acquisition. Several variation schemes with different starting flip angles αmin and ramp length M are considered. For example, using αmin=1° and M=96, αmax can be set to 47° without exceeding SAR limits at 3 T and gaining up to 50% in SNR, while, conventionally, α=34° is the maximal possible flip angle. Resolution seems unaffected in volunteer imaging. In all cases, no transient artifacts due to flip-angle variation were observed. This article demonstrates the use of flip-angle variations in bSSFP to increase SNR and CNR while keeping SAR constant, which is especially important at higher field strengths. Flip-angle variation can also be combined with other methods such as parallel imaging techniques for further SAR reduction.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Magnetic Resonance Imaging - Volume 27, Issue 7, September 2009, Pages 933–941
نویسندگان
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