Noncontrast-enhanced magnetic resonance angiography and venography imaging with enhanced angiography
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PURPOSE: To achieve simultaneous high-resolution magnetic resonance angiography and venography (MRAV) imaging in terms of enhanced time-of-flight (TOF) angiography and susceptibility-weighted imaging (SWI), with a clear separation of arteries and veins. MATERIALS AND METHODS: A new flow rephase/dephase interleaved double-echo sequence was introduced that facilitates multiple types of imaging contrast, i.e., TOF, SWI, and dark blood, in a single acquisition. A nonlinear subtraction (NLS) method is proposed and assessed to maximally enhance angiography contrast with minimum venous contamination. RESULTS: Fully flow rephased TOF MRA and SWI MRV data were acquired simultaneously, along with an extra flow dephased dark blood image for angiography enhancement calculation. Compared to linear subtraction methods, the proposed NLS method was able to enhance angiography contrast while effectively eliminating vein-tissue contrast. The NLS method even outperformed low-dose contrast-enhanced MRA for a clean, enhanced angiography map. CONCLUSION: Using the proposed interleaved double-echo sequence along with the NLS postprocessing method, one can simultaneously obtain both high-quality SWI and significantly enhanced TOF MRA with clear separation of arterial and venous maps.
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