Borup, Daniel D.

AbstractPurposeTo develop a method that achieves simultaneous brain and neck time‐of‐flight (ToF) magnetic resonance angiography (MRA) within feasible scan timeframes.MethodsLocalized quadratic (LQ) encoding is efficient for both signal‐to‐noise ratio (SNR) and in‐flow enhancement. We proposed a spiral multiband LQ method to enable simultaneous intracranial and carotid ToF‐MRA within a single scan. To address the venous signal contamination that becomes a challenge with multiband (MB) ToF, tilt‐optimized non‐saturated excitation (TONE) and partial‐Fourier slice selection (PFSS) were further introduced in the LQ framework to mitigate the venous signal and improve artery contrast. A sequential spiral MB and LQ reconstruction pipeline was employed to obtain the brain‐and‐neck image volumes.ResultsThe proposed MB method was able to achieve simultaneous brain and neck ToF‐MRA within a 2:50‐min scan. The complementarily boosted SNR‐efficiency by MB and LQ acquisitions allows for the increased spatial coverage without increase in scan time or noticeable compromise in SNR. The incorporation of both TONE and PFSS effectively alleviated the venous contamination with improved small vessel sensitivity. Selection of scan parameters such as the LQ factor and flip angle reflected the trade‐off among SNR, blood contrast, and venous suppression.ConclusionsA novel MB spiral LQ approach was proposed to enable fast intracranial and carotid ToF‐MRA with minimized venous corruption. The method has shown promise in MRA applications where large spatial coverage is necessary.

PurposeTo generate efficient gradient waveforms for spiral MRI which mitigate the high‐frequency attenuation inherent in gradient systems.Theory and MethodsSpiral MRI has many clinical advantages, including high temporal and SNR efficiency. One of the challenges for robust spiral MRI is a high sensitivity to imperfections in the gradient system, which requires some form of correction in order to map data correctly in k‐space. A previous numerical algorithm for generating spiral gradient waveforms was modified to reduce its high‐frequency content with minimal increase in waveform duration.ResultsExamples are shown of compact frequency gradient waveforms. Software implementing the algorithm is made available.ConclusionAn algorithm to produce gradient waveforms with a compact frequency spectrum is described. This algorithm results in greatly reduced overall error and better compatibility with gradient systems than the original algorithm from which it was derived.