Convex optimized diffusion encoding ( <scp>CODE</scp> ) gradient waveforms for minimum echo time and bulk motion–compensated diffusion‐weighted <scp>MRI</scp>

Author(s): Aliotta, Eric; Wu, Holden H; Ennis, Daniel B | Abstract: PurposeTo evaluate convex optimized diffusion encoding (CODE) gradient waveforms for minimum echo time and bulk motion-compensated diffusion-weighted imaging (DWI).MethodsDiffusion-encoding gradient waveforms were designed for a range of b-values and spatial resolutions with and without motion compensation using the CODE framework. CODE, first moment (M1 ) nulled CODE-M1 , and first and second moment (M2 ) nulled CODE-M1 M2 were used to acquire neuro, liver, and cardiac ADC maps in healthy subjects (n=10) that were compared respectively to monopolar (MONO), BIPOLAR (M1 = 0), and motion-compensated (MOCO, M1 + M2 = 0) diffusion encoding.ResultsCODE significantly improved the SNR of neuro ADC maps compared with MONO (19.5 &#177; 2.5 versus 14.5 &#177; 1.9). CODE-M1 liver ADCs were significantly lower (1.3 &#177; 0.1 versus 1.8 &#177; 0.3 &#215; 10-3 mm2 /s, ie, less motion corrupted) and more spatially uniform (6% versus 55% ROI difference) than MONO and had higher SNR than BIPOLAR (SNR = 14.9 &#177; 5.3 versus 8.0 &#177; 3.1). CODE-M1 M2 cardiac ADCs were significantly lower than MONO (1.9 &#177; 0.6 versus 3.8 &#177; 0.3 x10-3 mm2 /s) throughout the cardiac cycle and had higher SNR than MOCO at systole (9.1 &#177; 3.9 versus 7.0 &#177; 2.6) while reporting similar ADCs (1.5 &#177; 0.2 versus 1.4 &#177; 0.6 &#215; 10-3 mm2 /s).ConclusionsCODE significantly improved SNR for ADC mapping in the brain, liver and heart, and significantly improved DWI bulk motion robustness in the liver and heart. Magn Reson Med 77:717-729, 2017. &#169; 2016 International Society for Magnetic Resonance in Medicine.