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Local Parameter Estimation: Methods

Data acquisition DT-MRI datasets were acquired on a single healthy volunteer. The images were obtained on a 3.0 T Varian Inova scanner using a diffusion-weighted single-shot EPI sequence. To minimize eddy currents, a doubly-refocused spin-echo sequence was implemented [17]. A birdcage radio-frequency head coil was used for both pulse transmission and signal detection. The diffusion gradients achieved a maximum gradient strength of 22 $ mTm^{-1}$. Each data set consisted of 3 non-diffusion-weighted and 60 diffusion-weighted images acquired with a b-value of 1000 $ smm^{-2}$. The diffusion gradients were uniformly distributed through space using the optimized scheme proposed by Jones [18]. Each set of images contained 42 contiguous slices with a 2.5 $ mm$ thickness. A half k-space acquisition was performed with a matrix size set to $ 62\times96$ and a field of view of $ 240\times240 mm^2$. The images were interpolated to achieve a matrix size of $ 128\times128$ and a final resolution of $ 1.875\times1.875\times2.5 mm^3$. To minimize motion artifacts, peripheral gating was used such that triggering occurred on every cardiac cycle. The echo time was set to 106 ms while the effective repetition time was 14 R-R intervals. The total scan time for each dataset was approximately 15 minutes, depending on heart rate.



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Next: Estimation Up: Local Parameter Estimation Previous: Increasing the Complexity -
Tim Behrens 2004-01-22