Diffusion-weighted MR imaging of the abdomen with pulse triggering.

Purpose: The aim of this work was to reduce the influence of motion on diff usion-weighted MR images of the abdomen by pulse triggering of single-shot sequences. Methods: Five healthy volunteers were examined both without and with finger pulse-triggering of a diffusion-weighted single-shot echo plana r MR imaging sequence at 1.5 T. Series of diffusion-weighted images were ac quired at different phases of the cardiac cycle by varying the time delay b etween finger pulse and sequence acquisition. The measurements were repeate d three times. The diffusion weighted images were analysed by measuring the signal intensities and by determining the ADC values within the spleen, ki dney and liver. Results: The magnitude of motion artifacts on diffusion wei ghted images shows a strong dependence on the trigger delay. The optimum tr igger delay is found to be between 500 and 600 ms. For these values the abd ominal organs appear homogeneous on all diffusion weighted images and the s trongest signal intensities are defected. At optimum triggering the accurac y of the apparent diffusion coefficients is up to 10 times better than with out triggering. Moreover, the standard deviation of the repeated measuremen ts is smaller than 12% for all volunteers and for all organs. Without trigg ering the standard deviation is larger by a factor of 4 on average. Conclus ion: Pulse triggering of singleshot sequences leads to significant reductio n of motion related artifacts on diffusion weighted images of the abdomen a nd provides more accurate and reproducible ADC values.