Minimizing the echo time in diffusion imaging using spiral readouts and a head gradient system
Bertram J. Wilm, Franciszek Hennel, Manuela Barbara Roesler, Markus Weiger, Klaas P. Pruessmann
Abstract
Purpose Diffusion weighted imaging (DWI) is commonly limited by low signal‐to‐noise ratio (SNR) as well as motion artifacts. To address this limitation, a method that allows to maximize the achievable signal yield and increase the resolution in motion robust single‐shot DWI is presented. Methods DWI was performed on a 3T scanner equipped with a recently developed gradient insert (gradient strength: 200 mT/m, slew rate: 600 T/m/s). To further shorten the echo time, Stejskal‐Tanner diffusion encoding with a single‐shot spiral readout was implemented. To allow non‐Cartesian image reconstruction using such strong and fast gradients, the characterization of eddy current and concomitant field effects was performed based on field‐camera measurements. Results An echo time of only 19 ms was achieved for a b‐factor of 1000 s/mm 2 . An in‐plane resolution of 0.68 mm was encoded by a single‐shot spiral readout of 40.5 ms using 3‐fold undersampling. The resulting images did not suffer from off‐resonance artifacts and blurring that are common to single‐shot images acquired with regular gradient systems. Conclusion Spiral diffusion imaging using a head gradient system, together with an accurate characterization of the encoding process allows for a substantial reduction of the echo time, and improves the achievable resolution in motion‐insensitive single‐shot DWI.