Abstract
A fundamental modification to the conventional chemical shift imaging (CSI) method is described that improves the imaging of species with short T~2~'s (i.e., less than βΌ2 ms). This approach minimizes the delay before each kβspace point is collected. This results in different time delays, T~d~, for different free induction decay (FID) acquisitions in kβspace. On a clinical 1.5T system this yields an effective delay due to transmit/receive switching of 70 ΞΌs and an echo time (TE) from the center of the excitation pulse to the center of kβspace of 170 ΞΌs, as compared with 1β2 ms for conventional CSI techniques. Using this method, the signal decay before acquisition is greatly reduced, thus enabling imaging of species with very short T~2~ (e.g., 200 ΞΌs) and increasing the signalβtoβnoise ratio (SNR) of species with intermediate T~2~. Increases in the SNR of the short T~2~ components of ^23^Na in the heart, and ^31^P acquisitions of bone are about 27% and 400%, respectively, compared to an optimized conventional CSI approach. The imperfections of this approach are also described, and the magnitude of the resultant image artifacts is quantified for different practical imaging situations. These artifacts were not found to be significant in the described applications. This new method allows us to obtain information on short T~2~ components without degrading the image quality from long T~2~ components. Magn Reson Med 53:267β274, 2005. Β© 2005 WileyβLiss, Inc.