Room: Exhibit Hall | Forum 8
Purpose: As a variant of multi-shot echo-planar-imaging, DIADEM (distortion-free imaging: a double encoding method) can achieve distortion-free, high-resolution diffusion imaging [1,2]. The prolonged scan time of this approach was substantially reduced through the use of high-performance gradients on a compact 3T scanner  and a novel parallel imaging technique, termed tilted-CAIPI . This study demonstrates that the SE-DIADEM combined with tilted-CAIPI and high-performance gradients can be a high-speed alternative to fast-spin-echo (FSE) based acquisition.
Methods: For a comparison of T2 imaging using FSE and SE-DIADEM, a phantom and in-vivo scan were performed on a compact 3T scanner after the protocols was adjusted to fully take the advantage of the high-performance gradients (700T/m/s, 80mT/m). A phantom developed for the Alzheimerâ€™s disease neuroimaging initiative (ADNI) study, which includes a resolution insert and various spherical inclusions with different T2s, was used to evaluate the resolution and the reliability of T2 measurements. The measured contrasts of the spherical inclusions inside the phantom were compared with the reference signals S calculated from the known T1, T2, TR, and TE values by: Sâ‰ˆ(1-e^(-TR/T1))âˆ™e^(-TE/T2) (1)
Results: Compared to the standard FSE acquisition, the acquisition time for the DIADEM is faster by a factor of 2.18 and 2.71 for phantom (Fig. 1) and in-vivo (Fig. 2) imaging, respectively. Despite this considerable acceleration, the spatial resolution and contrast was not compromised. In fact, the resolution insert was better depicted using SE-DIADEM than conventional FSE. When compared to the reference T2 signals calculated by Eq. 1, the overall differences were smaller in SE-DIADEM rather than FSE (4.2Â±4.7% vs. 10.7Â±12.6%).
Conclusion: T2-weighted SE-DIADEM combined with the tilted-CAIPI and high performance gradients enables not only faster acquisition, but also more reliable T2 measurements than T2-weighted FSE imaging. This approach can potentially serve as a high-speed alternative to FSE for clinical T2 imaging.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH U01 EB024450-01.