This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction EPI suffers from various artifacts such as geometric distortions, Nyquist ghosting, T2* blurring, Maxwell effects and eddy currents (especially for DW-EPI). The magnitude of these artifacts is inversely scaled by the speed of k-space traversal along the phase encoding direction (a.k.a. pseudo bandwidth), which is determined by two factors: a) the time between two consecutive echoes in the EPI readout train and b) the phase field-of-view (FOV Materials and methods A 1.5T GE Excite system equipped with 50 mT/m gradients was used for the experiments. Our proposed SAP-EPI was compared with LAP-EPI w.r.t. blurring due to Nyquist ghosting and susceptibility. To compare the ghosting levels for the individual blades between LAP-EPI and SAP-EPI, a small cylindrical phantom measuring 10 cm in diameter was used with a FOV of 24 24 cm. The acquired resolutions were 256 32 (LAP-EPI) and 32 256 (SAP-EPI) using 25 blades swept from 0 to 180 . Images were also acquired on a volunteer using conventional ssEPI, LAP-EPI and SAP-EPI, with the same parameters and target resolution of 256 256. References 1. Pipe JG. Motion correction with PROPELLER MRI: application to head motion and free-breathing cardiac imaging. Magn Reson Med 1999;42(5):963-969. 2. Wang FN, Huang TY, Lin FH, Chuang TC, Chen NK, Chung HW, Chen CY, Kwong KK. PROPELLER EPI: An MRI technique suitable for diffusion tensor imaging at high field strength with reduced geometric distortions. Magn Reson Med 2005;54(5):1232-1240. 3. Chuang TC, Huang TY, Lin FH, Wang FN, Chung HW, Chen CY, Kwong K. Propeller EPI with SENSE parallel imaging using a circularly symmetric phase array RF coil. 2004; Kyoto. p 535. 4. Forbes KP, Pipe JG, Bird CR, Heiserman JE. PROPELLER MRI: clinical testing of a novel technique for quantification and compensation of head motion. J Magn Reson Imaging 2001;14(3):215-222. 5. Grieve SM, Blamire AM, Styles P. Elimination of Nyquist ghosting caused by read-out to phase-encode gradient cross-terms in EPI. Magn Reson Med 2002;47(2):337-343. Acknowledgements This work was supported in part by the NIH (1R01EB002771), the Center of Advanced MR Technology at Stanford (P41RR09784), Lucas Foundation, and Oak Foundation.
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