Phase Accrual During Excitation in Ultrashort TE (UTE) Imaging: an Alternate Definition of TE for Phase Measurements

Jing-Tzyh Alan Chiang¹, Michael Carl², Mark Bydder¹, Jiang Du¹, Robert F. Mattrey¹, Graeme Bydder¹

MR imaging of tissues with submillisecond T2s is possible with UTE (ultrashort TE) sequences that utilize half RF excitation pulses and radial projection readouts. For UTE sequences, TE is customarily defined to be from the end of the half RF pulse to the beginning of radial projection readout. We present data here that show phase accrual in UTE imaging to be more than expected for this customary definition of TE. Numerical calculations show this is largely due to phase accrual before the end of the RF pulse, and we suggest an alternate definition of TE for phase calculations in UTE.