Abstract
Purpose: To increase the efficiency of densely encoded magnetization transfer imaging of the brain, we time-multiplex multiple slices within the same readout using simultaneous echo refocusing FLASH imaging with magnetization transfer (MT) preparation (MT-SER-FLASH). Materials and Methods: Inefficiency in total scan time results from the number of frequency samples needed for sufficient quality of quantitative parameter maps for a binary spin bath model. We present a highly efficient multiplexing method, simultaneous echo refocused magnetization transfer imaging (MT-SER-FLASH) for reducing the total scan time of MT imaging by one-third. The specific absorption rate (SAR) was also reduced by reducing the number of MT-pulses per volume. Results: 2D-MT-SER-FLASH is performed in 19 minutes rather than 1 hour, acceptable for routine clinical application. The SAR could be reduced to 69% instead of more than 100% with a standard 2D or 3D-FLASH with MT-preparation. Conclusion: The net reduction of scan time and SAR enables the use of quantitative model based magnetization transfer imaging within a clinical environment.
Highlights
Beside T1 and T2 relaxation time, the magnetization transfer (MT) contrast [1]-[3] is a diagnostic relevant parameter as shown in [4]
Beside approaches such as Cramer-Rao lower bounds (CRLB) to obtain optimal acquisition schemes [5], which are not discussed within this note, the focus is on the acceleration of model based MT (mMT) sequences covering an off-frequency range from 500 to 16000 Hz with a step size Δf less than 900 Hz
The MT-SER-FLASH is performed in 19 minutes rather than 1 hour and provides images of good quality (Figure 4)
Summary
Beside T1 and T2 relaxation time, the magnetization transfer (MT) contrast [1]-[3] is a diagnostic relevant parameter as shown in [4]. MRI, Magnetization Transfer Imaging, Fast Imaging, Pulse Sequences, Simultaneous Echo Refocusing
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