Rapid fat-water separated T<sub>1</sub> mapping using a single-shot radial inversion-recovery spoiled gradient recalled pulse sequence.
Zhitao LiManoj MathewAli B SyedLi FengRyan L BrunsingJohn M PaulyShreyas S VasanawalaPublished in: NMR in biomedicine (2022)
T<sub>1</sub> mapping is increasingly used in clinical practice and research studies. With limited scan time, existing techniques often have limited spatial resolution, contrast resolution and slice coverage. High fat concentrations yield complex errors in Look-Locker T<sub>1</sub> methods. In this study, a dual-echo 2D radial inversion-recovery T<sub>1</sub> (DEradIR-T1) technique was developed for fast fat-water separated T<sub>1</sub> mapping. The DEradIR-T1 technique was tested in phantoms, 5 volunteers and 28 patients using a 3 T clinical MRI scanner. In our study, simulations were performed to analyze the composite (fat + water) and water-only T<sub>1</sub> under different echo times (TE). In standardized phantoms, an inversion-recovery spin echo (IR-SE) sequence with and without fat saturation pulses served as a T<sub>1</sub> reference. Parameter mapping with DEradIR-T1 was also assessed in vivo, and values were compared with modified Look-Locker inversion recovery (MOLLI). Bland-Altman analysis and two-tailed paired t-tests were used to compare the parameter maps from DEradIR-T1 with the references. Simulations of the composite and water-only T<sub>1</sub> under different TE values and levels of fat matched the in vivo studies. T<sub>1</sub> maps from DEradIR-T1 on a NIST phantom (P<sub>comp</sub> = 0.97) and a Calimetrix fat-water phantom (P<sub>water</sub> = 0.56) matched with the references. In vivo T<sub>1</sub> was compared with that of MOLLI: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>R</mml:mi> <mml:mtext>comp</mml:mtext> <mml:mn>2</mml:mn></mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.77</mml:mn></mml:math> ; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>R</mml:mi> <mml:mtext>water</mml:mtext> <mml:mn>2</mml:mn></mml:msubsup> <mml:mo>=</mml:mo> <mml:mn>0.72</mml:mn></mml:math> . In this work, intravoxel fat is found to have a variable, echo-time-dependent effect on measured T<sub>1</sub> values, and this effect may be mitigated using the proposed DRradIR-T1.