Assessment of fractional anisotropy of heart using ECG gating and second moment nulling pulse
Tomoya Nakamura1, Shuhei Shibukawa2, Yuma Sainokami2, Tomohiko Horie1, Isao Muro2, Terumitsu Hasebe1, Yutaka Imai2, and Tetsuo Ogino3

1Tokai University Hachioji Hospital, Hachioji, Japan, 2Tokai University Hospital, Isehara, Japan, 3Philips Healthcare Asia Pacific, Shinagawa, Japan

Synopsis

The purpose of this study is to assess the fractional anisotropy (FA) of heart using ECG gating and second moment nulling pulse which is intrinsically insensitive to motion. The FA at motion correction (MC) gradient was significantly higher than at acceleration motion correction (aMC) gradient, therefore, cardiac motion artifact resluts in an overestimation of FA. In conclusion, the use of second order motion correction gradient enables the quantification of FA at heart and has the potential to contribute to clinical cardiac imaging.

Introduction

Although conventional-diffusion-weighted imaging (C-DWI) of the human heart is sensitive to motion, we reported the simultaneous use of electrocardiogram (ECG) gating and motion correction (MC), including second-order velocity compensation makes it possible to assess the water molecular dynamics [1,2]. The purpose of this study is to assess the fractional anisotropy (FA) of heart using ECG gating and second moment nulling pulse which is intrinsically insensitive to motion.

Methods

MC is achieved by a bipolar gradient pulse that compensates the phase dispersion caused by the velocity term of motion. Further, motion correction until the acceleration term of motion is achieved by second-moment nulling pulse, shape is shown as Figure 1. Cardiac diffusion tensor imaging was done with ECG gating and free breathing on a 1.5T scanner (Achieva nova dual, Philips Healthcare) using a 32-channel coil. Each b-value of 300 and 600s/mm2 was set for the acceleration motion correction DWI (aMC-DWI) and the MC-DWI, and TE value was 78ms (shortest TE of aMC-DWI, b-value of 600s/mm2). Six healthy volunteers (age 23-28) were scanned and written informed consent was obtained from all volunteers. FA was calculated and compared among aMC and MC sequence, and the statistical difference between each secquence was determined by Mann Whitney-U test. Moreover, FA color map was compared between aMC and MC sequence. Further parameters were; TR: 5 heartbeats, FOV: 280mm, RFOV: 80%, voxel size: 8×2.19×2.43 mm3, SENSE fc: 2, half scan fc: 0.6, NSA: 6, fat suppression: SPIR.

Results

Figure 2 shows the FA at aMC and MC in each b-value, the FA at aMC was significantly lower than at MC in each b-value. Figure 3 shows the FA color map at aMC and MC, fiber orientation in each sequence was also varied.

Discussion and Conclusion

The FA at MC was significantly higher than at aMC, therefore, cardiac motion artifact resluts in an overestimation of FA. Moreover, first order motion correction gradient which is sensitive to bulk motion also caused the visualization of fiber architecture to vary as well. In conclusion, the use of second order motion correction gradient enables the quantification of FA at heart and has the potential to contribute to clinical cardiac imaging.

Acknowledgements

No acknowledgement found.

References

[1] Nakamura et.al, 24th Annual Meeting of ISMRM, Toronto, 2015 (Abstract2015), [2] Nakamura et.al, Nichidoku-Iho 2015 (in press).

Figures

Sequence design of first and second order motion correction diffusion gradient.

FA at aMC and MC in each b-value, and the correlation is significant at the 0.01 level.

FA color map at aMC and MC in b-value of 600 s/mm2, and the fiber orientation is differ in each sequence.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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