Reduction of Through-Plane Flow Artifacts in Contrast-Enhanced Liver MRI Using Motion-Sensitized Driven-Equilibrium (MSDE): Comparison of MSDE types
Seiichiro Noda1, Nobuyuki Toyonari1, Yukari Horino1, Masami Yoneyama2, and Kazuhiro Katahira1

1Kumamoto Chuo Hospital, Kumamoto, Japan, 2Philips Electronics Japan, Tokyo, Japan

Synopsis

Gadoxetic acid enhanced mDIXON liver MRI has excellent utility for diagnosing hepatocellular carcinoma; however, it often suffers from ghosting flow artifacts from aorta due to increased signal by contrast enhancement. To solve this problem, we attempt to use motion-sensitized driven-equilibrium (MSDE) for reducing through-plane flow artifacts particularly in dynamic contrast-enhanced studies. We showed the effect of MSDE in reducing through-plane flow artifacts particularly in dynamic contrast-enhanced studies. Two types MSDE schemes (MSDE and iMSDE) could significantly decrease flow signals and could therefore reduce flow artifacts sufficiently. In current sequence, iMSDE would be better for clinical studies because of its less sensitivity to field inhomogeneities.

Purpose

Gadoxetic acid enhanced liver MRI has excellent utility for diagnosing hepatocellular carcinoma (HCC), distinguishing hypervascular pseudolesions from small HCCs, and facilitating the discrimination between focal nodular hyperplasia and hepatic adenoma1,2.

Recently, a new sequence combined with DIXON-based fast suppression technique, called mDIXON-enhanced T1 High-Resolution Isotropic Volume Examination (mDIXON-eTHRIVE) has been reported that this sequence showed improved homogeneity of fat suppression and higher overall image quality compared with conventional spectral inversion recovery-based eTHRIVE in contrast-enhanced liver MRI3. However, it often suffers from ghosting flow artifacts from aorta due to increased signals by contrast enhancement. Furthermore, flow-induced phase shift may potentially be cause misallocation artifacts4.

To solve this problem, we attempt to use motion-sensitized driven-equilibrium (MSDE)5,6, which has previously been used for blood-suppression technique in the carotid5, intracranial7 and peripheral nerves8, for reducing through-plane flow artifacts particularly in dynamic contrast-enhanced studies. The purpose of this study was to compare two types of MSDE pulses that have been proposed so far and to evaluate whether MSDE can reduce the artifacts in contrast enhanced studies.

Methods

Fig.1 shows the scheme of two types of MSDE pulses. The original MSDE preparation consists of T2 preparation (90°/180°/-90°) pulses with motion- sensitizing gradients sandwiched between the RF pulses5. iMSDE6 has been developed to address the sensitivity of MSDE to eddy currents and the inhomogeneity of MSDE image quality. The iMSDE preparation consists of a 90° excitation pulse, two 180° Malcom-Levitt (MLEV) refocusing pulses, and a 190° flip-back pulse with motion-sensitizing gradients sandwiched between the RF pulses. We compared both in this study.

A total of 12 patients who underwent contrast-enhancement were examined on 3.0T whole-body clinical systems (Ingenia, Philips Healthcare). The study was approved by the local IRB, and written informed consent was obtained from all subjects.

All patients underwent 3 sequences (conventional mDIXON-FFE, mDIXON-TFE with MSDE, and mDIXON-TFE with iMSDE) with randomized acquisition order in between dynamic study and hepatobiliary phase (4~10min after contrast enhancement) to minimize the timing bias in estimating the signal intensity of the vessel signal.

To evaluate the effect of the MSDE or iMSDE in suppression of ghost artifacts quantitatively, we measured the contrast-ratio (CR) between the aorta and the subcutaneous fat. Theoretically the fat should be less affected by MSDE, which is based on T2prep, than muscle because this is based on Dixon sequence). The CR was assessed by using one-way repeated measures ANOVA and post-hoc Tukey test. Subsequently, we visually assessed and compared the presence of ghosting artifacts and overall image quality including SNR and contrast in all acquired images of three sequences.

Results and Discussion

Table 1 shows the results of the comparison of CR. Both mDIXON-TFE MSDE and iMSDE showed significantly higher CR compared to conventional mDIXON-FFE. mDIXON-TFEMSDE indicated slight higher CR compared to mDIXON-TFE iMSDE, but there was no significant difference.

In visual evaluation, both mDIXON-TFE MSDE and iMSDE could reduce the presence of ghost artifacts (Fig.2). The incidence of artifacts in both methods was significant lower than that of conventional mDIXON-FFE, but there was no significance between mDIXON-TFE MSDE and iMSDE. On the other hand, signal-to-noise ratio and image contrast of mDIXON-TFE MSDE images was visually higher than those of iMSDE images because preparation time of MSDE (10ms) significantly shorter than that of iMSDE (40ms). However, severe signal inhomogeneities on the liver could be observed in the images of MSDE in many cases (8/12 cases) compared to iMSDE (5/12 cases) probably due to higher sensitivity to field inhomogeneities of MSDE (Fig.3). Hence, iMSDE would be better for clinical studies in current sequence; however, further technical improvements for MSDE would be needed.

Conclusion

In this study, we showed the effect of MSDE in reducing through-plane flow artifacts particularly in dynamic contrast-enhanced studies. Both MSDE schemes could significantly decrease flow signals and could therefore reduce flow artifacts sufficiently. In current sequence, iMSDE would be better for clinical studies because of its less sensitivity to field inhomogeneities.

Acknowledgements

No acknowledgement found.

References

1. Motosugi U, et al. Rules, roles, and room for discussion in gadoxetic acid-enhanced magnetic resonance liver imaging: current knowledge and future challenges. Magn Reson Med Sci 2013;12:161-175

2. Ringe KI, et al. Gadoxetate disodium–enhanced MRI of the liver: part 1, protocol optimization and lesion appearance in the noncirrhotic liver. AJR Am J Roentgenol 2010;195:13–28

3. Lee MH, et al. Gadoxetic acid-enhanced fat suppressed three-dimensional T1-weighted MRI using a multiecho dixon technique at 3 tesla: emphasis on image quality and hepatocellular carcinoma detection. J Magn Reson Imaging 2013;38:401-10

4. Rahimi MS, et al. Flow-induced signal misallocation artifacts in two-point fat-water chemical shift MRI. Magn Reson Med 2015;73:1926-31

5. Wang J, et al. improved Suppression of Plaque-Mimicking Artifacts in Black-Blood Carotid Atherosclerosis Imaging Using a Multislice Motion-Sensitized Driven-Equilibrium (MSDE) Turbo Spin-Echo (TSE) Sequence. Magn Reson Med 2007;58: 973-981

6. Wang J, et al. Improved Suppression of Plaque-Mimicking Artifacts in Black-Blood Carotid Atherosclerosis Imaging Using a Multislice Motion-Sensitized Driven-Equilibrium (MSDE) Turbo Spin-Echo (TSE) Sequence. Magn Reson Med 2007;58: 973-98

7. Nagao E, et al. 3D Turbo Spin-Echo Sequence with Motion-Sensitized Driven-Equilibrium Preparation for Detection of Brain Metastases on 3T MR Imaging. AJNR Am J Neuroradiol 2011;32:664-670

8. Yoneyama M, et al. Rapid high resolution MR neurography with a diffusion-weighted pre-pulse. Magn Reson Med Sci. 2013;12:111-9

Figures

Fig.1. Scheme of two MSDE pre-pulses.

Table 1. Results of the comparison of contrast-ratio between aorta and fat.

Fig.2. Representative two cases of contrast-enhanced liver images. In mDXION-FFE, ghosting flow artifacts (red arrow) can be seen. On the other hand, both mDIXON-TFE MSDE and iMSDE could reduce the presence of ghost artifacts.

Fig.3. Representative contrast-enhanced liver images. Signal inhomogeneities on the liver could be observed in the image of mDIXON-TFE MSDE compared to iMSDE (red arrows).



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
1859