Diffusional kurtosis imaging study in idiopathic normal pressure hydrocephalus patients, before and after shunt placement surgery analysis
Chanon Ngamsombat 1, Zhe Zhang2, Hua Gua2, Theerapol Witthiwej3, Weerasak Muangpaisan4, Sith Sathornsumetee5, Suwit Charoensak6, Panida Charnchaowanish1, and Orasa Chawalparit1

1Department of Radiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, Bangkok, Thailand, 2Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, Beijing, China, People's Republic of, 3Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, Bangkok, Thailand, 4Department of Preventive and Social Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, Bangkok, Thailand, 5Departments of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, Bangkok, Thailand, 6Department of Psychiatry, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand, Bangkok, Thailand

Synopsis

Idiopathic normal pressure hydrocephalus(iNPH) is important reversible cause of dementia and gait abnormality in elderly patients. Diffusional kurtosis imaging(DKI) moreover explains the complexity of white matter abnormality with inclusion of non-Gaussian effects. We aim to identify difference of complexity of white matter alteration in iNPH patients before and after shunt placement surgery by using high resolution DKI. We report significant increase of mean diffusional kurtosis(Kmean), mean diffusivity(MD) and decrease of radial diffusional kurtosis(Krad) , fractional ansiotropy(FA) after shunt placement surgery. High resolution DKI can be used for monitoring and detection complexity of white matter alteration in iNPH patients.

PURPOSE

Idiopathic normal pressure hydrocephalus (iNPH) is important reversible cause of dementia and gait abnormality in elderly patients. Diffusional kurtosis imaging (DKI) moreover explains the complexity of white matter abnormality with inclusion of non-Gaussian effects 1. We aim to identify difference of complexity of white matter alteration in iNPH patients before and after shunt placement surgery by using high resolution DKI.

METHODS

Nine patients fulfilled the criteria for definite iNPH underwent MRI study (Philips Ingenia 3.0T) with high resolution DKI using multi-shot spin-echo EPI (echo planar imaging), 4-shot reconstructed with self-feeding MUSE 2, intra-slice resolution = 0.86x0.86 mm2 ; thickness = 4mm, b-Values 0, 1000 and 2000 s/mm2 and 15 diffusion-sensitizing directions, scanned before and after shunt placement surgery (mean interval±SD = 200±54 days after surgery). Processing of the diffusional raw data included brain extraction and correction for eddy current distortions by using FSL (FMRIB Software Library) 3 were done. Post-processing DKI datasets by using diffusional kurtosis estimator (DKE) 4 to generate a set of diffusional kurtosis and diffusional tensor parameters and analysis by using standard template region of interest for corticospinal tracts in transformed standard space were performed (Figure 1). Differences of diffusional tensor and kurtosis parameters before and after shunt placement surgery were compared.

RESULTS

All patients were clinically improved after shunt placement surgery by using iNPH grading scale evaluation including gait symptom. Mean diffusional kurtosis (Kmean) and mean diffusivity (MD) of corticospinal tracts were statistically significant increased after shunt placement surgery, whereas radial diffusional kurtosis (Krad) and fractional ansiotropy (FA) were statistically significant decreased after shunt placement surgery (Table 1).

DISCUSSION

The corticospinal tracts were compressed by dilate ventricle in normal pressure hydrocephalus. When improvement of patient symptom after shunt placement, Kmean and MD were increased, whereas Krad and FA were decreased probably due to partial relieved compression to cortical tracts by dilate ventricle after shunt placement surgery , decreased tightness and density in the compressed corticospinal tracts and decreased of interstitial edema.

CONCLUSION

High resolution DKI can be used for monitoring and detection complexity of white matter alteration in iNPH patients. Further study for comparing diffusional parameters between shunt responsive and shunt non-responsive groups with long term clinical outcome will be helpful.

Acknowledgements

This research project was supported by Faculty of Medicine Siriraj Hospital, Mahidol University, Grant Number R015733016 and Philips for clinical science keys for advanced diffusion weighted imaging and for data export.

References

1. Jensen JH, Helpern JA, Ramani A, Lu H, Kaczynski K (2005) Diffusional kurtosis imaging: the quantification of non-Gaussian water diffusion by means of magnetic resonance imaging. MagnReson Med 53:1432–1440

2. Zhang Z, Huang F, Ma X, Xie S, Guo H. Self-feeding MUSE: A robust method for high resolution diffusion imaging using interleaved EPI. Neuroimage, 2015;105:552–60.

3. M. Jenkinson, C.F. Beckmann, T.E. Behrens, M.W. Woolrich, S.M. Smith. FSL. NeuroImage, 62:782-90, 2012

4. Tabesh A, Jensen JH, Ardekani BA, and Helpern JA. Estimation of tensors and tensor-derived measures in diffusional kurtosis imaging. Mag Reson Med. 2011 Mar; 65(3):823-36.

Figures

Figure 1 : Diffusional kurtosis parameters were measured by standard template region of interest of corticospinal tracts in standard space.

Table 1 : Diffusional kurtosis imaging parameters of the corticospinal tracts (mean +/- SD) of the patients before and after shunt placement surgery (*** indicates statistical significance)



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
3497