Double Diffusion Encoding Based Diffusional Kurtosis Imaging And Fast Multi-slice T_1sat Mapping For Arterial Spin Labeling Methods

Diffusion and perfusion magnetic resonance imaging?MRI?are two of the most recently developed and rapidly evolving areas of biomedical imaging,with applications ranging from diagnosis of hyperacute and chronic disease to the study of the microvascular and haemodynamic changes associated with functional cerebral activation.Diffusion Kurtosis Imaging?DKI?and Arterial Spin Labeling?ASL?as representative diffusion and perfusion imaging techniques have been widely used in pre-clinical and clinical applications.DKI measures the deviation of the displacement probability from a normal distribution,complementing the data commonly acquired by diffusion MRI.It is important to elucidate the sources of kurtosis contrast,particularly in biological tissues where microscopic kurtosis?intrinsic kurtosis?and diffusional heterogeneity may co-exist.We have developed a technique for microscopic kurtosis MRI,dubbed microscopic diffusional kurtosis imaging??DKI?,using a symmetrized double diffusion encoding?s-DDE?echo planer imaging?EPI?sequence.We also developed accelerated ?DKI for in vivo applications and preliminarily evaluated it in a rodent model of epilepsy.Our study showed that ?DKI is less susceptible than conventional DKI to sub-voxel diffusional heterogeneity,also provided important preliminary demonstration of our technique in vivo.Our work revealed that ?DKI provides different and complementary information to conventional DKI method,suggesting that expedient and advanced DKI sequences are promising to elucidate tissue microstructure in neurological diseases.We also proposed a novel T_1sat?longitudinal relaxation time under RF pulse saturation?mapping method to improve the quantification of multi-slice cerebral blood flow?CBF?in ASL magnetic resonance imaging?MRI?.Tisat values measured from the proposed multi-slice method were found to be highly consistent with those obtained from single-slice T_1sat imaging.The induced CBF values were demonstrated to be immune to labeling time influence,whereas the conventional Tiapp-normalized scheme was observed to typically underestimate CBF values,especially under unsteady state.The proposed multi-slice T_1sat imaging facilitates fast and accurate CBF quantification,promising for clinical translation of ASL techniques in diagnosis and evaluation of neurological disease.