Axial Kurtosis Research Articles

Diffusion kurtosis imaging in liver: a preliminary reproducibility study in healthy volunteers.

To systematically test the reproducibility of DKI technique in normal liver and report a complete set of DKI measurement data. Thirty-two healthy volunteers were examined with liver DKI twice on the GE 3.0T MRI scanner and reviewed by three professional experts. DKI-derived parameters fractional anisotropy of kurtosis (FAk), mean diffusivity (Md), axial diffusivity (Da), radial diffusivity (Dr), mean kurtosis (Mk), axial kurtosis (Ka), and radial kurtosis (Kr) in eight segments divided by Couinaud octagonal method were collected. Inter-class correlation coefficient (ICC) was used toassess the agreement between three experts. For each expert, the reproducibility of twice scans was evaluated by Bland-Altman method. Multivariate analysis of variance was to explore the regional distribution characteristics of DKI-derived parameters, and showed with box-plot graph. Using ICC analysis, except for FAk (ICC 0.312, 0.307), other DKI metric values showed high reproducibility (0.716 < ICC < 0.907) between three experts for each of two DKI measurements. With Bland-Altman method, liver segment 5 (S5) showed the best reproducibility between two DKI measurement, and the reproducibility of segment 4 (S4) was the worst. The reproducibility of the right lobe was significantly higher than the left lobe. The values of diffusion metrics (Md, Da, and Dr) and kurtosis metrics (Mk, Ka, and Kr) existed significantly difference between the right and left hepatic lobes. DKI has shown excellent reproducibility in liver imaging. The range of values for multiple DKI parameters, derived from the normal liver, was reported, and may provide data reference for further clinical DKI applications. Additionally, DKI technique is a non-invasive method to reflect the perfusion or structural differences between the left and right hepatic lobes from the molecular level.

Diffusion kurtosis imaging combined with molecular markers as a comprehensive approach to predict overall survival in patients with gliomas

PurposeThe purpose of this study was to explore the usefulness of diffusion kurtosis imaging (DKI) and molecular markers in predicting the prognosis of glioma patients. MethodFifty-one patients with gliomas were examined by conventional MRI and DKI at 3.0 T before operation. The mean kurtosis (MK), mean diffusivity (MD), axial kurtosis (AK), and radial kurtosis (RK) values of tumors were measured and normalized to the contralateral normal-appearing white matter. The molecular markers of gliomas, including isocitrate dehydrogenase-1 (IDH1), α thalassemia/mental retardation syndrome x-linked (ATRX) and O6-methylguanine-DNA methyltransferase (MGMT), were immunohistochemically stained on the resected tumor tissues. Statistical methods, including the chi-square test, independent sample t-test, receiver operating characteristic curve analysis, Kaplan-Meier curve analysis, and Cox regression analysis were performed. ResultsThe patients with lower MK, AK, RK, and higher MD values showed significantly better prognosis (P < 0.001). Survival time was better in glioma patients with IDH1 mutation (P < 0.01), ATRX loss of expression (P < 0.05), and MGMT negative expression (P < 0.05). However, among the groups of gliomas with IDH1 wild type, ATRX retention and those with MGMT positive expression, the patients with lower MK showed better outcome (P < 0.01). Cox multivariate regression analysis demonstrated that MK, RK values and ATRX retention could be used as independent prognostic risk factors, and high MK values had the highest risk for prognosis (HR = 65.288). ConclusionsMolecular markers and DKI parameters, especially MK values, can be used to effectively evaluate the prognosis of glioma patients.

Diffusion Kurtosis Imaging of Microstructural Changes in Gray Matter Nucleus in Parkinson Disease.

Objective: To explore the microstructural damage of extrapyramidal system gray matter nuclei in Parkinson disease (PD) using diffusion kurtosis imaging (DKI).Materials and Methods: We enrolled 35 clinically confirmed PD patients and 23 healthy volunteers. All patients underwent MR examination with conventional MRI scan sequences and an additional DKI sequence. We subsequently reconstructed the DKI raw images and analyzed the data. A radiologist in our hospital collected the Mini-Mental State Examination (MMSE) score of all subjects.Results: In the PD group, the mean kurtosis and axial kurtosis level decreased in the red nucleus (RN) and thalamus; the radial kurtosis increased in the substantia nigra (SN) and globus pallidus (GP). Fractional anisotropy decreased in the putamen. The largest area under the ROC curve of mean diffusion in GP was 0.811. Most kurtosis parameters demonstrated a positive correlation with the MMSE score, while several diffusion parameters showed a negative correlation with the same.Conclusion: DKI can qualitatively distinguish PD from healthy controls; furthermore, DKI-derived parameters can quantitatively evaluate the modifications of microstructures in extrapyramidal system gray matter nucleus in PD.

Evaluating the Therapeutic Effect of Low-Intensity Transcranial Ultrasound on Traumatic Brain Injury With Diffusion Kurtosis Imaging.

Low-intensity transcranial ultrasound (LITUS) has a therapeutic effect on traumatic brain injury (TBI). Diffusion kurtosis imaging (DKI) might be able to evaluate the effect changes of injured brain microstructure. To evaluate the therapeutic effect of LITUS in a moderate TBI rat model with DKI parameters. Prospective case-control animal study. Forty-five rats were randomly divided into sham control, TBI, and LITUS treatment groups (n = 15). Single-shot spin echo echo-planar imaging and fast T2 WI sequences at 3.0T. DKI parameters were obtained on days 1, 7, 14, 21, 28, 35, and 42 after TBI. For the mean kurtosis (MK), axial kurtosis (Ka), and radial kurtosis (Kr) values, groups were compared using a two-way analysis of variance (ANOVA). LITUS inhibited TBI and caused MK values to increase significantly during the early stage (LITUS vs. TBI, day 7, adjusted P < 0.0001) and decrease during the late stage (LITUS vs. TBI, day 42, adjusted P = 0.0156) in the damaged cortex. In the thalamus, the MK value of the TBI group began to rise on day 7, with no change observed in the LITUS group. TBI increases Ka value during the early stage in the cortex and decreases during the late stage in the cortex and thalamus. LITUS inhibited these Ka changes (LITUS vs. TBI, day 7, adjusted P = 0.0014; LITUS vs. TBI, day 42, adjusted P = 0.0026 and 0.0478, respectively, for cortex and thalamus). The Kr value increased slightly during the early stage in the cortex (TBI vs. Sham, day 1, adjusted P = 0.0016). The DKI parameter, particularly the MK value, evaluates primary cortical injury as well as the secondary brain injury that could not be detected by conventional T2 WI. 1 Technical Efficacy Stage: 4 J. Magn. Reson. Imaging 2020;52:520-531.

Changes in the Corticospinal Tract Beyond the Ischemic Lesion Following Acute Hemispheric Stroke: A Diffusion Kurtosis Imaging Study.

The degeneration of the corticospinal tract (CST) in chronic stroke has been widely described using diffusion tensor imaging and correlates with the extent of motor deficits. However, only a few studies have reported the early degeneration in the distal CST during the acute stage of stroke and pathological changes in the distal CST have not been described. To study the microstructural changes along the CST beyond the ischemic lesion in acute stroke using diffusion kurtosis imaging (DKI). Prospective. In all, 48 patients (26 males, 22 females; mean age 58.27 ± 12.89 years) with acute ischemic stroke. A DKI sequence with three b-values (0, 1000, and 2000 s/mm2 ) at 3.0T MRI. The kurtosis and tensor parameters were derived from DKI and were compared along the length of the CST beyond the ischemic lesion between the affected and unaffected hemispheres using both voxelwise and slicewise analysis. The degree of neurological deficits was evaluated using the National Institute of Health Stroke Score (NIHSS) and the Barthel index and the clinical outcome at 3 months was evaluated using a modified Rankin scale. Paired t-tests, a linear mixed model, and multivariate linear regression. Voxelwise analysis demonstrated increased mean kurtosis, increased axial kurtosis, and decreased axial diffusivity in the affected CST, which were seen only at the level of the cerebral peduncle (all corrected P < 0.05). Slicewise analysis also demonstrated increased axial kurtosis in the cerebral peduncle of the affected CST (corrected P < 0.05). The axial kurtosis from slicewise analysis independently correlated with the motor component of NIHSS (β = 0.297, P = 0.040). Our findings suggest that early anterograde degeneration occurs along the axon direction in the distal CST in acute stroke, and can be detected using DKI. Moreover, acute axonal degeneration along the CST correlated with motor deficits. 2 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:512-519.

MR Diffusional Kurtosis Imaging-Based Assessment of Brain Microstructural Changes in Patients with Moyamoya Disease before and after Revascularization.

Conventional imaging examinations are insufficient to accurately assess brain damage in patients with Moyamoya disease. Our aim was to observe brain microstructural changes in patients with Moyamoya disease by diffusional kurtosis imaging and provide support data for application of this technique in individualized assessment of disease severity and surgical outcome among patients with Moyamoya disease. A total of 64 patients with Moyamoya disease and 15 healthy volunteers underwent diffusional kurtosis imaging, and a second scanning was offered to surgical patients 3-4 months after revascularization. The diffusional kurtosis imaging parameter maps were obtained for mean kurtosis, axial kurtosis, radial kurtosis, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. The parameter values were measured in sensory pathway-related regions for all subjects. Differences in diffusional kurtosis imaging parameters of these brain regions were examined for healthy volunteers, patients without acroparesthesia, and asymptomatic and symptomatic sides of patients with acroparesthesia. Changes in diffusional kurtosis imaging parameters of patients with Moyamoya disease before and after revascularization were compared. Compared with healthy volunteers, patients with Moyamoya disease showed decreased mean kurtosis, axial kurtosis, radial kurtosis, and fractional anisotropy in the corona radiata. Similarly, mean kurtosis, radial kurtosis, and fractional anisotropy decreased in the posterior limb of the internal capsule, whereas axial kurtosis decreased and radial kurtosis increased in the thalami of patients with Moyamoya disease compared with healthy volunteers. Compared with the asymptomatic contralateral hemisphere, the symptomatic group showed increased mean kurtosis in the contralateral primary somatosensory cortex, increased fractional anisotropy in the contralateral corona radiata and posterior limb of the internal capsule, and decreased axial kurtosis in the contralateral thalamus. Among patients with Moyamoya disease with acroparesthesia, mean kurtosis decreased in the primary somatosensory cortex on the operated side following revascularization. The diffusional kurtosis imaging technique is applicable to patients with Moyamoya disease for detecting brain microstructural changes in white and gray matter before and after revascularization; this feature is useful in the assessment of disease severity and surgical outcome.

The correlation of diffusional kurtosis imaging parameters with cognitive function and cytokine secretion in patients with Alzheimer's disease

Objective To detect the diffusional kurtosis imaging (DKI) parameters of patients with Alzheimer's disease (AD), and evaluate the inner link of DKI parameters with cognitive function and serum nerve injury index. Methods 78 patients who were first diagnosed with AD in our hospital between December 2015 and January 2018 were enrolled in AD group, and 50 healthy volunteers who had physical examination in our hospital during the same period were enrolled in normal control group. The corpus callosum DKI parameters [mean kurtosis (MK), axial kurtosis (AK) and radial kurtosis (RK)] values, Mini-Mental State Examination (MMSE) score as well as serum nerve damage indexes [β amyloid 1-42 (Aβ1-422), S100B protein (S100B) and brain-derived neurotrophic factor (BDNF)] were compared between the two groups of subjects. Pearson test was used to evaluate the correlation of DKI parameters with MMSE score as well as serum nerve injury index in patients with AD. Results MK, AK and RK levels in AD group were lower than those in normal control group; MMSE score was lower than that of normal control group; serum Aβ1-42 and S100B contents were higher than those of normal control group while BDNF content was lower than that of normal control group (P<0.05). Correlation analysis revealed that the MK, AK and RK values in AD patients were directly correlated with the MMSE score as well as Aβ1-42, S100B and BDNF levels (P<0.05). Conclusions The corpus callosum DKI parameter levels decrease in AD patients, and the specific levels are closely related to the severity of cognitive function and nerve injury, which may be one of the effective methods for early assessment of AD condition. Key words: Alzheimer disease; Corpus callosum; Diffusion magnetic resonance imaging; Cognition; Cytokines

Correlations Between the Microstructural Changes of the Medial Temporal Cortex and Mild Cognitive Impairment in Patients With Cerebral Small Vascular Disease (cSVD): A Diffusion Kurtosis Imaging Study.

Object: The purpose of our study was to investigate the microstructural changes of the medial temporal cortex in mild cognitive impairment (MCI) patients with cerebral small vascular disease (cSVD) using diffusion kurtosis imaging (DKI) and to examine whether DKI parameters are correlated with MCI.Method: A total of 82 cSVD patients admitted to the Department of Neurology Beijing Chaoyang Hospital, Capital Medical University, were retrospectively enrolled in this study. The Montreal cognitive assessment scale (MoCA) score was used to assess overall cognitive function. According to the presence or absence of MCI, these patients were divided into an MCI group (n = 48) and a non-MCI group (n = 34). The general clinical data of the two groups were collected and analyzed. The regions of interest (ROIs) in the medial temporal cortex were selected for investigation. The averaged values of DKI parameters were measured in each ROI and compared between the two groups, and the correlations between DKI parameters and MoCA score and between diffusion and kurtosis parameters were examined.Results: Compared to the non-MCI group, MCI patients showed significantly increased mean diffusion (MD) and radial diffusion (RD) and significantly decreased mean kurtosis (MK) in the left hippocampus (P = 0.005, 0.006, 0.002, respectively). In the left hippocampus, fractional anisotropy (FA), MK, radial kurtosis (RK), and kurtosis fractional anisotropy (KFA) showed significantly positive correlations with MoCA score (r = 0.374, 0.37, 0.392, 0.242, respectively, all P < 0.05), while MK and RD were negatively correlated with MoCA score (r = −0.227, −0.255, respectively, both P < 0.05). In the left parahippocampal region, axial kurtosis (AK) and KFA were positively correlated with MoCA score (r = 0.228, 0.282, respectively, both P < 0.05), while RK was positively correlated with MoCA score in the right parahippocampal region (r = 0.231, P < 0.05). Significant correlations of MD with MK, RD with RK, and FA with KFA were observed in the medial temporal cortex (r = −0.254, −0.395, 0.807, respectively, all P < 0.05) but not of axial diffusion (AD) with AK.Conclusion: The DKI technique can be used to observe microstructural changes of the medial temporal cortex in MCI patients with cSVD. The DKI-derived parameters might be a feasible means of evaluating patients with MCI.

Early Stage Markers of Late Delayed Neurocognitive Decline Using Diffusion Kurtosis Imaging of Temporal Lobe in Nasopharyngeal Carcinoma Patients.

Purpose: To determine whether the early assessment of temporal lobe microstructural changes using diffusion kurtosis imaging (DKI) can predict late delayed neurocognitive decline after radiotherapy in nasopharyngeal carcinoma (NPC) patients.Methods and Materials: Fifty-four NPC patients undergoing intensity-modulated radiotherapy (IMRT) participated in a prospective DKI magnetic resonance (MR) imaging study. MR imaging was acquired prior to IMRT (-0), 1 month (-1), and 3 (-3) months after IMRT. Kurtosis (Kmean, Kax, Krad) and Diffusivity (Dmean, Dax, Drad) variables in the temporal lobe gray and white matter were computed. Neurocognitive function tests (MoCA) were administered pre-radiotherapy and at 2 years post-IMRT follow-up. All the patients were divided into neurocognitive function decline (NFD group) and neurocognitive function non-decline groups (NFND group) according to whether the MoCA score declined ≥3 2 years after IMRT. All the DKI metrics were compared between the two groups, and the best imaging marker was chosen for predicting a late delayed neurocognitive decline.Results: Kurtosis (Kmean-1, Kmean-3, Kax-1, Kax-3, Krad-1, and Krad-3) and Diffusivity (Dmean-1 and Dmean-3) of white matter were significantly different between the two groups (p<0.05). Axial Kurtosis (Kax-1, Kax-3) of gray matter was significantly different between the two groups (p<0.05). By receiver operating characteristic (ROC) curves, Kmean-1 of white matter performed best in predicting of MoCA scores delayed decline (p<0.05). The radiation dose was also significantly different between NFD and NFND group (p=0.031).Conclusions: Temporal lobe white matter is more vulnerable to microstructural changes and injury following IMRT in NPC. Metrics derived from DKI should be considered as imaging markers for predicting a late delayed neurocognitive decline. Both temporal lobe white and gray matter show microstructural changes detectable by DKI. The Kmean early after radiotherapy has the best prediction performance.

Diffusion kurtosis imaging differs between primary central nervous system lymphoma and high-grade glioma and is correlated with the diverse nuclear-to-cytoplasmic ratio: a histopathologic, biopsy-based study.

To determine whether water kurtosis and diffusional metrics derived from diffusional kurtosis imaging (DKI) within primary central nervous system lymphomas (PCNSLs) and high-grade gliomas (HGGs) correlate with cellularity and/or nuclear-to-cytoplasmic (N/C) ratio. Forty-four and 43 pathologically confirmed high-grade glioma and primary central nervous system lymphoma specimens between May 2013 and November 2016 were retrospectively reviewed. Diffusional metrics, kurtosis metrics, cellularity, and N/C ratios in PCNSLs and HGGs were compared using the Mann-Whitney U test (significant level, p < 0.007 [0.05/7]); Bonferroni correction). Mean kurtosis (MK), axial kurtosis (K//), and radial kurtosis (K⊥) in PCNSLs were 0.857 (0.693-0.924), 0.837 (0.660-0.941), and 0.834 (0.685-0.937), respectively; and 0.629 (0.524-0.716), 0.575 (0.511-0.689), and 0.675 (0.532-0.766), respectively, in HGGs (all p < 0.001). No significant differences in fractional anisotropy (FA), mean diffusion (MD), axial diffusion (λ//), and radial diffusion (λ⊥) were found between HGGs and PCNSLs. Cellularity was higher in PCNSLs than in HGGs (p = 0.125); whereas, the N/C ratio in PCNSLs was significantly higher than that in HGGs (p < 0.001). All DKI metrics (FA, MD, λ//, λ⊥, MK, K//, and K⊥) were significantly correlated with N/C ratio in PCNSLs with correlation coefficients being rho = 0.418, - 0.722, - 0.525, - 0.768, 0.704, 0.579, and 0.686, respectively. Cellularity in PCNSLs and HGGs did not correlate with any kurtosis or diffusional metrics. Difference of kurtosis parameters between PCNSLs and HGGs is correlated with their diverse N/C ratio. • DKI has considerable value in differentiating between PCNSLs and HGGs. • DKI can provide important information on nuclear-to-cytoplasmic ratio. • Difference of kurtosis parameters between PCNSLs and HGGs correlated well with their diverse N/C ratios.

Abstract 286: Cerebral Microstructure Disruptions are Associated With Poor Neurologic Outcomes in Comatose Cardiac Arrest Patients

Background: For cardiac arrest survivors who are initially comatose after restoration of spontaneous circulation, the extent of brain injury and expected recovery are crucial for management decisions. Advanced diffusion imaging approaches may provide additional insight into microstructural integrity and potential for arousal recovery (AR). Methods: Multi-shell diffusion imaging was acquired in a prospective study. Neurite orientation dispersion (OD), intracellular volume fraction (ICVF), free water fraction (ISO), mean kurtosis (MK), axial kurtosis (AK), radial kurtosis (RK), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and fractional anisotropy (FA) were calculated (see Figure). Median whole-brain values in patients with AR by discharge were compared with those with no AR and to controls (ANOVA, post-hoc 2-tailed Wilcoxon test). Multivariable backward stepwise logistic regression was performed to predict AR. Results: 19 patients (mean ±SD 48±23 y, 42% men) and 5 controls (37±19 y, 40% men) were analyzed (10 patients with AR, 9 without). Median [IQR] time-to-MRI was 5 [4-8] days. Patients with no AR had higher AK (P=0.037), and RK (P=.045) than those with AR. Controls exhibited higher FA than either AR (P=.009) or no AR (P=.02), lower MK than no AR (P=.02), lower AK than no AR (P=.02), lower RK than no AR (P=0.02), lower OD than no AR (P=.008), and lower ICVF than no AR (P=.046). AK (P=.049) and ICVF (P=.01) were found in multivariable regression to be significant predictors of AR with 81% area under the receiver operating curve (AUC). Discussion: Advanced diffusion imaging metrics, AK and ICVF, were able to predict which patients were likely to regain consciousness, with 81% AUC. Despite the small sample size, we note statistically significant differences using more sensitive measures of microstructural injury compared to more commonly used diffusivity metrics. Further investigation of advanced diffusion imaging methods is warranted.

Diffusion kurtosis imaging characteristics of brain gray matter nucleus microstructure in Parkinson's disease with different movement disorder subtypes

Objective To investigate the difference in the microstructure of gray matter nucleus in different movement subtypes of Parkinson’s disease (PD) by diffusion kurtosis imaging (DKI) technique, and to analyze the correlation with clinical manifestations. Methods Ninety-seven patients with PD and 83 healthy controls performed conventional MRI sequence and DKI sequence scan. The PD patients were classified into gait disorder subtype (PIGD, n=57) and tremor dominant subtype (TD, n=40)subtypes according to motor symptoms. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), radial diffusivity(Dr), mean kurtosis (MK), axial kurtosis (Ka) and radial kurtosis (Dr) maps and data were generated by software after processing. DKI was performed for all subjects and data was collected from different brain regions in both hemispheres, including red nucleus(RN), substantia nigra pars reticulate(SNr), substantia nigra pars compacta(SNc), putamen(PUT), globus pallidus(GP), head of caudate nucleus (CN)and thalamus(THA). Results TD showed a higher MMSE score(P=0.019), but lower modified Hoehn-Yahr score than that in PIGD (P 0.05). Moreover, there was no significant correlation between DKI value and disease duration, MMSE score or Hoehn-Yahr scale (P>0.05) in TD and PIGD. Conclusion There is heterogeneity of clinical symptoms between these two subgroups of PD. DKI can quantify the microstructural changes of grey matter nucleus in different type PD patient. Key words: Parkinson's disease; Movement disorder subtypes; Diffusion kurtosis imaging; Heterogeneity

Evaluation of cerebral microstructural changes in adult patients with obstructive sleep apnea by MR diffusion kurtosis imaging using a whole-brain atlas

Purpose:The association between obstructive sleep apnea (OSA) and cognitive impairment is well-recognized, but little is known about neural derangements that underlie this phenomenon. The purpose of this study was to evaluate the utility of diffusion kurtosis imaging (DKI) using a whole-brain atlas to comprehensively assess microstructural tissue changes in the brain of patients with OSA.Methods:This prospective study was conducted in 20 patients with moderate-to-severe OSA and 20 age- and gender-matched controls. MRI data acquisition was performed with 3 Tesla and data was analyzed using a whole-brain atlas. DKI data were processed and transformed into a brain template space to obtain various kurtosis parameters including axial kurtosis (AK), radial kurtosis (RK), mean kurtosis (MK), and kurtosis fractional anisotropy (KFA) using a 189-region brain atlas in the same template space. These kurtosis measurements were further analyzed using a student t-test in order to determine kurtosis measurements that present significant differences between the OSA patient set and the control set.Results:Significant differences (P < 0.05) were found in AK (54 regions), RK (10 regions), MK (6 regions) and KFA (41 regions) values in patients with OSA as compared to controls. DKI indices, using an atlas-based whole-brain analysis approach used in our study, showed widespread involvement of the anatomical regions in patients with OSA.Conclusion:The kurtosis parameters are more sensitive in demonstrating abnormalities in brain tissue structural organization at the microstructural level before any detectable changes appear in conventional MRI or other imaging modalities.

Role of Diffusional Kurtosis Imaging in Evaluating the Efficacy of Transcatheter Arterial Chemoembolization in Patients with Liver Cancer

Objective: To explore the role of diffusional kurtosis imaging (DKI) in evaluating the efficacy of transcatheter arterial chemoembolization (TACE) in patients with liver cancer. Materials and Methods: A total of 54 patients with primary liver cancer underwent TACE were selected as the study subjects. Magnetic resonance imaging and DKI scans were carried out before and after TACE, and the relevant parameters were analyzed. Results: Compared with those before TACE, the values of radial diffusivity (Dr), axial diffusivity (Da), and mean diffusivity (MD) of tumor tissues in the patients after TACE were significantly increased, whereas the values of axial kurtosis (Ka), fractional anisotropy of kurtosis (FAk), hepatic blood volume (HBV), hepatic blood flow (HBF), and hepatic artery perfusion (HAP) were notably decreased (p < 0.05). There were no significant changes regarding FA, radial kurtosis (Kr), mean kurtosis (MK), hepatic arterial fracture (HAF), permeability-surface area product (PS), mean transit time (MTT), and portal vein perfusion (PVP) (p > 0.05). The differences in apparent diffusion coefficients (ADCs) of different liver cancer tissues in patients under different b values after operation were statistically significant, and the ADC values of liver cancer tissues were evidently higher than those of other tumor tissues (p < 0.05). Conclusion: DKI is characterized with advantages such as fastness, simpleness, high resolution, and impregnability of the density of lipiodol. It can not only directly reflect the changes in blood perfusion at the lesion but also accurately and efficiently evaluate the remnants, necrosis, and recurrence of tumor tissues based on changes in ADC under different b values. It provides certain clinical assistance for the evaluation of the efficacy before and after TACE.

Detecting normal pediatric brain development with diffusional kurtosis imaging

PurposeTo characterise the pattern of change of diffusional kurtosis imaging (DKI) parameters (including kurtosis and diffusion parameters) in both white matter and gray matter in normal brain development with a large sample of subjects from term-born neonates to 14-years old children. MethodsTwo hundred and eighteen normal children (136 male, 82 female) underwent conventional magnetic resonance imaging and DKI. Regions of interest (ROIs) were placed in 7 white matter areas and 4 gray matter areas. Then the DKI-derived parameters were automatically calculated, including fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (Da), radial diffusivity (Dr), mean kurtosis (MK), axial kurtosis (Ka) and radial kurtosis (Kr). The correlation between the DKI parameters and ages were analyzed using nonlinear fit, and the rate of parameter change was computed compared to the baseline value of the neonates. ResultsFor all ROIs in the white matter and gray matter, the FA, MK, Kr, Ka values increased with age, while the MD and Dr values decreased with age. The correlations were good to excellent, which changed rapidly within the first 2 years and relatively slowly after 2 years. The Da values in peripheral white matters and some gray matter structures (caudate nucleus and putamen) decreased with age. The amplitude of kurtosis parameters variation was greater than that of the diffusion parameters in both white matter and gray matter. ConclusionsThe DKI parameters correlated well with age, and kurtosis parameters showed a potential advantage in detecting the normal brain development of children.

Characterization of brain microstructural abnormalities in cirrhotic patients without overt hepatic encephalopathy using diffusion kurtosis imaging

Cirrhosis is a major public health concern. However, little is known about the neurobiological mechanisms underlying brain microstructure alterations in cirrhotic patients. The purpose of this prospective study was to investigate brain microstructural alterations in cirrhosis with or without minimal hepatic encephalopathy (MHE) and their relationship with patients’ neurocognitive performance and disease duration using voxel-based analysis of diffusion kurtosis imaging (DKI). DKI data were acquired from 30 cirrhotic patients with MHE, 31 patients without MHE (NMHE) and 59 healthy controls. All DKI-derived parametric maps were compared across the three groups to investigate their group differences. Correlation analyses were further performed to assess relationships between altered imaging parameters and clinical data. Voxel-based analysis of DKI data results showed that MHE/NMHE patients had increased radial diffusivity, axial diffusivity (AD) and mean diffusivity in addition to decreased axial kurtosis (AK) and fractional anisotropy of kurtosis in several regions. Compared to controls, these regions were primarily the cingulum, temporal and frontal cortices. The DKI metrics (i.e., AK and AD) were correlated with clinical variables in the two patient groups. In conclusion, DKI is useful for detecting brain microstructural abnormalities in MHE and NMHE patients. Abnormal DKI parameters suggest alterations in brain microstructural complexity in cirrhotic patients, which may contribute to the neurobiological basis of neurocognitive impairment. These results may provide additional information on the pathophysiology of cirrhosis.

Assessment of renal fibrosis in a rat model of unilateral ureteral obstruction with diffusion kurtosis imaging: Comparison with α-SMA expression and 18F-FDG PET

PurposeTo investigate the utility of diffusion kurtosis imaging (DKI) MRI for evaluation of renal fibrosis in rats with unilateral ureteral obstruction (UUO). MethodsTwenty-five rats had UUO, and ten rats were subjected to sham operation as control. DKI was performed on a 3.0 T MRI scanner on days 1, 3, 5, and 7 after ligation. All rats then underwent 18F-FDG dynamic PET to evaluate unilateral renal function, followed by histological analysis to examine α-smooth muscle actin (α-SMA) expression. DKI metrics were assessed among the time points and between two sides, and compared with maximum standardized uptake value (SUVmax), serum levels of creatinine and urea, and fibrosis marker α-SMA. ResultsMean kurtosis (MK) on day 7, axial kurtosis (Ka) on days 3 and 7, mean diffusivity (MD) on days 1, 3, 5, and 7, and fractional anisotropy (FA) on days 3, 5, and 7 of cortex and medulla between the UUO and contralateral sides were significantly different (all p < 0.05). Over the course of UUO progression, there were significant changes in Ka, MD and FA of medulla (all p < 0.05). FA of medulla was positively correlated with SUVmax (r = 0.641, p < 0.001), and MD of cortex was negatively correlated with urea (r = −0.534, p = 0.001). MD of cortex was negatively correlated with α-SMA on UUO sides (r = −0.710, p < 0.001). ConclusionsDKI shows the potential for noninvasive assessment of renal fibrosis and unilateral renal function induced by UUO.

Diffusion kurtosis imaging as an imaging biomarker for predicting prognosis of the patients with high-grade gliomas

PurposeTo retrospectively explore the utilization of MR diffusion kurtosis imaging (DKI) in predicting prognosis of the patients with high-grade gliomas. Materials and methodsThirty-three consecutive patients with cerebral gliomas underwent pretreatment DKI and diffusion-weighted imaging examination on a 3.0-T MR scanner. Diffusion parameters, including conventional tensor parameters, kurtosis metrics (mean kurtosis [MK], radial kurtosis [AK], and axial kurtosis [RK]), and minimum apparent diffusion coefficient (minADC), were obtained and normalized to the contralateral normal-appearing white matter. Correlations among each diffusion parameter and overall survival were analyzed by a Spearman method. The diagnostic efficiency of each parameter in predicting survival for patients with high-grade gliomas was assessed by a receiver operating characteristic curve. The favorable prognostic imaging biomarkers were further analyzed by using a Kaplan-Meier method with log-rank test. ResultsIn 33 patients, 17 patients reached overall survival >15 months (long survival group), whereas 16 showed overall survival <15 months (short survival group). Negative correlations between kurtosis metrics (MK, AK, and RK) and overall survival were obtained by using Spearman analysis (r = −0.63, −0.57, and −0.61, respectively, all P < 0.01), whereas minADC was positively correlated with overall survival (r = 0.56, P < 0.01). The kurtosis parameters of the long survival group were significantly lower than that of the short survival group (P < 0.001), while the minADC of the long survival group was significantly higher than that of the short survival group (P = 0.002). Among these diffusion parameters, the optimal cut-off value of MK (0.688) provided the best combination of sensitivity (93.75%) and specificity (76.47%) for differentiation of patients with long survival from those with short survival. High kurtosis metrics and low minADC were significant predictors of poor outcome. (P < 0.05). ConclusionBoth kurtosis metrics and minADC have the potential to predict survival for the patients with high-grade gliomas. The preoperative kurtosis parameters, especially MK, can be taken as a preoperative prognostic biomarker to predict prognosis in patients with high-grade gliomas.

Altered Relationship between Working Memory and Brain Microstructure after Mild Traumatic Brain Injury.

Working memory impairment is one of the most troubling and persistent symptoms after mild traumatic brain injury (MTBI). Here we investigate how working memory deficits relate to detectable WM microstructural injuries to discover robust biomarkers that allow early identification of patients with MTBI at the highest risk of working memory impairment. Multi-shell diffusion MR imaging was performed on a 3T scanner with 5 b-values. Diffusion metrics of fractional anisotropy, diffusivity and kurtosis (mean, radial, axial), and WM tract integrity were calculated. Auditory-verbal working memory was assessed using the Wechsler Adult Intelligence Scale, 4th ed, subtests: 1) Digit Span including Forward, Backward, and Sequencing; and 2) Letter-Number Sequencing. We studied 19 patients with MTBI within 4 weeks of injury and 20 healthy controls. Tract-Based Spatial Statistics and ROI analyses were performed to reveal possible correlations between diffusion metrics and working memory performance, with age and sex as covariates. ROI analysis found a significant positive correlation between axial kurtosis and Digit Span Backward in MTBI (Pearson r = 0.69, corrected P = .04), mainly present in the right superior longitudinal fasciculus, which was not observed in healthy controls. Patients with MTBI also appeared to lose the normal associations typically seen in fractional anisotropy and axonal water fraction with Letter-Number Sequencing. Tract-Based Spatial Statistics results also support our findings. Differences between patients with MTBI and healthy controls with regard to the relationship between microstructure measures and working memory performance may relate to known axonal perturbations occurring after injury.

The value of diffusion kurtosis imaging in early diagnosis of diabetic nephropathy model in Guangxi Bama mini pig

Objective To investigate the value of diffusion kurtosis imaging (DKI) in diagnosing early diabetic nephropathy. Methods Twelve pigs were divided into the experimental group (7 pigs) and the control group (5 pigs), used the random number table method. The experimental group was fed with high-fat high-sugar diet,and then repeatedly injected small doses (50 mg/kg) of Streptozotocin (STZ) through the ear vein. Meanwhile,the control group was fed with normal diet and injected with the same dose of citric acid-sodium citrate buffer solution.After the type 2 diabetes was established successfully, T1WI, T2WI and DKI sequence imaging were performed every month for 2 pigs from the experimental group and the control group,respectively.Mean kurtosis(MK), axial kurtosis (K∥), radial kurtosis (K⊥), fractional anisotropy (FA) and mean diffusivity(MD) were measured on the pseudo-color map of the post-processing workstation. fasting blood glucose(GLU),insulin (INS),renal function, urine routines and random albumin creatinine ratio(RACR) were measured before MRI scan. Specimens from bilateral kidneys were taken for pathological examination after MRI scan. The paired t test was used to compare the parameter values of the cortex and medulla.Independent sample t test was used tocompare the parameter values of the experimental group and the control group. Results In the experimental group,the MK, FA values of medulla were 0.66±0.07 and 0.19±0.04, the MK, FA values of cortex were 0.60±0.06 and 0.16±0.03.In the control group,the MK, FA values of medulla were 0.59±0.03 and 0.20±0.04, the MK, FA values of cortex were 0.53±0.03 and 0.17±0.04.The MK and FA values of medulla were increased compared with the cortex and the difference were statistically significant (P 0.05). Conclusion DKI sequencehas certain value in the diagnosis of early diabetic nephropathy,and to some extent reveals the pathological change in early diabetic nephropathy. Key words: Diabetic nephropathies; Magnetic resonance imaging; Disease models, animal