Parameters of diffusional kurtosis imaging for the diagnosis of acute cerebral infarction in different brain regions

Application of Diffusional Kurtosis Imaging on Normal-Appearing White Matter in Cerebral Small Vessel Disease

BACKGROUND

This study aimed to investigate the diagnostic potential of diffusional kurtosis imaging (DKI) parameters in detecting pathological alterations in the normal-appearing white matter (NAWM) associated with cerebral small vessel disease (CSVD).

METHODS

A total of 56 patients diagnosed with CSVD were enrolled, all exhibiting confirmed lacunar infarction in the corticospinal tract (CST) as verified by conventional magnetic resonance imaging. A control group of 24 healthy individuals who exhibited no discernible abnormalities on conventional magnetic resonance imaging (MRI) scans was also included. The following DKI parameters were recorded, including mean kurtosis (MK), axial kurtosis (Ka), and radial kurtosis (Kr). Regions of interest were placed at representative levels of the CST on the affected side, encompassing the pons, anterior part of the posterior limb of the internal capsule (PLIC), corona radiata, and subcortex.

RESULTS

Variations in MK, Ka, and Kr values in the pons, anterior part of the PLIC, corona radiata, and subcortex of the control group were observed. Notably, the MK and Kr values of the normal-appearing pons in CSVD patients were significantly elevated compared with the control group. The MK, Ka value of the normal-appearing anterior part of the PLIC was significantly higher in the CSVD group than in the control group. The Kr value of the normal-appearing corona radiata exhibited a significant elevation in CSVD patients compared with the control group. Lastly, patients with CSVD displayed lower Ka values and higher Kr values in the normal-appearing subcortex compared with the control group.

CONCLUSIONS

DKI is an effective tool for assessing NAWM in patients with CSVD. These findings potentially offer novel insights into the prognosis of CSVD and serve as a foundational platform for future DKI studies on NAWM in other diffuse brain lesions.

Diffusion tensor imaging in cerebral small vessel disease applications: opportunities and challenges

Cerebral small vessel disease (CSVD) is a syndrome of pathology, imaging, and clinical manifestations caused primarily by a variety of functional or structural lesions in the small blood vessels of the brain. CSVD contributes to approximately 45% of dementia and 25% of ischemic strokes worldwide and is one of the most important causes of disability. The disease progresses insidiously, and patients often have no typical symptoms in the early stages, but have an increased risk of stroke, death, and poor long-term prognosis. Therefore, early diagnosis of CSVD is particularly important. Neuroimaging is the most important diagnostic tool used for CSVD. Therefore, it is important to explore the imaging mechanisms of CSVD for its early diagnosis and precise treatment. In this article, we review the principles and analysis methods of DTI, analyze the latest DTI studies on CSVD, clarify the disease-lesion mapping relationships between cerebral white matter (WM) microstructural damage and CSVD, explore the pathogenic mechanisms and preclinical imaging features of CSVD, and summarize the latest research directions of CSVD and research methods to provide a comprehensive and objective imaging basis for the diagnosis and treatment of CSVD.

Diffusional kurtosis imaging in differentiating nonarteritic anterior ischemic optic neuropathy from acute optic neuritis

PURPOSE

We aimed to determine the feasibility of using DKI to characterize pathological changes in nonarteritic anterior ischemic optic neuropathy (NAION) and to differentiate it from acute optic neuritis (ON).

METHODS

Orbital DKI was performed with a 3.0 T scanner on 75 patients (51 with NAION and 24 with acute ON) and 15 healthy controls. NAION patients were further divided into early and late groups. The mean kurtosis (MK), axial kurtosis (AK), radial kurtosis (RK), mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were calculated to perform quantitative analyses among groups; and receiver operating characteristic curve analyses were also performed to determine their effectiveness of differential diagnosis. In addition, correlation coefficients were calculated to explore the correlations of the DKI-derived data with duration of disease.

RESULTS

The MK, RK, and AK in the affected nerves with NAION were significantly higher than those in the controls, while the trend of FA, RD, and AD was a decline; in acute ON patients, except for RD, which increased, all DKI-derived kurtosis and diffusion parameters were significantly lower than controls (all P < 0.008). Only AK and MD had statistical differences between the early and late groups. Except for MD (early group) and FA, all other DKI-derived parameters were higher in NAION than in acute ON; and parameters in the early group showed better diagnostic efficacy in differentiating NAION from acute ON. Correlation analysis showed that time was negatively correlated with MK, RK, AK, and FA and positively correlated with MD, RD, and AD (all P < 0.05).

CONCLUSION

DKI is helpful for assessing the specific pathologic abnormalities resulting from ischemia in NAION by comparison with acute ON. Early DKI should be performed to aid in the diagnosis and evaluation of NAION.

Clinical and imaging markers for the prognosis of acute ischemic stroke

Background and purpose

Significant differences in the outcomes observed in patients with acute ischemic stroke (AIS) have led to research investigations for identifying the predictors. In this retrospective study, we aimed to investigate the relationship of different clinical and imaging factors with the prognosis of AIS.

Materials and methods

All clinical and imaging metrics were compared between the good and poor prognosis groups according to the modified Rankin Scale (mRS) score at 90 days after discharge. Clinical factors included gender, age, NIHSS scores at admission, and other medical history risk factors. Imaging markers included the lesion's size and location, diffusion, and perfusion metrics of infarction core and peripheral regions, and the state of collateral circulation. Spearman's correlations were analyzed for age and imaging markers between the different groups. The Chi-square test and Cramer's V coefficient analysis were performed for gender, collateral circulation status, NIHSS score, and other stroke risk factors.

Results

A total of 89 patients with AIS were divided into the good (mRS score ≤ 2) and poor prognosis groups (mRS score ≥ 3). There were differences in NIHSS score at the admission; relative MK (rMK), relative MD (rMD), relative CBF (rCBF) of the infarction core; relative mean transit time (rMTT), relative time to peak (rTTP), and relative CBF (rCBF) of peripheral regions; and collateral circulation status between the two groups (p < 0.05). Among them, the rMK of infarction lesions had the strongest correlation with the mRS score at 90 days after discharge (r = 0.545, p < 0.001).

Conclusion

Perfusion and diffusion metrics could reflect the microstructure and blood flow characteristics of the lesion, which were the key factors for the salvage ability and prognosis of the infarction tissue. The characteristics of the infarction core and peripheral regions have different effects on the outcomes. Diffusion of infarction core has strong relations with the prognosis, whereas the time metrics (MTT, TTP) were more important for peripheral regions. MK had a more significant association with prognosis than MD. These factors were the primary markers influencing the prognosis of cerebral infarction patients.

Neuroinflammation-associated miR-106a-5p serves as a biomarker for the diagnosis and prognosis of acute cerebral infarction

BACKGROUND

Acute cerebral infarction (ACI) is a common cerebrovascular disease. Previous studies have shown that some abnormally expressed microRNAs (miRNAs) play important roles in ACI. This study aimed to investigate the role of miR-106a-5p in the diagnosis and prognosis of ACI patients, and analyze the regulatory potential of miR-106a-5p on the inflammation of BV-2 microglial cells.

METHOD

Serum and cerebrospinal fluid (CSF) samples were collected from 98 ACI patients, and the expression of serum miR-106a-5p was analyzed using qRT-PCR. A receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic value of miR-106a-5p. The association of miR-106a-5p with ACI prognosis was evaluated using the logistic analysis. In vitro experiments were performed in BV-2 cells by oxygen glucose deprivation (OGD) treatment, and the effects of miR-106a-5p on BV-2 inflammation were assessed using an enzyme linked immunosorbent assay (ELISA).

RESULT

It was observed that miR-106a-5p was significantly upregulated in the serum and CSF of ACI patients (all P < 0.001), and had considerable diagnostic accuracy. The highest serum miR-106a-5p was observed in severe ACI cases, and miR-106a-5p expression was significantly increased in unfavorable prognosis patients. Serum and CSF expression of miR-106a-5p was positively correlated with proinflammatory cytokines in ACI patients, and the inflammation of OGD-induced BV-2 cells was suppressed by miR-106a-5p reduction.

CONCLUSION

MiR-106a-5p is overexpressed in ACI patients and may serve as a diagnostic and prognostic biomarker for ACI. Furthermore, miR-106a-5p may be involved in ACI progression by regulating neuroinflammation.

Predictive value of intravoxel incoherent motion combined with diffusion kurtosis imaging for breast cancer axillary lymph node metastasis: a retrospective study

BACKGROUND

Non-invasive imaging technologies for assessing axillary lymph node (ALN) metastasis of breast cancer are needed in clinical practice.

PURPOSE

To explore the clinical value of intravoxel incoherent motion (IVIM) and diffusional kurtosis imaging (DKI) for predicting ALN metastasis of breast cancer.

MATERIAL AND METHODS

A total of 194 patients with pathologically confirmed breast cancer who underwent IVIM and DKI examination were reviewed retrospectively. The IVIM derived parameters of D, D*, and f and DKI-derived parameters of MD and MK were measured. The independent samples t-test was used to compare the parameters between the ALN metastasis and non-ALN metastasis groups. Receiver operating characteristic (ROC) curve analysis was also performed.

RESULTS

The D and MD in the ALN metastasis group were significantly lower than those in the non-ALN metastasis group (P < 0.001, P < 0.001). The D*, f, and MK were higher in the ALN metastasis group than in the non-ALN metastasis group (P = 0.015, P = 0.014, and P = 0.001, respectively). The area under the ROC curve (AUC) of D (0.768) was highest. In addition, the diagnostic efficiency of both IVIM and DKI were higher than that of the conventional MRI (P = 0.002, P = 0.048). The diagnostic efficiency of IVIM + DKI were higher than that of the IVIM or DKI alone (P = 0.021, P = 0.004).

CONCLUSION

IVIM and DKI can be used for predicting breast cancer ALN metastasis with D as the most meaningful parameter.

Preliminary research of the classification of the brain acute stroke lesions by the Diffusion Kurtosis Imaging (DKI) and Diffusion Weighted Imaging (DWI) parameters

BACKGROUND

Diffusion-weighted magnetic resonance imaging (DWI) is a mature scanning technique. With high sensitivity in detecting cerebral infractions, it has become an essential part of the clinical evaluation of acute stroke. However, with the update in medical ideals and treatment, clinicians are now focusing on distinguishing between reversible and irreversible brain tissue damage rather than detecting ischaemic lesions alone.

OBJECTIVE

We supposed that Diffusion Kurtosis Imaging (DKI) could classify heterogeneous DWI lesions, deepening the understanding of tissue injury. We systematically studied the different parameters of DKI in acute stroke patients in the literature.

METHODS

We collected 41 patients (26 male, 15 female), including different infarctions with acute cerebral infarction in different brain regions. Of all patients, 20 were single-infarction, while others were multi-infarctions. In this paper, we categorized acute cerebral infarction lesions into two types according to the parametric characteristics of both DKI and DWI. Type I means the DKI and DWI were matched, and Type II means the DKI and DWI were mismatched. Based on each parametric map, the region of interest (ROI) is outlined in each most severe lesion area (as large as possible in the center of the lesion). In the control group, ROIs of the same size are located in the corresponding regions of the contralateral hemisphere.

RESULTS

In both Type I and Type II, all parameters conform to a normal distribution. An independent sample T-test was used to compare the differences between each group. In Type I, we found the FA, MD, Da, Dr, MK and Ka values were statistically different (P< 0.05), while in Type II, only the MK and Ka values were statistically different (P< 0.05).

CONCLUSION

DKI, compared to DWI, can provide more imaging information about intracranial ischemic infarction, which can deepen the understanding of the mechanism of ischemic tissue damage. Our classification of the brain acute stroke lesions by DKI parameters and DWI may help us rediscover the real core of infraction.

Evaluation of crossed cerebellar diaschisis after cerebral infarction in MCAO rats based on DKI

OBJECTIVE

To observe the expression of N-methyl-D-aspartate (NMDA), apoptosis and the effect on neurological function recovery in rat model with middle cerebral artery occlusion (MCAO). Diffusion kurtosis imaging (DKI) was used to evaluate crossed cerebellar diaschisis (CCD) and to provide experimental and theoretical basis for the clinical treatment.

MATERIALS AND METHODS

The MCAO models were established in rats. Eighty-four rats were randomly and evenly divided into 7 groups, including control group, 6-h group, 12-h group, 24-h group, 48-h group, 7-day group and 14-day group. The rats were scanned by MRI at the above time points. Then, rats were sacrificed for H&E staining, immunohistochemical staining and TUNEL staining to detect the expression of NMDA in the core infarct area and cerebellum. At the end, the discussion of relationships between molecular biology and MRI parameters (ADC derived from DWI, and MD, MK and FA derived from DKI) was performed.

RESULTS

The values of MD, ADC and FA in MCAO rats were all lower than those in the control group. All MRI parameters of the contralateral cerebellum were lower than those of the ipsilateral cerebellum (p < .05). The parameters reached the lowest value at 12 h, except that the MK reached the highest at 12 h. The expression of NMDA showed a fluctuation along time in the MCAO group. Overall, it is higher in the MCAO group than in the control group, reaching the maximum at 24 h (p < .05). At the same time, the expression of NMDA in the contralateral cerebellum was higher than in the ipsilateral cerebellum.

CONCLUSION

It is found that NMDA and DKI of CCD have the same changing trend, which indicates that the intervention of NMDA receptor apoptosis may become a new target for the treatment of cerebral infarction, and MRI parameters can predict the occurrence and development of CCD.

Refined Ischemic Penumbra Imaging with Tissue pH and Diffusion Kurtosis Magnetic Resonance Imaging

Imaging has played a vital role in our mechanistic understanding of acute ischemia and the management of acute stroke patients. The most recent DAWN and DEFUSE-3 trials showed that endovascular therapy could be extended to a selected group of late-presenting stroke patients with the aid of imaging. Although perfusion and diffusion MRI have been commonly used in stroke imaging, the approximation of their mismatch as the penumbra is oversimplified, particularly in the era of endovascular therapy. Briefly, the hypoperfusion lesion includes the benign oligemia that does not proceed to infarction. Also, with prompt and effective reperfusion therapy, a portion of the diffusion lesion is potentially reversible. Therefore, advanced imaging that provides improved ischemic tissue characterization may enable new experimental stroke therapeutics and eventually further individualize stroke treatment upon translation to the clinical setting. Specifically, pH imaging captures tissue of altered metabolic state that demarcates the hypoperfused lesion into ischemic penumbra and benign oligemia, which remains promising to define the ischemic penumbra's outer boundary. On the other hand, diffusion kurtosis imaging (DKI) differentiates the most severely damaged and irreversibly injured diffusion lesion from the portion of diffusion lesion that is potentially reversible, refining the inner boundary of the penumbra. Altogether, the development of advanced imaging has the potential to not only transform the experimental stroke research but also aid clinical translation and patient management.

Amide signal intensities may be reduced in the motor cortex and the corticospinal tract of ALS patients

OBJECTIVES

The aim of the study is to assess amide concentration changes in ALS patients compared with healthy controls by using quantitative amide proton transfer (APT) and multiparameter magnetic resonance imaging, and testing its correlation with clinical scores.

METHODS

Sixteen ALS patients and sixteen healthy controls were recruited as part of the Canadian ALS Neuroimaging Consortium, and multimodal magnetic resonance imaging was performed at 3 T, including APT and diffusion imaging. Lorentz fitting was used to quantify the amide effect. Clinical disability was evaluated using the revised ALS functional rating scale (ALSFRS-R), and its correlation with image characteristics was assessed. The diagnostic performance of different imaging parameters was evaluated with receiver operating characteristic analysis.

RESULTS

Our results showed that the amide peak was significantly different between the motor cortex and other gray matter territories within the brain of ALS patients (p < 0.001). Compared with controls, amide signal intensities in ALS were significantly reduced in the motor cortex (p < 0.001) and corticospinal tract (p = 0.046), while abnormalities were not detected using routine imaging methods. There was no significant correlation between amide and ALSFRS-R score. The diagnostic accuracy of the amide peak was superior to that of diffusion imaging.

CONCLUSIONS

This study demonstrated changes of amide signal intensities in the motor cortex and corticospinal tract of ALS patients.

KEY POINTS

• The neurodegenerative disease amyotrophic lateral sclerosis (ALS) has a lack of objective imaging indicators for diagnosis and assessment. • Analysis of amide proton transfer imaging revealed changes in the motor cortex and corticospinal tract of ALS patients that were not visible on standard magnetic resonance imaging. • The diagnostic accuracy of the amide peak was superior to that of diffusion imaging.

Brain pH Imaging and its Applications

Acid-base homeostasis and pH regulation are critical for normal tissue metabolism and physiology, and brain tissue pH alters in many diseased states. Several noninvasive tissue pH Magnetic Resonance (MR) techniques have been developed over the past few decades to shed light on pH change during tissue function and dysfunction. Nevertheless, there are still challenges for mapping brain pH noninvasively at high spatiotemporal resolution. To address this unmet biomedical need, chemical exchange saturation transfer (CEST) MR techniques have been developed as a sensitive means for non-invasive pH mapping. This article briefly reviews the basic principles of different pH measurement techniques with a focus on CEST imaging of pH. Emerging pH imaging applications in the tumor are provided as examples throughout the narrative, and CEST pH imaging in acute stroke is discussed in the final section.

Plasma miR-409-3p promotes acute cerebral infarction via suppressing CTRP3

Abnormal expression of miR-409-3p has been found in several neurodevelopmental disorders, but whether it is dysregulated in the patients with acute cerebral infarction (ACI) has not been evaluated. The current study mainly focused on the clinical significance and the underlying mechanism of plasma miR-409-3p in the progression of ACI. The level of plasma miR-409-3p was determined in ACI patients (n = 80) and healthy controls (n = 30). Pearson correlation assay was performed to evaluate the association and cardiovascular risk factors. A receiver operating characteristic curve (ROC) was used to evaluate the diagnostic value of plasma miR-409-3p levels in patients with ACI. Dual luciferase reporter assay and western blot were performed to determine the possible target gene of miR-409-3p. Our data showed that the expression of plasma miR-409-3p in the ACI group was higher than that in the healthy controls. Furthermore, Pearson correlation analysis indicated a positive correlation between plasma miR-409-3p and the NIHSS score. ROC analysis indicated that plasma miR-409-3p could differentiate plasma miR-409-3p in ACI patients from healthy controls. Then, we explored the possible target genes of miR-409-3p. Interestingly, C1q and TNF-related 3 (CTRP3), a novel adipose tissue-derived secreted factor, was found to be a target gene of miR-409-3p. We found that knockdown of CTRP3 significantly induced PC12 cell apoptosis, even in PC12 cells transfected with miR-409-3p inhibitor. These data suggested that miR-409-3p induced PC12 cell apoptosis by targeting CTRP3. Altogether, elevated plasma miR-409-3p is correlated with disease severity and may be efficient for the early diagnosis of ACI.

Diffusion kurtosis imaging and pathological comparison of early hypoxic-ischemic brain damage in newborn piglets

To investigate the application value of magnetic resonance diffusion kurtosis imaging (DKI) in hypoxic–ischemic brain damage (HIBD) in newborn piglets and to compare imaging and pathological results. Of 36 piglets investigated, 18 were in the experimental group and 18 in the control group. The HIBD model was established in newborn piglets by ligating the bilateral common carotid arteries and placing them into hypoxic chamber. All piglets underwent conventional MRI and DKI scans at 3, 6, 9, 12, 16, and 24 h postoperatively. Mean kurtosis (MK) and mean diffusivity (MD) maps were constructed. Then, the lesions were examined using light and electron microscopy and compared with DKI images. The MD value of the lesion area gradually decreased and the MK value gradually increased in the experimental group with time. The lesion areas gradually expanded with time; MK lesions were smaller than MD lesions. Light microscopy revealed neuronal swelling in the MK- and MD-matched and mismatched regions. Electron microscopy demonstrated obvious mitochondrial swelling and autophagosomes in the MK- and MD-matched region but normal mitochondrial morphology or mild swelling in the mismatched region. DKI can accurately evaluate early ischemic–hypoxic brain injury in newborn piglets.

Diffusion Kurtosis Imaging of Leptin Intervention in Early Hypoxic-Ischemic Brain Edema

The role of leptin in neuroprotection has recently been recognized. However, there are few reports on the use of imaging methods to dynamically evaluate the neuroprotection role of leptin. Diffusion kurtosis imaging (DKI), which is a method used to measure non-Gaussian water diffusion, can reflect the real water diffusion in brain tissues. In this study, a newborn piglet model was used to dynamically evaluate the leptin intervention in early hypoxic-ischemic brain edema via DKI. Thirty-two Yorkshire newborn piglets were divided into three groups: the hypoxic-ischemic encephalopathy (HIE) group, the leptin group, and the control group. DKI scanning was performed at time points of 3, 6, 9, 12, 16, and 24 h after hypoxic-ischemic exposure. After scanning, arterial blood was extracted from all piglets to measure NSE and S100β levels. Then, the brain was completely extracted for pathological examination. In the lesion areas, the MK, Ka, and Kr values in the leptin group were significantly lower than those in the HIE group, the MD, Da, and Dr values showed an opposite trend. The lesion areas in the leptin group were smaller than those of in the HIE group. In addition, the pathological results showed that less cell and organelle injury occurred in the leptin group. Our findings indicate that leptin can effectively reduce hypoxic-ischemic brain edema, and DKI can be more sensitive than conventional diffusivity metrics for visualizing the microstructural changes of HIE. This provides a new clue for the treatment and evaluation of HIE.

Influence of butyphthalide combined with urinary kallikrein in ACI treatment on neuro-cytokines and vascular endothelial function and its clinical effect

Objective: To study the influence of butyphthalide combined with urinary kallikrein in acute cerebral infarction (ACI) treatment on neuro-cytokines and indicators of vascular endothelial function, observe the curative effect and adverse effects, and discuss its safety and feasibility.Method: 110 ACI patients were chosen as the objects, and classified into observation group (55 cases) and control group (55 cases) according to the method of random number table. Butyphthalide injection combined with urinary kallikrein was adopted for the observation group based on conventional treatment, while cinepazide maleate injection combined with alprostadil injection was applied for the control group based on conventional treatment. The following indicators of both groups were compared before and after treatment: neurotrophic factor (NTF), nerve growth factor (NGF), neuron specific enolase (NSE); content of CXC chemotactic factor ligand 16 (CXCL16), soluble CD ligand (CD40L), Fibulin-5 and high mobility group box B1 (HMGB1); the content of indicators of vascular endothelial function including plasma endothelin -1 (ET-1) and no therapeutic effects and adverse effects were recorded.Results: NSE of both groups after treatment decreased obviously, and the content of NTF and NGF increased obviously. NSE content of observation group was lower than that of control group. NTF content and NGF content of observation group were higher than those of control group. The differences had statistical significance (p < 0.05). The levels of CXCL16, CD40L, Fibulin-5 and HMGB1 declined obviously, compared with pre-treatment, and the levels of observation groups were significantly lower than those of control grip. The differences had statistical significance (p < 0.05). ET-1 level rose significantly after treatment, and NO level declined obviously after treatment. ET-1 level of observation group was significantly higher than that of control group, and NO level of observation group was significantly lower than that of control group. The difference had statistical significance (p < 0.05). Clinical effect of observation group was significantly higher than that of control group. The difference had statistical significance (p < 0.05). The comparison difference of both groups in the occurrence rate of adverse effects had no statistical significance (p > 0.05).Conclusion: The application of butyphthalide combined with urinary kallikrein in ACI treatment can effectively inhibit secretion and release of neuro-cytokines, and improve patients' vascular endothelial function, with significant treatment effect and high safety. Therefore, it deserves to be promoted clinically.

Evaluation of Diffusional Kurtosis Imaging in Sub-acute Ischemic Stroke: Comparison with Rehabilitation Treatment Effect

Stroke is a serious worldwide medical condition that causes neurological function disability. Diffusional kurtosis imaging, which measures the non-Gaussianity of water diffusion, has been demonstrated to be a sensitive biomarker in many neuro-pathologies. This study explores the relationship between neural function recovery and transformation of the ischemic lesion and/or corticospinal tract during the sub-acute phase after stroke by using diffusional kurtosis imaging. We performed a prospective study of function recovery and K metrics of 43 patients with sub-acute ischemic stroke in the middle cerebral artery territory. The effect of rehabilitation treatment was evaluated using both the Fugl-Meyer motor function score and modified Barthel index score at post-treatment compared with admission, and patients were allocated to two groups: good and poor rehabilitation effect (GRE and PRE). Metrics of diffusional kurtosis imaging within ischemic lesion and along the corticospinal tract were acquired, respectively. All three relative axial diffusional kurtoses (rKas) along the corticospinal tract in the GRE group ( n = 21) were significantly larger than those of the PRE group ( n = 22), including rKa in the posterior limb of internal capsule, rKa in the cerebral peduncle, and rKa in the basal part of the pons ( p = 0.014, 0.005, and 0.021, respectively). This multi-parametric magnetic resonance imaging study showed that diffusional kurtosis imaging has the potential to complement existing stroke imaging techniques and revealed its own advantages in elucidating the possible biophysical mechanism of functional restoration underlying ischemic stroke.

Abnormalities of diffusional kurtosis imaging and regional homogeneity in idiopathic generalized epilepsy with generalized tonic-clonic seizures

Neuroimaging techniques have been used to investigate idiopathic generalized epilepsy with generalized tonic-clonic seizures (IGE-GTCS) and different studies employing these methods have produced varying results. However, there have been few studies exploring diffusional kurtosis imaging (DKI) and regional homogeneity (ReHo) techniques in patients with IGE-GTCS. In the current study, resting-state functional magnetic resonance imaging (fMRI) and DKI data were collected from 28 patients with IGE-GTCS and 28 healthy controls. The ReHo method and tract-based spatial statistical (TBSS) analysis were performed to compare differences between the groups. Compared with healthy controls, patients with IGE-GTCS exhibited markedly increased ReHo in the bilateral putamen, the thalamus, right pallidum, right supplementary motor area and the bilateral paracentral lobules. Compared with healthy controls, patients with IGE-GTCS also exhibited markedly decreased ReHo in the posterior cingulate/precuneus, left angular gyrus and dorsolateral prefrontal cortex. In patients with IGE-GTCS, DKI revealed lower fractional anisotropy in the left anterior/superior corona radiata, left superior longitudinal fasciculus and genu/body of the corpus callosum. Higher mean diffusivity was detected in the bilateral anterior corona radiata, left superior corona radiata, left cingulum, and genu/body/splenium of the corpus callosum. Furthermore, reduced mean kurtosis values were identified over the bilateral superior/posterior corona radiate, left anterior corona radiata, right superior longitudinal fasciculus, left posterior thalamic radiation and the genu/body/splenium of the corpus callosum. Therefore, the results of the current study revealed abnormalities in spontaneous activity in the gray and white matter tracts in patients with IGE-GTCS. These results suggest that novel MRI technology may be useful to help determine the pathogenesis of IGE-GTCS.

JOURNAL CLUB: Evaluation of Diffusion Kurtosis Imaging of Stroke Lesion With Hemodynamic and Metabolic MRI in a Rodent Model of Acute Stroke

OBJECTIVE

Diffusion kurtosis imaging (DKI) has emerged as a new acute stroke imaging approach, augmenting routine DWI. Although it has been shown that a diffusion lesion without kurtosis abnormality is more likely to recover after reperfusion, whereas a kurtosis lesion shows poor response, little is known about the underlying pathophysiologic profile of the kurtosis lesion versus the kurtosis lesion-diffusion lesion mismatch.

MATERIALS AND METHODS

We performed multiparametric MRI, including arterial spin labeling, pH-sensitive amide proton transfer, and DKI, in a rodent model of acute stroke caused by embolic middle cerebral artery occlusion. Diffusion and kurtosis lesions were semiautomatically segmented, and multiparametric MRI indexes were compared among the kurtosis lesion, diffusion lesion, kurtosis lesion-diffusion lesion mismatch, and the contralateral normal tissue area.

RESULTS

We confirmed a significant difference between diffusion lesion and kurtosis lesion volumes (mean [± SD] volume, 151 ± 65 vs 125 ± 47 mm³; p < 0.05). Although ischemic lesions have significantly reduced cerebral blood flow compared with contralateral normal tissue, we did not find a significant difference in cerebral blood flow between the kurtosis lesion and the kurtosis lesion-diffusion lesion mismatch (mean cerebral blood flow, 0.53 ± 0.10 vs 0.47 ± 0.14 mL/g of tissue per minute; p > 0.05). Of importance, the pH of the kurtosis lesion was significantly lower than that of the lesion mismatch (mean pH, 6.81 ± 0.08 vs 6.89 ± 0.09; p < 0.01).

CONCLUSION

The present study confirms that DKI provides an expedient approach for refining the heterogeneous DWI lesion that is associated with graded metabolic derangement, which is promising for improving the infarction core definition and ultimately helping to guide stroke treatment.

Diffusion parameter mapping with the combined intravoxel incoherent motion and kurtosis model using artificial neural networks at 3 T

Artificial neural networks (ANNs) were used for voxel-wise parameter estimation with the combined intravoxel incoherent motion (IVIM) and kurtosis model facilitating robust diffusion parameter mapping in the human brain. The proposed ANN approach was compared with conventional least-squares regression (LSR) and state-of-the-art multi-step fitting (LSR-MS) in Monte-Carlo simulations and in vivo in terms of estimation accuracy and precision, number of outliers and sensitivity in the distinction between grey (GM) and white (WM) matter. Both the proposed ANN approach and LSR-MS yielded visually increased parameter map quality. Estimations of all parameters (perfusion fraction f, diffusion coefficient D, pseudo-diffusion coefficient D*, kurtosis K) were in good agreement with the literature using ANN, whereas LSR-MS resulted in D* overestimation and LSR yielded increased values for f and D*, as well as decreased values for K. Using ANN, outliers were reduced for the parameters f (ANN, 1%; LSR-MS, 19%; LSR, 8%), D* (ANN, 21%; LSR-MS, 25%; LSR, 23%) and K (ANN, 0%; LSR-MS, 0%; LSR, 15%). Moreover, ANN enabled significant distinction between GM and WM based on all parameters, whereas LSR facilitated this distinction only based on D and LSR-MS on f, D and K. Overall, the proposed ANN approach was found to be superior to conventional LSR, posing a powerful alternative to the state-of-the-art method LSR-MS with several advantages in the estimation of IVIM-kurtosis parameters, which might facilitate increased applicability of enhanced diffusion models at clinical scan times.