Value of multiple models of diffusion-weighted imaging to predict hepatic lymph node metastases in colorectal liver metastases patients

BACKGROUND About 10%-31% of colorectal liver metastases(CRLM)patients would concomitantly show hepatic lymph node metastases(LNM),which was considered as sign of poor biological behavior and a relative contraindication for liver resection.Up to now,there’s still lack of reliable preoperative methods to assess the status of hepatic lymph nodes in patients with CRLM,except for pathology examination of lymph node after resection.AIM To compare the ability of mono-exponential,bi-exponential,and stretchedexponential diffusion-weighted imaging(DWI)models in distinguishing between benign and malignant hepatic lymph nodes in patients with CRLM who received neoadjuvant chemotherapy prior to surgery.METHODS In this retrospective study,97 CRLM patients with pathologically confirmed hepatic lymph node status underwent magnetic resonance imaging,including DWI with ten b values before and after chemotherapy.Various parameters,such as the apparent diffusion coefficient from the mono-exponential model,and the true diffusion coefficient,the pseudo-diffusion coefficient,and the perfusion fraction derived from the intravoxel incoherent motion model,along with distributed diffusion coefficient(DDC)andαfrom the stretched-exponential model(SEM),were measured.The parameters before and after chemotherapy were compared between positive and negative hepatic lymph node groups.A nomogram was constructed to predict the hepatic lymph node status.The reliability and agreement of the measurements were assessed using the coefficient of variation and intraclass correlation coefficient.RESULTS Multivariate analysis revealed that the pre-treatment DDC value and the short diameter of the largest lymph node after treatment were independent predictors of metastatic hepatic lymph nodes.A nomogram combining these two factors demonstrated excellent performance in distinguishing between benign and malignant lymph nodes in CRLM patients,with an area under the curve of 0.873.Furthermore,parameters from SEM showed substantial repeatability.CONCLUSION The developed nomogram,incorporating the pre-treatment DDC and the short axis of the largest lymph node,can be used to predict the presence of hepatic LNM in CRLM patients undergoing chemotherapy before surgery.This nomogram was proven to be more valuable,exhibiting superior diagnostic performance compared to quantitative parameters derived from multiple b values of DWI.The nomogram can serve as a preoperative assessment tool for determining the status of hepatic lymph nodes and aiding in the decision-making process for surgical treatment in CRLM patients.

Role of diffusion-weighted magnetic resonance imaging in the diagnosis of extrahepatic cholangiocarcinoma

AIM: To determine the clinical value of diffusion-weight- ed imaging (DWI) for the diagnosis of extrahepatic cholangiocarcinoma (EHCC) by comparing the diagnostic sensitivity of DWI and magnetic resonance cholan-giopancreatography (MRCP). METHODS: Magnetic resonance imaging examination was performed in 56 patients with suspected EHCC. T1- weighted imaging, T2-weighted imaging, MRCP and DWI sequence, DWI using single-shot spin-echo echoplanar imaging sequence with different b values (100, 300, 500, 800 and 1000 s/mm2), were performed. All cases were further confirmed by surgery or histopathological diagnosis. Two radiologists jointly performed the analysis of the DWI and MRCP images. Apparent diffusion coefficient (ADC) value and signal-noise ratio were calculated for EHCC. Sensitivity, specificity, accuracy, positive predictive value and negative predictive value were tested using DWI with a b value of 500 s/mm2 and MRCP images, respectively. RESULTS: Histopathological diagnosis confirmed that among the 56 cases, 35 were EHCC (20 hilar and 15 distal extrahepatic), 16 were cholangitis, and 5 were cal-culus of bile duct. Thirty-three out of the 35 EHCC cases were detected by DWI. EHCC exhibited differential levels of high signal intensity in DWI and low signal intensity in the ADC map. The mean value for ADC was (1.31 ± 0.29) × 10-3 mm2/s. The detection rate of EHCC was significantly higher by DWI (94.3%) than by MRCP (74.3%) (P < 0.05). There was a significant difference in sensitivity (94.3% vs 74.3%), specificity (100% vs 71.4%), accu- racy (96.4% vs 73.2%), positive predictive value (100% vs 81.3%), and negative predictive value (91.3% vs 62.5%) between DWI and MRCP in diagnosing EHCC. CONCLUSION: DWI has a high sensitivity for the detection of EHCC as it shows the EHCC lesion more unambiguously than MRCP does. DWI can also provide additional clinically important information in EHCC patients when added to routine bile duct MR imaging protocols.

Magnetic resonance diffusion tensor imaging-based evaluation of optic-radiation shape and position in meningioma

Employing magnetic resonance diffusion tensor imaging, three-dimensional white-matter imaging and conventional magnetic resonance imaging can demonstrate the tumor parenchyma, peritumoral edema and compression on surrounding brain tissue. A color-coded tensor map and three-dimensional tracer diagram were applied to clearly display the optic-radiation location, course and damage. Results showed that the altered anisotropy values of meningioma patients corresponded with optic-radiation shape, size and position on both sides. Experimental findings indicate that the magnetic resonance diffusion tensor imaging technique is a means of tracing and clearly visualizing the optic radiation.

Progress of intravoxel incoherent motion diffusion-weighted imaging in liver diseases

Traditional magnetic resonance(MR)diffusion-weighted imaging(DWI)uses a single exponential model to obtain the apparent diffusion coefficient to quantitatively reflect the diffusion motion of water molecules in living tissues,but it is affected by blood perfusion.Intravoxel incoherent motion(IVIM)-DWI utilizes a double-exponential model to obtain information on pure water molecule diffusion and microcirculatory perfusion-related diffusion,which compensates for the insufficiency of traditional DWI.In recent years,research on the application of IVIM-DWI in the diagnosis and treatment of hepatic diseases has gradually increased and has achieved considerable progress.This study mainly reviews the basic principles of IVIM-DWI and related research progress in the diagnosis and treatment of hepatic diseases.

Verifying the hypothesis of disconnection syndrome in patients with conduction aphasia using diffusion tensor imaging

BACKGROUND： It is thought in disconnection theory that connection of anterior and posterior language function areas, i.e. the lesion of arcuate fasciculus causes conduction aphasia. OBJECTIVE： To verify the theory of disconnection elicited by repetition disorder in patients with conduction aphasia by comparing the characteristics of diffusion tensor imaging between healthy persons and patients with conduction aphasia. DESIGN： Case-control observation. SETTING： Department of Neurology, Hongqi Hospital Affiliated to Mudanjiang Medical College. PARTICIPANTS： Five male patients with cerebral infarction-involved arcuate fasciculus conduction aphasia, averaged （43±2） years, who hospitalized in the Department of Neurology, Hongqi Hospital Affiliated to Mudanjiang Medical College from February 2004 to February 2005 were involved in this experiment. The involved patients were all confirmed as cerebral infarction by skull CT and MRI, and met the diagnosis criteria revised in 1995 4^th Cerebrovascular Conference. They were examined by the method of Aphasia Battery of Chinese （ABC） edited by Surong Gao. The results were poorer than auditory comprehension disproportionately, and consistented with the mode of conduction aphasia. Another 5 male healthy persons, averaged （43 ± 1 ） years, who were physicians receiving further training in the Department of Neurology, Beijing Tiantan Hospital were also involved in this experiment. Informed consents of detected items were obtained from all the subjects. METHODS： All the subjects were performed handedness assessment with assessment criteria of handedness formulated by Department of Neurology, First Hospital Affiliated to Beijing Medical University. Arcuate fasciculus of involved patients and health controls were analyzed with diffusion tensor imaging （DTI） and divided into 3 parts （anterior, middle and posterior segments） for determining FA value （mean value was obtained after three times of measurements）, and a comparison of FA value was made between two sides. MAIN OUTCOME MEASURES： Analysis results of arcuate fasciculus DTI of healthy controls and patients with conduction aphasia. RESULTS： Five patients with conduction aphasia and 5 healthy controls participated in the final analysis. ①All the subjects were right-handedness.② The left FA value of anterior, middle and posterior segments of arcuate fasciculus was larger than the right one in most normal volunteers, i.e. arcuate fasciculus with normal function on the left side was more than that on the right side. Because the amount of healthy controls was small, so positive conclusion has not been obtained, and only above-mentioned tendency was demonstrated. Healthy controls had good bilateral arcuate fasciculus; Three patients with conduction aphasia presented left FA value of anterior segment of arcuate fasciculus smaller than the right one, and two patients presented the left FA value larger than the right one. Four patients presented the left FA value of middle segment of arcuate fasciculus smaller than the right one, and one patient presented the left FA value larger than the right one, i.e. middle segment of arcuate fasciculus of 5 patients with conduction aphasia was all involved in at different degrees. Four patients with conduction aphasia presented the left FA value of posterior segment of arcuate fasciculus smaller than the right one, and one patient presented the left FA value larger than the right one, i.e. posterior segment of arcuate fasciculus of 5 patients was all injured at different degrees. CONCLUSION： Arcuate fasciculus of patients with conduction aphasia all is involved in at different degrees, which verifies the theory of disconnection of repetition disorder in patients with conduction aphasia.

COMPARISON OF OPTICAL POLARIMETRY AND DIFFUSION TENSOR MR IMAGING FOR ASSESSING MYOCARDIAL ANISOTROPY

We have recently proposed an optical method for assessing heart structure that uses polarized light measurement of birefringence as an indicator of tissue anisotropy.The highly aligned nature of healthy cardiac muscle tissue has a detectable effect on the polarization of light,resulting in a measurable phase shift(“retardance”).When this organized tissue structure is perturbed,for example after cardiac infarction(heart attack),scar tissue containing disorganized collagen is formed,causing a decrease in the measured retardance values.However,these are dependent not only on tissue anisotropy,but also on the angle between the tissue’s optical anisotropy direction and the beam interrogating the sample.To remove this experimental ambiguity,we present a method that interrogates the sample at two different incident beam angles,thus yielding enough information to uniquely determine the true magnitude and orientation of the tissue optical anisotropy.We use an infarcted porcine heart model to compare these polarimetryderived anisotropy metrics with those obtained with diffusion tensor magnetic resonance imaging(DT-MRI).The latter yields the anisotropy and the direction of tissue water diffusivity,providing an independent measure of tissue anisotropy.The optical and MR results are thus directly compared in a common ex vivo biological model of interest,yielding reasonable agreement but also highlighting some technique-specific differences.

Evaluating transcatheter arterial chemoembolization for primary hepatic cancer by magnetic resonance diffusion-weighted imaging

Hepatic cancer is associated with very high mortality and morbidity, and the world＇s highest morbidity and mortality rates for this malignant tumor are found in China. Each year, the number of people who die of hepatic cancer in China amounts for 53% of the world total. Although resection is the first-choice treatment for hepatic cancer, only 20%-30% of patients have the opportunity to undergo resection. Transcatheter arterial chemoembolization （TACE） is a typical intervention therapy. Its advantages include minimal trauma, precise efficacy,

Neurite Orientation Dispersion and Density Imaging of Rat Brain Microstructural Changes due to Middle Cerebral Artery Occlusion at a 3T MRI

The purpose of this work was to demonstrate the feasibility of neurite orientation dispersion and density imaging(NODDI)in characterizing the brain tissue microstructural changes of middle cerebral artery occlusion(MCAO)in rats at 3T MRI,and to validate NODDI metrics with histology.A multi-shell diffusion MRI protocol was performed on 11 MCAO rats and 10 control rats at different post-operation time points of 0.5,2,6,12,24 and 72 h.NODDI orientation dispersion index(ODI)and intracellular volume fraction(V_(ic))metrics were compared between MCAO group and control group.The evolution of NODDI metrics was characterized and validated by histology.Infarction was consistent with significantly increased ODI and V_(ic)in comparison to control tissues at all time points(P<0.001).Lesion ODI increased gradually from 0.5 to 72 h,while its V_(ic)showed a more complicated and fluctuated evolution.ODI and V_(ic)were significantly different between hyperacute and acute stroke periods(P<0.001).The NODDI metrics were found to be consistent with the histological findings.In conclusion,NODDI can reflect microstructural changes of brain tissues in MCAO rats at 3T MRI and the metrics are consistent with histology.This study helps to prepare NODDI for the diagnosis and management of ischemic stroke in translational research and clinical practice.

Magnetic resonance diffusion-weighted imaging in the diagnosis of diffuse liver diseases in rats

Background The diagnosis of diffuse hepatic lesions in early stage is a tough task at any time for clinical conventional imaging. Magnetic resonance diffusion-weighted imaging (MR DWI) can detect the changes of tissue structure at molecular level. This study was designed to determine the value of DWI in the diagnosis of diffuse liver lesions in early stage. Methods Diffuse liver lesions were induced by diethylnitrosamine in 42 rats of test group. Fourteen rats in control group were fed with pure water. Dynamic changes of MR DWI were observed every week in both groups during the early stage of diffuse liver lesions (1 to 12 weeks after drug administration in the test group). Apparent diffusion coefficient (ADC) values of liver parenchyma in different stages and pathologic changes were analyzed. Results The process of diffuse hepatic lesions in the test group was classified into three stages according to pathological changes, namely hepatitis, hepatic fibrosis and cirrhosis. No obvious morphological changes were shown by conventional imaging in both groups during this stage. But MR DWI demonstrated heterogeneous signal changes in early stage of hepatic cirrhosis in the test group. No significant change of ADC values was found in the control group between different weeks ( P >0.05). The ADC values of the test group declined from the fifth week, and after the tenth week the ADC values were significantly different between the test and control groups at gradient factor (b) value 300 sec/mm 2 ( P <0.05). At b value 600 and 1000 sec/mm 2, significant difference was seen between the two groups from the sixth week onward. The range of ADC value of the groups was (1.7-0.9)±(0.40-0.04) mm 2/sec (b=600) and (1.38-0.75)±(0.07-0.35) mm 2/sec (b=1000), respectively. Dominant pathological changes included swelled hepatocytes within 1 to 4 weeks after the administration of diethylnitrosamine in the test group, hyperplasia of fibrous tissues in 5-8 weeks and formation of cirrhotic nodules in 9-12 weeks. Conclusions MR functional DWI could detect diffuse liver lesions earlier than conventional morphological imaging. ADC value as a marker for early diagnosis of diffuse liver lesions could also be used to inspect changes of the lesions

Diffusion-weighted MRI in abdominal oncology:Clinical applications

Diffusion-weighted magnetic resonance imaging(DWI) provides image contrast that is different from that obtained by conventional magnetic resonance techniques.Although previously,DWI has been used to evaluate various diseases of the central nervous system,several technical advances have expanded the clinical applications of DWI beyond the central nervous system.As a result,many reports have been published on the use of DWI in abdominal diseases.Particularly,abdominal DWI has now being focused on evaluation of patients with abdominal cancer.DWI can be used for pretreatment tumor detection,characterization including predicting tumor response to therapy,monitoring tumor response during therapy,and follow-up study after treatment to detect possible tumor recurrence.

Magnetic resonance diffusion tensor imaging with fluorescein sodium dyeing for surgery of gliomas in brain motor functional areas

Background Tumor surgery in brain motor functional areas remains challenging. Novel techniques are being developed to gain maximal and safe resection for brain tumor surgery. Herein, we assessed the magnetic resonance diffusion tensor imaging （MR-DTI） and fluorescein sodium dyeing （FLS） guiding technique for surgery of glioma located in brain motor functional areas. Methods Totally 83 patients were enrolled according to our inclusion and exclusion criteria （56 patients in experimental group, 27 patients in control group）. In the experimental group, the surgical approach was designed by DTI imaging, which showed the relationship between the tumor and motor tract. The range of resection in the operation was determined using the FLS-stained area, which recognized the tumor and its infiltrated tissue. The traditional routine method was used in the control group. Postoperatively, all patients underwent enhanced brain MRI within 72 hours to ascertain the extent of resection. Patients were followed in our outpatient clinic over 6-24 months. Neurological deficits and Karnofsky scoring （KPS） were evaluated. Results There were no significant differences in balance test indexes of preoperative data （sex, age, lesion location and volume, and neurological deficits before operation） and diagnosis of histopathology between the two groups. There was a trend in the experimental group for greater rates of gross total resection （80.4% vs. 40.7%）, and the paralysis rate caused by surgery was lower in experimental （25.0%） vs. control （66.7%） groups （P 〈0.05）. The 6-month KPS in the low-grade and high-grade gliomas was 91＋11 and 73＋26, respectively, in the experimental group vs. 82＋9 and 43＋27, respectively, in the control group （P 〈0.05 for both）. Conclusions MR-DTI and FLS dye guiding for surgery of glioma located in brain motor functional areas can increase the gross total resection rate, decrease the paralysis rate caused by surgery, and improve patient quality of life compared with traditional glioma surgery.

Tissue Microstructure Estimation of SANDI Based on Deep Network

Diffusion magnetic resonance imaging(dMRI)is a noninvasive method to capture the anisotropic pattern of water displacement in the neuronal tissue.The soma and neurite density imaging(SANDI)model introduced soma size and density to biophysical model for the first time.In addition to neurite density,it can achieve their joint estimation non-invasively using dMRI.In the traditional method,parameters of the SANDI are estimated in a maximum likelihood frame-work,where the nonlinear model fitting is computationally intensive.Also,the present methods require a large number of diffusion gradients.Efficient and accurate algorithms for tissue microstructure estimation of SANDI is still a challenge currently.Consequently,we introduce deep learning method for tissue microstructure estimation of the SANDI model.The model comprises two functional components.The first component produces the sparse representation of diffusion sig-nals of input patches.The second component computes tissue microstructure from the sparse repre-sentation given by the first component.The deep network can produce not only tissue microstruc-ture estimates but also the uncertainty of the estimates with a reduced number of diffusion gradi-ents.Then,multiple deep networks are trained and their results are fused for the final prediction of tissue microstructure and uncertainty quantification.The deep network was evaluated on the MGH Connectome Diffusion Microstructure Dataset.Results indicate that our approach outperforms the traditional methods in terms of estimation accuracy.

Value of diffusion-weighted imaging in distinguishing pancreatic carcinoma from mass-forming chronic pancreatitis： a meta-analysis

Background Several previous studies have shown that diffusion-weighted imaging （DWl） can provide additional information for focal pancreatic lesions by demonstrating more restricted diffusion in solid malignant tumors than in chronic pancreatitis, which can be indicated by a decreased apparent diffusion coefficient （ADC）. However, these studies have a modest sample size and convey inconclusive results. The aim of this study was to determine, in a meta-analysis, the diagnostic performance of quantitative diffusion-weighted magnetic resonance imaging in distinguishing pancreatic carcinoma from mass-forming chronic pancreatitis. Methods We determined the sensitivities and specificities across studies. A summary receiver operator characteristic （sROC） curve was constructed to calculate the area under the curve （AUC）. Results The pooled sensitivity of DWI was 0.86 （95% Cl： 0.80-0.91） and the pooled specificity was 0.82 （95% CI： 0.72- 0.89）. The AUC of the sROC was 0.91 （95% CI： 0.88-0.93）. Conclusions DWl may be a potentially technically feasible tool for differentiating pancreatic carcinoma from mass- forming chronic pancreatitis. However, large-scale randomized control trials are necessary to assess its clinical value.

Value of intravoxel incoherent motion in detecting and staging liver fibrosis: A meta-analysis

BACKGROUND Liver fibrosis(LF) is a common pathological feature of all chronic liver diseases.With the accumulation of extracellular matrix in the fibrotic liver, true molecular water diffusion and perfusion-related diffusion are restricted. Intravoxel incoherent motion(IVIM) can capture the information on tissue diffusivity and microcapillary perfusion separately and reflect the fibrotic severity with diffusion coefficients.AIM To investigate the diagnostic performance of IVIM in detecting and staging LF with histology as a reference standard.METHODS A comprehensive literature search was conducted to identify studies on the diagnostic accuracy of IVIM for assessment of histologically proven LF. The stages of LF were classified as F0(no fibrosis), F1(portal fibrosis without septa),F2(periportal fibrosis with few septa), F3(septal fibrosis), and F4(cirrhosis)according to histopathological findings. Data were extracted to calculate the pooled sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio, as well as the area under the summary receiver operating characteristic curve(AUC) in each group.RESULTS A total of 12 studies with 923 subjects were included in this meta-analysis with 5 studies(n = 465) for LF ≥ F1, 9 studies(n = 757) for LF ≥ F2, 4 studies(n = 413) for LF ≥ F3, and 6 studies(n = 562) for LF = F4. The pooled sensitivity and specificity were estimated to be 0.78(95% confidence interval: 0.73-0.82) and 0.81(0.74-0.86)for LF ≥ F1 detection with IVIM;0.82(0.79-0.86) and 0.80(0.75-0.84) for staging F2 fibrosis;0.85(0.79-0.90) and 0.83(0.77-0.87) for staging F3 fibrosis, and 0.90(0.84-0.94) and 0.75(0.70-0.79) for detecting F4 cirrhosis, respectively. The AUCs for LF≥ F1, F2, F3, F4 detection were 0.862(0.811-0.914), 0.883(0.856-0.909), 0.886(0.865-0.907), and 0.899(0.866-0.932), respectively. Moderate to substantial heterogeneity was observed with inconsistency index(I2) ranging from 0% to 77.9%. No publication bias was detected.CONCLUSION IVIM is a noninvasive tool with good diagnostic performance in detecting and staging LF. Optimized and standardized IVIM protocols are needed to further improve its diagnostic accuracy in clinical practice.

Differences in brain pathological changes between rotenone and 6-hydroxydopamine Parkinson＇s disease models

Rotenone and 6-hydroxydopamine are two drugs commonly used to generate Parkinson＇s disease animal models.They not only achieve degenerative changes of dopaminergic neurons in the substantia nigra,but also satisfy the requirements for iron deposition.However,few studies have compared the characteristics of these two models by magnetic resonance imaging.In this study,rat models of Parkinson＇s disease were generated by injection of 3 μg rotenone or 10 μg 6-hydroxydopamine into the right substantia nigra.At 1,2,4,and 6 weeks after injection,coronal whole-brain T2-weighted imaging,transverse whole-brain T2-weighted imaging,and coronal diffusion tensor weighted imaging were conducted to measure fractional anisotropy and T2＊ values at the injury site.The fractional anisotropy value on the right side of the substantia nigra was remarkably lower at 6 weeks than at other time points in the rotenone group.In the 6-hydroxydopamine group,the fractional anisotropy value was decreased,but T2＊ values were increased on the right side of the substantia nigra at 1 week.Our findings confirm that the 6-hydroxydopamine-induced model is suitable for studying dopaminergic neurons over short periods,while the rotenone-induced model may be appropriate for studying the pathological and physiological processes of Parkinson＇s disease over long periods.

A brief report on MRI investigation of experimental traumatic brain injury

Traumatic brain injury is a major cause of death and disability. This is a brief report based on a symposium presentation to the 2014 Chinese Neurotrauma Association Meeting in San Francisco, USA. It covers the work from our laboratory in applying multimodal MRI to study experimental traumatic brain injury in rats with comparisons made to behavioral tests and histology. MRI protocols include structural, perfusion, manganese-enhanced, diffusion-tensor MRI, and MRI of blood-brain barrier integrity and cerebrovascular reactivity.

Why do stroke patients with negative motor evoked potential show poor limb motor function recovery?

Negative motor evoked potentials after cerebral infarction, indicative of poor recovery of limb motor function, tend to be accompanied by changes in fractional anisotropy values and the cerebral pe-duncle area on the affected side, but the characteristics of these changes have not been reported. This study included 57 cases of cerebral infarction whose motor evoked potentials were tested in the 24 hours after the first inspection for diffusion tensor imaging, in which 29 cases were in the negative group and 28 cases in the positive group. Twenty-nine patients with negative motor evoked potentials were divided into two groups according to fractional anisotropy on the affected side of the cerebral peduncle： a fractional anisotropy 〈 0.36 group and a fractional anisotropy 〉 0.36 group. All patients underwent a regular magnetic resonance imaging and a diffusion tensor imaging examina- tion at 1 week, 1, 3, 6 and 12 months after cerebral infarction. The FugI-Meyer scores of their hemiplegic limbs were tested before the magnetic resonance and diffusion tensor imaging exami-nations. In the negative motor evoked potential group, fractional anisotropy in the affected cerebral peduncle declined progressively, which was most obvious in the first 1-3 months after the onset of cerebral infarction. The areas and area asymmetries of the cerebral peduncle on the affected side were significantly decreased at 6 and 12 months after onset. At 12 months after onset, the area asymmetries of the cerebral peduncle on the affected side were lower than the normal lower limit value of 0.83. FugI-Meyer scores in the fractional anisotropy ≥0.36 group were significantly higher than in the fractional anisotropy 〈 0.36 group at 3-12 months after onset. The fractional anisotropy of the cerebral peduncle in the positive motor evoked potential group decreased in the first 1 month after onset, and stayed unchanged from 3-12 months; there was no change in the area of the cerebral peduncle in the first 1-12 months after cerebral infarction. These findings confirmed that if the fractional anisotropy of the cerebral peduncle on the affected side is 〈 0.36 and the area asym-metries 〈 0.83 in patients with negative motor evoked potential after cerebral infarction, then poor hemiplegic limb motor function recovery may occur.

Planning for selective amygdalohippocampectomy involving less neuronal fiber damage based on brain connectivity using tractography

Temporal lobe resection is an important treatment option for epilepsy that involves removal of potentially essential brain regions. Selective amygdalohippocampectomy is a widely performed temporal lobe surgery. We suggest starting the incision for selective amygdalohippocampectomy at the inferior temporal gyrus based on diffusion magnetic resonance imaging（MRI） tractography. Diffusion MRI data from 20 normal participants were obtained from Parkinson＇s Progression Markers Initiative（PPMI） database（www.ppmi-info.org）. A tractography algorithm was applied to extract neuronal fiber information for the temporal lobe, hippocampus, and amygdala. Fiber information was analyzed in terms of the number of fibers and betweenness centrality. Distances between starting incisions and surgical target regions were also considered to explore the length of the surgical path. Middle temporal and superior temporal gyrus regions have higher connectivity values than the inferior temporal gyrus and thus are not good candidates for starting the incision. The distances between inferior temporal gyrus and surgical target regions were shorter than those between middle temporal gyrus and target regions. Thus, the inferior temporal gyrus is a good candidate for starting the incision. Starting the incision from the inferior temporal gyrus would spare the important（in terms of betweenness centrality values） middle region and shorten the distance to the target regions of the hippocampus and amygdala.

Can multi-modal neuroimaging evidence from hippocampus provide biomarkers for the progression of amnestic mild cognitive impairment?

Impaired structure and function of the hippocampus is a valuable predictor of progression from amnestic mild cognitive impairment（a MCI） to Alzheimer＇s disease（AD）. As a part of the medial temporal lobe memory system,the hippocampus is one of the brain regions affected earliest by AD neuropathology,and shows progressive degeneration as a MCI progresses to AD. Currently,no validated biomarkers can precisely predict the conversion from a MCI to AD. Therefore,there is a great need of sensitive tools for the early detection of AD progression. In this review,we summarize the specifi c structural and functional changes in the hippocampus from recent a MCI studies using neurophysiological and neuroimaging data. We suggest that a combination of advanced multi-modal neuroimaging measures in discovering biomarkers will provide more precise and sensitive measures of hippocampal changes than using only one of them. These will potentially affect early diagnosis and disease-modifying treatments. We propose a new sequential and progressive framework in which the impairment spreads from the integrity of fibers to volume and then to function in hippocampal subregions. Meanwhile,this is likely to be accompanied by progressive impairment of behavioral and neuropsychological performance in the progression of a MCI to AD.