Diffusion weighted imaging in the liver

Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique to each type of tissue. DWI has been originally used in neuroradiology. More recently, DWI has increasingly been used in addition to conventional unenhanced and enhanced magnetic resonance imaging (MRI) in other parts of the body. The reason for this delay was a number of technical problems inherent to the technique, making DWI very sensitive to artifacts, which had to be overcome. With assessment of ADC values, DWI proved to be helpful in characterization of focal liver lesions. However, DWI should always be used in conjunction to conventional MRI since there is considerable overlap between ADC values of benign and malignant lesions. DWI is useful in the detection of hepatocellular carcinoma in the cirrhotic liver and detection of liver metastases in oncological patients. In addition, DWI is a promising tool in the prediction of tumor responsiveness to chemotherapy and the follow-up of oncological patients after treatment, as DWI may be capable of detecting recurrent disease earlier than conventional imaging.This review focuses on the most common applications of DWI in the liver.

Diffusion weighted imaging for the detection and evaluation of cholesteatoma

Cholesteatoma is a collection of keratinous debris and stratified squamous epithelium.It is trapped in the middle ear and can lead to bony erosion.The disease is treated surgically often followed by a second-look procedure to check for residual tissue or recurrence.Cholesteatoma has specific signal-intensity characteristics on magnetic resonance imaging with very high signal intensity on diffusion weighted imaging(DWI).Various DWI techniques exist:Echo-planar imaging(EPI)-based and non-EPI-based techniques as well as new approaches like multi-shot EPI DWI.This article summarizes all techniques,discusses the significance in detecting cholesteatoma and mentions actual studies.Further recommendations for daily clinical practise are provided.

Susceptibility weighted imaging in the evaluation of hemorrhagic diffuse axonal injury

Diffuse axonal injury（DAI）is axonal and small vessel injury produced by a sudden acceleration of the head by an external force,and is a major cause of death and severe disability（Paterakis et al.,2000）.Prognosis is poorer in patients with apparent hemorrhage than in those without（Paterakis et al.,2000）.Therefore,it is important to identify the presence and precise position of hemorrhagic foci for a more accurate diagnosis.CT and magnetic resonance imaging（MRI）have long been applied in the diagnosis of DAI, but they are not sensitive enough for the detection of small hemorrhagic foci, and cannot meet the requirements for early diagnosis. A major advance in MRI has been the development of susceptibility weighted imaging （SWI）, which has greatly increased the ability to detect small hemorrhagic foci after DAI （Ashwal et al., 2006）.

1H magnetic resonance spectroscopy and diffusion weighted imaging findings of medulloblastoma in 3.0T MRI A retrospective analysis of 17 cases

1H magnetic resonance spectroscopy and diffusion weighted imaging features of the cerebellar vermis in 17 medulloblastoma patients were retrospectively analyzed, and 17 healthy volunteers were selected as controls. 1H magnetic resonance spectroscopy showed that in all 17 medulloblastoma patients, N-acetyl aspartate and creatine peaks were significantly decreased, the choline peak was significantly increased, and there was evidence of a myo-inositol peak. Further, 11 patients showed a low taurine peak at 3.4 ppm, five patients showed a lipid peak at 0.9-1.3 ppm, and three patients showed a negative lactic acid peak at 1.33 ppm. Compared with the control group, the ratios of N-acetyl aspartate/choline and N-acetyl aspartate/creatine were significantly decreased, and the ratio of choline/creatine was increased, in medulloblastoma patients. Diffusion weighted imaging displayed hyperintensity and decreased apparent diffusion coefficient in medulloblastoma patients. These findings indicate that 1H magnetic resonance spectroscopy and diffusion weighted imaging are useful for qualitative diagnosis of medulloblastoma.

Three-dimensional time-of-flight magnetic resonance angiography combined with high resolution T2-weighted imaging in preoperative evaluation of microvascular decompression

BACKGROUND Neurovascular compression(NVC) is the main cause of primary trigeminal neuralgia(TN) and hemifacial spasm(HFS). Microvascular decompression(MVD) is an effective surgical method for the treatment of TN and HFS caused by NVC. The judgement of NVC is a critical step in the preoperative evaluation of MVD, which is related to the effect of MVD treatment. Magnetic resonance imaging(MRI) technology has been used to detect NVC prior to MVD for several years. Among many MRI sequences, three-dimensional time-of-flight magnetic resonance angiography(3D TOF MRA) is the most widely used. However, 3D TOF MRA has some shortcomings in detecting NVC. Therefore, 3D TOF MRA combined with high resolution T2-weighted imaging(HR T2WI) is considered to be a more effective method to detect NVC.AIM To determine the value of 3D TOF MRA combined with HR T2WI in the judgment of NVC, and thus to assess its value in the preoperative evaluation of MVD.METHODS Related studies published from inception to September 2022 based on PubMed, Embase, Web of Science, and the Cochrane Library were retrieved. Studies that investigated 3D TOF MRA combined with HR T2WI to judge NVC in patients with TN or HFS were included according to the inclusion criteria. Studies without complete data or not relevant to the research topics were excluded. The Quality Assessment of Diagnostic Accuracy Studies checklist was used to assess the quality of included studies. The publication bias of the included literature was examined by Deeks’ test. An exact binomial rendition of the bivariate mixed-effects regression model was used to synthesize data. Data analysis was performed using the MIDAS module of statistical software Stata 16.0. Two independent investigators extracted patient and study characteristics, and discrepancies were resolved by consensus. Individual and pooled sensitivities and specificities were calculated. The I_(2) statistic and Q test were used to test heterogeneity. The study was registered on the website of PROSERO(registration No. CRD42022357158).RESULTS Our search identified 595 articles, of which 12(including 855 patients) fulfilled the inclusion criteria. Bivariate analysis showed that the pooled sensitivity and specificity of 3D TOF MRA combined with HR T2WI for detecting NVC were 0.96 [95% confidence interval(CI): 0.92-0.98] and 0.92(95%CI: 0.74-0.98), respectively. The pooled positive likelihood ratio was 12.4(95%CI: 3.2-47.8), pooled negative likelihood ratio was 0.04(95%CI: 0.02-0.09), and pooled diagnostic odds ratio was 283(95%CI: 50-1620). The area under the receiver operating characteristic curve was 0.98(95%CI: 0.97-0.99). The studies showed no substantial heterogeneity(I2 = 0, Q = 0.001 P = 0.50).CONCLUSION Our results suggest that 3D TOF MRA combined with HR T2WI has excellent sensitivity and specificity for judging NVC in patients with TN or HFS. This method can be used as an effective tool for preoperative evaluation of MVD.

The Clinical Application Value of Susceptibility Weighted Imaging in the Central Nervous System

Susceptibility weighted imaging(SWI)is a relatively new magnetic resonance imaging(MRI)technique that uses the difference in tissue magnetic susceptibility to image,and has unique value compared to traditional magnetic resonance imaging.This article summarizes its application in the central nervous system and provides a reference for imaging diagnosis and clinical treatment.

Value of MRI diffusion weighted imaging in localization of prostate cancer with whole-mount step section pathology

Objective To evaluate the value of MRI diffusion weighted imaging in localization of prostate cancer with whole-mount step section pathology. Methods We treated 36 patients using laparoscopic radical prostatectomy from Oct. 2009 to Jun. 2010. Patients who did not have an MRL /DWI examination or a surgical history of pros-

Magnetic resonance susceptibility weighted imaging in detecting intracranial calcification and hemorrhage

Background Computed tomography （CT） is better than routine magnetic resonance imaging （MRI） in detecting intracranial calcification. This study aimed to assess the value of MR susceptibility weighted imaging （SWI） in the detection and differentiation of intracranial calcification and hemorrhage. Methods Enrolled in this study were 35 patients including 13 cases of calcification demonstrated by CT and 22 cases of intracerebral hemorrhage. MR sequences used in all the subjects included axial T1WI, T2WI and SWI. The phase shift （PS） of calcification and hemorrhage on SWI was calculated and their signal features on corrected phase images were compared. The sensitivity of T1WI, T2WI and SWI in detecting intracranial calcification and hemorrhage was analyzed statistically. Results The detection rate of SWI for cranial calcification was 98.2%, significantly higher than that of T1WI and T2WI. It was not significantly different from that of CT （P 〉0.05）. There were 49 hemorrhagic lesions at different stages detected on SWI, 30 on T2WI and 18 on T1WI. The average PS of calcification and hemorrhage was ＋0.734±0.073 and -0.112±0.032 respectively （P 〈0.05）. The PS of calcification was positive and presented as a high signal or the mixed signal dominated by a high signal on the corrected phase images, whereas the PS of hemorrhage was negative and presented as a low signal or the mixed signal dominated by a low signal.Conclusions SWI can accurately demonstrate intracranial calcification, not dependant on CT. Being more sensitive than routine MRI in detecting micro-hemorrhage, SWI may play an important role in differentiating cerebral diseases associated with calcification or hemorrhage.

Diffusion weighted magnetic resonance imaging of liver: Principles, clinical applications and recent updates

Diffusion-weighted imaging(DWI), a functional imaging technique exploiting the Brownian motion of water molecules, is increasingly shown to have value in various oncological and non-oncological applications. Factors such as the ease of acquisition and ability to obtain functional information in the absence of intravenous contrast, especially in patients with abnormal renal function, have contributed to the growing interest in exploring clinical applications of DWI. In the liver, DWI demonstrates a gamut of clinical applications ranging from detecting focal liver lesions to monitoring response in patients undergoing serial follow-up after loco-regional and systemic therapies. DWI is also being applied in the evaluation of diffuse liver diseases such as non-alcoholic fatty liver disease, hepatic fibrosis and cirrhosis. In this review, we intend to review the basic principles, technique, current clinical applications and future trends of DW-MRI in the liver.

Differential diagnosis of metastasis from non-metastatic lymph nodes in cervical cancers： pilot study of diffusion weighted imaging with background suppression at 3T magnetic resonance

Background Diffusion weighted imaging with background suppression （DWIBS） is potentially useful in detecting metastatic lymph nodes. This study aimed to evaluate the efficacy of DWIBS at 3T magnetic resonance （MR） for diagnosing metastatic lymph nodes in cervical cancer.Methods This retrospective study included 25 patients with cervical cancer who underwent MR examination and were treated by hysterectomy and lymphadenectomy. The metastatic and non-metastatic lymph nodes were histologically proven by operation. Apparent diffusion coefficient （ADC） values, long-axis diameters, short-axis diameters, ratio of short- to long-axis diameters of all the identifiable lymph nodes were measured and compared.Results Twenty-five primary tumor lesions, 17 metastatic lymph nodes and 140 non-metastatic lymph nodes were pathologically confirmed in 25 cases with cervical cancer. The difference of ADC values between primary tumor lesions,metastatic and non-metastatic lymph nodes were statistically significant （F=7.93, P=0.001）. There was no statistically significant difference between primary tumor lesions of cervical cancer and metastatic lymph nodes （t=-0.75, P=-0.456）,and the difference between primary tumor lesions and non-metastatic lymph nodes was statistically significant （t =4.68, P〈0.001）. The ADC values, long-axis diameters, short-axis diameters, ratio of short- to long-axis diameters of metastatic and non-metastatic lymph nodes were （0.86±0.36）×10-3 mm2/s vs. （1.12±0.34）×10-3 mm2/s, （1.51±0.41） cm vs.（1.19±0.36） cm, （1.16±0.35） cm vs. （0.77±0.22） cm, 0.78±0.17 vs. 0.68±0.19 respectively, and statistically significant difference existed between two groups.Conclusions DWIBS at 3T MR has the distinct advantages in detecting pelvic lymph nodes of cervical cancer.Quantitative measurement of ADC values could reflect the degree of restriction of diffusion of metastatic and non-metastatic lymph nodes. The combination of size and ADC value would be useful in the accurate diagnosis of metastatic lymph nodes.

In vivo evaluation of renal function using diffusion weighted imaging and diffusion tensor imaging in type 2 diabetics with normoalbuminuria versus microalbuminuria

This work aims to estimate the value of diffusion weighted imaging （DWI） and diffusion tensor imaging （DTI） in detecting early-stage kidney injury in type 2 diabetic patients with normoalbuminuria （NAU） versus microalbuminuria （MAU） prospectively. A total of 30 T2DM patients with normal kidney function were recruited and assigned to the NAU group （n = 14） or MAU group （n = 16） according to 8 h overnight urinary albuminuria excretion rate （AER） results. A contemporary cohort of health check-up recipients were included as controls （n = 12）. DWI and DTI scans were performed on bilateral kidney using SE single-shot EPI, and apparent diffusion coefficient （ADC） and fractional anisotropy （FA） of the renal parenchyma was determined from ADC and FA maps of the three groups. ADC and FA values were compared among the three groups. According to DWI with a b value of 400 s/mm^2, the MAU and NAU groups showed significantly lowered mean ADC values compared with the healthy controls （P 〈 0.01）. The mean ADC in the MAU group [（2.22± 0.07） × 10^-3 mm^2/s] was slightly lower than that of the NAU group [（2.31 ± 0.22） × 10^- 3 mm^2/s], but this difference was not statistically significant （P 〉 0.05）. The FAvalue in the MAU group was higher than that in the control group （0.45 ± 0.07 vs. 0.3±0.03, P = 0.004） but did not differ from that in the NAU group （0.42 ± 0.03） （P 〉 0.05）. ADC and FA values may be more sensitive than urine AER in reflecting early-stage kidney injury and, hence, may facilitate earlier detection and quantitative evaluation of kidney injury in T2DM patients. Combined evaluation of ADC and FA values may provide a better quantitative approach for identifying diabetic nephropathy at early disease stages.

Role of diffusion-weighted imaging in early ankylosing spondylitis

Background With the advanced MRI techniques, pathologic features can be detected at an early stage and quantitatively evaluated, resulting in the advantages of early diagnosis and prompt treatment. This study aimed to determine the value of diffusion-weighted MR imaging （DWI） in detection of early ankylosing spondylitis （AS） and investigate the characteristic manifestations of AS on whole body DWl （WB-DWl）. Methods Twenty patients with the diagnosis of early AS, twenty patients with low back pain （LBP）, and twenty-five healthy volunteers were included in this study. The subchondral bone apparent diffusion coefficients （ADC） among these groups in the bilateral ilia and sacrum along the sacroiliac joints were compared. An independent sample t-test was utilized to analyze ADC value differences among groups. P-values less than 0.05 denoted statistical significance. The mean ADC values of focal DWl lesions in AS patients were also measured. Whole body diffusion-weighted imaging was performed in fifteen additional AS patients, and analyzed with MIP and MPR techniques in comparison to conventional MR images in order to evaluate the ability to detect AS lesions with whole body DWI. Results Mean ADC values in AS patients were （0.518±0.122）×10^-3 mm2/s in the ilium and （0.503＋0.168）x103 mm2/s in the sacrum. These were significantly greater than the values measured in the ilium and sacrum of LBP patients, （0.328±0.053）×10^-3 mm2/s in the ilium and （0.311±0.081）×10^-3 m2/s in the sacrum, and control group, （0.325±0.015）×10-3 mm2/s in the ilium and （0.318±0.011）×10^-3 mm2/s in the sacrum respectively. No statistically significant differences were found between LBP group and control group. The mean ADC value of focal DWI lesions in early AS patients was （0. 899±0.265）×10^-3 mm2/s, which was significantly higher than that of adjacent normal-appearance areas （（0.454±0.079）×10^-3 mm2/s）. WB-DWl detected abnormalities in the 15 additional AS patients both within the sacroiliac joints and at other sites mean ADC value of focal DWl lesions of this patient （1.220±0.299） ×10^-3 mm2/s in the ilium. corresponding to the clinical symptoms of the patients. The cohort was （1.286±0.311）×10^-3 mm2/s in the sacrum and Conclusions Subchondral marrow ADC values of subchondral marrows near the sacroiliac joints allow for the differentiation of patients with early AS from normal volunteers and LBP patients. Combined with post-processing techniques such as MIP and MPR, WB-DWl allows for the comprehensive assessment of AS patients, an evaluation potentially helpful in determining prognosis and following the therapeutic response.

Detection of siderotic nodules in the liver with susceptibility weighted imaging： correlations to serum ferritin, Child-Pugh grade and hyaluronic acid levels

Background Chronic liver disease causes aberrant formation of fibrous tissue that impedes normal liver function, ultimately resulting in liver cirrhosis. Iron uptake can occur within the hepatic parenchyma or within the various nodules that form in a cirrhotic liver, termed siderotic nodules （SN）. We aimed to investigate the diagnostic performance of susceptibility weighted imaging （SWI） for detection of SN in patients with liver cirrhosis, and to evaluate the potential of SN numbers for assessing the degree of hepatic iron deposition, liver function, and liver fibrosis stage. Methods Ninety-one patients with chronic liver cirrhosis, who underwent megnetic resonance imagine （MRI） scanning in our department between November 2010 and April 2011, were included in the study. A 3.0T MRI scanner was used to acquire T1WI, T2WI, T2＊WI, and SWI images. The number of nodules, signal intensity ratio （SIR）, and contrast noise ratio （CNR） were recorded and analyzed by chi-square and ANOVA statistical tests. Correlation analysis was performed to evaluate the correlations between the number of SN and Child-Pugh classification, ferritin and hyaluronic acid levels. Results The sensitivity of SWI, T1WI, T2WI, and T2＊WI for detecting SN was 62.5%, 12.1%, 24.2% and 41.8%, respectively. SWI detected significantly more nodules than routine T1WI, T2WI, and T2＊WI procedures （P 〈0.05）. The SIR was the lowest in SWI （0.361±0.209）, as compared to T1WI （0.852±0.163）, T2WI （0.584±0.172）, and T2＊WI （0.497±0.196）. The CNR was the highest in SWI （13.932±5.637）, as compared to T1WI （9.147±5.785）, T2WI （9.771±5.490）, and T2＊WI （11.491±4.573）. The correlation coefficients of the number of SN with ferritin, Child-Pugh classification, and hyaluronic acid levels were 0.672, -0.055, and 0.163, respectively. Conclusions The sensitivity and contrast of SWI for detecting SN in patients with liver cirrhosis are higher than conventional MRI. The number of SN can help to assess the degree of iron deposition in patients with liver cirrhosis.

Diffusion-weighted magnetic resonance imaging reflects activation of signal transducer and activator of transcription 3 during focal cerebral ischemia/reperfusion

Signal transducer and activator of transcription（STAT）is a unique protein family that binds to DNA,coupled with tyrosine phosphorylation signaling pathways,acting as a transcriptional regulator to mediate a variety of biological effects.Cerebral ischemia and reperfusion can activate STATs signaling pathway,but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging（DWI）in rats after cerebral ischemia/reperfusion.Here,we established a rat model of focal cerebral ischemia injury using the modified Longa method.DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient.STAT3 protein expression showed no significant change after reperfusion,but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours.Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area.These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.

Application Progress of Intravoxel Incoherent Motion Diffusion Weighted Magnetic Resonance Imaging in Pancreatic Cancer

Intravoxel incoherent motion imaging (IVIM), on the traditional diffusion weighted imaging (DWI) technology, uses the biexponential model and adopts the multi-b-value analysis to obtain the perfusion information of water molecule diffusion and microcirculation without the use of contrast agent. It is more and more used in pancreatic diseases, which is of great significance for the diagnosis and identification of pancreatic cancer. This article will review the principles of IVIM imaging and its application in pancreatic diseases, especially in pancreatic cancer diagnosis, the prediction of pathological grade of pancreatic ductal adenocarcinoma, the judgment of lymph node metastasis, and differentiation of pathological classification.

Monoexponential, biexponential and stretched-exponential models based diffusion weighted imaging: a comparative study in the differential diagnosis of benign and malignant breast lesions

Objective To investgate the value of various parameters obtained from monoexponential,biexponential,and stretched exponential diffusion-weighted imaging models in the differential diagnosis of breast lesions.Methods A retrospective study was performed in 54 patients with pathologically confirmed malignant tumors(n=30),benign lesions(n=34)and normal fibroglandular

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

Complementary comments on diagnosis,severity and prognosis prediction of acute pancreatitis

The radiological differential diagnosis of acute pancreatitis includes diffuse pancreatic lymphoma,diffuse autoimmune pancreatitis and groove located mass lesions that may mimic groove pancreatitis.Dual energy computed tomography and diffusion weighted magnetic resonance imaging are useful in the early diagnosis of acute pancreatitis,and dual energy computed tomography is also useful in severity assessment and prognosis prediction.Walled off necrosis is an important complication in terms of prognosis,and it is important to know its radiological findings and distinguish it from pseudocyst.

Feasibility of establishing cerebral ischemia models by using aerocyst-blocking bilateral ascending pharyngeal artery of piglets Imaging assessment

BACKGROUND： The cerebral ischemia and ischemia/reperfusion animal models are used to simulate the human cerebrovascular diseases is one of the popular topics of neurological science recently. To study the pathophysiology, pathogenesis, prophylaxis and treatment of ischemic cerebrovascular diseases and to establish the ideal animal model that is the most similar to the human cerebral ischemia, are the topics that the people generally cared about. OBJECTIVE： To evaluate the effects of aerocyst-blocking bilateral ascending pharyngeal artery on the establishment of cerebral ischemia models by using digital subtraction angiography （DSA）, magnetic resonance diffusion-weighted imaging （DWI） and magnetic resonance perfusion-weighted imaging （PWI）. DESIGN： Repetitive measure animal experiment. SETTING： Zhongshan Hospital Affiliated to Dalian University. MATERIALS： The experiment was carried out in the Animal Laboratory （Provincial Laboratory）, Zhongshan Hospital of Dalian Univeristy from January to May 2006. A total of 14 domestic piglets, of 6 months old, weighing 12-15 kg, of either gender, were selected from Animal Experimental Center, Dalian University. Multistar T.O.P digital subtraction angiography machine was provided by Siemens Company, German. METHODS： Aerocyst-blocking bilateral ascending pharyngeal artery was used to establish cerebral ischemia models. And then, Multistar T.O.P. DSA was used for imaging of cerebral vessels before blocking, during blocking and at 0.5 and 2 hours after ischemia perfusion. GE Signa 1.5 T supraconduction magnetic resonance imaging was used for DWI examination; in addition, PWI was used based on focal sites and areas. Otherwise, magnetic resonance imaging （MRI） was used to detect signal changes of T1WI and T2WI in ischemic areas. MAIN OUTCOME MEASURES： Analytic results of DSA, DWI, PWI and MRI. RESULTS： All 14 experimental piglets were involved in the final analysis. ① DSA： The blood flow of bilateral ascending pharyngeal arteries and its branch were blocked at blocking phase, which restored 0.5 and 2 hours after reperfusion. ② DWI and PWI： There were no observable abnormalities in PWI and DWI at pre-blocking. Abnormal increased signals were found on both DWI and PWI at during and post-blocking. There were reduction in ADC and rCBF and delay in rTTP at all time points except pre-blocking. ③ MRI： There were no abnormal signals observable at any time of pre- and post-blocking in T1WI and T2WI. CONCLUSION： It is feasible to establish this kind of animal experimental models, and it can simulate the ischemic state; meanwhile, the existence and extent can be showed directly by DSA, DWI, and PWI.

Diffuse axonal injury after traumatic cerebral microbleeds: an evaluation of imaging techniques

Previous neuropathological studies regarding traumatic brain injury have primarily focused on changes in large structures, for example, the clinical prognosis after cerebral contusion, intrace- rebral hematoma, and epidural and subdural hematoma. In fact, many smaller injuries can also lead to severe neurological disorders. For example, cerebral microbleeds result in the dysfunc- tion of adjacent neurons and the disassociation between cortex and subcortical structures. These tiny changes cannot be adequately visualized on CT or conventional MRI. In contrast, gradient echo sequence-based susceptibility-weighted imaging is very sensitive to blood metabolites and microbleeds, and can be used to evaluate traumatic cerebral microbleeds with high sensitivity and accuracy. Cerebral microbleed can be considered as an important imaging marker for dif- fuse axonal injury with potential relevance for prognosis. For this reason, based on experimental and clinical studies, this study reviews the role of imaging data showing traumatic cerebral microbleeds in the evaluation of cerebral neuronal injury and neurofunctional loss.