Staging liver fibrosis with various diffusion-weighted magnetic resonance imaging models

BACKGROUND Diffusion-weighted imaging(DWI)has been developed to stage liver fibrosis.However,its diagnostic performance is inconsistent among studies.Therefore,it is worth studying the diagnostic value of various diffusion models for liver fibrosis in one cohort.AIM To evaluate the clinical potential of six diffusion-weighted models in liver fibrosis staging and compare their diagnostic performances.METHODS This prospective study enrolled 59 patients suspected of liver disease and scheduled for liver biopsy and 17 healthy participants.All participants underwent multi-b value DWI.The main DWI-derived parameters included Mono-apparent diffusion coefficient(ADC)from mono-exponential DWI,intravoxel incoherent motion model-derived true diffusion coefficient(IVIM-D),diffusion kurtosis imaging-derived apparent diffusivity(DKI-MD),stretched exponential model-derived distributed diffusion coefficient(SEM-DDC),fractional order calculus(FROC)model-derived diffusion coefficient(FROC-D)and FROC model-derived microstructural quantity(FROC-μ),and continuous-time random-walk(CTRW)model-derived anomalous diffusion coefficient(CTRW-D)and CTRW model-derived temporal diffusion heterogeneity index(CTRW-α).The correlations between DWI-derived parameters and fibrosis stages and the parameters’diagnostic efficacy in detecting significant fibrosis(SF)were assessed and compared.RESULTS CTRW-D(r=-0.356),CTRW-α(r=-0.297),DKI-MD(r=-0.297),FROC-D(r=-0.350),FROC-μ(r=-0.321),IVIM-D(r=-0.251),Mono-ADC(r=-0.362),and SEM-DDC(r=-0.263)were significantly correlated with fibrosis stages.The areas under the ROC curves(AUCs)of the combined index of the six models for distinguishing SF(0.697-0.747)were higher than each of the parameters alone(0.524-0.719).The DWI models’ability to detect SF was similar.The combined index of CTRW model parameters had the highest AUC(0.747).CONCLUSION The DWI models were similarly valuable in distinguishing SF in patients with liver disease.The combined index of CTRW parameters had the highest AUC.

Deep learning-based magnetic resonance imaging reconstruction for improving the image quality of reduced-field-of-view diffusionweighted imaging of the pancreas

BACKGROUND It has been reported that deep learning-based reconstruction(DLR)can reduce image noise and artifacts,thereby improving the signal-to-noise ratio and image sharpness.However,no previous studies have evaluated the efficacy of DLR in improving image quality in reduced-field-of-view(reduced-FOV)diffusionweighted imaging(DWI)[field-of-view optimized and constrained undistorted single-shot(FOCUS)]of the pancreas.We hypothesized that a combination of these techniques would improve DWI image quality without prolonging the scan time but would influence the apparent diffusion coefficient calculation.AIM To evaluate the efficacy of DLR for image quality improvement of FOCUS of the pancreas.METHODS This was a retrospective study evaluated 37 patients with pancreatic cystic lesions who underwent magnetic resonance imaging between August 2021 and October 2021.We evaluated three types of FOCUS examinations:FOCUS with DLR(FOCUS-DLR+),FOCUS without DLR(FOCUS-DLR−),and conventional FOCUS(FOCUS-conv).The three types of FOCUS and their apparent diffusion coefficient(ADC)maps were compared qualitatively and quantitatively.RESULTS FOCUS-DLR+(3.62,average score of two radiologists)showed significantly better qualitative scores for image noise than FOCUS-DLR−(2.62)and FOCUS-conv(2.88)(P<0.05).Furthermore,FOCUS-DLR+showed the highest contrast ratio and 600 s/mm^(2)(0.72±0.08 and 0.68±0.08)and FOCUS-DLR−showed the highest CR between cystic lesions and the pancreatic parenchyma for the b-values of 0 and 600 s/mm2(0.62±0.21 and 0.62±0.21)(P<0.05),respectively.FOCUS-DLR+provided significantly higher ADCs of the pancreas and lesion(1.44±0.24 and 3.00±0.66)compared to FOCUS-DLR−(1.39±0.22 and 2.86±0.61)and significantly lower ADCs compared to FOCUS-conv(1.84±0.45 and 3.32±0.70)(P<0.05),respectively.CONCLUSION This study evaluated the efficacy of DLR for image quality improvement in reduced-FOV DWI of the pancreas.DLR can significantly denoise images without prolonging the scan time or decreasing the spatial resolution.The denoising level of DWI can be controlled to make the images appear more natural to the human eye.However,this study revealed that DLR did not ameliorate pancreatic distortion.Additionally,physicians should pay attention to the interpretation of ADCs after DLR application because ADCs are significantly changed by DLR.

Evaluation of diffusion weighted imaging of magnetic resonance imaging in small focal hepatic lesions:a quantitative study in 56 cases

Diffusion-weighted imaging (DWI) as a new technique of magnetic resonance imaging (MRI) is used to detect focal hepatic lesions. This study was designed to evaluate the significance of DWI to differentiate focal hepatic lesions less than 3 cm in diameter by the quantitation of apparent diffusion coefficient (ADC) values. METHODS:DWI using 1.5T MRI scanner unit was performed with a spin-echo single-shot echo planar imaging (EPI) in 56 cases of small focal hepatic lesions, including hepatocellular carcinoma (11), hepatic metastatic tumor (15 ), hepatic cavernous hemangioma (14), and hepatic cyst (16).The ADC values of these lesions were calculated respectively. The ratios of the ADC values of lesion/liver in hepatocellular carcinomas and hepatic metastatic tumors were also estimated. RESULTS:The mean ADC values (mm2/s) were (0.93±0.06) ×10-3 in hepatocellular carcinomas, (1.09±0.18)×10-3 in hepatic metastatic tumors,(1.95±0.38)×10-3 in hepatic cavernous hemangiomas, and (3.18±0.33) ×10-3 in hepatic cysts. The ratios of ADC values of lesion/liver were 0.90±0.06 and 1.15±0.14 in hepatocellular carcinoma and hepatic metastatic tumors respectively, which were significantly different (P<0.05). CONCLUSION:The measurement of ADC values and the ratios of ADC values of lesion/liver are helpful in MR diagnosis and differentiation of focal hepatic lesions.

Apparent diffusion coefficient by diffusion-weighted magnetic resonance imaging as a sole biomarker for staging and prognosis of gastric cancer

Objective： To investigate the role of apparent diffusion coefficient （ADC） from diffusion-weighted magnetic resonance imaging （DW-MRI） when applied to the 7th TNM classification in the staging and prognosis of gastric cancer （GC）. Methods： Between October 2009 and May 2014, a total of 89 patients with non-metastatic, biopsy proven GC underwent 1.5T DW-MRI, and then treated with radical surgery. Tumor ADC was measured retrospectively and compared with final histology following the 7th TNM staging （local invasion, nodal involvement and according to the different groups -- stage Ⅰ, Ⅱ and Ⅲ）. Kaplan-Meier curves were also generated. The follow-up period is updated to May 2016. Results： Median follow-up period was 33 months and 45/89 （51%） deaths from GC were observed. ADC was significantly different both for local invasion and nodal involvement （P〈0.001）. Considering final histology as the reference standard, a preoperative ADC cut-offof 1.80×10-3 mm^2/s could distinguish between stages I and Ⅱ and an ADC value of ≤1.36-10-3 mm^2/s was associated with stage Ⅲ（P〈0.001）. Kaplan-Meier curves demonstrated that the survival rates for the three prognostic groups were significantly different according to final histology and ADC cut-offs （P〈0.001）. Conclusions： ADC is different according to local invasion, nodal involvement and the 7th TNM stage groups for GC, representing a potential, additional prognostic biomarker. The addition of DW-MRI could aid in the staging and risk stratification of GC.

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.

Feasibility of 3.0 T diffusion-weighted nuclear magnetic resonance imaging in the evaluation of functional recovery of rats with complete spinal cord injury

Diffusion tensor imaging is a sensitive way to reflect axonal necrosis and degeneration, glial cell regeneration and demyelination following spinal cord injury, and to display microstructure changes in the spinal cord in vivo. Diffusion tensor imaging technology is a sensitive method to diagnose spinal cord injury; fiber tractography visualizes the white matter fibers, and directly displays the structural integrity and resultant damage of the fiber bundle. At present, diffusion tensor imaging is restricted to brain examinations, and is rarely applied in the evaluation of spinal cord injury. This study aimed to explore the fractional anisotropy and apparent diffusion coefficient of diffusion tensor magnetic resonance imaging and the feasibility of diffusion tensor tractography in the evaluation of complete spinal cord injury in rats. The results showed that the average combined scores were obviously decreased after spinal cord transection in rats, and then began to increase over time. The fractional anisotropy scores after spinal cord transection in rats were significantly lower than those in normal rats （P 〈 0.05）; the apparent diffusion coefficient was significantly increased compared with the normal group （P 〈 0.05）. Following spinal cord transection, fractional anisotropy scores were negatively correlated with apparent diffusion coefficient values （r = -0.856, P 〈 0.01）, and positively correlated with the average combined scores （r = 0.943, P 〈 0.01）, while apparent diffusion coefficient values had a negative correlation with the average combined scores （r = -0.949, P 〈 0.01）. Experimental findings suggest that, as a non-invasive examination, diffusion tensor magnetic resonance imaging can provide qualita- tive and quantitative information about spinal cord injury. The fractional anisotropy score and apparent diffusion coefficient have a good correlation with the average combined scores, which reflect functional recovery after spinal cord injury.

Diagnostic Power of Diffusion-weighted Magnetic Resonance Imaging for the Presence of Lymph Node Metastasis:A Meta-analysis

Present work was designed to quantitatively evaluate the performance of diffusion-weighted magnetic resonance imaging（DWI） in the diagnosis of the presence of metastasis in lymph nodes（LNs）. Eligible studies were identified from systematical Pub Med and EMBASE searches. Data were extracted. Meta-analyses were performed to generate pooled sensitivity and specificity on the basis of per-node, per-lesion and per-patient, respectively. Fourteen publications（2458 LNs, 404 lesions and 334 patients） were eligible. Per-node basis demonstrated the pooled sensitivity and specificity was 0.82（P〈0.0001） and 0.90（P〈0.0001）, respectively. Per-lesion basis illustrated the pooled sensitivity and specificity was 0.73（P=0.0036） and 0.85（P〈0.0001）, respectively. Per-patient basis indicated the pooled sensitivity and specificity was 0.67（P=0.0909） and 0.86（P〈0.0001）, respectively. In conclusion, DWI has rather a negative predictive value for the diagnosis of LN metastasis presence. The difference of the mean apparent diffusion coefficients between benign and malignant LNs is not yet stable. Therefore, the DWI technique has to be further improved.

Is combined functional magnetic resonance imaging and diffusion tensor tractography a useful tool for evaluation of somatosensory dysfunction recovery after intracerebral hemorrhage?

Diffusion tensor tractography allows the sensory fiber course of the medial lemniscus to be visualized. But diffusion tensor tractography for accurate evaluation of the repair of injured somatosensory tracts in stroke patients has been rarely reported. A 55-year-old female patient presented with severe somatosensory dysfunction of the left side caused by a spontaneous intracerebral hemorrhage on the right side. The somatosensory function of the affected side recovered to a nearly normal state at 7 weeks from onset. Functional magnetic resonance imaging revealed that at 3 weeks from onset, there was no cortical activation by touch at each hand; at 7 weeks, the contralateral cortex centered on the primary sensory cortex was found to be activated during touch and passive movements, and activation by passive movements was increased compared with that at 3 weeks. Diffusion tensor tractography revealed that a medial lemniscus on the affected （right） hemisphere was not observed at 3 weeks from onset, however, at 7 weeks, the unaffected （left） hemisphere passed along the medial lemniscus pathway from the pons to the primary sensory cortex. These findings indicate that combined functional magnetic resonance imaging and diffusion tensor tractography would allow more accurate evaluation of the architecture and integrity of somatosensory tracts and is a useful method to investigate the recovery of somatosensory dysfunction in stroke patients.

Changes in brain function and anatomical structure following treatment of hyperbaric oxygen for visual pathway abnormalities in 16 cases Evaluation of functional magnetic resonance imaging combined with diffusion tensor imaging

BACKGROUND： There is a growing research focus on the combination of blood oxygenation level dependent functional magnetic resonance imaging （BOLD-fMRI） and diffusion tensor imaging （DTI） to evaluate visual cortical function and structural changes in the cerebrum, as well as morphological changes to the white matter fiber tracks, after visual pathway lesions. However, the combined application of BOLD-fMRI and DTI in treating of visual pathway abnormalities still requires further studies. OBJECTIVE： To observe and evaluate the effects of hyperbaric oxygen on visual pathway abnormalities, and to evaluate the characteristics of cerebral function and anatomic structural changes by using BOLD-fMRI combined with DTI technique. DESIGN： Case contrast observation. SETTING： Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA. PARTICIPANTS： Sixteen patients （9 males and 7 females, 15-77 years old） with lateral or bilateral visual disorder induced by visual pathway lesions were selected from the Department of Neurology, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA from January 2006 to May 2007. These patients comprised the lesion group. Measures of interventional therapy： hyperbaric oxygen of two normal atmospheres for three courses （10 d/course） and routine internal medicine treatment. In addition, 12 healthy subjects of similar sex and age to the lesion group were regarded as the control group. The control group underwent routine ophthalmological and ocular fundus examinations; diagnostic results were normal. The experiment received confirmed consent from the local ethic committee, and all patients provided informed consent. METHODS： BOLD-fMRI and DTI manifestations in the lesion group were observed before and after hyperbaric oxygen intervention, and the results were compared with the control group. The subjects were positioned on their back, and BOLD-fMRI images were collected with the following GRE EPI sequence： TR = 2 000 ms, TE = 40 ms, layer thickness = 5 mm, and 20-layer successive scanning to cover the whole brain. While, DTI images were collected with SE EPI sequence of single excitation： TR=10 000 ms, TE = 112 ms, layer thickness = 4 mm, layer spacing = 0.5 mm, and a 30-layer successive scanning, matrix = 128×128. A diffusion gradient was applied at 13 directions, and one layer without diffusion weighted imaging was collected at b =1 000 s/mm^2. Numbers of activated voxels in cortical-activated regions, and fractional anisotropy in bilateral cerebral optical radiation regions, were calculated. Displacement, continuity, and destruction of fibrous tracts were analyzed. MAIN OUTCOME MEASURES： Results of BOLD-fMRI and DTI examinations. RESULTS： All 16 patients and 12 controls were included in the final analysis. ① Numbers of activated voxels through the use of BOLD-fMRI： prior to hyperbaric oxygen therapy, the number of activated voxels in the bilateral cortex of occipital lobe were significantly less in the lesion group than in the control group （t =3.23, P 〈 0.01）. In addition, the number of activated voxels significantly increased after treatment compared to before treatment （t = 2.46, P 〈 0.05）. ② Fractional anisotropy in optical radiation regions of bilateral cerebrum： fractional anisotropy in the lesion group was significantly less than the control group （t =2.89, P 〈 0.05）. In addition, fractional anisotropy after treatment was significantly higher than before treatment （t = 2.48, P 〈 0.05）. Moreover, fractional anisotropy of optical neuropathy was significantly higher in 6 patients in the lesion group than the occipital lobe optical central lesion （t = 2.35, P 〈 0.05）. CONCLUSION： BOLD-fMRI combined with DTI can indicate the occurrence, development, and therapeutic course of action for optical pathway lesions. The results acquired from these methods can provide information for function and structure, which can provide reliable verification in the treatment of cerebral function.

Dynamic contrast-enhanced magnetic resonance imaging and diffusion-weighted imaging in the activity staging of terminal ileum Crohn's disease

BACKGROUND The activity staging of Crohn’s disease(CD)in the terminal ileum is critical in developing an accurate clinical treatment plan.The activity of terminal ileum CD is associated with the microcirculation of involved bowel walls.Dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI)and diffusionweighted imaging(DWI)can reflect perfusion and permeability of bowel walls by providing microcirculation information.As such,we hypothesize that DCE-MRI and DWI parameters can assess terminal ileum CD,thereby providing an opportunity to stage CD activity.AIM To evaluate the value of DCE-MRI and DWI in assessing activity of terminal ileum CD.METHODS Forty-eight patients with CD who underwent DCE-MRI and DWI were enrolled.The patients’activity was graded as remission,mild and moderate-severe.The transfer constant(Ktrans),wash-out constant(Kep),and extravascular extracellular volume fraction(Ve)were calculated from DCE-MRI and the apparent diffusion coefficient(ADC)was obtained from DWI.Magnetic Resonance Index of Activity(MaRIA)was calculated from magnetic resonance enterography.Differences in these quantitative parameters were compared between normal ileal loop(NIL)and inflamed terminal ileum(ITI)and among different activity grades.The correlations between these parameters,MaRIA,the Crohn’s Disease Activity Index(CDAI),and Crohn’s Disease Endoscopic Index of Severity(CDEIS)were examined.Receiver operating characteristic curve analyses were used to determine the diagnostic performance of these parameters in differentiating between CD activity levels.RESULTS Higher Ktrans(0.07±0.04 vs 0.01±0.01),Kep(0.24±0.11 vs 0.15±0.05)and Ve(0.27±0.07 vs 0.08±0.03),but lower ADC(1.41±0.26 vs 2.41±0.30)values were found in ITI than in NIL(all P<0.001).The Ktrans,Kep,Ve and MaRIA increased with disease activity,whereas the ADC decreased(all P<0.001).The Ktrans,Kep,Ve and MaRIA showed positive correlations with the CDAI(r=0.866 for Ktrans,0.870 for Kep,0.858 for Ve,0.890 for MaRIA,all P<0.001)and CDEIS(r=0.563 for Ktrans,0.567 for Kep,0.571 for Ve,0.842 for MaRIA,all P<0.001),while the ADC showed negative correlations with the CDAI(r=-0.857,P<0.001)and CDEIS(r=-0.536,P<0.001).The areas under the curve(AUC)for the Ktrans,Kep,Ve,ADC and MaRIA values ranged from 0.68 to 0.91 for differentiating inactive CD(CD remission)from active CD(mild to severe CD).The AUC when combining the Ktrans,Kep and Ve was 0.80,while combining DCE-MRI parameters and ADC values yielded the highest AUC of 0.95.CONCLUSION DCE-MRI and DWI parameters all serve as measures to stage CD activity.When they are combined,the assessment performance is improved and better than MaRIA.

Functional magnetic resonance imaging and diffusion tensor tractography of the corticopontocerebellar tract in the human brain

The anatomical organization of the corticopontocerebellar tract （CPCT） in the human brain remains poorly understood. The present study investigated probabilistic tractography of the CPCT in the human brain using diffusion tensor tractography with functional magnetic resonance imaging. CPCT data was obtained from 14 healthy subjects. CPCT images were obtained from functional magnetic resonance imaging and diffusion tensor tractography, revealing that the CPCT originated from the primary sensorimotor cortex and descended to the pontine nucleus through the corona radiata, the posterior limb of the internal capsule, and the cerebral peduncle. After crossing the pons through the transverse pontine fibers, the CPCT entered the cerebellum via the middle cerebral peduncle. However, some variation was detected in the midbrain （middle cerebral peduncle and/or medial lemniscus） and pons （ventral and/or dorsal transverse pontine fibers）. The CPCT was analyzed in 3 dimensions from the cerebral cortex to the cerebellum. These results could be informative for future studies of motor control in the human brain.

Correlation of magnetic resonance imaging quantitative parameters and apparent diffusion coefficient value with pathological breast cancer

BACKGROUND China ranks 120th worldwide for the incidence of breast cancer and 163rd for mortality.Early screening,diagnosis,and timely determination of the optimal treatment plan can help ensure clinical efficacy and prognosis.AIM To investigate the relationship between quantitative magnetic resonance imaging parameters,apparent diffusion coefficient value,pathological immunohistochemical status,and patient prognosis.METHODS A total of 108 patients with breast cancer(breast cancer group)and 110 patients with benign breast tumors(benign group)confirmed by pathological examination at our Hospital from September 2013 to August 2016 were selected.All patients had undergone preoperative magnetic resonance imaging(MRI)examinations,and the quantitative parameters of MRI and apparent diffusion coefficient(ADC)values for the two groups were compared.The MRI quantitative parameters and ADC values of patients with different estrogen receptor(ER),progesterone receptor,and human epidermal growth factor receptor-2 expression were statistically analyzed.The relationship between the quantitative parameters of MRI and ADC values and patient recurrence was analyzed using receiver operating curves.RESULTS The measured values of the quantitative parameters of MRI-Ktrans,Kep,and Ve in the breast cancer group were higher than those in the benign group;the ADC value in the breast cancer group was lower than that in the benign group,and the difference was statistically significant(P<0.05).The Ktrans,Ve,and ADC values in patients with ER-positive breast cancer were significantly lower than those in patients with negative ER expression(P<0.05).After 5 years of follow-up,22 patients with breast cancer experienced postoperative recurrence.The Kep,Ve,and ADC values of the recurrence group were significantly lower than those of the non-recurrence group,and the difference was statistically significant(P<0.05).CONCLUSION MRI quantitative parameters and ADC are related to the expression of breast cancer-related immunological receptor factors and have certain clinical value in assessing postoperative recurrence in patients.

Quantitative volumetric analysis of the optic radiation in the normal human brain using diffusion tensor magnetic resonance imaging-based tractography

To attain the volumetric information of the optic radiation in normal human brains, we per- formed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are help- ful in the study of optic radiation fiber tract information.

Longitudial observation of dynamic changes in cortical function and white matter fibrous structure of patients with visual pathway lesions by blood oxygenation level dependent-functional magnetic resonance imaging combined with diffusion tensor imaging

BACKGROUND： Functional magnetic resonance imaging （fMRI） is initially used for visual cortex location. However, the application of fMRI in investigating the development of visual pathway lesions needs to be further observed. OBJECTIVE： This study is to longitudially observe the dynamic changes in cortical function and white matter fibrous structure of patients with visual pathway lesions by blood oxygenation level dependent-functional magnetic resonance imaging （BOLD-fMRI） combined with diffusion tensor imaging （DTI）, and to analyze the characteristics of brain function and structural recombination at convalescent period of lesions. DESIGN： Randomized controlled observation. SETTING： Department of Radiology, the General Hospital of Nanjing Military Area Command of Chinese PLA. PARTICIPANTS： Eight patients with unilateral or bilateral visual disorder caused by visual pathway lesions, who admitted to Department of Radiology, the General Hospital of Nanjing Military Area Command of Chinese PLA from January to September 2006 were involved, and served as experimental subjects. The patients, 6 males and 2 females, were aged 16 - 67 years. They had visual disorder confirmed by clinical examination, i.e. visual pathway lesion, which was further diagnosed by MR or CT. Another 12 subjects generally matching to those patients of experimental group in gender, age and sight, who received health examination in synchronization were involved and served as controls. The subjects had no history of eye diseases. Their binocular visual acuity （or corrected visual acuity） was over 1.0. Both routine examination of ophthalmology and examination of fundus were normal. Informed consents of detected items were obtained from all the subjects. METHODS： Signa Excite HD 1.5T magnetic resonance imaging system with 16 passages （GE Company, USA） and coil with 8 passages were used; brain functional stimulus apparatus （SAV-8800. Meide Company） was used for showing experimental mission. At the early stage and convalescent period of lesions, the patients with visual pathway lesion were examined by BOLD-fMRI combined with DTI, respectively, and brain activation volume, optic radiation anatomical structure and fractional anisotropy （FA） value were compared before and after symptomatic treatment under the stimulation to both eyes. The above-mentioned indexes were observed and compared between experimental and control groups. MAIN OUTCOME MEASURES： BOLD-fMRI and DTI manifestations before and after treatment in the experimental group and control group. RESULTS： All the 8 patients and 12 healthy subjects participated in the final analysis. ①BOLD-fMRI manifestation： Bilateral occipital lobes and calcarine gyri of control subjects were obviously activated. The activation volume of striate cortex under the stimulation to two eyes was obviously reduced in the experimental subjects than in the control subjects （P 〈 0.05）. After treatment, the amount of activated pixel in the stimulated cortex was increased, and the activation area was expanded. ②DTI results： Bilateral optic radiation of healthy controls could be traced in the subcortex. Complete optic radiation of patients with visual pathway lesion could be shown. There was no significant difference in optic radiation between experimental subjects and healthy controls. No significant difference in optic radiation was found

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.

Magnetic resonance imaging of extraocular rectus muscles abnormalities in acute acquired concomitant esotropia

AIM:To investigate the difference of medial rectus(MR)and lateral rectus(LR)between acute acquired concomitant esotropia(AACE)and the healthy controls(HCs)detected by magnetic resonance imaging(MRI).METHODS:A case-control study.Eighteen subjects with AACE and eighteen HCs were enrolled.MRI scanning data were conducted in target-controlled central gaze with a 3-Tesla magnetic resonance scanner.Extraocular muscles(EOMs)were scanned in contiguous image planes 2-mm thick spanning the EOM origins to the globe equator.To form posterior partial volumes(PPVs),the LR and MR cross-sections in the image planes 8,10,12,and 14 mm posterior to the globe were summed and multiplied by the 2-mm slice thickness.The data were classified according to the right eye,left eye,dominant eye,and non-dominant eye,and the differences in mean cross-sectional area,maximum cross-sectional area,and PPVs of the MR and LR muscle in the AACE group and HCs group were compared under the above classifications respectively.RESULTS:There were no significant differences between the two groups of demographic characteristics.The mean cross-sectional area of the LR muscle was significantly greater in the AACE group than that in the HCs group in the non-dominant eyes(P=0.028).The maximum cross-sectional area of the LR muscle both in the dominant and non-dominant eye of the AACE group was significantly greater than the HCs group(P=0.009,P=0.016).For the dominant eye,the PPVs of the LR muscle were significantly greater in the AACE than that in the HCs group(P=0.013),but not in the MR muscle(P=0.698).CONCLUSION:The size and volume of muscles dominant eyes of AACE subjects change significantly to overcome binocular diplopia.The LR muscle become larger to compensate for the enhanced convergence in the AACE.

Various diffusion magnetic resonance imaging techniques for pancreatic cancer

Pancreatic cancer is one of the most common malignanttumors and remains a treatment-refractory cancer with a poor prognosis. Currently, the diagnosis of pancreatic neoplasm depends mainly on imaging and which methods are conducive to detecting small lesions. Compared to the other techniques, magnetic resonance imaging(MRI) has irreplaceable advantages and can provide valuable information unattainable with other noninvasive or minimally invasive imaging techniques. Advances in MR hardware and pulse sequence design have particularly improved the quality and robustness of MRI of the pancreas. Diffusion MR imaging serves as one of the common functional MRI techniques and is the only technique that can be used to reflect the diffusion movement of water molecules in vivo. It is generally known that diffusion properties depend on the characterization of intrinsic features of tissue microdynamics and microstructure. With the improvement of the diffusion models, diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique to the more complex. In this review, the various diffusion MRI techniques for pancreatic cancer are discussed, including conventional diffusion weighted imaging(DWI), multi-b DWI based on intra-voxel incoherent motion theory, diffusion tensor imaging and diffusion kurtosis imaging. The principles, main parameters, advantages and limitations of these techniques, as well as future directions for pancreatic diffusion imaging are also discussed.

Diffusion-weighted magnetic resonance imaging in cancer: Reported apparent diffusion coefficients,in-vitro and invivo reproducibility

There is considerable disparity in the published apparent diffusion coefficient(ADC) values across different anatomies. Institutions are increasingly assessing repeatability and reproducibility of the derived ADC to determine its variation,which could potentially be used as an indicator in determining tumour aggressiveness or assessing tumour response. In this manuscript,a review of selected articles published to date in healthy extracranial body diffusion-weighted magnetic resonance imaging is presented,detailing reported ADC values and discussing their variation across different studies. In total 115 studies were selected including 28 for liver parenchyma,15 for kidney(renal parenchyma),14 for spleen,13 for pancreatic body,6 for gallbladder,13 for prostate,13 for uterus(endometrium,myometrium,cervix) and 13 for fibroglandular breast tissue. Median ADC values in selected studies were found to be 1.28 × 10-3 mm2/s in liver,1.94 × 10-3 mm2/s in kidney,1.60 × 10-3 mm2/s in pancreatic body,0.85 × 10-3 mm2/s in spleen,2.73 × 10-3 mm2/s in gallbladder,1.64 × 10-3 mm2/s and 1.31 × 10-3 mm2/s in prostate peripheral zone and central gland respectively(combined median value of 1.54×10-3 mm2/s),1.44 × 10-3 mm2/s in endometrium,1.53 × 10-3 mm2/s in myometrium,1.71 × 10-3 mm2/s in cervix and 1.92 × 10-3 mm2/s in breast. In addition,six phantom studies and thirteen in vivo studies were summarized to compare repeatability and reproducibility of the measured ADC. All selected phantom studies demonstrated lower intra-scanner and inter-scanner variation compared to in vivo studies. Based on the findings of this manuscript,it is recommended that protocols need to be optimised for the body part studied and that system-induced variability must be established using a standardized phantom in any clinical study. Reproducibility of the measured ADC must also be assessed in a volunteer population,as variations are far more significant in vivo compared with phantom studies.

Quantitative evaluation of diffusion-weighted magnetic resonance imaging of focal hepatic lesions

AIM: To explore the quantitative analysis of diffusionweighted magnetic resonance imaging (DWMRI) in differential diagnosis of focal hepatic lesions.METHODS: DWMRI was performed in 149 hepatic lesions, including hepatocellular carcinoma (34 cases),hepatic metastases (37 cases), cavernous hemangioma (42 cases), hepatic cyst (36 cases). Apparent diffusion coefficient (ADC) values were evaluated using four different b values in different sequences. The ratio of ADC values of lesion/liver in hepatocellular carcinoma and hepatic metastases was also calculated.RESULTS: The mean ADC values of hepatic lesions were as follows: hepatocellular carcinoma (0.95 ± 0.11) × 10-3 mm2/s, hepatic metastasis (1.13 ± 0.21)× 10-3 mm2/s, cavernous hemangioma (1.86±0.36)×10-3 mm2/s,hepatic cyst(3.14±0.31)×10-3 mm2/s. The ratio of ADC values in lesion/liver in hepatocellular carcinoma was 0.91 ±0.11, being significantly different from that in hepatic metastasis (1.21 ± 0.18, P＜ 0.05).CONCLUSION: ADC values and quantitative analysis of focal hepatic lesions are of significant values in differential diagnosis of focal hepatic lesions.

Three-Tesla magnetic resonance elastography for hepatic fibrosis:Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging

AIM:To evaluate the feasibility of 3-Tesla magnetic resonance elastography(MRE)for hepatic fibrosis and to compare that with diffusion-weighted imaging(DWI)and gadoxetic acid-enhanced magnetic resonance(MR)imaging.METHODS:Forty-two patients were included in the study.On MRE,mean stiffness values were measured on the elastograms in kilopascals.The apparent diffusion coefficient(ADC)of the liver was measured using DWI.On gadoxetic acid enhanced MR,the contrast enhancement index(CEI)was calculated as signal intensity(SI)post/SIpre,where SIpost is liver-to-muscle SI ratio on hepatobiliary phase images and SIpre is that on nonenhanced images.Correlation between aspartate aminotransferase to the platelet ratio index(APRI)and three MR parameters was assessed.Each MR parameter was compared between a hepatic fibrosis(HF)group and non-hepatic fibrosis(n HF)group.RESULTS:Liver stiffness showed strong positive correlation with APRI[Spearman correlation coeffiecient(r)=0.773,P<0.0001],while ADC and CEI showed weak or prominent negative correlation(r=-0.28 and-0.321,respectively).In the HF group,only liver stiffness showed strong correlation with APRI(r=0.731,P<0.0001).Liver stiffness,ADC,and APRI were significantly different between the HF group and n HF group.CONCLUSION:MRE at 3-Tesla could be a feasible method for the assessment of hepatic fibrosis.