用MR扩散加权成像评价新生儿缺氧缺血性脑病的初步研究

目的应用扩散加权成像(DWI)方法评价新生儿缺氧缺血性脑病(HIE)，并同常规MRI对照，以了解扩散成像的价值及限度。方法对临床确诊的36例缺氧缺血性脑病的新生儿(年龄3h至22d，平均8．44d)，进行常规MRT，WI和DWI检查(b=700s／mm^2)。观察皮层及皮层下白质、深部白质、基底节及丘脑、脑室及脑外间隙等部位。结果缺血缺氧所致脑损害在DWI表现为弥漫性损害：区域性皮层、皮层下及深部白质较广泛的高信号19．4％(7／36)；局灶性损害：沿侧脑室壁和三角部白质的高信号27．8％(10／36)，额叶深部白质点状高信号5．6％(2／36)。相应部位的T1WI分别为16．7％(6／36)，36．1％(13／36)，30．6％(11／36)。出血性病变，在T1WI上为高信号，而在DWI上表现为无信号。结论MR DWI适于早期检查HIE，T1WI适于亚急性期和慢性期。     

MR imaging with diffusion-weighted imaging in acute and chronic Wernicke encephalopathy

Wernicke encephalopathy is a neurologic disorder that results from thiamine deficiency. It is associated with a classic triad of symptoms consisting of ataxia, ocular motor cranial neuropathies, and changes in consciousness. We report 3 cases of Wernicke encephalopathy in which MR imaging, including diffusion-weighted imaging, was performed at the onset and during follow-up. MR imaging findings were correlated with the clinical status of both the acute and chronic stage of Wernicke encephalopathy.     

Pituitary apoplexy: early detection with diffusion-weighted MR imaging

Pituitary apoplexy is defined as a clinical syndrome that may include headache, visual deficits, ophthalmoplegia, or altered mental status. It may result from either infarction or hemorrhage of the pituitary gland. Prognosis is significantly improved with early diagnosis and surgical treatment. We report two cases in which diffusion-weighted MR imaging assisted in the early detection of acute pituitary infarction and led, in one case, to surgical intervention early in the course of clinical apoplexy, with resulting complete recovery.     

MR imaging of metronidazole-induced encephalopathy: lesion distribution and diffusion-weighted imaging findings

BACKGROUND AND PURPOSE: MR imaging features of metronidazole-induced encephalopathy (MIE) have not been fully established. This study was undertaken to determine the topographic distributions and diffusion-weighted imaging (DWI) findings of MIE. MATERIALS AND METHODS: We retrospectively evaluated the initial MR images (n = 7), including DWI (n = 5), and follow-up MR images (n = 4) after drug discontinuation in 7 patents with clinically diagnosed MIE. The topographic distributions of lesions were evaluated on MR images, and DWI signal intensities and apparent diffusion coefficient (ADC) values of the lesions were assessed. RESULTS: MR images demonstrated bilateral symmetric T2 hyperintense lesions in the cerebellar dentate nucleus (n = 7), midbrain (n = 7), dorsal pons (n = 6), medulla (n = 4), corpus callosum (n = 4), and cerebral white matter (n = 1). Brain stem lesions involved the following: tectum (n = 5), tegmentum (n = 4), red nucleus (n = 3) of the midbrain, vestibular nucleus (n = 6), and a focal tegmental lesion involving the superior olivary nucleus (n = 6) and abducens nucleus (n = 4) of the pons and vestibular nucleus (n = 4) and inferior olivary nucleus (n = 1) of the medulla. DWI (n = 5) showed isointensity or hyperintensity of lesions, and the decreased ADC value was found only in the corpus callosum lesions (n = 2). All detected lesions were completely reversible at follow-up except for the single corpus callosum lesion with an initial low ADC value. CONCLUSION: Brain lesions were typically located at the cerebellar dentate nucleus, midbrain, dorsal pons, medulla, and splenium of the corpus callosum. According to DWI, most of the lesions in MIE probably corresponded to areas of vasogenic edema, whereas only some of them, located in the corpus callosum, corresponded to cytotoxic edema.     

Improved detection of skull metastasis with diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: Metastasis to the skull is clinically important, but routine MR imaging offers moderate sensitivity for skull-metastasis detection in our experience. We sought to determine if diffusion-weighted MR imaging (DWI) could improve the detection of skull metastasis in patients with primary carcinomas that metastasized to bone compared with conventional MR imaging. MATERIALS AND METHODS: Seventy-five patients from the tumor registry of our institution with extracranial primary malignancy who had brain MR imaging with DWI and radionuclide bone scanning (RNBS, gold standard) within a 6-week interval were evaluated. Thirty-eight patients demonstrated increased radiopharmaceutical uptake on RNBS, consistent with skull metastasis of any size, and the remaining 37 were control subjects. Two readers correlated the DWI and conventional MR imaging with RNBS. RESULTS: The overall sensitivity of DWI for detection of skull metastases was 68.4%-71.1% (kappa=0.68) versus 42.1%-55.3% (kappa=0.65) for conventional MR imaging. Breast cancer (n=20) was detected with greatest sensitivity of 86.7%-93.3% (kappa=0.80) for DWI versus 60%-80% (kappa=0.5) for conventional MR imaging. Lung cancer (n=32) was detected with 63.6%-72.7% sensitivity (kappa=0.56), and prostate cancer (n=8) with 14.3% sensitivity (kappa=0.5) for DWI versus 27.3%-36.4% (kappa=0.81) and 14.3-42.9% (kappa=0), respectively, for conventional MR imaging. CONCLUSIONS: DWI is a useful sequence for identifying focal skull metastases for breast and lung malignancies and, compared with conventional MR imaging, provides improved detection of these lesions. DWI is insensitive for detecting skull metastases from prostate carcinoma.     

磁共振弥散加权成像在新生儿缺氧缺血性脑病的诊断价值

目的:以磁共振弥散加权成像(DWI)技术并与常规MR T1WI、T2WI结合应用,探讨DWI对新生儿缺氧缺血性脑病(HIE)的早期诊断价值。方法:对我院2004年1月~2010年1月临床确诊缺氧缺血性脑病的新生儿62例(4h~15天)进行DWI和常规T1WI、T2WI检查。结果:DWI出现高信号病灶59例,T1WI信号异常32例,T2WI信号异常13例。DWI高信号病灶多见于大脑皮层、侧脑室周围白质区及室管膜下,T1WI高信号以脑室周围白质区多见。出血性病变,在T1WI呈高信号,而DWI表现为无信号。结论:DWI适用于早期HIE,T1WI及T2WI在亚急性期、恢复期或随访应用显示病灶较好。     

MR imaging of hypoglycemic encephalopathy: lesion distribution and prognosis prediction by diffusion-weighted imaging

Introduction

The aim of this study was to evaluate the patterns of hypoglycemic encephalopathy on diffusion-weighted imaging (DWI) and the relationship between the imaging patterns and clinical outcomes.

Methods

This retrospective study included 17 consecutive patients that had hypoglycemic encephalopathy with DWI abnormalities. The topographic distributions of the DWI abnormalities of the cortex, deep gray matter, and white matter structures were assessed. In addition, possible correlation between the patterns of brain injury on DWI and clinical outcomes was investigated.

Results

There were three patterns of DWI abnormalities: involvement of both gray and white matter (n?=?8), selective involvement of gray matter (n?=?4), and selective involvement of white matter (n?=?5). There was no significant difference in the initial blood glucose levels among patients for each of the imaging patterns. Most patients (16/17) had bilateral symmetrical abnormalities. Among patients with bilateral symmetrical gray and/or white matter injuries, one had moderate to severe disability and 14 remained in a persistent vegetative state. The two patients with a focal unilateral white matter abnormality and a localized splenial abnormality recovered without neurological deficits.

Conclusion

The results of this study showed that white matter was more sensitive to hypoglycemia than previously thought and there was no specific association between the patterns of injury and clinical outcomes whether the cerebral cortex, deep gray matter, and/or white matter were affected. Diffuse and extensive injury observed on the DWI predicts a poor neurologic outcome in patients with hypoglycemic injuries.     

模拟计算型扩散加权MR成像有望提高肿瘤的检出率

目的介绍以低b值行扩散加权(DW)MR成像来获得高b值图像的模拟计算型DWI法,并探讨其在肿瘤中提高病灶检出率的可行性。材料与方法本研究获得机构审查委员会批准,并获得所有受检者的书面知情同意。采用     

Minimal hepatic encephalopathy in children with liver cirrhosis: diffusion-weighted MR imaging and proton MR spectroscopy of the brain

Introduction

The aim of this work was to detect minimal hepatic encephalopathy (minHE) in children with diffusion-weighted MR imaging (DWI) and proton magnetic resonance spectroscopy (¹H-MRS) of the brain.

Methods

Prospective study conducted upon 30 consecutive children (age range 6–16 years, 21 boys and 9 girls) with liver cirrhosis and 15 age- and sex-matched healthy control children. Patients with minHE (n?=?17) and with no minHE (n?=?13) groups and control group underwent DWI, ¹H-MRS, and neuropsychological tests (NPTs). The glutamate or glutamine (Glx), myoinositol (mI), choline (Cho), and creatine (Cr) at the right ganglionic region were determined at ¹H-MRS. The apparent diffusion coefficient (ADC) value and metabolic ratios of Glx/Cr, mI/Cr, and Cho/Cr were calculated.

Results

There was elevated ADC value and Glx/Cr and decreased mI/CI and Ch/Cr in patients with minHE compared to no minHE and control group. There was significant difference between minHE, no minHE, and control group in the ADC value (P?=?0.001 for all groups), GLx/Cr (P?=?0.001 for all groups), mI/Cr (P?=?0.004, 0.001, and 0.001, respectively), Ch/Cr (P?=?0.001 for all groups), and full-scale IQ of NPT (P?=?0.001, 0.001, and 0.143, respectively). The NPT of minHE had negative correlation with ADC value (r?=??0.872, P?=?0.001) and GLx/Cr (r?=??0.812, P?=?0.001) and positive correlation with mI/Cr (r?=?0.732, P?=?0.001).

Conclusion

DWI and ¹H-MRS are imaging modalities that can detect minHE in children with liver cirrhosis and correlate well with parameters of NPT.     

Computed diffusion-weighted MR imaging for visualization of pancreatic adenocarcinoma: Comparison with acquired diffusion-weighted imaging

ObjectiveTo assess the feasibility of computed diffusion-weighted imaging (cDWI) in comparison with directly acquired DWI for visualizing pancreatic adenocarcinomas.Materials and methodsPatients with pancreatic adenocarcinoma underwent DWI at b-values of 0, 1000 (DWI₁₀₀₀), 1500 (DWI₁₅₀₀) and 2000 (DWI₂₀₀₀) s/mm². From DWIs at b-values of 0 and 1000 s/mm², we generated cDWIs at b-values of 1500 (cDWI₁₅₀₀) and 2000 (cDWI₂₀₀₀) s/mm². DWI findings of pancreatic adenocarcinomas (clear hyperintensity; hyperintensity with an unclear distal border; and isointensity), the image quality and the tumor to pancreas contrast ratio (CR) were compared between directly acquired DWI and cDWI.ResultsAmong the 63 included patients, clear hyperintense tumors were seen in 35 on DWI₁₀₀₀, 50 on DWI₁₅₀₀, 50 on cDWI₁₅₀₀, 53 on DWI₂₀₀₀ and 44 on cDWI₂₀₀₀. Incidence of clear hyperintense tumors was significantly higher on cDWI₁₅₀₀ than on DWI₁₀₀₀ (P = 0.013). There was no significant difference in the incidence of clear hyperintense tumors between DWI₁₅₀₀ and cDWI₁₅₀₀ (P > 0.999), but a lower incidence was seen on cDWI₂₀₀₀ than on DWI₂₀₀₀ (P = 0.028). Image quality was lower on cDWI than on DWI at b-values of 1500 (P = 0.002) and 2000 s/mm² (P < 0.001). The tumor to distal pancreas CR was significantly higher on cDWI₂₀₀₀ than on cDWI₁₅₀₀ (P < 0.001), and on cDWI₁₅₀₀ than on DWI₁₀₀₀ (P < 0.001). The cDWI showed a significantly higher tumor to distal pancreas CR than DWI at b-values of 1500 (P = 0.004) and 2000 s/mm² (P < 0.001).ConclusionscDWI₁₅₀₀ generated from b-values of 0 and 1000 s/mm² should be considered more effective than DWI₁₀₀₀ and at least as effective as DWI₁₅₀₀.     

Abdomen: diffusion-weighted MR imaging with pulse-triggered single-shot sequences

Magnetic resonance (MR) diffusion measurements of the abdomen were performed in 12 healthy volunteers by using a diffusion-weighted single-shot sequence both without and with pulse triggering for different trigger delays. Pulse triggering to the diastolic heart phase led to reduced motion artifacts on the diffusion-weighted MR images and to significantly improved accuracy and reproducibility of measurements of the apparent diffusion coefficients, or ADCs, of abdominal organs.     

Semiautomated spleen volumetry with diffusion-weighted MR imaging

In this article, we determined the relative accuracy of semiautomated spleen volumetry with diffusion-weighted (DW) MR images compared to standard manual volumetry with DW-MR or CT images. Semiautomated spleen volumetry using simple thresholding followed by 3D and 2D connected component analysis was performed with DW-MR images. Manual spleen volumetry was performed on DW-MR and CT images. In this study, 35 potential live liver donor candidates were included. Semiautomated volumetry results were highly correlated with manual volumetry results using DW-MR (r = 0.99; P < 0.0001; mean percentage absolute difference, 1.43 ± 0.94) and CT (r = 0.99; P < 0.0001; 1.76 ± 1.07). Mean total processing time for semiautomated volumetry was significantly shorter compared to that of manual volumetry with DW-MR (P < 0.0001) and CT (P < 0.0001). In conclusion, semiautomated spleen volumetry with DW-MR images can be performed rapidly and accurately when compared with standard manual volumetry.     

新生儿缺氧缺血性脑病的MR诊断及随访观察

目的：研究新生儿缺氧缺血性脑病（hypoxic-ischemic encephalopathy HIE)MR影像学表现发展规律及其预后情况。方法：选择有围产期窒息史，头颅MRI诊断为不同程度的HIE新生儿150例，30例患儿分别于3、6月，1、2、4岁以前进行头颅MRI复查。结果：3个月65％病例有头颅MR异常，大部分表现为外部性脑积水，28％病例有神经系统的症状和体征。6个月时40%病例有MR异常，33％病例有临床表现。1岁后约25％病例MR异常，表现为局限性脑软化和脑萎缩，并有相应的临床表现。结论：①HIE所致脑内小淤斑稍长T2信号于生后2－3个月内吸收消散。②HIE在3个月时有半数病例头颅MR表现异常，可见有髓鞘化不良，大部分表现为外部性脑积水，1岁以后外部性脑积水愈合，约20％病例留有局限性脑白质软化和脑萎缩等严重后遗症。③HIE的预后与MR分度密切相关，轻度预后良好，中及重度预后差。     

Cytotoxic brain edema: assessment with diffusion-weighted MR imaging.

To determine whether cytotoxic brain edema is associated with a decrease in diffusion, it was induced in rats, in the absence of ischemia, with an established model of acute hyponatremic encephalopathy. Cytotoxic brain edema secondary to acute hyponatremia was induced with intraperitoneal injections of 2.5% dextrose in water and subcutaneous injection of arginine-vasopressin. Coronal spin-echo magnetic resonance (MR) images were obtained with and without strong diffusion-sensitizing gradients before and after induction of acute hyponatremia. The apparent diffusion coefficient (ADC) was measured at two coronal section locations. In hyponatremic rats, the brain ADC was significantly reduced (P = .0153 and .0001) and was positively correlated with increased total brain water content (P = .0011). Plots of ADC versus total brain water showed a statistically significant inverse linear relationship between ADC and increasing brain water at the anterior coronal section location. The results indicate that the ADC may be a sensitive indicator of cytotoxic brain edema and thus may enable quantitative evaluation of such edema with diffusion-weighted MR imaging.     

脑白质疏松症的MR扩散加权成像及波谱研究

目的通过MR扩散加权成像(DWI)及MR波谱(MRS)分析脑白质疏松症(LA)的表观扩散值(ADC)和不同代谢产物比值的变化,探讨LA中脑白质缺血过程中出现的病理、生化改变与MR功能成像改变之间的关系。方法30例经常规MRI检查诊断为LA患者,及30例年龄相匹配的正常脑白质表现的患者作为对照组,进行DWI检查,分析病变不同区域ADC值的变化,同时对LA患者进行MRS分析N-乙酰天门冬氨酸(NAA)/肌酸(Cr)、胆碱复合物(Cho)/肌酸(Cr)比值的变化,比较不同位置和不同程度病变在ADC值和代谢变化中的差异。结果LA患者病灶区(双侧侧脑室枕角、体部旁脑白质)ADC值升高与对照组差异有显著的统计学意义(P<0.01),相应病灶区的NAA/Cr均值明显降低,Cho/Cr均值升高,与正常白质比较差异有显著统计学意义(P<0.01),而枕角的NAA/Cr均值低于体部,差异有显著统计学意义(P<0.01)。结论磁共振功能成像能够反映脑白质疏松症发展中的微观结构变化和局部代谢的异常。     

Cholecystitis: detection with MR imaging

The role of magnetic resonance (MR) imaging in the detection of gallbladder disease was evaluated in 39 individuals (16 healthy, five with asymptomatic gallstones, and 18 with clinical symptoms of gallbladder disease). MR imaging was performed after they fasted for 12 hours. Imaging sequences included a combination of repetition times (TR) of 0.5 and 1.5 sec and echo times (TE) of 28 and 56 msec. On the images obtained at TR = 0.5 sec and TE = 56 msec, gallbladder bile was hyperintense compared with the liver in all healthy and asymptomatic subjects and was hypointense (n = 9), isointense (n = 4), or hyperintense (n = 5) in symptomatic patients, eight of whom had surgical confirmation of cholecystitis. Comparison of normal versus pathologically proved cases for the presence of gallbladder disease yielded a specificity of 100%, sensitivity of 75%, and a significant difference of P less than .01. Thus, with a pulse sequence of TR = 0.5 sec and TE = 56 msec, MR was sensitive in detecting gallbladder disease. However, the role of MR in the radiologic workup of gallbladder disease will be determined by more experience with this modality.     

Improved image quality and detection of acute cerebral infarction with PROPELLER diffusion-weighted MR imaging

PURPOSE: To compare periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) multishot fast spin-echo diffusion-weighted magnetic resonance (MR) imaging with single-shot echo-planar diffusion-weighted MR imaging for image quality and visualization of acute cerebral infarction. MATERIALS AND METHODS: Seventy subjects (35 men, 35 women; mean age, 55 years +/- 24 [SD]) who were suspected of having acute cerebral infarction (symptom duration, 2.8 days +/- 2.7) underwent PROPELLER and echo-planar MR imaging (b = 1,000 sec/mm(2)). Two neuroradiologists compared unlabeled images for presence of artifacts, visualization of infarction, and their preference of images. Interobserver agreement and image comparison were assessed by using the kappa statistic and the chi(2) test, respectively. RESULTS: PROPELLER MR imaging reduced susceptibility artifacts (n = 70 subjects), which limited visualization of temporal (echo-planar, n = 64; PROPELLER, n = 0; P <.01, chi(2) test), frontal (echo-planar, n = 58; PROPELLER, n = 1; P <.01), and parietal lobes (echo-planar, n = 5; PROPELLER, n = 0; P <.05) and cerebellum (echo-planar, n = 36; PROPELLER, n = 0; P <.01) and brainstem (echo-planar, n = 23; PROPELLER, n = 0; P <.01). Acute infarction (n = 31 subjects) was better demonstrated at PROPELLER MR imaging (PROPELLER better, n = 18; echo-planar better, n = 1; PROPELLER and echo-planar equal, n = 12; P <.01, chi(2) test). PROPELLER MR imaging was preferred in all (n = 70) but one case in which the lesion lay within the intersection gap (PROPELLER preferred, n = 69; echo-planar preferred, n = 1; P <.01, chi(2) test). CONCLUSION: With a short increase in imaging time, PROPELLER MR imaging offers better image quality and detection of acute cerebral infarction than does echo-planar MR imaging.