Diffusion-weighted and conventional MR imaging findings of neuroaxonal dystrophy

BACKGROUND AND PURPOSE: Neuroaxonal dystrophy is a rare progressive disorder of childhood characterized by mental deterioration and seizures. The diffusion-weighted and conventional MR imaging findings are reported for six cases. METHODS: Six patients aged 19 months to 9 years with proved neuroaxonal dystrophy (one with the infantile form, five juvenile forms) underwent imaging at 1.5 T. Echo-planar diffusion-weighted images were acquired with a trace imaging sequence in five patients and with a three-gradient protocol (4000/110) in one. Images obtained with a b value of 1000 s/mm2 and corresponding apparent diffusion coefficient (ADC) maps were studied. ADCs from lesion sites and normal regions (pons and temporal and occipital lobes) were evaluated. RESULTS: A hyperintense cerebellum (a characteristic of the disease) was evident on fluid-attenuated inversion recovery images in all cases. Four patients had associated cerebral changes. Diffusion-weighted images, especially ADC maps, showed an elevated diffusion pattern in the cerebellum in the five juvenile cases (normal images at b = 1000 s/mm2, ADCs of 1.30-2.60 x 10(-3) mm2/s). A restricted diffusion pattern was evident in the infantile case (hyperintensity at b = 1000 s/mm2, low ADCs of 0.44-0.55 x 10(-3) mm2/s). ADCs were normal in the pons and temporal and occipital lobes (0.64-1.00 x 10(-3) mm2/s). CONCLUSION: An elevated cerebellar diffusion pattern is a predominant feature of juvenile neuroaxonal dystrophy. Coexistent elevated and restricted diffusion patterns were evident in different brain regions in different forms of the disease. Dystrophic axons likely account the restricted diffusion, whereas spheroid formation (swelling) and abnormal myelination result in elevated diffusion.     

Diffusion-weighted imaging of patients with subacute cerebral ischemia: comparison with conventional and contrast-enhanced MR imaging

BACKGROUND AND PURPOSE: The importance of diffusion-weighted imaging (DWI) for delineating acute ischemic lesions has been investigated extensively; however, few studies have investigated the role of DWI in the subacute stage of stroke. Because these lesions tend to appear bright throughout the first days of ischemia, owing to restricted diffusion, we speculated that DWI could also improve the detection of subacute infarcts as compared with conventional and contrast-enhanced MR imaging. METHODS: Interleaved echo-planar DWI with phase navigation was performed on a 1.5-T MR unit in a consecutive series of 53 patients (mean age, 66 +/- 14 years) with suspected recent cerebral ischemia. The interval between onset of clinical symptoms and MR imaging ranged from 1 to 14 days (mean, 6 +/- 4 days). Contrast material was given to 28 patients in a dose of 0.1 mmol/kg. RESULTS: DWI clearly delineated recent ischemic damage in 39 patients (74%) as compared with 33 (62%) in whom lesions were identified or suspected on conventional T2-weighted images. DWI provided information not accessible with T2-weighted imaging in 17 patients when evidence of lesion multiplicity or detection of clinically unrelated recent lesions was included for comparison. Subacute ischemic lesions were also seen more frequently on DWI sequences than on contrast-enhanced images (20 versus 13 patients). DWI was more likely to make a diagnostic contribution in the first week of stroke and in patients with small lesions or preexisting ischemic cerebral damage than was conventional MR imaging. CONCLUSION: Recent ischemic damage is better shown on DWI sequences than on conventional and contrast-enhanced MR images throughout the first days after stroke and may provide further information about the origin of clinical symptoms. Adding DWI to imaging protocols for patients with subacute cerebral ischemia is recommended.     

Diffusion-weighted and conventional MR imaging in neurotrichinosis

Central nervous system involvement in trichinosis is not rare. Brain lesions in trichinosis have been defined on computed tomography and magnetic resonance imaging (MRI) as multifocal small lesions located in the cerebral cortex and white matter. We present a case of trichinosis with multifocal lesions of the brain detected by MRI and diffusion weighted MRI. Evolutions of these lesions from acute through chronic stages on follow up studies are also presented. This is the first report describing sequential MRI findings and diffusion weighted imaging appearance of brain lesions in trichinosis. Sequential evaluation of conventional and diffusion MR data allowed us to conclude that multifocal lesions in the brain were related to multiple infarctions rather than true inflammatory infiltration of the brain parenchyma.     

Peroxisomal biogenesis disorder: comparison of conventional MR imaging with diffusion-weighted and diffusion-tensor imaging findings

BACKGROUND AND PURPOSE: Peroxisomal biogenesis disorders (PBDs) refer to a group of disorders of peroxisomal biogenesis causing neuronal migration disorder, delayed myelination, and demyelination. The aim of this study was to evaluate the added value of diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) compared with that of conventional T2-weighted imaging in assessing the extent of white matter damage in patients with PBDs. METHODS: Three patients (aged 12, 16, and 80 months) with PBD (type 1 protein targeting sequence [PTS1]) and three age-matched control subjects underwent MR imaging on a 1.5-T system. The protocol included axial T2-weighted, DWI, and DTI sequences. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) changes were calculated using regions of interest at several predefined white matter areas and compared with those of age-matched control subjects. Color-coded maps were obtained to visualize the range of FA values. RESULTS: On the T2-weighted images, one patient revealed severe hypomyelination throughout the brain; the two other patients showed focal abnormal high-signal-intensity areas. All patients had significantly decreased FA values in white matter areas that appeared abnormal on the T2-weighted images. In two of the three patients, significant FA reduction was also found in normal-appearing white matter. The ADC values of the patients were significantly increased compared with those of the age-matched controls. CONCLUSION: Although based on a small number of patients, our data suggest that DWI and DTI can be used to characterize and quantify white matter tract injury in patients with PBD-PTS1. Furthermore, our data suggest that these techniques have the potential to identify neurodegenerative changes not yet visible on T2-weighted images.     

MR扩散加权成像在眼眶良恶性肿块鉴别诊断中的应用

目的 分析眶内良恶性肿块的扩散加权成像(DWI)特征,评价表观扩散系数(ADC)值对其诊断价值.方法 对77例眶内肿块进行常规MRI及DWI,其中良性肿块55例,恶性肿块22例.扩散敏感系数(b)值=0、1000 s/mm2,测量病变对侧颞叶脑白质感兴趣区DWI信号,获得相应的肿块区ADC(ADCM)值、病变对侧颞叶脑白质ADC(ADCw)值,计算二者比值(ADCR).以不同ADCM值及ADCR作为临界点区分眶内良恶性肿块绘制出受试者工作特征曲线(ROC).结果 眶内良性肿块ADCM值及ADCR分别为(1.56±0.75)×10-3mm2/s、1.85±0.91;恶性肿块ADCM值及ADCR分别为(1.09±0.42)×10-3mm2/s、1.28±0.53;良性肿块ADCM值及ADCR显著高于恶性肿块(t值分别为2.803、2.735,P值均＜0.01).以不同ADCM值、ADCR作为临界点判断眶内良恶性肿块绘制ROC,曲线下面积均为0.71±0.07.以ADCM值为1.05×10-3mm2/s作为判断眶内良恶性肿块的决定值,灵敏度、特异度和准确率分别为59.1%(13/22)、78.2%(43/55)和72.7%(56/77);以ADCR为1.24作为决定值,灵敏度、特异度和准确率分别为59.1%(13/22)、76.4%(42/55)和71.4%(55/77).结论 DWI可揭示眼眶肿块的扩散特征,ADC值对于良恶性肿块的鉴别诊断具有辅助诊断价值.     

Diffusion-weighted MR imaging findings of acute necrotizing encephalopathy

Multiple, symmetrical brain lesions affecting the bilateral thalami and cerebral white matter, which often show a concentric structure on CT and MR images, characterize acute necrotizing encephalopathy (ANE) of childhood. We describe the imaging findings of a 2-year-old child with ANE obtained with diffusion-weighted MR imaging. We discuss the significance of these findings, as well as the pathophysiology of ANE lesions, with reference to the appearance of the disease as revealed by diffusion-weighted MR imaging.     

Diffusion-weighted MR imaging findings of ovarian adenocarcinofibromas and adenofibromas

We retrospectively evaluated pelvic magnetic resonance imaging including diffusion-weighted imaging (DWI) of 16 ovarian lesions (5 adenocarcinofibromas, 2 borderline adenofibromas, and 9 benign adenofibromas). All adenocarcinofibromas were detected as large solid areas of strong high signal on DWI, and seven of nine benign adenofibromas and both borderline adenofibromas demonstrated no areas of high signal or small areas of weak high signal. Solid components that appear as areas of strong high signal on DWI might represent a characteristic finding of adenocarcinofibromas.     

Diffusion-weighted MR imaging findings in carbon monoxide poisoning

Diffusion-weighted MR imaging (DWI) of two patients with carbon monoxide (CO) poisoning demonstrated white matter and cortical hyperintensities. In one patient, the changes on the FLAIR sequence were more subtle than those on DWI. The DWI abnormality in this patient represented true restriction. In the second patient, repeated exposure to CO caused restricted diffusion. DWI may be helpful for earlier identification of the changes of acute CO poisoning.     

Diffusion-weighted imaging of metastatic brain tumors: comparison with histologic type and tumor cellularity

BACKGROUND AND PURPOSE: On diffusion-weighted imaging (DWI), metastatic tumors of the brain may exhibit different signal intensities (SI) depending on their histology and cellularity. The purpose of our study was to verify the hypotheses (1) that SI on DWI predict the histology of metastases and (2) that apparent diffusion coefficient (ADC) values reflect tumor cellularity. MATERIALS AND METHODS: We assessed conventional MR images, DWI, and ADC maps of 26 metastatic brain lesions from 26 patients, 13 of whom underwent surgery after the MR examination. Two radiologists performed qualitative assessment by consensus of the SI on DWI in areas corresponding to their enhancing portions. We measured the contrast-to-noise ratio (CNR) on T2-weighted images and normalized ADC (nADC) values, and compared them with tumor cellularity. RESULTS: The mean SI on DWI and the CNR on T2-weighted images were significantly lower in well differentiated than in poorly differentiated adenocarcinomas and lesions other than adenocarcinoma. The mean nADC value was significantly higher in well differentiated than poorly differentiated adenocarcinomas and lesions other than adenocarcinoma. All 3 small-cell carcinomas and 1 large-cell neuroendocrine carcinoma exhibited high SI on DWI. The nADC value showed a significant inverse correlation with tumor cellularity. There was no significant correlation between the CNR and tumor cellularity. CONCLUSION: The SI on DWI may predict the histology of metastases; well differentiated adenocarcinomas tended to be hypointense, and small- and large-cell neuroendocrine carcinomas showed hyperintensity. Their ADC values reflect tumor cellularity.     

MR arthrography of the shoulder: comparison with conventional MR imaging

Twenty-three patients underwent both conventional MR imaging of the shoulder and MR shoulder arthrography for clinically suspected labral or rotator cuff abnormalities. Images obtained before and after contrast administration were studied independently, and without knowledge of clinical findings, by two radiologists for the presence of abnormalities of the glenoid labrum or rotator cuff. Results were correlated with surgical findings in all patients. Nine patients had surgically proved labral tears. MR arthrography detected all nine labral abnormalities, while six of the nine were missed on conventional MR imaging. Fourteen patients had surgically proved rotator cuff tears. MR arthrography detected 11 of the 14 tears and missed three partial tears on the bursal surface. Conventional MR imaging detected nine cuff tears and missed five tears; two of these were complete rotator cuff tears and three were partial tears of the undersurface of the rotator cuff. Our results suggest that MR arthrography enhances the accuracy of MR in the evaluation of the glenoid labrum and rotator cuff tendon.     

Diffusion-weighted MR imaging in multiple sclerosis: comparison with contrast-enhanced study

OBJECTIVE: To assess the utility of cerebral diffusion-weighted MR imaging in the diagnosis of multiple sclerosis (MS) in comparison with contrast-enhanced T1-weighted imaging. METHODS AND MATERIALS: We reviewed T2-weighted spin-echo (SE), fluid-attenuated inversion-recovery (FLAIR), contrast-enhanced T1-weighted SE and echo-planar diffusion-weighted images (DWIs) obtained in seven patients with definite MS on nine occasions. RESULTS: In total, 94 plaques were demonstrated on T2-weighted SE and/or FLAIR images. A total of 13 of these plaques showed enhancement on contrast-enhanced T1-weighted images and hyperintensity on DWIs, and five non-enhancing plaques showed hyperintensity on DWIs. CONCLUSION: Diffusion-weighted imaging, which provides information based on pathophysiology different from contrast-enhanced imaging, is a potential supplementary technique for characterizing MS plaques.     

Acromioclavicular joint osteoarthritis: comparison of findings derived from MR imaging and conventional radiography

The purpose of this study was to determine the correlation between routine radiography and magnetic resonance (MR) imaging in the analysis of the acromioclavicular (AC) joint osteoarthritis (OA). MR imaging studies of the shoulder in 50 patients performed over a 1-year period at a single institution with corresponding conventional radiographic examinations performed within 1 month of the MR imaging study were restrospectively evaluated by the consensus of two musculoskeletal radiologists with special attention to the AC joint. As conclusion, information provided by conventional radiography in the analysis of AC joint OA does not correlate with that provided by MR imaging. AC joint OA is more frequently detected with MR imaging than with radiography. MR imaging provides better assessment of the full extent of AC joint OA and its effect on the underlying RC.     

MR portography: Preliminary comparison with CT portography and conventional MR imaging

Magnetic resonance (MR) imaging with arterial portography (MRAP) was compared with computed tomography with arterial portography (CTAP) and conventional MR imaging for preoperative evaluation of hepatic masses in eight patients (nine studies). Twenty contiguous, 10-mm-thick-section CTAP images were obtained. MR imaging included T1- and T2-weighted spin-echo and fast multiplanar SPGR (spoiled gradient-recalled acquisition in the steady state) techniques. For MRAP, 0.1 mmol/kg gadopentetate dimeglumine was injected into the superior mesenteric artery. Portographic-phase, 8-mm-thick-section, axial SPGR images were first obtained, followed by “systemic phase” SPGR images. Lesions were seen best on the portographic-phase MRAP images and were less conspicuous on the systemic-phase MRAP, CTAP and conventional MR images. Of 19 visualized lesions, 18 were seen with MRAP; however; five subcentimeter lesions seen with MRAP were not seen with conventional MR imaging or CTAP. Systemic recirculation of iodinated contrast material from the bolus and from previous angiography is a potential limitation of CTAP. For both CTAP and MRAP, optimal results are expected if all images are obtained during a single breath hold, within seconds of the onset of contrast agent administration.     

Diffusion-weighted MR imaging findings in a patient with herpes simplex encephalitis

INTRODUCTION: Herpes simplex meningoencephalitis is one of the most common viral central nervous system infection in adults. Early diagnosis is essential for treatment. CASE REPORT: We present a case of a 68-year-old female patient with herpes simplex infection. On admission, she was in severe clinical condition. Diffusion-weighted (DW) magnetic resonance imaging detected brain involvement better than conventional sequences. After acyclovir therapy, the patient fully recovered. CONCLUSION: DW magnetic resonance imaging is expected to provide a more sensitive imaging in herpes simplex patients than conventional sequences.     

Diffusion-weighted cranial MR imaging findings in a patient with hemophagocytic syndrome

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder of the immune system that is associated with frequent involvement of the central nervous system (CNS). The MR imaging and CT findings of the CNS infiltration have been reported in the past; however, the diffusion-weighted imaging (DWI) findings have not been previously described. We present MR imaging findings in a case of secondary HLH with CNS involvement, with an emphasis on the DWI findings.     

肾肿物的动脉自旋标记MR成像:与组织病理结果的对照研究

目的以组织病理学结果为参照,评价肾脏实性肿物的动脉自旋(ASL)MRI灌注特征与价值。材料与方法这项前瞻性研究符合HIPAA原则,获得单位伦理委员会的批准。所有病人均于检查前签署了知情同意书。42例怀疑肾肿物的病人在进行常规1.5T临床MRI检查前,进行了ASL检查。1名放射医师在不知最终病理结果的情况下,通过对兴趣区的分析,计算肿瘤灌注的平均值和峰值水平。通过方差分析检验灌注值与病理学结果的相关性。采用线性模型评价肾透明细胞癌的肿瘤体积与灌注值之间的相关性。P<0.05为差异具有统计学意义。结果 34例病人[男28例,女6例;(60.4±11.7)岁]获得组织病理学结果。乳头型肾细胞癌的平均灌注值[(27.0±15.1)mL/(min.100g)]低于透明细胞型[(171.6±61.2)mL/(min.100g),P=0.001]、嫌色细胞型[(152.9±80.7)mL/(min.100g),P=0.04]、未分类型肾细胞癌[(208.0±41.1)mL/(min.100g),P=0.001]和肾嗜酸细胞瘤[(373.9±99.2)mL/(min.100g),P<0.001]。肾嗜酸细胞瘤的灌注平均值和峰值水平[分别为(373.9±99.2)mL/(min.100g)和(512.3±146.0)mL/(min.100g)]高于乳头型[(27.0±15.1)mL/(min.100g)和(78.2±39.7)mL/(min.100g),两者P<0.001],嫌色细胞型[分别为(152.9±80.7)mL/(min.100g),P<0.001和(260.9±61.9)mL/(min.100g),P=0.02]和未分类型肾细胞癌[分别为(208.0±41.1)mL/(min.100g),P=0.01和(273.3±83.4)mL/(min.100g),P=0.03]。肾嗜酸细胞瘤的平均肿瘤灌注值高于透明细胞癌(P<0.001)。结论动脉自旋标记MR成像可在灌注水平上区分和诊断不同病理类型的肾脏肿物。肾嗜酸细胞瘤的灌注水平高于肾细胞癌,乳头型肾细胞癌的灌注水平低于其他亚型的肾细胞癌。