脑膜瘤的MRI表现与组织病理对照研究

目的　研究脑膜瘤的磁共振表现与其病理分类之间的关系。方法　回顾分析 12 8例经手术病理证实为脑膜瘤患者的MRI表现。结果　T1WI图像 ,上皮型脑膜瘤 2 9例 ( 4 9% )呈低信号 ,11例 ( 19% )呈稍低信号 ,17例 ( 2 9% )呈等信号。而纤维型脑膜瘤T1WI信号类型分别为 2 3例 ( 5 9% ) ,5例 ( 13 % )和 9例 ( 2 3 % )。在T2 WI图像上 ,3 4例 ( 5 8% )上皮型脑膜瘤呈高信号 ,15例 ( 2 5 % )呈稍高信号 ,10例 ( 17% )呈等信号 ,而纤维型分别为 2例 ( 5 % ) ,8例 ( 2 0 .5 % )和 11例 ( 2 8% )。上皮型、纤维型、移行型在T1WI上均呈现等、低信号 ,而在T2 WI图像上 ,上皮型、血管瘤型及移行型呈现为高信号或稍高信号 ;纤维型脑膜瘤T1WI以低或稍低信号为主。结论　在MRIT1WI图像上 ,各组织学类型之间信号强度的分布无显著性差别 ,而在T2 WI上 ,信号强度与病理类型具有统计学的相关性     

Magnetic resonance imaging spectrum of spinal meningioma

PurposeTo evaluate magnetic resonance (MR) imaging findings of spinal meningioma and to determine the radiological subtypes based on the MR imaging findings and their respective clinical features.Material and methodsData for 105 patients with surgically treated and histopathologically diagnosed spinal meningiomas at our hospital between May 1, 2003 and May 1, 2017 were evaluated in this study. Two radiologists reviewed the characteristics of spinal meningiomas on MR images and categorized the spinal meningiomas into subtypes based on MR imaging findings.ResultsMost spinal meningiomas showed higher signal intensity than that of the spinal cord but lower than that of the subcutaneous fat on T2-weighted images (WI). 56 cases (54%) showed adjacent spinal cord signal changes. Meningiomas could be categorized according to MR imaging findings into type A: dural-based tumors with a homogeneous signal intensity and intense contrast enhancement (81 cases, 77%); type B: round or oval-shaped tumors with an internal hypointense portion on T2-weighted images (18 cases, 17%); type C: en plaque tumors (three cases, 3%); and type D: tumors with unusual findings and a heterogeneous appearance (three cases, 3%). All type C patients showed spinal cord signal changes.ConclusionsSpinal meningioma showed slightly high signal intensity rather than high signal intensity on T2-weighted images. Spinal cord signal changes were present in more than half of the cases. Clinical differences were observed among the different MR imaging types.     

Correlation of MR imaging and histologic findings in mouse melanoma.

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 microns thick, with an in-plane resolution of 195 microns. The distribution of melanin within the histologic slices correlated well with the high-signal-intensity regions on the T1-weighted images (T1WIs), while these regions had low signal intensity on the T2-weighted images (T2WIs), providing evidence that melanin or melanin-associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton-density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton-density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin-rich, viable-melanoma, and necrotic regions on MR images.     

Relationship between MR imaging and histopathologic findings of the brain in extremely sick preterm infants.

BACKGROUND AND PURPOSE: MR imaging can now be used safely in extremely preterm infants. The aim of this study was to compare the MR imaging appearance of the immature brain with neuropathologic findings at postmortem examination. METHODS: Seven extremely sick preterm infants, born at a median of 24 weeks' gestation, were studied using T1- and T2-weighted MR sequences. Infants died at a median of 3 days after initial MR imaging, and postmortem examinations were carried out. RESULTS: The cortex and germinal matrix were seen as areas of low signal intensity on T2-weighted images, which corresponded to their highly cellular histologic appearance. The periventricular and subcortical layers of white matter had a high signal intensity, corresponding to high fiber and relatively low cellular density; the intermediate layer of low signal intensity corresponded to a dense band of migrating cells. Regions of acute hemorrhage were seen as low signal intensity and regions of infarction as high signal intensity on T2-weighted images. One infant with mild periventricular leukomalacia had some low signal intensity on T1-weighted images, but no focal changes on T2-weighted images. Regions of neuronal mineralization, seen in association with infarction and capillary proliferation, within the basal ganglia and thalami were characterized by very low signal intensity on T2-weighted images and by very high signal intensity on T1-weighted images. There were no imaging abnormalities detected in regions with more subtle histologic abnormalities, such as increased glial or apoptotic cells. CONCLUSION: MR imaging can be used to observe normal developing brain anatomy in extremely premature infants; it can detect areas of hemorrhage and infarction within the developing brain, but conventional MR imaging may not detect more subtle histologic abnormalities.     

MR imaging of the larynx at 1.5 T

The normal magnetic resonance (MR) anatomy of the larynx at high field strength (1.5 T) was studied in 2 normal excised larynges and 62 subjects without laryngopharyngeal disease. The two normal excised larynges were imaged using a 1.5 T MR scanner with a 3 in diameter circular surface coil and a GE 9800 CT scanner. The larynges were sectioned transversely and the MR and CT images compared to gross and histologic sections. Unossified hyaline cartilage was intermediate in signal intensity on T1-weighted and proton density images and low in intensity on T2-weighted images. The signal intensity from ossified cartilage was determined by the amount of fatty marrow and was high in intensity on T1-weighted and proton density images and low to intermediate in intensity on T2-weighted images. A chemical shift artifact from high intensity fatty marrow obscured the calcified or ossified cortex of the major laryngeal cartilages along the frequency encoding axis. The epiglottic cartilage demonstrated an intermediate signal intensity on T1-weighted images and higher intensity on proton density and T2-weighted images. The intralaryngeal muscles were well demonstrated as low intensity structures. The conus elasticus and the vocal ligaments were not recognized as distinct structures. However, the quadrangular membrane and a previously undescribed membrane separating the preepiglottic and paralaryngeal spaces were shown on MR as low intensity linear structures. In the 62 subjects, MR at 1.5 T proved excellent for demonstrating the anatomical details of the major laryngeal cartilages, extra- and intralaryngeal muscles, ligaments, and soft tissues including the vocal cords, false vocal cords, laryngeal ventricles, aryepiglottic folds, preepiglottic space, and paralaryngeal spaces. Visibility and intensity of muscles, ligaments, and soft tissues did not depend on age or sex. The intensity pattern of the thyroid and cricoid cartilages demonstrated wide variations in the same sex and age groups, depending on the degree of ossification. However, they did show more high intensity foci in older men than in younger women. Magnetic resonance showed better contrast resolution and finer detail than CT scans in the same subjects. Magnetic resonance imaging at 1.5 T, with either a saddle-shaped neck surface coil or a 3 in diameter circular surface coil, provides high contrast and high spatial resolution images and could be useful for the diagnosis of lesions of the larynx.(ABSTRACT TRUNCATED AT 400 WORDS)     

Radiological findings of spinal schwannomas and meningiomas: focus on discrimination of two disease entities

This study evaluates the effectiveness of CT and MR imaging in differentiating intradural extramedullary spinal schwannomas and meningiomas in a large group of patients. In addition, the study correlates tumour location, morphologic characteristics and enhancement pattern. From January 2000 to June 2007, we retrospectively reviewed 128 consecutive patients (51 male, 77 female; mean age at admission 53.8 years; range 17–83 years) with spinal intradural extramedullary tumours (92 schwannomas, 36 meningiomas) at our institution. Fifty-one of ninety-two schwannomas (55.4%) showed fluid signal intensity on T2-weighted MR images. Twenty-two of thirty-six meningiomas (61.1%) showed hyperintense signal intensity and thirteen of thirty-six meningiomas (36.1%) showed isointense signal on T2-weighted MR images. Fifty-four schwannomas (58.7%) showed rim enhancement and thirty-three meningiomas (91.7%) showed diffuse enhancement on contrast-enhanced T1-weighted MR imaging. Twenty-one meningiomas (58.3%) showed dural tail sign in contrast-enhanced T1-weighted MR imaging. Twenty-one meningiomas (58.3%) showed calcification on CT images. MR and CT imaging results are therefore useful for the differentiation of schwannomas from meningiomas of the spine.     

Normal adrenal gland: in vivo observations, and high-resolution in vitro chemical shift MR imaging-histologic correlation

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether adrenal cortical lipid affects signal intensity on magnetic resonance (MR) images and to evaluate contrast between cortex and medulla. MATERIALS AND METHODS: From their clinical database, the authors selected 37 MR imaging studies of patients with adrenal adenomas. Two independent readers compared in-phase and fat-suppressed T1-weighted images, looking for visible lipid-induced signal intensity loss in the adrenal gland. Six adrenal gland specimens obtained after radical nephrectomy were also studied with high-resolution MR imaging, including in-phase, opposed-phase, and fat-suppressed T1-weighted images, and T2-weighted images. Adjacent histologic sections were stained with oil red O for neutral fats and with hematoxylin-eosin, and they were also viewed with polarization light microscopy. The relative amount of lipid was graded as mild, moderate, or intense, and the appearance of the cortex and medulla was compared with that on the MR images. RESULTS: On the 37 clinical MR studies, there was no visible signal intensity loss within the limbs of the ipsilateral adrenal glands. T2-weighted images of the adrenal specimens showed a thin high-intensity band, corresponding to the appearance of medulla on histologic slices. This could not be seen on any of the T1-weighted images. Region-of-interest measurements were nearly identical for in-phase and opposed-phase images. Histologic analysis showed abundant cortical lipid. CONCLUSION: Adrenal corticomedullary contrast can be depicted on high-resolution T2-weighted images but not on any T1-weighted images. There is abundant cortical lipid in adrenal specimens, but comparison of in-phase with opposed-phase MR images does not depict it.     

Uterine leiomyoma: correlation between signal intensity on magnetic resonance imaging and pathologic characteristics.

To correlate the signal intensity of uterine leiomyoma with its pathologic characteristics, with particular emphasis on the fibrous component, 33 magnetic resonance (MR) examinations that revealed 93 leiomyomas were prospectively studied. All patients were imaged in axial and sagittal planes with different spin-echo pulse sequences to obtain T1-, T2-weighted, and proton density images. Nondegenerative leiomyomas (n = 62) showing a homogeneous signal of low intensity, and degenerative leiomyomas (n = 31) with a heterogeneous signal of variable intensity on T2-weighted images could be correlated. Histopathological assessment of fiber constitution and degeneration, and MR intensity were interpreted by independent observers. There was excellent accord between the averages for MR intensity, T2 relaxation time and fiber content, although the intensity values in each fiber grade showed a wide range. The greater the fiber content the lower the MR intensity on T2-weighted images, and the shorter the T2 relaxation time (p < 0.0001). In addition, the manner in which fiber distribution affected MR appearance was also elucidated. These data contribute guidelines for precise tissue differentiation of myogenic tumors on MR images, and for MR imaging tissue diagnosis of any lesion with a considerable fibrous element.     

MR imaging of solitary pulmonary lesion: emphasis on tuberculomas and comparison with tumors

The aim of this study was to determine whether solitary pulmonary tuberculoma and malignant tumor can be differentiated on the basis of magnetic resonance (MR) signal intensity. Twenty-eight patients with solitary pulmonary lesions were prospectively studied with MR imaging: T1-weighted, enhanced T1-weighted, proton density-weighted, and T2-weighted spin echo images were obtained. The confirmation methods used were computed tomography (CT)-guided biopsy in seven patients with lung cancer and four patients with tuberculosis; surgery in ten patients with lung cancer and five patients with tuberculosis; and laboratory data in two patients with tuberculosis. Morphologic features and MR signal intensity were examined in detail. As the test for detection of tuberculoma, signal difference on T2-weighted images was carefully analyzed. The signal intensity ratio of the nodule to thoracic muscle signal intensity was measured. The signal intensities obtained from the lung cancers and tuberculomas were variable on pre-and post-enhanced T1-weighted images and proton density-weighted images. Masses were hypointense in 2 of 17 patients with lung cancer and in 9 of 11 patients with tuberculoma on T2-weighted images (sensitivity 82%, specificity 89%, accuracy 87%). The mean signal intensity ratios of the tuberculomas to muscle were significantly lower than those of malignant tumors on T1-weighted, enhanced T1-weighted, proton density-weighted, and T2-weighted images (P < 0.0001). After gadolinium-DTPA enhancement, 2 malignant tumors and 7 tuberculomas showed a marginal rim enhancement pattern, whereas 15 malignant tumors and 2 tuberculomas revealed a diffuse enhancement. The results of MR imaging were consistent with those of CT in 84% of the patients. MR imaging is a helpful adjunctive method in terms of differentiating a tuberculoma from a malignant tumor.     

High signal intensity in MR images of calcified brain tissue

Calcified lesions of the brain occasionally appear bright on T1-weighted MR images. This report shows that particulate calcium can reduce T1 relaxation times by a surface relaxation mechanism. Calcium particles with greater surface area show greater T1 relaxivity. Reduced proton density and reduced T2 tend to diminish signal intensity, but reduced T1 increases signal intensity. Thus, for concentrations of calcium particulate of up to 30% by weight, the signal intensity on standard T1-weighted images increases but subsequently decreases.     

Peripheral focal low signal intensity areas in the degenerated annulus fibrosus on T2-weighted fast spin echo MR images: correlation with macroscopic and microscopic findings in elderly cadavers

Objective. To correlate the peripheral focal low signal intensity areas in the degenerated annulus fibrosus on T2-weighted fast spin echo MR images with the macroscopic and microscopic findings in cadavers derived from elderly subjects. Design. Twenty-eight intervertebral disks (16 lumbar and 12 cervical) derived from four nonembalmed cadavers were examined with T1-weighted spin echo and proton density-weighted and T2-weighted fast spin echo MR imaging. The signal intensities of the annulus fibrosus were evaluated on sagittal MR images and correlated with the findings on corresponding sagittal anatomic sections. The MR imaging-histologic correlation was then studied. Results. Peripheral focal low signal intensity areas and adjacent regions of high signal intensity were found in five lumbar intervertebral disks. Peripheral focal low signal intensity regions consisted of disorganized compact annular fibers, tiny fissures, and dense fibrosis. The high signal intensity regions, adjacent to the areas of low signal intensity, consisted of mucoid degeneration, tiny fissures, and chondroid metaplasia. Conclusions. Awareness of the histologic findings in regions that reveal peripheral focal low signal intensity with adjacent regions of high signal intensity in the degenerated annulus fibrosus on T2-weighted images may facilitate effective interpretation of clinical MR images of the spine. Received: 11 November 1998 Accepted: 20 January 1999     

MR imaging of tuberculous arthritis: Clinical and experimental studies

Signal-intensity characteristics of magnetic resonance (MR) images were assessed in five patients and in 10 rabbits with tuberculous arthritis. MR imaging findings were compared with histologic findings in the animal study. In both of clinical and experimental cases, tuberculous lesions showed both intermediate and high signal intensity on T2-weighted images, while they showed heterogeneously intermediate signal intensity on T1-weighted images. As T2-weighted images were compared with pathologic specimens, intermediate signal intensity corresponded to caseous necrosis, whereas high signal intensity related to granulomas or effusion. Postcontrast T1-weighted images showed enhancement at the peripheries rather than the centers of tuberculous lesions. These results indicate that tuberculous arthritis should be included in the differential diagnosis when intra-articular lesions with low or intermediate signal intensity are found on T2-weighted images.     

Hepatocellular carcinoma: correlation of MR imaging and histopathologic findings.

Seventy-two histologically proved nodular hepatocellular carcinomas (HCCs) were studied with magnetic resonance (MR) imaging at 1.5 T. Capsules were present in 56 of the 72 tumors. Thirty-seven capsules were depicted on T1-weighted spin-echo MR images, and 16 were depicted on T2-weighted MR images. Visualization was dependent on thickness and structure of the capsules. Of the 72 tumors, 36 had a mosaic pattern. A mosaic pattern was visualized in 12 of the 36 tumors on T1-weighted images and in 27 of the 36 tumors on T2-weighted images. Six tumors were determined to be histologic grade 1, and all were hyperintense on T1-weighted images, regardless of whether intracellular fat deposits were present. Four of the six grade 1 tumors were isointense on T2-weighted images. In contrast, grades 2 and 3 tumors had various signal intensities on T1-weighted images and most were hyperintense on T2-weighted images. Twenty-one of 32 tumors (66%) with focal areas of increased signal intensity on T2-weighted images had intratumoral dilated sinusoids at histologic examination.     

Transient osteoporosis of the hip: MR imaging

Three patients with transient osteoporosis of the hip underwent magnetic resonance (MR) imaging. MR images showed decreased signal intensity of bone marrow in the femur on T1-weighted images and increased signal intensity relative to the intensity of normal bone marrow on T2-weighted images. Joint effusions were seen on MR images of all patients on T2-weighted images. The findings on MR images concurred with histologic findings, such as increased bone turnover and mild inflammatory reaction, in one patient. The clinical symptoms and abnormalities on MR images regressed completely within 6-10 months. Familiarity with the distinct features of transient osteoporosis on MR images may be important in the differential diagnosis of adults with hip pain.     

MR signal intensity of parathyroid adenomas: correlation with histopathology

Recent experience has shown that parathyroid adenomas vary in their MR signal intensity, which raises the question of whether the signal intensity is related to different histologic characteristics. In order to address this question, 10 patients who had MR imaging studies (four at 0.35 T, six at 1.5 T) showing large- to medium-sized parathyroid adenomas and who subsequently underwent surgery with histologic proof of the lesion were evaluated. The MR appearance was compared with histologic characteristics. The adenomas were classified into three groups according to the MR appearance: group I, low signal intensity on short TR/TE images, high signal intensity on long TR/TE images (n = 5); group II, low signal intensity on short and long TR/TE images (n = 3); group III, high signal intensity on short and long TR/TE images (n = 2). Histologic analysis revealed that the major features of each group were different. High cellularity without degeneration or fibrosis was observed for all five adenomas from group I. In group II, all three adenomas showed cellular degenerative changes, old hemorrhage with hemosiderin-loaded macrophages, and/or fibrosis. In group III, both adenomas showed evidence of acute hemorrhage without significant degenerative or fibrotic changes. These data suggest that the signal intensity of parathyroid adenomas on T1- and T2-weighted images corresponds at least in part to differences in histologic composition.     

Analysis of imaging parameters, relaxation time (T1,T2), and relative proton density as they influence the signal intensity of spin echo images

It is difficult to recognize signal intensity changes on spin echo (SE) images. Clinically both T1-weighted and T2-weighted images are now used in most institutions to evaluate signal intensity changes due to different T1 and T2 of the lesions in MRI. However, these are not sufficient to understand signal intensity changes completely. The authors attempted to summarize on a two-dimensional graph the effects of T1, T2, proton density, and imaging parameters that influence signal intensities on SE images. Both end point (E) and start point (S), as defined later, depended mainly on proton density, but the former also depended on T2 and the later on T1 value. The image obtained in the former situation (near point E) was then called the T2-weighted image. Conditions to accelerate recovery and attenuation velocities (VR and VA), also mentioned later, were the same as those that increased points E and S, respectively. However, when TR was relatively short, the effect of a shorter T1 on VR was greatly emphasized. Such an image was then called the T1-weighted image.     

Triangular fibrocartilage and intercarpal ligaments of the wrist: MR imaging. Cadaveric study with gross pathologic and histologic correlation

To provide further understanding of the magnetic resonance (MR) signal intensities in the triangular fibrocartilage (TFC) and interosseous ligaments of the wrist, the authors performed MR imaging with gross pathologic and histologic analysis in 10 cadaveric wrists. Spin-echo T1- and T2-weighted coronal images were obtained, and 3-mm coronal sections of the specimens were then made that correlated precisely with the MR images. Normal portions of the TFC showed asymmetrical bow tie-like low signal intensity, except near the radial and ulnar attachments. Degeneration of the TFC, present in all cases, was more severe on the proximal surface and was characterized by high signal intensity on T1-weighted images and less high signal intensity on T2-weighted images. These findings differed from those in TFC perforation, which showed high signal intensity on T2-weighted images. Similar signal intensity characteristics could allow differentiation of degeneration and perforation of the scapholunate and lunotriquetral ligaments. These findings suggest that in vivo MR imaging may accurately delineate degeneration and perforation of the TFC and intercarpal ligaments.     

Occult intraosseous fracture: detection with MR imaging

Magnetic resonance (MR) images were retrospectively evaluated in eight patients who had recent, symptomatic knee injuries and in whom plain radiographs showed no fractures. T2-weighted images revealed irregular, intraosseous areas of high signal intensity; T1-weighted and proton density images revealed speckled or linear regions of low signal intensity in corresponding areas. In the seven patients whose injuries did not result from direct contusion, abnormalities occurred in subchondral locations. Two patients underwent bone scintigraphy, which showed increased activity in locations corresponding to areas of abnormality noted on MR images. Two patients underwent follow-up MR imaging at 6 weeks and 3 months, which showed complete resolution of the abnormalities. The authors speculate that the MR imaging findings represent microscopic compression fracture of trabecular bone and discuss the related entity, stress fracture.     

Alterations in the supraspinatus tendon at MR imaging: correlation with histopathologic findings in cadavers

To determine the histopathologic correlates of alterations in the rotator cuff at magnetic resonance (MR) imaging, 13 cadaveric shoulders (in subjects aged 26-83 years at the time of death) underwent MR imaging in the coronal oblique plane at 1.5 T with proton-density- and T2-weighted spin-echo sequences. Areas corresponding to sites of MR imaging alterations were then examined histologically. Increased signal intensity on proton-density-weighted images (without further increased signal intensity on T2-weighted images) and an indistinct margin at the articular side of the supraspinatus tendon corresponded to eosinophilic, fibrillar, and mucoid degeneration and scarring. Areas of increased signal intensity on T2-weighted images were associated with severe degeneration and disruption of the supraspinatus tendon. Although other authors have suggested that certain MR findings are indicative of tendinitis, the histologic data in this study were not those of active inflammation but rather tendon degeneration.     

Subcortical low intensity in early cortical ischemia.

PURPOSETo describe subcortical low intensity on T2- and proton density-weighted MR images in early cortical ischemia and to discuss a cause of these findings.METHODSNine patients with early cortical ischemia were studied with proton density- and T2-weighted images, and T1-weighted images at 1.5 T. Gadolinium enhancement was added in six cases.RESULTSIn all cases there was high to intermediate intensity in the cortex and low intensity in the subcortical white matter (subcortex) on the proton density- and T2-weighted images. No significant signal abnormalities were shown on T1-weighted images in the subcortex; gyriform enhancement was seen in the affected cortex in all of the six patients studied with gadolinium. Of the four patients with follow-up MRs, the subcortical low intensity changed to high intensity in two and remained low in two patients in the chronic stage. Neither hemorrhage nor calcification was seen on CT.CONCLUSIONIron accumulation in the subcortex caused by disruption of the axonal transportation and continuous production of free radicals caused by the hypoxic-ischemic state most likely reduces the signal intensity of the subcortex on the proton density- and T2-weighted images. The subcortical low intensity on the proton density- and T2-weighted images is an important diagnostic sign of early cortical ischemia.