Focal hepatic lesions: differentiation with MR imaging at 0.5 T

Magnetic resonance (MR) examinations of 43 patients with 95 focal hepatic lesions (diameter, greater than 1 cm) were analyzed for lesion shape, homogeneity, and relative signal intensity compared with normal liver parenchyma, spleen, and skeletal muscle. On T1-weighted, balanced, and T2-weighted images, most metastases (74%), cavernous hemangiomas (76%), and cysts (82%) were smooth and round or oval, while the hepatocellular carcinomas all had irregular borders (40%) or were lobulated (60%). All lesions with irregular borders were malignant. Seventy percent of metastatic lesions, 85% of cavernous hemangiomas, and 100% of simple hepatic cysts were of homogeneous signal intensity, while 60% of hepatocellular carcinomas were inhomogeneous. Logistic regression analysis of multiple lesion characteristics showed that inhomogeneous lesions had a high likelihood of malignancy, while markedly hyperintense lesions had a very low probability of being malignant, regardless of other traits. Homogeneous lesions that were isointense or hyperintense compared with spleen on balanced images but were not markedly hyperintense on T2-weighted images also had a high likelihood of malignancy.     

MR of the submandibular gland: normal and pathologic states.

PURPOSETo evaluate the MR appearance of normal and pathologic states of the submandibular gland.METHODSMR images of 22 healthy subjects and 21 patients with histopathologically confirmed disorders of the submandibular gland (five pleomorphic adenomas, two hemangiomas, two malignant lymphomas, one adenoid cystic carcinoma, one squamous cell carcinoma, and 10 cases of sialadenitis) were reviewed.RESULTSAll normal submandibular glands showed higher signal intensity than surrounding muscle but lower intensity than fat on T1-weighted and T2-weighted images. Postcontrast images showed moderate enhancement of the gland. All the tumors had lower signal intensity than the normal submandibular gland on T1-weighted images and had intermediate to high (n = 8) or high (n = 3) signal intensity relative to the normal submandibular gland on T2-weighted images. Six of seven benign tumors were well defined, and three of four malignant tumors were poorly defined. In all cases of sialadenitis, the submandibular gland showed diffusely different signal intensities from the normal gland on both T1-weighted and T2-weighted images. Eight cases of chronic sialadenitis showed lower T2-weighted signal intensities than the normal gland, and this can be explained histopathologically by marked fibrosis and cellular infiltration.CONCLUSIONSMR imaging can show the presence, extent, margins, and signal intensity changes of pathologic conditions of the submandibular gland.     

Ovarian fibromas and cystadenofibromas: MRI features of the fibrous component

Ovarian fibromas and cystadenofibromas are neoplasms that share a similar distinctive tissue component of dense fibrous tissue. We sought to describe the MRI features of these neoplasms and to determine if the fibrous component shows distinctive characteristics. Fourteen patients in whom MR images performed with multicoil and fast-spin-echo images and who subsequently underwent surgery for resection of ovarian fibromas or cystadenofibromas were identified from two institutions. Five patients had ovarian fibromas, and nine patients had fourteen cystadenofibromas. 1.5-T MR studies used T1-weighted spin echo and multiplanar T2-weighted fast-spin-echo images, with fat saturation gadoliniumenhanced fast multiplanar gradient-echo images in seven patients. Studies were reviewed for findings of low (≈ skeletal muscle) signal intensity solid components on T2-weighted images, characteristics of gadolinium enhancement, and associated endometrial findings. Images were obtained ex vivo from three adnexal surgical specimens with an 8-cm field of view and correlated with histology. All five of the fibromas showed predominantly very low signal intensity, similar to skeletal muscle, on T2-weighted images. Two of five fibromas were in patients with endometrial polyps and increased amounts of fluid in the pelvis. Thirteen cystadenofibromas were multicystic masses with bands of very low signal intensity ranging from 2 to 20 mm in the wall of the mass, and one was predominantly solid fibrous tissue. Pathologic correlation with specimen images showed that the low signal intensity material was the subepithelial fibrous component of the Cystadenofibromas. Fibrous components of ovarian fibromas and cystadenofibromas are demonstrable by MR as solid components representing fibrous tissue of very low signal intensity on T2-weighted images.     

MR imaging of malignant pleural mesothelioma

The magnetic resonance (MR) findings in three patients with malignant pleural mesothelioma are described. All patients had a circumferential pleural mass surrounding the lung on the affected side. These tumors had a signal of intermediate intensity on T1-weighted images. The T2-weighted images showed a slight increase in signal intensity of the mass, with focal areas of very high signal intensity due to pleural fluid. Adenopathy was demonstrated by CT and MR in two patients. The extent of the tumor and its effects on adjacent structures were well appreciated on the coronal MR 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.     

Bone bruises: MR characteristics and histological correlation in the young pig

PURPOSE: To correlate magnetic resonance (MR) signal characteristics of bone bruises with histological findings. MATERIALS AND METHODS: In 14 tibiae of young pigs, bone bruises were created in the proximal tibial metaphysis. The signal intensity seen on the MR images were correlated with histological findings. The following findings were evaluated: (a) changes of signal intensity on the tibiae; (b) changes of histology on the tibiae; and (c) changes of (a) and (b) on follow-up examinations. RESULTS: We observed three types of injuries on T1-weighted images: focal or diffuse low signal, normal signal and linear low signal intensities. Severe hemorrhagic areas showed low signal intensities on all sequences of MR imaging. Fast spin-echo (FSE) T2-weighted images showed a more distinct low signal intensity than T1-weighted images. FSE short tau inversion recovery (STIR) and FSE fat saturated (FSE-FS) T2-weighted images showed similar signal intensities with FSE T2-weighted images. FS T1-weighted enhanced images showed low signal intensities with variable enhancements. Upon histological examination, hemorrhages and edemas were prominent at the subcortical areas of the contusion sites. The areas of dense, low signal intensities in all imaging sequences showed signs of severe hemorrhage. The areas of diffuse low signal and enhanced areas showed mixed areas of hemorrhages and edemas. Follow-up MR imaging showed evolution of the processes of hemorrhages and edemas with fatty marrow changes. CONCLUSIONS: MR imaging can depict changes in the bone marrow resulting from direct injury to the bone. MR imaging is a useful tool for evaluating the evolution of bone bruises.     

Variable MR findings in ovarian functional hemorrhagic cysts

PURPOSE: To describe the magnetic resonance (MR) findings in ovarian functional hemorrhagic cysts (FHC). MATERIALS AND METHODS: A total of 21 patients with 22 FHC, proven by follow-up ultrasound (US) in 11 women and surgery in 10 women, had US and MR examinations within 24 hours. The study was limited to cysts with obvious an echogenic pattern. All patients had T2-weighted fast spin echo (FSE), T1-weighted spin echo (SE), and T1-weighted SE fat-suppressed sequences. RESULTS: Four cysts (18%) were hypointense on T1-weighted-images without and with fat suppression, and hyperintense on T2-weighted-images. Five cysts (23%) were hypointense on T1-weighted images without and with fat suppression but heterogenous on T2-weighted images. Five cysts (23%) were hypointense on T1-weighted images but showed intermediate signal intensity on T1-weighted fat suppression images and heterogenous signal intensity on T2-weighted images. Two cysts (9%) were entirely intermediate on T1-weighted images. Five cysts (23%) displayed high signal intensity occupying less than 30% of the cystic content on T1-weighted images and one cyst (5%) displayed high signal intensity occupying more than 30% of the cystic content. CONCLUSION: Despite an obvious echogenic pattern on US, 64% of FHC were hypointense on T1-weighted images and 18% were also hyperintense on T2-weighted images. Only 36% demonstrated intermediate or high signal intensity on T1-weighted images.     

Lymphangiomas in children: MR imaging

Seventeen lymphangiomas in 15 patients were imaged with magnetic resonance (MR) to define the nature, extent, and anatomic relationships of these lesions. The MR and pathologic findings were then compared to determine the histologic basis for the signal-intensity characteristics of these lesions. The signal intensity of 13 lesions was similar to or slightly less than that of muscle on T1-weighted images and greater than that of fat on T2-weighted images. This appearance correlated with the presence of ectatic lymphatic channels containing clear fluid on histologic section. Four lymphangiomas had high signal intensity, approximately equal to that of fat, on T1-weighted images, reflecting the presence of clotted blood or small cystic spaces with a higher ratio of fat to fluid. Sixteen of 17 lesions had visible septations on MR images. The authors' experience suggests that most lymphangiomas have a characteristic appearance on MR images. The information obtained with MR imaging can help in providing a preoperative diagnosis, in planning surgical resection, and in defining recurrence.     

Vertebral hemangiomas: MR imaging

Vertebral hemangiomas, unlike most bone lesions, show increased signal on T1- and T2-weighted magnetic resonance (MR) images. To define the basis for these signal characteristics, a retrospective review was done of the MR imaging findings in ten vertebral hemangiomas (eight patients), and these were correlated with the findings from plain radiographic, computed tomographic (CT), and histopathologic studies. MR images showed mottled increased signal in T1- and T2-weighted images from the osseous portions of the tumors. In three patients, the extraosseous components failed to show increased signal on T1-weighted images. Chemical shift images and histologic studies demonstrated that adipose tissue caused the increased signal on T1-weighted images. The extraosseous components of the tumor contained little, if any, adipose tissue, which explained the lack of high-intensity signal on T1-weighted images. These signal changes appear to make a specific constellation of findings for the diagnosis of vertebral hemangioma with MR imaging.     

Spinal angiolipomas: MR features.

PURPOSETo determine the MR features of spinal angiolipomas and to compare these findings with their histologic appearance.METHODSThe MR examinations of three patients with surgically proved angiolipomas were reviewed for tumor location and extent, signal characteristics, and pattern of contrast enhancement, and were then compared with the histologic findings.RESULTSFour tumors were found in the three patients, all located in the posterior epidural compartment, averaging about 2.5 vertebral bodies in length. On noncontrast T1-weighted images, all lesions were inhomogeneous and hypointense relative to epidural fat. Inhomogeneous enhancement was seen in three lesions on postcontrast T1-weighted images obtained with fat-saturation techniques. Angiolipomas were least conspicuous on T2-weighted images. A high vascular content correlated with the presence of large hypointense regions on T1-weighted images.CONCLUSIONSpinal angiolipomas are typically hyperintense on noncontrast T-1-weighted images relative to other tumors. Angiolipomas that contain large hypointense foci on noncontrast T1-weighted images can be expected to have a high degree of vascularity.     

Mucocutaneous and peripheral soft-tissue hemangiomas: MR imaging

Hemangiomas are common congenital lesions that may have devastating sequelae. The extent and location of a lesion determines the therapeutic approach. We describe 11 patients with mucocutaneous or peripheral soft-tissue hemangiomas to illustrate the ability of magnetic resonance (MR) imaging to define clearly and noninvasively the extent and anatomic relationships of hemangiomas. The major advantage of MR imaging over computed tomography or angiography is the exquisite difference in contrast between hemangiomas and the surrounding structures on T2-weighted MR images, in which hemangiomas have a relatively intense signal. Hemangiomas demonstrated relatively low signal intensity (similar to muscle) on T1-weighted images, which were markedly inferior to T2-weighted images in defining the extent of the lesions. Phleboliths and feeding or draining vessels were rarely visible. The information obtained with MR imaging may be valuable clinically in planning surgical resection or laser therapy of aggressive lesions, in evaluating effectiveness of medical or embolic therapy, and in defining recurrence.     

Magnetic resonance imaging of myositis ossificans: analysis of seven cases

Myositis ossificans typically presents as soft tissue swelling with progressive ossification on radiographs. Since magnetic resonance imaging (MRI) is commonly used to evaluate soft tissue masses, we analyzed eight MR examinations in seven patients with myositis ossificans to determine if typical patterns were present. One acute lesion had homogeneous intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Two subacute lesions had low signal intensity margins with slightly increased signal intensity centers on T1-weighted images and very high signal intensity on T2-weighted images. Five chronic lesions had two different patterns. All five were well-defined with low signal intensity borders. Three had signal intensity patterns characteristic of fat on T1-weighted and T2-weighted images. The other two lesions had intermediate signal intensity on T1-weighted images and slightly increased signal intensity on T2-weighted images.We conclude that typical MR appearances of myositis ossificans do exist. A low signal intensity rim is a common finding. However, these patterns are not unique to myositis ossificans and resemble those that have been reported in other lesions. It is important to be aware of the spectrum of MR findings of myositis ossificans when considering the differential diagnosis of a soft tissue mass.     

MR imaging differentiation of soft-tissue hemangiomas from malignant soft-tissue masses

OBJECTIVE: The purpose of this study was to determine whether MR imaging features can reliably distinguish hemangiomas from malignant soft-tissue masses. MATERIALS AND METHODS: We retrospectively reviewed MR imaging studies of 22 patients with soft-tissue hemangiomas and 22 patients with malignant soft-tissue masses. Images were reviewed and agreement reached by a consensus interpretation of two observers and by an independent observer. Masses were evaluated for signal intensity on T1- and T2-weighted images, for enhancement with gadolinium administration, and for morphology (lobulation, septation, central low-intensity dots). Lesion T2 signal and lesion enhancement with gadolinium administration were also objectively measured using regions of interest and comparison with skeletal muscle. RESULTS: Signal intensity on T1-weighted imaging of hemangiomas and malignant soft-tissue masses was similar. Subjective analysis showed greater T2 signal and gadolinium enhancement in hemangiomas; however, the differences were not statistically significant on objective analysis. Lobulation, septation, and central low-signal-intensity dots were all more common in hemangiomas, with statistical significance achieved; the combination of all three findings was specific for hemangioma. CONCLUSION: Although no single MR imaging feature was diagnostic in this study, analysis of lesion morphology, signal intensity, and enhancement with gadolinium allowed MR imaging differentiation of hemangiomas from malignant soft-tissue masses.     

四肢黏液样脂肪肉瘤的MRI诊断

目的探讨四肢黏液样脂肪肉瘤的临床和MRI特点。方法对7例经病理证实的四肢黏液样脂肪肉瘤的临床和MRI资料进行了回顾性分析。患者年龄41-59岁，中位年龄51岁。结果3例肿瘤发生在大腿，2例在小腿，1例在足部，1例在肩部；6例位置深在，1例位置表浅。与肌肉相比病变在T1WI上主要呈等或稍低信号，6例可见“线”状、“花边”状或“云絮”状高信号；在T2WI上病变与脂肪相比大部分区域呈高信号；增强扫描病变均呈不均匀的显著强化；病变内部可见分隔，边缘清楚，周围无明显水肿，均未侵犯邻近骨骼。结论四肢黏液样脂肪肉瘤MRI表现有一定特点，在T1WI上主要呈等或稍低于肌肉的信号，并可见脂肪成分所致的“线”状、“花边”状或“云絮”状高信号，在T2WI上则以高于脂肪的信号为主，增强扫描呈不均匀的显著强化。     

MR appearance of skeletal neoplasms following cryotherapy

Cryotherapy is an increasingly popular mode of therapy adjunctive to surgical curettage in the treatment of certain skeletal neoplasms, such as giant cell tumors or chondrosarcomas. The magnetic resonance (MR) findings following cryotherapy have not been previously reported. We reviewed the MR findings in seven patients with skeletal neoplasms following curettage and cryotherapy. In six cases we found a zone of varying thickness extending beyond the surgical margins, corresponding to an area of cryoinjury to medullary bone. This zone displayed low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, consistent with the presence of marrow edema. This zone of edema almost certainly reflects underlying thermal osteonecrosis. This zone may vary in size and intensity over time as the area of cryoinjury evolves or resolves. MR is currently the imaging procedure of choice for follow-up of most musculoskeletal neoplasms. Knowledge of the MR findings following cryotherapy should help prevent confusion during the interpretation of follow-up MR examinations.     

MR imaging of intradural extramedullary tumors.

Thirty-one consecutive intradural extramedullary spinal tumors examined with MR at 0.3 T were reviewed. In 13 of the patients myelography had been performed. There were 11 patients with meningeoma, 14 with neuroma, one ependymoma, 3 metastases, and 2 lipomas. All tumors were surgically removed and verified by histology. The intradural extramedullary location of the tumors was accurately assessed by MR imaging in all patients and by myelography in 10 of 13. The MR diagnoses were in accordance with the histologic findings in 74% of cases. Compression of the spinal cord or cauda equina with widening of the subarachnoid space above and below the mass or outward displacement of epidural fat was characteristic of the intradural extramedullary tumors. The signal intensity of meningeoma as well as of neuroma was slightly lower or equal to that of the cord on T1-weighted images, and equal to or higher than cord signal on T2-weighted images. Neuroma had a lower signal intensity on T1-weighted images and a higher signal intensity on T2-weighted images than meningeoma. Meningeoma appeared more homogeneous than neuroma and had a broad base towards the dura.     

Using superparamagnetic iron oxide-enhanced MRI to differentiate metastatic hepatic tumors and nonsolid benign lesions

OBJECTIVE: We evaluated the ability of superparamagnetic iron oxide (SPIO)-enhanced MRI to differentiate solid metastatic tumors and nonsolid benign lesions by clarifying the characteristic signal-intensity pattern of each lesion on SPIO-enhanced T2-weighted and heavily T1-weighted gradient-echo images. MATERIALS AND METHODS: SPIO-enhanced MRI was performed using a 1.5-T system in 33 consecutive patients without cirrhosis who had 81 focal hepatic lesions (42 cysts, 13 hemangiomas, 26 metastatic tumors). The relative signal intensity of lesions on SPIO-enhanced heavily T1- and T2-weighted gradient-echo images was classified into one of the following three categories: high intensity, isointensity, or low intensity relative to the surrounding liver parenchyma. The diagnostic accuracy for differentiating solid metastatic tumors from nonsolid benign lesions (cysts or hemangiomas) was determined. RESULTS: A combination of the relative signal intensity of the lesion on T2- and heavily T1-weighted gradient-echo images could be classified into the following five categories: high intensity and high intensity (category 1), high intensity and isointensity (category 2), high intensity and low intensity (category 3), isointensity and isointensity (category 4), and isointensity and low intensity (category 5). According to these categories, category 1 contained two hemangiomas, category 2 had 11 hemangiomas, category 3 had 25 metastatic tumors and two cysts, category 4 had three cysts, and category 5 had 37 cysts and one metastatic tumor. When a tumor with a relative signal intensity of categories 1 or 2 was considered to be a hemangioma (category 3 metastatic tumors and categories 4 and 5 cysts), diagnostic accuracy for characterizing such hepatic lesions was 96% (78/81). CONCLUSION: When evaluating metastatic liver tumors on SPIO-enhanced MRI, we recommend that heavily T1- and T2-weighted gradient-echo images be obtained with our parameters to exclude hemangiomas or cysts.     

周围软组织血管瘤和血管畸形MRI鉴别诊断

目的探讨血管瘤和血管畸形MRI的鉴别诊断。方法回顾性分析61例手术证实的血管瘤和血管畸形MRI表现并与病理进行对照。结果29例血管瘤中,在T1WI上,20例为等信号(等于肌肉信号),9例为高等混杂信号;在T2WI上,24例呈较高信号(接近脂肪信号),5例呈高信号(高于脂肪信号),另见25例条状低信号分隔,其中4例增强呈分块状强化。32例血管畸形中,T1WI图,16例为等信号,16例为高等混杂信号;T2WI图,3例呈较高信号,29例呈高信号。其中15例增强呈不均匀强化。结论MRI对血管瘤和血管畸形的鉴别诊断有重要价值。     

Multiple myeloma: appearance at MR imaging.

Magnetic resonance (MR) imaging examinations of the lumbar spine and clinical and laboratory findings in 32 patients with multiple myeloma were reviewed. On T1-weighted images, signal intensity (SI) of the vertebrae approximated that of muscle in 14 cases and was intermediate (between the SIs of muscle and fat) in 18. Definite foci of decreased SI were seen in eight cases (25%), and foci of increased SI, representing fatty infiltration, were seen in 12 (38%). On T2-weighted images, SI approximated that of muscle in 17 cases and was intermediate in 15. Definite foci of increased SI were seen in 17 (53%). Of 38 vertebral compression fractures (including 18 in nine additional patients), foci of abnormal SI consistent with tumor on either T1- or T2-weighted images were seen in 19 cases (50%). There was no correlation between MR imaging findings and laboratory or bone marrow findings. Foci of presumed tumor were better or exclusively shown on T2-weighted images in 11 of 17 patients (65%) with identifiable focal disease. Other suggestions of multiple myeloma on T1-weighted images may be the absence of fatty replacement or a generalized decrease in SI.     

Tumors of the parapharyngeal space and upper neck: MR imaging characteristics

Magnetic resonance (MR) imaging characteristics of 40 tumors involving the parapharyngeal space and the upper part of the neck were reviewed. These lesions could be classified as being either hypervascular (glomus tumors or metastatic kidney, thyroid, or venous hemangiomas) or hypovascular (salivary gland tumors, neurogenic tumors, lymphomas, sarcomas). Detailed analysis of the contour of the neoplasm combined with clinical findings allowed further refinement of the differential diagnosis in each category. Most lesions had an intermediate signal intensity on T1-weighted images and a fairly high signal intensity on T2-weighted images. Hypervascular tumors had a number of "channel voids" caused by high-flow vessels on T1- and T2-weighted images, and on T2-weighted images there were areas of high signal intensity, presumably due to sites of slow flow within the image plane. The hypovascular lesions were quite homogeneous, and it was therefore more difficult to differentiate among the neoplasms in this group.