MR imaging of primary thyroid lymphoma

Magnetic resonance (MR) images of a patient with primary malignant lymphoma of the thyroid gland and Hashimoto thyroiditis are presented. On T1-weighted images the intensity of the thyroid lymphoma was similar to that of Hashimoto thyroiditis. On T2-weighted images the thyroid lymphoma was seen as a homogeneous area of high intensity compared with Hashimoto thyroiditis. Magnetic resonance was equal to CT in diagnosing and staging of primary thyroid lymphoma. Direct coronal images of MR were useful in planning the radiation port.     

Giant cell tumor of the proximal tibia: MR and CT appearance

The magnetic resonance (MR) appearance of four cases of giant cell tumor (GCT) of the proximal tibia are described and the MR grading of these tumors is compared with CT and conventional radiography. Magnetic resonance showed the lesions to be well defined with respect to adjacent marrow and cortical bone. Homogeneous intermediate signal intensity or low signal within the tumors was seen on T1-weighted images. T2-weighted images showed mixed signal intensity with small "bright patches" of increased signal intensity in all four cases. No fluid levels were identified. Magnetic resonance was superior to CT and plain radiography in radiologic grading of the tumors. Computed tomography was superior in determining if cortical invasion was present. Intraarticular tumor extension was more accurately detected by MR and arthrotomography than CT. An MR manifestation of GCT of the proximal tibia is described which may be a common appearance of this tumor by this modality. Magnetic resonance is the procedure of choice in the radiologic grading of GCT.     

Magnetic resonance findings of primary uterine malignant lymphoma.

To clarify the magnetic resonance (MR) characteristics of primary uterine malignant lymphoma, we identified 4 patients with primary uterine lymphoma in the MR database of our institute from 1994 to 2005 and evaluated their clinical and MR findings for tumor extension, size, shape, and signal intensity, multinodular growth pattern, preservation of normal endometrium, and lymphadenopathy. In all 4 patients, tumors extended to the uterus and vagina or parametrium, and uterine tumors showed relatively homogeneous intensity on both T(1)- and T(2)-weighted MR imaging. Two patients showed multinodular tumor growth; three revealed pelvic lymphadenopathy; and none had intact endometrium or normal uterine zonal structure. Thus, large tumors with relatively homogeneous signal intensity seemed to be a specific MR finding of uterine lymphoma, and findings of multinodular growth were considered a possible characteristic suggesting the uterine involvement of malignant lymphoma.     

原发性骨骼肌非霍奇金淋巴瘤的影像学表现

目的 分析原发性骨骼肌非霍奇金淋巴瘤（NHL）的影像学表现，以期提高对其的认识。方法 经病理证实的原发性骨骼肌NHL5例，均为B细胞来源。其中3例有MR和CT检查，1例仅有CT检查，1例仅有MR检查。2例有X线平片，2例有核素骨显像。结果所有患者均表现为受累肌肉弥漫性肿胀，肌肉轮廓可辨。4例CT平扫密度均匀，与未受累肌肉相近；增强扫描呈轻度强化2例，中等强化1例，强化密度均匀。MR扫描4例，平扫T1WI与周围肌肉相比呈稍低信号，T2WI信号明显高于周围未受累的肌肉。肿瘤内部的信号均匀，未见明显液化坏死区。增强扫描2例肿瘤为均匀强化，强化信号明显高于周围正常肌肉信号。X线平片2例显示骨质未被破坏。核素骨显像2例显示软组织肿块浓聚，骨髓的信号未见异常。结论 原发性骨骼肌NHL的影像学表现有一定的特点，MRI是其最佳的影像学检查方法。     

MR imaging of pituitary adenomas using a prototype resistive magnet: preliminary assessment

Magnetic resonance (MR) images were obtained with a prototype resistive magnet system in 10 patients, all of whom had been shown to have pituitary tumors by enhanced high-resolution computed tomography (CT). Histologic verification was obtained in eight cases. Inversion-recovery (IR) T1-weighted images revealed the tumor in six of nine cases; saturation-recovery (SR) images with less T1 weighting identified seven of nine tumors; Carr-Purcell-Meiboom-Gill (CPMG) spin-echo T2-weighted images revealed two of four tumors. MR images failed to demonstrate three microadenomas: 5 X 5 X 8 mm, 6 X 6 X 6 mm, and one less than 5 mm in estimated size. In the last pretreatment study, CT had demonstrated a 13 mm maximum diameter adenoma. Repeat CT at the time of MR imaging also showed a partially empty sella and did not resolve the residual adenoma. The larger adenomas were identified readily by MR imaging, which, unlike CT, suggested old tumor hemorrhage in two cases, which was confirmed at surgery and histologic examination. MR and CT images were also compared for relative effectiveness in identifying important perisellar structures.     

Segmental intensity differences in the liver on MR images: a sign of intrahepatic portal flow stoppage

Segmental intensity differences (SIDs) in hepatic parenchyma free of tumor were noted in six patients with hepatic masses (hepatocellular carcinoma in five and metastatic liver cancer in one). Areas of SID were homogeneous in intensity. The intensity of the affected region was high in all six patients on T2-weighted magnetic resonance (MR) images and low in two on T1-weighted images. Three of five patients examined with plain computed tomography (CT) had corresponding segmental areas of low attenuation. Angiograms obtained in five patients showed occlusion of the intrahepatic portal vein, segmental staining corresponding to the region of the SID, or both. Twelve of 82 patients examined with MR imaging and angiography had similar findings on angiograms, and ten of them had abnormal intensity of anatomic distribution around or beside the liver tumors on MR images. MR imaging may be more sensitive than plain CT in the detection of secondary changes caused by intrahepatic portal flow stoppage.     

MR imaging of thyroid hemochromatosis

We present the magnetic resonance (MR) images of exogenous hemochromatosis in the thyroid gland. On both T1-weighted images and T2-weighted images the thyroid showed low intensity similar to that of the background. Magnetic resonance is of value in imaging the tissue deposition of iron. In assessing thyroid iron accumulation, MR is superior to CT because CT can not differentiate iron deposition from normal iodine concentration.     

MR imaging of primary epidermoid tumors

The magnetic resonance (MR) imaging characteristics of five primary intradural epidermoid tumors are described. At 0.35 T, the most consistent finding on spin echo imaging was a tumor signal intensity that differed from brain and CSF. On T1-weighted images [repetition time (TR) 0.5 s, echo time (TE) 30-40 ms] all tumors exhibited a signal intensity intermediate between brain and CSF. On moderately T2-weighted images (TR 2.0 ms, TE 60-80 ms) the tumor signal intensity was greater than brain and CSF in all cases. The tumor signal consistency was mixed in four of five lesions and homogeneous in one. The tumor margins were well defined in all cases; in three cases the tumor margins were irregular, in one case smooth, and in the last case, one margin was irregular and the remaining margins were smooth. These findings are contrasted with the MR appearance of arachnoid cysts. Using identical imaging factors, four arachnoid cysts were studied and exhibited a homogeneous signal intensity that was identical to CSF on all pulse sequences; their margins were smooth and well defined in each case. These MR findings contribute to the characterization of extraaxial lesions.     

Primary bladder carcinoma: evaluation with MR imaging

Magnetic resonance (MR) imaging was performed in 23 patients (25 tumors) with proved bladder neoplasms. MR studies were retrospectively evaluated and compared with computed tomographic (CT) and pathologic findings. Bladder neoplasms, having a signal intensity intermediate between those of urine and perivesical fat, were best seen on T1-weighted and proton-density images. MR imaging was as accurate as technically well-performed CT studies in detecting extravesical tumor extension. MR could additionally be used to assess the integrity of the bladder wall. On T2-weighted images the normal bladder wall appeared as a thin, linear, low-intensity structure. The disruption of this low-intensity line was indicative of deep muscle invasion, whereas preservation of this low intensity line implied a more localized lesion. Although chemical shift artifacts might cause apparent disruption of the bladder wall, knowledge of this artifact coupled with additional imaging along different planes helps avoid misinterpretation of this artifact as deep muscle invasion.     

Synovial sarcomas of the head and neck: CT and MR imaging findings of eight patients

BACKGROUND AND PURPOSE: Synovial sarcomas are soft-tissue tumors that rarely occur in the head and neck. The purpose of this study was to evaluate their CT and MR imaging appearance and to show that they may have a surprisingly benign imaging appearance. METHODS: Eight patients with histologically proved synovial sarcoma underwent CT; additionally, MR imaging examinations were performed in five of the eight cases. Attenuation and signal intensity on CT scans and MR images, respectively, were studied by two radiologists. They analyzed the location, size, margins, homogeneity, presence of adenopathies and infiltrative signs, and enhancement after injection of contrast medium. RESULTS: Four tumors were located in the hypopharynx, two arose from the infratemporal fossa, one arose from the maxillary sinus, and one arose from the faucial tonsil. Tumor sizes ranged from 27 to 70 mm. On CT scans and MR images, six lesions were homogeneous and well defined, with smooth margins. The remaining tumors were heterogeneous. In two cases, adjacent tissues were invaded. Calcifications were observed in one case and adenopathy in two cases. In three cases, the lesions were isointense on T1-weighted MR images and hypointense on T2-weighted MR images, and in the other two cases in which MR imaging was performed, the lesions were both isointense and hypointense on both T1- and T2-weighted images. Only the two local recurrent lesions were multilocular. CONCLUSION: Synovial sarcomas are aggressive sarcomas that may appear "benign" in some cases. In a young man, a synovial sarcoma may be suspected when a well-demarcated, homogeneous lesion is found in the head and neck.     

Brachial plexus: correlation of MR imaging with CT and pathologic findings

Thirty-two patients with symptoms referable to the brachial plexus were evaluated with magnetic resonance (MR) imaging. Sixteen patients had undergone concurrent computed tomography (CT). MR imaging demonstrated normal findings in 16, 12 neoplasms, three cases of trauma, and one case of possible neural edema. Of the 16 patients with normal findings on MR images, eight had CT scans that were also normal. In one patient, MR images showed that the "mass" seen on CT was actually a tortuous blood vessel. In six of the 12 cases of neoplasm in which CT scans were available, MR imaging revealed more extensive disease. In the other six cases of tumor, MR imaging provided sufficient clinical information to obviate the need for CT or any other imaging modality. MR imaging provided definitive diagnoses in the three cases of trauma without further imaging. In one patient with paresthesia, MR imaging showed high signal intensity of the nerves on T2-weighted images, which was compatible with neural edema. A concurrent CT scan was normal.     

Cystic synovial sarcomas: imaging features with clinical and histopathologic correlation

Objective To characterize the radiological and clinicopathologic features of cystic synovial sarcoma.Design and patients Seven patients with primary cystic synovial sarcoma were evaluated. Computed tomography (CT) and magnetic resonance (MR) imaging were undertaken at the first presentation. The diagnosis of synovial sarcoma was made on the basis of histological examinations followed by molecular analysis. Radiological and clinicopathologic findings were reviewed.Results CT showed well-defined soft tissue mass without cortical bone erosion and invasion. Calcification was seen at the periphery of the mass in three cases. T2-weighted MR images showed multilocular inhomogeneous intensity mass in all cases, five of which showed fluid-fluid levels. On gross appearance, old and/or fresh hematomas were detected in six cases. In the one remaining case, microscopic hemorrhage in the cystic lumen was proven. Four cases had poorly differentiated areas. In five cases prominent hemangiopericytomatous vasculature was observed. Histologic grade was intermediate in one tumor and high in six. One case had a history of misdiagnosis for tarsal tunnel syndrome, one for lymphadenopathy, two for sciatica and two for hematoma.Conclusion All cystic synovial sarcomas demonstrated multilocularity with well-circumscribed walls and internal septae. Synovial sarcoma should be taken into consideration in patients with deeply situated multicystic mass with triple signal intensity on T2-weighted MR imaging.     

Findings in primary hepatic carcinoid tumor: US, CT, MRI, and angiography.

Two asymptomatic patients with surgically proven solitary primary hepatic carcinoid tumors are reported. Ultrasonography showed hyperechoic masses containing multiple small cystic areas in both cases. On unenhanced CT, one tumor was of low density and one was isodense with multiple low density foci. One tumor showed marked retention of contrast medium on post-angiographic CT. Magnetic resonance imaging revealed low intensity masses on T1-weighted images and high intensity tumors with multiple areas of higher intensity on T2-weighted imaging. The small low density areas in these masses corresponded histopathologically to multiple vascular lakes. Late enhancement of the mass was presumed to correspond with proliferative fibrous tissue within the mass.     

Neck neoplasms: MR imaging. Part I. Initial evaluation

Untreated neoplasms of the neck (tumors of the oropharynx, supraglottic area, carotid body, and thyroid, in addition to malignant lymphadenopathy) were evaluated in 23 patients with magnetic resonance (MR) imaging. The results were compared with computed tomographic (CT) scans in 20 patients. Contrast between tumor and fat was best on relatively T1-weighted images (500/30-35 [TR msec/TE msec]), whereas separation of tumor and muscle was best with relatively T2-weighted pulse sequences (1,500/90). Balanced images (1,500/30-35) provided best overall image quality and best demonstrated vascular anatomy. MR imaging was usually superior to CT in showing the relationship of tumor mass to muscle. MR imaging and contrast material-enhanced CT were equivalent in most patients in defining vascular anatomy, but MR imaging was superior when intravenous contrast material was not administered. However, CT was more helpful in showing bone and cartilage anatomy, and in some patients CT also was better in showing airway abnormalities. Despite these limitations, MR imaging is a promising imaging technique for studying neoplasms of the neck.     

Intramedullary spinal cord tumors: significance of associated hemorrhage at MR imaging.

Magnetic resonance (MR) images obtained in 35 patients with intramedullary spinal tumors were reviewed. Hypointense areas on both T1- and T2-weighted images were seen within or around eight tumors, all of which were in the cervical cord. Hypointensity at the tumor margin was seen in seven cases. Hypointensity within the tumor was seen in two cases. (One case had both types of hypointensity). In seven surgically confirmed cases, hypointensity at the tumor margin was found to be a relatively firm pseudocapsule, and hypointensity within the tumor corresponded to intratumoral hematoma. All of the tumors with hypointensity were ependymomas at histologic examination. When MR imaging shows an intramedullary tumor with hypointensity at the tumor margin, it is suggestive, but not pathognomonic, of an ependymoma.     

Fibrolamellar hepatocellular carcinoma: imaging and pathologic findings in 31 recent cases.

PURPOSE: To review characteristic findings of fibrolamellar hepatocellular carcinoma (HCC) at computed tomography (CT) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: The authors retrospectively reviewed the clinical, pathologic, and preoperative imaging findings in 31 patients with histologically proved fibrolamellar HCC. Dynamic contrast material-enhanced CT of the liver was performed in 31 patients, helical multiphase CT in 21, and MR imaging in 11. Complete resection was performed in 17 patients, and imaging-pathologic correlation was performed. RESULTS: Large tumors (mean diameter, 13 cm) were depicted at CT and MR in all cases. At CT, the margins of the tumors were well defined in 24 (77%) of 31 cases calcifications were depicted in 21 (68%), a central scar in 22 (71%), and abdominal lymphadenopathy in 20 (65%). In 20 (80%) of 25 cases with hepatic arterial phase CT images, all tumors were heterogeneous and depicted areas of hypervascularity. At MR imaging, tumors were hypointense to liver on T1-weighted images (n = 11) and hyperintense to liver on T2-weighted images (n = 10). Calcification was not depicted on MR images, but a central scar was depicted as hypointense to surrounding tumor in nine cases. CONCLUSION: CT and MR images demonstrate characteristic features that may allow confident diagnosis of fibrolamellar HCC.     

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.     

MR imaging of adrenal myelolipomas

The magnetic resonance (MR) images in six patients with seven adrenal myelolipomas are presented. Four lesions involved the right gland, and three the left; they ranged from 3 to 12.5 cm in diameter. Magnetic resonance was able to image all lesions. Using T1-weighted sequences, three structural patterns were observed; (a) homogeneous masses with intensity equal to adjacent fat (three cases); (b) heterogeneous masses with fat intensity areas and areas similar to renal cortex (two cases); and (c) nodules quite different from fat, hypointense to the liver (two cases). On T2-weighted images, myelolipomas were slightly hypointense to fat and either hypo- or isointense to the liver. A comparison with the results of CT studies was possible in all cases, and good correlation with determination of the presence and quantity of fat density tissues within the lesions was observed. However, MR imaging did not seem to help in diagnosing adrenal myelolipoma in patients with equivocal CT findings, and needle biopsy is still needed in difficult cases.     

Computed tomography and magnetic resonance imaging findings of solitary fibrous tumors in the pelvis: Correlation with histopathological findings

Objective

We aimed to analyze the computed tomography (CT) and magnetic resonance imaging (MRI) findings of pelvic solitary fibrous tumors (SFTs) and to improve the diagnostic efficacy for such tumors.

Methods

Six cases of pelvic SFTs confirmed by histopathology were analyzed retrospectively. Of the 6 patients, 4 had undergone CT scanning, and 2 had undergone magnetic resonance imaging. All the patients had undergone unenhanced and contrast-enhanced examinations, and 2 had also undergone dynamic CT enhancement examination. Image characteristics such as shape, size, number, edge, attenuation or intensity for each lesion before and after contrast enhancement were analyzed and compared with the pathomorphology of the tumors.

Results

All the 6 cases showed oval or rounded and well-defined masses. Unenhanced CT images showed heterogeneous masses with patchy, necrotic foci in 3 cases and homogeneous mass in 1 case. None of the tumors showed calcification. Contrast-enhanced CT images showed marked, heterogeneous enhancement in the first and second cases. Dynamic enhancement scan demonstrated mild homogeneous enhancement in the third case and mild prolonged, delayed enhancement and washout in the fourth case. T1-weighted MR images showed heterogeneous mild hypointense lesion with linear hyperintensity in 1 case, and homogeneous isointensity in the other. T2-weighted images showed heterogeneous mixed intensity in 1 case and mostly hyperintensive lesion with hypointense foci in another case. A case showed marked heterogeneous enhancement and another showed marked homogeneous enhancement on contrast-enhanced T1-weighted images.

Conclusion

Radiological findings of pelvic SFTs are variable and nonspecific. However, a well-defined, ovoid or rounded mass with hypointense on MR T2-weighted images and variable enhancement on CT and MR images may suggest the diagnosis of SFTs. Pelvic SFTs should be included in the differential diagnosis of regional tumors.     

Preliminary experience with gadolinium-enhanced dynamic MR imaging for uterine neoplasms.

Usefulness of gadopentetate dimeglumine in magnetic resonance (MR) imaging of uterine neoplasms was evaluated in 53 patients with endometrial carcinoma and 15 patients with cervical carcinoma. T1- and T2-weighted MR images were obtained before the contrast material was administered. After a bolus injection of gadopentetate dimeglumine, dynamic MR images were acquired, followed by static T1-weighted images. Gadolinium-enhanced MR images revealed relatively small endometrial carcinomas in the uterine cavity as high signal intensity in four cases and invasion of the myometrium as low signal intensity in 20 cases. In eight cases, endometrial tumors showed irregular, early enhancement compared with that of the myometrium on dynamic images; these cases were associated with poor prognosis. Tumor extension into the lower part of the uterus, parametrium, and paracervical fat was well seen on enhanced images in cases of cervical carcinoma. The authors believe that gadolinium-enhanced MR imaging will prove helpful in the staging of uterine neoplasms.