Deep soft tissue leiomyoma of the thigh

A case of ossified leiomyoma of the deep soft tissues of the left thigh is presented. The radiographic appearance suggested a low-grade chondrosarcoma. MRI of the lesion showed signal characteristics similar to muscle on both T1- and T2-weighted spin echo sequences with linear areas of high signal intensity on T1-weighted images consistent with medullary fat in metaplastic bone. Histopathological examination of the resected specimen revealed a benign ossified soft tissue leiomyoma. Received: 23 December 1998 Revision requested: 31 January 1999 Revision received: 11 March 1999 Accepted: 16 March 1999     

Diabetic muscle infarction: atypical MR appearance

We describe a case of diabetic muscle infarction which had atypical features of hyperintensity of the affected muscle on T1-weighted images. Biopsy was performed which revealed diffuse extensive hemorrhage within the infarcted muscle. We believe increased signal intensity on T1-weighted images should suggest hemorrhage within the infarcted muscle. Received: 8 March 2000 Revision requested: 14 April 2000 Revision received: 5 May 2000 Accepted: 11 May 2000     

Juxta-articular hemangioma of long bone

We report on a rare case of an intraosseous hemangioma involving the proximal tibia in a 70-year-old man. Radiographically, the lesion was a well-defined osteolytic lesion with marginal sclerosis. The CT images demonstrated a well-defined osteolytic lesion with partial cortical breakthrough. T1-weighted MR images showed a hypointense lesion, while T2-weighted images revealed hyperintense areas, with internal, hypointense septa. Gadolinium-enhanced T1-weighted images showed lattice-like enhancement of the lesion. Received: 28 December 1999 Revision requested: 3 March 2000 Revision received: 23 May 2000 Accepted: 26 May 2000     

Epithelioid hemangioma of bone

Epithelioid hemangioma of bone is a rare type of angiomatous tumor. We report a documented case of epithelioid hemangioma occurring in the distal femur of a 35-year-old man. The clinical, radiographic, MR imaging and histologic findings of the tumor are described. Radiographs showed a well-defined expanding, osteolytic lesion in the diaphysis of the femur. MR imaging showed the lesion to have low signal intensity on T1-weighted images and intermediate signal intensity on T2-weighted images. Grossly the lesion was multiloculated with a dark brown, jelly-like content. To characterize the imaging appearances of epithelioid hemangioma, we reviewed the available literature on the subject. Received: 14 February 2000 Revision requested: 28 March 2000 Revision received: 31 May 2000 Accepted: 1 June 2000     

Solid aneurysmal bone cyst in the humerus

We report on a 69-year-old woman with a solid variant of aneurysmal bone cyst (solid ABC) in the left humerus with a pathological fracture. Radiographically, the lesion exhibited a relatively well-defined osteolytic lesion in the diaphysis of the left humerus. On magnetic resonance (MR) imaging, the medullary lesion exhibited a homogeneous signal intensity isointense with surrounding normal muscles on the T1-weighted images and a mixture of low and high signal intensity on the T2-weighted images. Contrast-enhanced T1-weighted images revealed diffuse enhancement of the entire lesion. The pathological study showed a proliferation of fibroblasts, histiocytes, chronic inflammatory cells and numerous multinucleated giant cells in a collagenous matrix. Abundant osteoid formation in the matrix was observed, but the cells were devoid of nuclear atypia. Aneurysmal cystic cavities were absent. A review of the English literature found 22 cases of solid ABC of the long bones. Received: 15 February 2000 Revision requested: 18 March 2000 Revision received: 17 April 2000 Accepted: 19 April 2000     

Increased signal intensity on fat-suppressed three-dimensional T1-weighted pulse sequences in patellar tendon: magic angle effect?

Objective. To assess the frequency of increased signal intensity in the patellar tendon using three-dimensional T1-weighted MRI pulse sequences. Design and patients. Sixty patients were examined with a 1.0 T scanner (15mT/m gradient strength) using a quadrature coil. Three pulse sequences were applied in the sagittal plane: PD turbo spin echo (PD-TSE), 3D T1-weighted gradient echo with fat suppression (3D-T1-FFE-FS) and 3D T1-weighted echo planar imaging with fat suppression (3D-T1-EPI-FS). The high signal intensity areas were measured in their maximum length. The angle of the patellar tendon relative to the main field position was measured in the same slice. In eight patients with anterior knee pain, and in 11 with no anterior knee pain, a fourth T2-weighted TSE pulse sequence (T2-TSE) was obtained to rule out patellar tendinitis. Results. The correlation of the high signal intensity areas with the relative position of the tendon was found to be significant with the 3D sequences (P=0.03 for 3D-T1-FFE-FS and P=0.003 for 3D-T1-EPI-FS). The length of the high signal intensity area in the tendon was 5.4 mm with 3D-T1-FFE-FS, 4.9 mm with 3D-T1-EPI-FS and 3.1 mm with PD-TSE images. No patellar tendinitis was demonstrated on the T2-TSE images. Conclusion. The magic angle effect is commonly observed in the 3D based T1-weighted pulse sequences with fat suppression. The presence of the above sign must be recognized by radiologists, so that misdiagnosis of patellar tendinitis is avoided. Received: 31 March 2000 Revision requested: 11 July 2000 Revision received: 2 August 2000 Accepted: 26 October 2000     

MRI of malignant fibrous histiocytoma of soft tissue: analysis of 13 cases with pathologic correlation

We reviewed the magnetic resonance (MR) appearances of 13 malignant fibrous histiocytomas (MFH) of soft tissue and correlated each with the respective lesion's histopathology. The MR images were evaluated for signal intensity on T1- and T2-weighted spin echo sequences, homogeneity of the lesion, presence of internal low signal septations, and margin definition. Histologic subtypes of MFH included storiform-pleomorphic, giant cell, myxoid, and inflammatory. We could not establish a correlation between MR appearance and histopathology. Instead, our series exhibited general features suggestive of malignant soft tissue neoplasms, namely poor margin definition, internal low signal septation, and heterogeneous high signal intensity on T2-weighted images.     

Reactive synovitis of the knee joint: MR imaging appearance with arthroscopic correlation

Objective. To evaluate the use of routine MR imaging sequences in detecting and characterizing secondary reactive synovitis of the knee joint using arthroscopy as the standard of reference. Design and patients. Fifty consecutive patients with a history of knee pain who were referred for MR imaging and subsequently underwent arthroscopy of the knee comprised the study group. MR images were evaluated for the presence and appearance of synovitis reflected in synovial thickening and irregularity. Synovial thickening was graded on MR imaging as follows: 0=normal, 1=thin line of increased signal intensity, 2=increased signal intensity with frond-like or hair-like projections and a granular appearance of joint fluid. Standard knee imaging protocols were used. Results. The sensitivity, specificity, and accuracy of MR imaging in detecting synovitis compared with arthroscopy were 88%, 97%, and 95%, respectively. Grade 1 synovitis was best seen on proton-density-weighted images, demonstrating increased signal intensity of the synovium against the relatively low signal intensity of the joint fluid. Grade 2 synovitis was best seen on proton-density images and T2-weighted spin echo and fast spin echo images with fat saturation, demonstrating a granular and linear hair-like appearance of joint fluid. Axial and sagittal imaging planes were most helpful in the diagnosis of synovitis. Conclusion. Routine MR pulse sequences are useful in identifying the presence and extent of synovial abnormalities. The detection of different stages of synovial pathology should become an important part of the evaluation of the post-traumatic patient as treatment may be altered as a result. Received: 17 March 2000 Revision requested: 5 May 2000 Revision received: 8 June 2000 Accepted: 8 June 2000     

Solitary infantile myofibromatosis involving the clavicle

A rare case of solitary infantile myofibromatosis of bone is reported in the right clavicle of a 15-year-old boy. A radiograph demonstrated an osteolytic lesion with a sharp margin and a sclerotic rim. CT revealed a circumscribed lesion with slight expansion of the cortex. On MRI the lesion appeared isointense to muscle on T1-weighted images, bright on T2-weighted images, and showed marked gadolinium enhancement. The patient was well, without evidence of recurrence or metastasis, 4 years and 5 months following resection. Received: 11 August 1998 Revision requested: 5 October 1998, 18 March 1999 Revision received: 15 March 1999, 23 April 1999 Accepted: 28 April 1999     

Isolated intraosseous gout in hallux sesamoid mimicking a bone tumor in a teenaged patient

We are reporting an unusual case of isolated intraosseous tophus in medial hallux sesamoid presenting as tumor-like lesion in a teenage patient without prior history of gouty attack and underlying systemic disorders. The lesion manifested isointensity to surrounding muscles with internal low signal on spin echo (SE) T1-weighted images, and heterogeneous low signal intensity on fast spin echo (FSE) T2-weighted images. Computed tomography (CT) scan disclosed expansion and diffusely increased attenuation of the medial hallux sesamoid with focal cortical erosion and extraosseous extension of high attenuation content. The subsequent resection and pathology revealed intraosseous tophus deposition, which is particularly rare at this site and at this age. Imaging studies revealed some characteristic imaging features which can retrospectively be attributed to gouty tophus. When an expansile osteolytic lesion manifesting low signal intensity on T2-weighted image and internal calcifications on CT scan is encountered, the possibility of intraosseous tophus should be included in the list of differential diagnoses, even in a teenage patient without prior history of gout.     

MR imaging of clear cell sarcoma (malignant melanoma of the soft parts): a multicenter correlative MRI-pathology study of 21 cases and literature review

Objective. To evaluate MR imaging and pathology findings in order to define the characteristic features of clear cell sarcoma of the soft tissues (malignant melanoma of the soft parts). Design and patients. MR examinations of 21 patients with histologically proven clear cell sarcoma of the musculoskeletal system were retrospectively reviewed and assessed for shape, homogeneity, delineation, signal intensities on T1- and T2-weighted images, contrast enhancement, relationship with adjacent fascia or tendon, secondary bone involvement, and intratumoral necrosis. In 19 cases the pathology findings were available for review and for a comparative MR-pathology study. Results. On T1-weighted images, lesions were isointense (n=3), hypointense (n=7) or slightly hyperintense to muscle (n=11). Immunohistochemical examination was performed in 17 patients. All 17 specimens showed positivity for HMB-45 antibody. In nine of 11 lesions with slightly increased signal intensity on T1-weighted images, a correlative MR imaging-pathology study was possible. All nine were positive to HMB-45 antibody. Conclusions. Clear cell sarcoma of the musculoskeletal system often has a benign-looking appearance on MR images. In up to 52% of patients, this lesion with melanocytic differentiation has slightly increased signal intensity on T1-weighted images compared with muscle. As the presence of this relative higher signal intensity on T1-weighted images is rather specific for tumors displaying melanocytic differentiation, radiologists should familiarize themselves with this rare entity and include it in their differential diagnosis when confronted with a well-defined, homogeneous, strongly enhancing mass with slightly higher signal intensity compared with muscle on native T1-weighted images. Received: 18 October 1999 Revision requested: 19 November 1999 Revision received: 21 January 2000 Accepted: 25 January 2000     

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     

MRI of musculoskeletal extraspinal tuberculosis

PURPOSE: The aim of this study was to describe the MR findings in extraspinal musculoskeletal tuberculosis (EMT). METHOD: A retrospective review was conducted of the MR findings of 18 patients with microbiologically and/or pathologically proven EMT. All MR studies were performed using T1-and T2-weighted spin echo sequences. T1-weighted spin echo sequences after Gd-DTPA injection were obtained for 12 patients. The MR images were evaluated for abnormalities in joints, bones, and soft tissues, and the results were grouped by anatomic localization, frequency distribution of structures affected, and morphologic patterns of involvement. RESULTS: Isolated soft tissue tuberculosis was found in 10 (55.5%) patients and involvement of more than one structure in 8 (44.4%). Pyomyositis (n = 6) and arthritis with involvement of adjacent soft tissues (n = 7) were the most common forms of presentation. One patient presented with isolated fascial superficial tissue involvement in one leg. Isolated pyomyositis involving one (n = 3) or two (n = 3) muscles was homogeneous in six cases and showed intermediate (n = 6), low (n = 2), or high (n = 1) signal intensity on T1-weighted images and a high and very hyperintense signal on T2-weighted images. The tenosynovitis synovial fluid was homogeneous (n = 1) or heterogeneous with multiple tiny hypointense nodules (n = 1) on T2-weighted images. The subdeltoid bursitis fluid was characterized by homogeneous low signal intensity with a hyperintense rim (n = 2) on T1-weighted images and homogeneous (n = 1) or heterogeneous hyperintense signals with areas of low signal intensity (n = 1) on T2-weighted images. In tuberculous arthritis, the synovial joint fluid (n = 7) showed heterogeneous (n = 4) or homogeneous (n = 3) low signal intensity on T1-weighted images and high or very high signal intensity on T2-weighted images. Where involved, the adjacent muscle(s) (n = 8) were usually hypointense on T1-weighted images and very hyperintense on T2-weighted images. Associated cellulitis was found in arthritis with involvement of neighboring soft tissues (n = 5), pyomyositis (n = 2), and tenosynovitis (n = 1). The images obtained after Gd-DTPA showed peripheral (n = 10) or heterogeneous (n = 1) enhancement or no enhancement (n = 1). CONCLUSION: The MR findings for EMT are variable. Although diagnosis is dependent largely on prior presumption and clinical context, MRI provides valuable guidelines in defining the extent of the lesions to select the appropriate treatment and for follow-up of abnormalities.     

MR imaging of middle ear cholesteatomas

We prospectively evaluated MR images of 14 patients who had chronic otitis media and who were suspected of having cholesteatomas on otologic examination and/or on high resolution CT. Cholesteatomas were verified in the middle ear and/or mastoid at surgery in nine patients. Cholesteatomas appeared isointense relative to gray matter on T1-weighted spin echo MR images (T1WI) and hyperintense on T2-weighted spin echo MR images (T2WI) in eight patients. Two cholesterol granulomas appeared hyperintense on both T1WI and T2WI. In three patients with chronic otitis media the associated mixed granulation tissue and fluid collection was revealed as nonspecific, heterogeneous signal intensity in two cases. In the third case the signal intensity was similar to that found in cholesteatomas.     

Benign vertebral hemangioma: MR-histological correlation

Objective: To explain the magnetic resonance (MR) appearance of benign vertebral hemangioma by correlating MR and histological findings from autopsy specimens. Design: Sagittal T1- and T2-weighted spin-echo images were obtained in 83 spine specimens. Focal lesions consistent with vertebral hemangioma at macroscopic examination of sagittal anatomical sections were sampled for histological and quantitative analysis. At histology, the proportion of surface area occupied by adipocytes, vessels and edema, and hematopoietic cells was determined (point-counting method) in normal marrow areas and in lesion areas whose signal intensity was either high and intermediate (pattern A) or intermediate and high (pattern B) on T1- and T2-weighted images, respectively. Results: Nine lesions were sampled and corresponded to cavernous hemangioma at histology. The proportion of surface area occupied by adipocytes was statistically significantly higher in pattern A (78.1%) than in pattern B lesion areas (42.7%) and than in normal marrow areas (47.5%). The proportion of surface area occupied by vessels and interstitial edema was statistically significantly higher in pattern B (47.0%) than in pattern A lesion areas (15.5%) and than in normal marrow areas (0). Conclusion: The presence of high signal intensity on T1- or T2-weighted images of vertebral hemangioma is related to the amount of adipocytes or vessels and interstitial edema, respectively. Received: 8 September 2000 Revision requested: 29 December 2000 Revision received: 27 March 2001 Accepted: 18 April 2001     

Intramuscular metastasis from malignant melanoma: MR findings

We present a rare case of intramuscular metastasis from malignant melanoma. The lesion showed intermediate to high signal intensity on T1-weighted magnetic resonance (MR) images and mixed signal intensities containing high and low signals on T2-weighted images. The signal intensity on T1-weighted images, which is due to the paramagnetic effect of melanin, is a characteristic MR finding of this entity. Received: 10 June 1999 Revision requested: 7 July 1999 Revision received: 9 August 1999 Accepted: 9 August 1999     

Quantitative assessment of an MR technique for reducing metal artifact: application to spin-echo imaging in a phantom

Objective. To quantify image artifact reduction using a new technique (MARS – metal artifact reduction sequence) in vitro. Design. Coronal T1-weighted MR images were obtained through two metal phantoms (titanium/chromium-cobalt and stainless steel femoral prostheses) immersed in water. Comparison of artifact volume was made with images obtained using conventional and modified (MARS) T1-weighted sequences. Signal intensity values outside a range of ±40% the average signal intensity for water were considered artifact and segmented into low or high signal artifact categories. Considering the arbitrary selection of this threshold value, volumetric calculations of artifact were also evaluated at ±50%, 60%, 70%, and 80% the mean signal for water. Results. Conventional T1-weighted images produced 87% more low signal artifact and 212% more high signal artifact compared with the MARS modified T1-weighted images of the stainless steel prosthesis. Conventional T1-weighted images of the titanium prosthesis produced 84% more low signal artifact and 211% more high signal artifact than the MARS modified sequence. The level of artifact reduction was essentially uniform for the various threshold levels tested and was greatest at ±20% the global signal intensity average for water. Conclusion. The MARS technique reduces the volume of image signal artifact produced by stainless steel and titanium/chromium-cobalt femoral prostheses on T1-weighted spin-echo images in a tissue phantom model. Received: 11 April 2000 Revision requested: 22 May 2000 Revision received: 26 October 2000 Accepted: 27 November 2000     

Angiomyolipoma arising in the thigh

A 41-year-old man presented with an asymptomatic mass in the right medial thigh. Magnetic resonance imaging (MRI) revealed a well-demarcated, 10-cm mass in the right adductor muscles. The margins of the mass exhibited high signal intensity and the rest showed low or iso signal intensity on T1-weighted MR images. However, the high signal intensity was decreased on T2-weighted images with fat suppression. The central part of the tumor was of inhomogeneous high signal intensity on T2-weighted images; after Gd-DTPA injection it enhanced inhomogeneously on T1-weighted images with fat suppression. On dynamic computed tomography (CT) in the arterial phase, there were strongly enhancing spotty areas in the tumor. At surgery, a yellow-whitish tumor was resected and a pathological diagnosis of angiomyolipoma (AML) in the thigh was made. Received: 21 June 1999 Revision requested: 28 July 1999 Revision received: 13 December 1999 Accepted: 15 December 1999     

Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients

BACKGROUND AND PURPOSE: Intracranial solitary fibrous tumors (ISFTs) are rare mesenchymal neoplasms originating in the meninges. The aim of this study was to describe the CT, MR imaging, and angiographic features of the solitary fibrous tumor and to identify imaging characteristics. MATERIALS AND METHODS: We retrospectively reviewed CT, MR, and angiographic findings in 6 cases of ISFT. We evaluated the size, shape, and location of the tumor; the internal content and margin of the lesion; the pattern of enhancement; and the change of the adjacent structures. Density on noncontrast CT scans, signal intensity on MR images, and angiographic features were also documented. RESULTS: Each lesion appeared as a discrete extra-axial mass (size, 3-7 cm; mean, 5 cm). Five lesions were entirely solid, and 1 had peritumoral cyst. All 5 of the noncontrast CT scans showed hyperattenuated masses, and the tumors exhibited marked heterogeneous enhancement. No lesion contained calcification, and 2 cases showed bone invasions. On the MR images, 4 lesions showed mixed signal intensity on T2-weighted imaging. All of the lesions revealed marked heterogeneous enhancement. All of the tumors had thickening of the meninges adjacent to the tumor. Angiography showed delayed tumor blushing in all, and 3 of them had dysplastic dilation of the tumor vessels. CONCLUSION: Although there are no pathognomonic imaging findings, some imaging features, such as the "black-and-white mixed" pattern on T2-weighted images and marked heterogeneous enhancement, might be helpful in the diagnosis of intracranial solitary fibrous tumor.     

Angiosarcoma associated with chronic lymphedema (Stewart-Treves syndrome) of the leg: MR imaging

Magnetic resonance (MR) imaging findings of two patients with Stewart-Treves syndrome are presented. MR imaging showed edematous changes in the subcutaneous fat and skin masses that proved to be angiosarcomas. MR signal intensity of the tumor was low compared with fat on T1-weighted images and intermediate and heterogeneous on T2-weighted images. In one patient, administration of intravenous Gd-DTPA showed marked enhancement in the early phase, which persisted until the delayed phase. These finding on dynamic MR imaging may reflect the abundant vascular spaces seen in these tumors. Received: 20 August 1999 Revision requested: 28 October 2000 Revision received: 31 January 2000 Accepted: 8 February 2000