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.     

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     

Multiple pulmonary metastases from intracranial meningioma: MR imaging findings (case report)

Extracranial metastases from meningioma are very rare and among those the lungs are the most common metastatic site. In the literature, pulmonary metastases of meningiomas have been emphasized on their rarity, non-specific imaging findings, and cytologic features. Some definitive MR imaging features of intracranial meningiomas have been described. However, MR imaging findings of the lung metastases of meningiomas have not been investigated with regard to these diagnostic imaging features. In this report, similarities between MR imaging features of primary intracranial meningioma and its rare lung metastases are presented.     

Choroidal hemangioma: MR findings and differentiation from uveal melanoma.

BACKGROUND AND PURPOSEThe aim of this study was to establish the MR imaging characteristics of choroidal hemangioma and to compare them with those of uveal melanoma.METHODSAmong 41 patients examined at 1.5 T (4-cm surface coil, T1-weighted and fast spin-echo T2-weighted sequences), 25 had uveal melanoma and 16 had circumscribed choroidal hemangioma. After i.v. bolus injection of gadopentetate dimeglumine, dynamic and T1-weighted sequences were acquired.RESULTSIn patients with choroidal hemangioma, uniform signal characteristics were detected on fast T2-weighted images. In 15 of 16 patients with choroidal hemangioma, lesions were isointense with vitreous on fast spin-echo T2-weighted images, whereas lesions in 24 of 25 patients with uveal melanoma were hypointense. Signal characteristics of uveal melanoma and hemangioma did not differ significantly on plain T1-weighted images. Enhancement was earlier and much stronger for circumscribed choroidal hemangioma than for uveal melanoma. After i.v. bolus application of gadopentetate dimeglumine, the increase of signal intensity was higher for circumscribed choroidal hemangioma (signal intensity ratio, 5.8) than for uveal melanoma (signal intensity ratio, 2.2).CONCLUSIONCircumscribed choroidal hemangioma may be difficult to differentiate from melanoma by ophthalmologic examination. Differentiation may not be possible if direct viewing of uveal space-occupying lesions is hampered by opaque vitreous media. The characteristic findings on fast spin-echo T2-weighted MR images and early enhanced images aid in differentiating choroidal hemangioma from uveal melanoma.     

Subcutaneous metastases from malignant melanoma: prevalence and findings on CT

We reviewed 197 body CT studies on 53 sequential patients who had a histologic diagnosis of malignant melanoma in order to determine the CT appearance, pattern of spread, and prevalence of subcutaneous melanoma metastases. Seventeen (38%) of 45 patients with CT evidence of metastatic melanoma had subcutaneous nodules shown on CT. Five patients (11%) had subcutaneous nodules as the only indication of metastatic disease on their CT scans. All patients who developed subcutaneous metastases had primary lesions classified as Clark level IV or V. (The Clark classification is based on the depth of tumor invasion and is rated I to V.) Metastases appeared as small, discrete rounded densities in the subcutaneous fat; lesions were occasionally subtle because of their small size and peripheral location. The location of subcutaneous nodules could not be predicted consistently on the basis of the site of the primary malignancy. We conclude that subcutaneous metastases are common with melanoma in patients with Clark level IV or V lesions. These subcutaneous nodules are readily detected on CT scans if the subcutaneous tissues are carefully examined. The detection of these lesions may affect management or prognosis of patients, especially in those cases where subcutaneous nodules are the only CT evidence of metastatic disease.     

Painful heel: MR imaging findings.

Heel pain is a common and frequently disabling clinical complaint that may be caused by a broad spectrum of osseous or soft-tissue disorders. These disorders are classified on the basis of anatomic origin and predominant location of heel pain to foster a better understanding of this complaint. The disorders include plantar fascial lesions (fasciitis, rupture, fibromatosis, xanthoma), tendinous lesions (tendinitis, tenosynovitis), osseous lesions (fractures, bone bruises, osteomyelitis, tumors), bursal lesions (retrocalcaneal bursitis, retroachilleal bursitis), tarsal tunnel syndrome, and heel plantar fat pad abnormalities. With its superior soft-tissue contrast resolution and multiplanar capability, magnetic resonance (MR) imaging can help determine the cause of heel pain and help assess the extent and severity of the disease in ambiguous or clinically equivocal cases. Careful analysis of MR imaging findings and correlation of these findings with patient history and findings at physical examination can suggest a specific diagnosis in most cases. The majority of patients with heel pain can be successfully treated conservatively, but in cases requiring surgery (eg, plantar fascia rupture in competitive athletes, deeply infiltrating plantar fibromatosis, masses causing tarsal tunnel syndrome), MR imaging is especially useful in planning surgical treatment by showing the exact location and extent of the lesion.     

Complex renal cysts: findings on MR imaging.

OBJECTIVE: We retrospectively evaluated our experience with complex cystic renal masses on MR imaging, using T1-weighted, T2-weighted, and gadolinium-enhanced images, to determine whether imaging features could permit distinction between benign and malignant lesions. MATERIALS AND METHODS: Thirty-seven patients with complex cystic renal lesions were included in this retrospective study. The patients selected had undergone T1-weighted, T2-weighted, and gadolinium-enhanced MR imaging examinations using 1.5-T scanners, with at least one of the following findings: cyst fluid of heterogeneous signal intensity, mural irregularity, septa, mural masses or nodules, increased mural thickness, or intense mural enhancement. The diagnosis was established by histology in 19 patients and by follow-up studies in the remaining 18 patients. RESULTS: Fifty-five complex renal cystic lesions were present in the 37 patients. Among the 55 lesions, of 37 that contained fluid of a heterogeneous signal intensity, eight were malignant (22%); of 16 with irregular walls, 10 were malignant (63%); of four with septa, two were malignant (50%); of four with mural masses or nodules, three were malignant (75%); of 14 with a thick wall (>2 mm), 10 were malignant (71%); and of 32 with intense mural enhancement, 14 were malignant (44%). As independent variables, mural irregularity, mural masses or nodules, increased mural thickness, and intense mural enhancement each were highly associated with malignancy (p = .0003-.0022). The combination of mural irregularity and intense mural enhancement had the highest correlation with malignancy (p = .0002). CONCLUSION: The combination of mural irregularity and intense mural enhancement is a strong predictor of malignancy in renal cystic lesions. However, the appearance of benign and malignant lesions may overlap, suggesting that distinct separation of these entities is not currently possible in all cases with MR imaging.     

Intertrabecular vertebral metastases: metastases only detectable on MR imaging

Metastatic intertrabecular vertebral tumors that infiltrate the marrow space without trabecular bone alteration are not visible on radiographs or bone scans. To understand the clinical importance of intertrabecular metastases, their histological and radiological aspects were reviewed based on an examination using 69 cadavers. Metastatic tumors were found in 940 of 1653 vertebral bodies. Radiography of the specimen demonstrated lesions in 485 of 940 vertebral bodies (51.6%). Bone scintigraphy showed lesions in 109 of 415 vertebral bodies (26.3%) with tumors examined within 3 months before autopsy, whereas magnetic resonance (MR) images detected 132 of 146 (90.4%) lesions. The intertrabecular metastases were found in 36.9% of the metastatic lesions and was difficult to see on radiography (5.8%) and bone scans (3.3%) whereas MR images detected most of them (94.6%). The intertrabecular metastasis is the most common type of skeletal metastases and is only detectable on MR images.     

Liver metastases from pancreatic adenocarcinoma: MR imaging characteristics

PURPOSE: To describe the magnetic resonance imaging spectrum of appearances of liver metastases from pancreatic ductal adenocarcinoma. MATERIALS AND METHODS: We retrospectively evaluated the MRI exams performed between July 1996 and August 2001 in all patients who had liver metastases from pancreatic adenocarcinoma and histopathologic diagnosis from either the primary pancreatic tumor, liver metastases, or both. Sixteen patients were included in the study. All MR studies were performed at 1.5 T with a standard protocol including T1- and T2-weighted images and serial post-gadolinium spoiled gradient echo (SGE) images. Location, size, number, signal characteristics on T1- and T2-weighted images, and pattern of enhancement on serial gadolinium-enhanced SGE images were assessed. RESULTS: The diameter of metastases ranged from a few millimetres to 4 cm, and 12 patients (75%) had only lesions of 1.5 cm or less. Capsular-based liver metastases were found in 13 patients (81%) and three patients had only capsular-based lesions with a diameter under 1.5 cm. Hypervascular lesions were found in six patients (38%) and hypovascular lesions in 10 patients (62%). Perilesional enhancement was present in 10 patients (62%), with six patients (38%) having ring perilesional enhancement and eight patients (50%) having wedge-shaped perilesional enhancement. CONCLUSION: On MR imaging, hepatic metastases from pancreatic adenocarcinoma show a range of enhancement patterns. Hypervascular metastases are not rare. Capsular based distribution, small diameter, and perilesional enhancement are common features. This retrospective study describes the MR imaging spectrum of appearances of liver metastases from pancreatic adenocarcinoma in patients with histopathologic confirmation of the diagnosis.     

Sacroiliitis: MR imaging findings

Magnetic resonance (MR) imaging was performed in seven asymptomatic volunteers and 17 patients with clinical and radiologic evidence of sacroiliitis. MR imaging findings were compared with those at computed tomography (CT) to determine the MR imaging appearance of the sacroiliac joint when normal and in sacroiliitis. The normal articulation was well depicted with MR imaging. Findings of sacroiliitis were identified in 20 sacroiliac joints (12 patients). MR imaging findings characteristic of sacroiliitis included abnormal cartilage signal intensity (95% of joints) and erosions (75% of joints) on T1-weighted images. Areas of increased intensity in the articulation (80% of joints) or in erosions (60% of joints) were seen on T2-weighted images. MR imaging was superior to CT for evaluation of cartilage and detection of erosions. Four sacroiliac joints (20%) and two patients (17%) with MR imaging findings of sacroiliitis were negative at CT. The authors conclude that MR imaging is a valuable method for detecting sacroiliitis, particularly when results of other imaging techniques are inconclusive.     

MR imaging of skeletal metastases from medulloblastoma

The findings of MR imaging in 3 patients with bone metastases from medulloblastoma are reported. The first patient showed focal lesions of low signal intensity on T1-weighted spin echo images at a time when bone scintigraphy was negative for metastases. This patient later developed extensive osteosclerotic lesions visible on plain films. The bone marrow of the second patient showed diffuse low signal intensity on T1-weighted images. After chemotherapy the signal intensity of the bone marrow increased which correlated with a return of normal hematopoietic tissue. A response to chemotherapy was also found on MR imaging and repeat bone marrow biopsies in a third patient. A consistent finding was a low signal intensity on pre-gadolinium images, but the pattern (focal or diffuse abnormal signal intensity) was different in each patient. To our knowledge, this is the first report on MR imaging findings in bone metastases from medulloblastoma.     

Intradural-extramedullary spinal cysticercosis: MR imaging findings.

A rare case with intradural-extramedullary cysticercosis is presented here. MR imaging with and without gd-DTPA were performed. There were multiple cysts in the basal cistern, cisterna magna, and cervical subarachnoid space which were isointense with cerebrospinal fluid both on T2- and T1-weighted images. Swelling and increased signal intensity in the cord parenchyma were detected on T2-weighted images. Gadolinium enhanced studies showed rim-shaped enhancement in the cysts and irregular, diffuse enhancement in the meninges.     

Diffuse mixed type osseous metastases of medulloblastoma in an adult: MR imaging findings

Medulloblastoma is a relatively common intracranial neoplasm in childhood, but is a rare condition in adult group. This tumor has a well-known tendency to seed along cerebrospinal fluid pathways; however, extraneural metastases are uncommon and have typically been associated with a fatal outcome. When extracranial metastases occur, most common site of involvement is bone (80%), especially pelvis, long bones and spine. Radiographically, blastic (sclerotic) metastases are most common (60%), but lytic (35%) and mixed patterns (5%) also do occur [Clin. Imaging 15 (1991) 286]. In this paper we present a case of medulloblastoma metastatic to bone involving almost the whole skeleton and describe the magnetic resonance appearance, with emphasis on the imaging findings of mixed (both lytic and sclerotic) forms.     

Sneddon's syndrome: MR imaging findings

Sneddon's syndrome is a systemic disease characterized by generalized livedo racemosa and cerebrovascular disease. We present a case of Sneddon's syndrome which has typical dermatological lesions and occipital infarct demonstrated by both CT and MRI.     

Tongue abscesses: MR imaging findings

BACKGROUND AND PURPOSE: A lingual abscess is difficult to diagnose in the absence of physical signs. MR imaging may provide an excellent and invaluable adjunct to clinical examination, but the literature is incomplete in defining the various MR imaging findings of abscess. The objective of this study was to determine the MR imaging features of tongue abscesses. METHODS: Seven surgically proved tongue abscesses were evaluated with MR imaging. Four patients underwent MR imaging because of suspected tumor, and 3 patients, to show the extent and precise anatomic location of the lesion. Lesions were assessed with regard to the location, size, signal-intensity characteristics, and pattern of contrast enhancement. RESULTS: Five lesions were located in the anterior tongue and 2, in the posterior tongue. The central parts of 4 anterior tongue abscesses were hypointense, surrounded by a hyperintense wall on T1-weighted precontrast images. On postcontrast images, marked wall enhancement was detected. On T2-weighted images, a markedly hyperintense central part surrounded by a hypointense rim was seen. In 2 of these patients, there was a hypointense halo surrounding the wall (target sign). In 3 patients, a perilesional hyperintense area that enhanced diffusely after contrast administration was detected on T2-weighted images. The smallest lesion located in the anterior tongue was hypointense on T1-weighted images and enhanced diffusely on postcontrast images. On T2-weighted images, a markedly hyperintense central part surrounded by a mildly hyperintense peripheral part was depicted. Posterior tongue lesions appeared as polypoid ill-defined masses and were hypointense on T1-weighted images and heterogeneously hyperintense on T2-weighted images. On postcontrast images, the lesion in 1 patient showed diffuse and heterogeneous contrast enhancement, whereas the lesion in another patient enhanced peripherally. The lesions were totally excised in 4 patients and drained with surgical incisions in 3 patients. No recurrence was detected on follow-up. CONCLUSION: An abscess typically presents as a cystic lesion surrounded by an enhancing capsule formation, but lesions may also present as solid masses that enhance diffusely or peripherally.     

Pituitary adenomas: findings of postoperative MR imaging.

Preoperative and postoperative magnetic resonance (MR) images obtained in 25 patients with pituitary macroadenomas (1.1-5.2 cm in diameter) were evaluated to determine normal (physiologic) and abnormal findings after transsphenoidal or subfrontal surgery. With a 1.5-T unit, T1-weighted sagittal and coronal images were obtained before and after administration of gadopentetate dimeglumine. The physiologic changes after surgery included resorption of packing material and sphenoid sinus opacifications, reexpansion of the pituitary gland, and lowering of the optic chiasm. Implanted gelatin foam appeared as an endosellar, circularly enhancing mass that was seen on follow-up studies to have decreased in size. Muscle-and-fat implants appeared as areas of high signal intensity. In 14 patients, residual tumors were found in the suprasellar (n = 4), retrosellar (n = 3), parasellar (n = 8), and/or endosellar (n = 3) space. Residual tumors were differentiated from implant materials by means of location, characteristic signal intensity, and enhancing pattern, which were identical to those of the corresponding preoperative adenoma in 13 cases (93%). Preoperative studies and clinical information are helpful in the evaluation of postoperative MR imaging examinations.     

Paget disease: MR imaging findings

Magnetic resonance (MR) images of 13 patients with Paget disease were reviewed, and findings were correlated with those from computed tomographic (CT) scans, radiographs, and, in two patients, surgical biopsy. MR imaging findings correlated with CT and radiographic findings of cortical thickening, increased size of bone, and coarse thickened trabeculae. Focal or diffuse decreased signal intensity, representing dense bone, was seen on images obtained with short and long repetition times (TRs) and echo times (TEs); high-signal foci, representing fat collections, were seen on short TR/TE images; and high-signal foci, representing fibrovascular marrow in active Paget disease, were seen on long TR/TE images. Complications of Paget disease-including basilar invagination, spinal stenosis, and sarcoma--were well identified on MR images. Although MR imaging is not generally used in diagnosis of Paget disease, the disease will be encountered more frequently as more MR imaging examinations are performed. An awareness of the range of findings in Paget disease is useful in evaluating MR images of the musculoskeletal and other systems.