MR imaging of extracranial nerve sheath tumors.

We retrospectively reviewed MR images of 32 histologically proven extracranial nerve sheath tumors (NSTs). There were 23 benign (10 neurofibromas, 13 schwannomas) and 9 malignant NSTs. On T1-weighted images (T1WIs) tumors were isointense or slightly hyperintense to muscle. On T2-weighted images (T2WIs) (11 lesions) and enhanced T1WIs (1 intraspinal lesion), a target pattern with peripheral hyperintense rim and central low intensity was seen in 12 of 23 (52%) benign NSTs (5 of 10 neurofibromas and 7 of 13 schwannomas). This pattern corresponded histologically to peripheral myxomatous tissue and central fibrocollagenous tissue. The pattern was absent in lesions with cystic, hemorrhagic, or necrotic degeneration. These tumors were hyperintense and variably inhomogenous on T2WIs. Malignant NSTs were hyperintense and variably inhomogenous on T2WIs and mimicked benign variably inhomogeneous lesions unless involvement of contiguous structures was visualized. A target pattern was not visible in malignant lesions. Magnetic resonance imaging cannot distinguish schwannomas from neurofibromas, and benign tumors may mimic malignant NSTs when cystic, hemorrhagic, and necrotic degeneration is present. A target pattern may be visualized in some benign NSTs, and evaluation of this sign with assessment of location and growth along nerves may help to avoid confusion with other lesions.     

Intraocular tumors: evaluation with MR imaging

Sixty-seven ocular tumors were studied with magnetic resonance (MR) imaging and computed tomography (CT). These tumors included primary uveal melanoma (n = 55), circumscribed choroidal hemangioma (n = 3), diffuse choroidal hemangioma (n = 1), retinal capillary hemangioma (n = 1), medulloepithelioma (n = 1), choroidal nevus (n = 1), retinoblastoma (n = 1), and choroidal metastases (n = 4). MR imaging demonstrated all these lesions, while CT demonstrated 88%. Associated retinal detachment was more easily distinguished from the neoplasms with MR imaging. Extrascleral extension of melanoma and hemorrhagic cystic necrosis within the melanoma were clearly demonstrated with MR imaging, but not with CT. Ninety-three percent of melanomas were markedly hyperintense, compared with the intensity of the vitreous body, on T1-weighted images and hypointense on T2-weighted images. All metastatic lesions were isointense on T1-weighted images and hypointense on T2-weighted images. The circumscribed choroidal hemangiomas were hyperintense on T1-weighted images and isointense on T2-weighted images. MR imaging is superior to CT in detection of intraocular tumors and may be more specific in diagnosis.     

Dysembryoplastic neuroepithelial tumors: MR and CT evaluation.

PURPOSETo evaluate dysembryoplastic neuroepithelial tumors (DNTs) on MR and CT studies and to compare DNT with other frequently encountered epileptogenic glioneuronal lesions.METHODSWe analyzed the MR images and CT scans of 16 patients who had complex partial epilepsy and DNT with respect to tumor location, size, CT density, MR signal intensity, mass effect, contrast enhancement, and heterogeneity, and compared these features with CT and MR findings in 51 cases of ganglioglioma and 33 cases of glioneuronal malformation.RESULTSDNTs were located in the temporal lobe in 14 patients and in the frontal lobe in 2 patients. The cortex was involved in all cases and the subcortical white matter in 10 cases. Fifty percent of the tumors had poorly defined contours. On MR images, 14 DNTs had multiple cysts and 2 had single cysts. Contrast enhancement was observed in 6 DNTs, and mass effect was present in 9. CT scans disclosed moderately hypodense lesions in 7 patients and markedly hypodense cystic lesions in 6 patients. Two DNTs were calcified. Tumor hemorrhage with perifocal edema was observed in 1 case. Contrary to previous reports, slow but definite tumor growth was present during a 13-year period in 2 of 6 patients in whom serial CT or MR studies were obtained.CONCLUSIONA multicystic appearance on MR images is a characteristic feature of DNT and corresponds to its myxoid matrix and multinodular architecture. This feature is rare in gangliogliomas and glioneuronal malformations, and, as such, may help differentiate DNTs from these disorders.     

Cardiac tumors and thrombus: evaluation with MR imaging

Thirty patients with a suspected cardiac or pericardial mass underwent MR imaging. Twenty-six also had two-dimensional (2D) echocardiography, and three also had CT; one patient had MR only. Overall, 18 (60%) of the 30 patients were found to have a mass lesion. The lesion was confirmed by biopsy, surgery, or unequivocal demonstration on CT, 2D echocardiography, and/or MR imaging. Fourteen of the lesions were soft-tissue or tumor masses, and four were thrombi. The findings on 2D echocardiography and MR were in agreement in 17 (65%) of 26 patients who had both studies. MR was equivocal or in error in two patients (7%), and 2D echocardiography was nondiagnostic in seven (27%). In all seven patients with equivocal 2D echocardiography, the diagnosis was made by MR. In the four patients who did not have 2D echocardiography, MR showed the mass clearly. MR imaging is useful in the diagnosis of cardiac mass lesions. It can be used effectively in addition to 2D echocardiography to increase the certainty of diagnosis, and it is useful when 2D echocardiography is equivocal or inadequate.     

Intratemporal vascular tumors: detection with CT and MR imaging

The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.     

Vagal neuropathy: evaluation with CT and MR imaging

The vagus nerve, as a result of its protracted course from the brain stem to the abdomen, can present a difficult imaging problem when it is compromised by a clinically occult lesion. The clinical and radiologic records of 48 patients with suspected vagus nerve dysfunction were reviewed to derive an efficient and effective approach to imaging this patient population. An imaging algorithm is proposed in which vagal neuropathies are divided both clinically and radiologically into proximal and distal categories. Proximal vagal lesions are part of a cranial neuropathy complex and have associated oropharyngeal signs and symptoms (e.g., abnormal gag reflex, uvular deviation). Distal vagal lesions occur as an isolated paralysis of the vagus nerve with no symptoms or signs referable to the oropharynx. Either computed tomography (CT) or magnetic resonance imaging can be used to diagnose proximal or distal lesions. However, CT will be insensitive in the detection of the more cephalic proximal lesions, especially those in the brain stem, basal cisterns, and skull base.     

Sphenochoanal polyps: evaluation with CT and MR imaging

A sphenochoanal polyp is a solitary mass of low attenuation on computed tomographic (CT) scans that arises from the sphenoid sinus and extends through the sphenoid ostium, across the sphenoethmoid recess, and into the choana (the boundary between the nasal cavity and nasopharynx). More often, however, a choanal polyp is an antrochoanal polyp, which arises from the maxillary antrum, protrudes through the middle meatus, extends into the nasal cavity, and continues back to the choana. Contiguous axial or coronal magnetic resonance and CT images help clearly differentiate the rare sphenochoanal polyp from the more common antrochoanal polyp. The sinus of origin is important to identify, as the surgical approach depends on the target sinus.     

Cirrhosis: CT and MR imaging evaluation

In this article, we present the CT and MR imaging characteristics of the cirrhotic liver. We describe the altered liver morphology in different forms of viral, alcoholic and autoimmune end-stage liver disease. We present the spectrum of imaging findings in portal hypertension, such as splenomegaly, ascites and varices. We describe the patchy and lacelike patterns of fibrosis, along with the focal confluent form. The process of hepatocarcinogenesis is detailed, from regenerative to dysplastic nodules to overt hepatocellular carcinoma. Different types of non-neoplastic focal liver lesions occurring in the cirrhotic liver are discussed, including arterially enhancing nodules, hemangiomas and peribiliary cysts. We show different conditions causing liver morphology changes that can mimic cirrhosis, such as congenital hepatic fibrosis, "pseudo-cirrhosis" due to breast metastases treated with chemotherapy, Budd-Chiari syndrome, sarcoidosis and cavernous transformation of the portal vein.     

Marfan syndrome: evaluation with MR imaging versus CT

Twenty-five patients with Marfan syndrome underwent computed tomography (CT) and magnetic resonance (MR) imaging. MR images were interpreted in blinded fashion and then the results were compared with findings from CT scans. MR imaging was found to be equivalent to CT in the depiction of aortic, dural, and hip abnormalities in patients who had not undergone surgery. MR imaging was superior to CT in evaluation of postoperative patients because the artifact produced by Bjork-Shiley or St. Jude valves precludes adequate evaluation of the aortic root on CT scans, while producing only a small inferior field distortion, a "pseudo-ventricular septal defect," on MR images. The absence of radiation exposure is another significant advantage for the relatively young Marfan syndrome population, who require serial studies. MR imaging is the modality of choice for evaluation and follow-up of patients with Marfan syndrome and offers an appropriate means of screening their kindred.     

Lipomatous tumors and tumors with fatty component: MR imaging potential and comparison of MR and CT results

This retrospective study was performed to assess the potential of magnetic resonance (MR) imaging for demonstrating various types of lipomatous tumors and tumors with fatty component and to compare the results of MR with those of computed tomography (CT). MR examinations of 17 patients with 18 lipomatous tumors (16, benign; two, liposarcoma) and two patients with fibrosarcomas were reviewed; CT scans were available for comparison in all patients. In the 16 benign lesions (12 benign lipomas, two ovarian dermoid cysts, and two renal angiomyolipomas), the fatty component of the tumors was readily demonstrated by both MR and CT. The T1 and T2 relaxation times and spin density of benign lipomatous tumors were in a range similar to those of normal subcutaneous fat. Differentiation between lipomas and liposarcomas was achieved with both MR and CT. On MR images using a short repetition time (TR = .5 sec), liposarcomas (long T1) were imaged with a lower MR intensity than lipomas (short T1).     

Comparison of CT with MR imaging of endobronchial tumors

Twenty-nine patients suspected of having an endobronchial mass were examined by magnetic resonance (MR) and CT. Seventy-nine pathological and 319 normal bronchi were confirmed by bronchoscopy and/or operation in these patients. The studies were evaluated by two observers (A and B): By MR, only 72% (A) or 71% (B) of the pathological and 45% (A) or 43% (B) of the normal bronchi, respectively, were visualized. Computed tomography identified all pathological and 97% of the normal bronchi (A and B). Therefore, comparison between MR and CT was based only on those bronchi that were adequately visualized on MR as well as CT. For these bronchi the sensitivity of MR was 88% (A) or 77% (B) and of CT 96% (A) and 93% (B). Specificity was 92% (A) and 94% (B) for MR and 97% (A and B) for CT. At the present stage of development CT proved to be superior to MR in demonstrating endobronchial lesions.     

Aortic stenosis: evaluation with multidetector CT angiography and MR imaging

Aortic valvular stenosis (AS) is the most common valve disease which results in the need for a valve replacement. Although a Doppler echocardiography is the current reference imaging method, the multidetector computerized tomograpghy (MDCT) and magnetic resonance imaging (MRI) have recently emerged as a promising method for noninvasive valve imaging. In this study, we briefly describe the usefulness and comparative merits of the MDCT and MRI for the evaluation of AS in terms of valvular morphology (as the causes of AS), quantification of aortic valve area, pressure gradient of flow (for assessment severity of AS), and the evaluation of the ascending aorta and cardiac function (as the secondary effects of AS). The familiarity with the MDCT and MRI features of AS is considered to be helpful for the accurate diagnosis and proper management of patients with a poor acoustic window.     

MR imaging of orbital tumors with CT and ultrasound correlations

Fourteen patients with various orbital space-occupying lesions were studied by magnetic resonance (MR) imaging with a 0.15 T imager using spin-echo and inversion-recovery pulse sequences. Computed tomographic and ultrasonographic (US) examinations were done in 13 of these patients. All 14 lesions could be demonstrated by MR. Magnetic resonance was found to be better than US but not as good as CT in providing morphological details. Regarding tissue characterization, US was the most useful among the three modalities. With the T2-weighted spin-echo pulse sequence, a possible trend in tissue characterization could be shown. From our preliminary experience, we conclude that MR imaging using a 0.15 T resistive magnet offers no distinct advantage over the combination of CT and US in the diagnosis of orbital tumors.     

Orbital tumors in children: CT and MR imaging features

The purpose of the article is to review the CT and MR imaging features of orbital tumors in children. Tumors in children are usually different than those in adults. Clinical symptoms are usually non-specific. Clinical examination combined with US may be sufficient for diagnosis and follow-up of benign and superficial lesions. CT and/or MRI are needed for deep or malignant lesions. CT is valuable for osseous and/or calcified lesions. MR is advantageous because of its superior spatial resolution and non-ionizing nature. Malignant tumors correspond to about 20% of lesions and include primary tumors (retinoblastoma, rhabdomyosarcoma) and metastases. Benign pathology is more frequent (80%) with dermoid cyst corresponding to about 50% of orbital masses.     

Recurrent postoperative sciatica: evaluation with MR imaging and enhanced CT

Magnetic resonance (MR) imaging and computed tomography enhanced with intravenous iodine injection (ECT) were prospectively compared in 80 patients in the diagnosis of recurrent postoperative sciatica. Diagnostic accuracy was determined with surgical verification. Isolated fibrosis was considered a contraindication to surgery. A decision to operate was made in 56 of the 80 patients on the basis of MR imaging findings; in 21 of the 56, the decision was also made on the basis of ECT findings. Of the 80 patients, 45 underwent surgery, In all but one of these patients, the diagnosis made on the basis of MR imaging findings was confirmed with surgical analysis. The only surgical finding that did not agree with MR imaging findings was a calcification of the common posterior ligament. The 21 diagnoses of disk herniation based on ECT findings were confirmed surgically, but among the 24 diagnoses of fibrosis made with the help of ECT, there were actually 19 recurrent herniations, four herniations with fibrosis, and one herniation at the level above the previously resected disk. MR imaging seems to be the investigation of choice in diagnosing the cause of recurrent postoperative sciatica.     

Prospective evaluation of pancreatic tumors: accuracy of MR imaging with MR cholangiopancreatography and MR angiography

PURPOSE: To prospectively assess accuracy of magnetic resonance (MR) imaging, MR cholangiopancreatography (MRCP), and MR angiography in patients suspected of having pancreatic tumors. MATERIALS AND METHODS: Sixty-six patients suspected of having pancreatic tumors underwent MR imaging (unenhanced and contrast material-enhanced MR, MRCP, and contrast-enhanced MR angiography). Two blinded readers prospectively analyzed the images by consensus, and results were correlated with surgery, biopsy, or follow-up findings. Results were tabulated in two-by-two tables. RESULTS: MR assessment of pancreatic lesion status (differentiation of benign vs malignant) resulted in 60 correct diagnoses (accuracy, 91%), and six (10%) false diagnoses. Among histologically proved malignant tumors, MR imaging yielded correct diagnoses in 42 of 44 patients (sensitivity, 95%; 95% CI: 85%, 99%), whereas 18 of 22 patients with benign findings were classified correctly. At MR imaging, findings in four patients with chronic pancreatitis were wrongly categorized as malignant tumors (specificity, 82%; 95% CI: 60%, 95%), and in one patient, a distal common bile duct carcinoma was not detected. In no patient with pancreatic adenocarcinoma was this tumor misdiagnosed as benign. In patients with malignant tumors who underwent resection, local-regional tumor growth and vascular infiltration were accurately classified in 89% and 94%, respectively. MR imaging depicted histologically proved synchronous hepatic metastases in 82%. The positive and negative predictive values for cancer nonresectability were 90% and 83%, respectively, and the accuracy, sensitivity, and specificity were 85%, 69%, and 95%, respectively. CONCLUSION: Unenhanced and contrast-enhanced MR imaging with MRCP and MR angiography offers potential as a noninvasive tool for assessment of patients suspected of having pancreatic tumors.