MR Imaging Characteristics of Intraocular Perfluoro-n-Octane.

We describe the unique MR imaging characteristics of intraocular perfluoro-n-octane, a liquid used for intraoperative and postoperative tamponade in the context of complex retinal detachment repair, and contrast it with other intraocular pathologies. Because trace amounts of perfluoro-n-octane may be left in the globe postoperatively, it may be confused for other abnormalities, such as foreign bodies or tumors.

Gadopentetate dimeglumine as a contrast agent in common carotid arteriography.

BACKGROUND AND PURPOSE: Despite improvements in noninvasive imaging, some patients with contraindications to iodine-based contrast material still require angiography for the evaluation of carotid stenosis. Our aim was to assess the utility of gadopentetate dimeglumine as an intraarterial contrast agent in common carotid angiography. METHODS: Twelve patients with suspected carotid artery stenosis were enrolled in the study. In addition to the standard injection sequences with iohexol, common carotid arteriograms were obtained after administration of gadopentetate dimeglumine. Neurologic status and vital signs were monitored during and for 6 hours after the examination. For each injection, five independent observers, blinded to the contrast agent used, measured the percentage of carotid stenosis and assessed their confidence in grading the stenosis, the overall quality of the examination, and, in cases of decreased quality, the reason(s) for it. Statistical analysis was done with paired and unpaired t-tests with equal variances. RESULTS: No patient had an adverse clinical outcome, and measurements of carotid artery stenosis showed no statistically significant differences between the gadopentetate dimeglumine and iohexol examinations. Overall image quality and observer confidence in measurements of stenosis on the gadolinium-based studies were slightly but significantly lower than those of identical iodine-based studies. CONCLUSION: Gadopentetate dimeglumine may be an alternative to iodine in selected patients undergoing carotid angiography. Although overall image quality of the gadolinium studies is slightly inferior to that of the iohexol studies, measurements of carotid artery stenosis are similar for the two examinations.

Disseminated coccidioidomycosis complicated by vasculitis: a cause of fatal subarachnoid hemorrhage in two cases.

We describe two cases of disseminated coccidioidomycosis that were complicated by fatal subarachnoid hemorrhage. In the first case, a left middle cerebral artery aneurysm and long-segment vasculitis occurred. In the second case, MR imaging revealed an enlarging coccidioidal granuloma at the tip of the basilar artery, and the artery subsequently ruptured. Fatal intracranial hemorrhage is a rare complication of disseminated coccidioidomycosis.

MR imaging of acute coccidioidal meningitis.

BACKGROUND AND PURPOSE: Our purpose was to describe the MR imaging findings in patients with acute coccidioidal meningitis. METHODS: Fourteen patients (11 men, three women; 22-78 years old; mean age, 47 years) with coccidioidal meningitis underwent neuroimaging within 2 months of diagnosis. Thirteen patients had MR imaging and one had an initial CT study with a follow-up MR examination 5 months later. Initial and follow-up MR images were evaluated for the presence of ventricular dilatation, signal abnormalities, enhancement characteristics, sites of involvement, and evidence of white matter or cortical infarction. The patterns of enhancement were characterized as focal or diffuse. Pathologic specimens were reviewed in two patients. RESULTS: Ten of the 14 images obtained at the time of initial diagnosis showed evidence of meningitis. All of the initially abnormal studies showed enhancement in the basal cisterns, sylvian fissures, or pericallosal region. Subsequent studies, which were available for three of the four patients with normal findings initially, all eventually became abnormal, with focal enhancement seen on the initial abnormal examination. Other abnormalities seen at presentation included ventricular dilatation (six patients) and deep infarcts (four patients). Pathologic specimens in two patients showed focal collections of the organism corresponding to the areas of intense enhancement on MR images. CONCLUSION: Early in its disease course, coccidioidal meningitis may show areas of focal enhancement in the basal cisterns, which may progress to diffuse disease. Pathologically, the areas of enhancement represent focal collections of the organism. Deep infarcts and communicating hydrocephalus are associated findings.

Hydrogen peroxide poisoning causing brain infarction: neuroimaging findings.

OBJECTIVE: We describe the CT and MR imaging findings of the brain in patients who inadvertently poisoned themselves with concentrated hydrogen peroxide. Thirty-five percent hydrogen peroxide is commercially available as an oxidant and disinfectant. This solution is currently sold and promoted in health food stores in the United States as a means of "improving oxygenation" in people with coronary artery disease and other health problems. CONCLUSION: Our findings show the high toxicity of concentrated hydrogen peroxide. CNS damage and death are likely consequences after ingestion of this agent.

Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients.

PURPOSE: To determine the computed tomographic (CT), magnetic resonance (MR) imaging, and angiographic findings of papillary endolymphatic sac tumors. MATERIALS AND METHODS: Clinical and imaging studies in 20 patients (aged 17-65 years) with histopathologically proved papillary endolymphatic sac tumors were retrospectively reviewed. Patients underwent CT (n = 18), MR imaging (n = 15), or angiography (n = 12). CT scans were evaluated for bone erosion and calcification; MR images, for signal intensity, enhancement patterns, and flow voids; and angiograms, for tumoral blood supply. RESULTS: All tumors were destructive and contained calcifications centered in the retrolabyrinthine region at CT. The MR imaging appearance varied with lesion size; 12 of 15 tumors showed increased signal intensity at T1-weighted imaging. The high-signal-intensity area was circumferential in lesions 3 cm or smaller and was scattered throughout the lesion in advanced tumors. Only tumors larger than 2 cm had flow voids. The blood supply arose predominantly from the external carotid artery. Large tumors had additional supply from the internal carotid and posterior circulation. CONCLUSION: Papillary endolymphatic sac tumors are destructive, hypervascular lesions that arise from the temporal bone retrolabyrinthine region. Increased signal intensity at unenhanced T1-weighted MR imaging is common and may help distinguish these lesions from more common, aggressive temporal bone tumors.

Orbital histiocytosis X.

In three patients with histiocytosis X of bone with orbital involvement, CT scans were reviewed. Consistent findings included a destructive lesion of the lateral wall of the orbit with a large soft-tissue component that extended into the extraconal space, the ocular adnexa, and the infratemporal fossa. The greater wing of the sphenoid was eroded in all cases, with epidural extension into the middle cranial fossa. Cavernous sinus involvement and a second bone lesion were seen in two patients.

Orbital and optic pathway sarcoidosis: MR findings.

PURPOSE: To identify and characterize the MR findings of sarcoidosis when it involves the orbit and visual pathways. METHODS: The MR scans of 15 patients, 3 with presumed and 12 with proved orbital or optic pathway sarcoidosis were retrospectively reviewed. RESULTS: Eight patients had MR evidence of optic nerve involvement by sarcoid granuloma. Perineural enhancement was seen in four cases, optic atrophy in one. Three who had had unenhanced scans showed optic nerve enlargement. Nine patients had optic chiasmal involvement. One patient had increased T2 signal in the optic radiations. Three patients had orbital masses that had MR signal characteristics similar to pseudotumor. Five patients had periventricular white matter abnormalities closely resembling multiple sclerosis. CONCLUSIONS: Sarcoidosis should be considered in the differential diagnosis of optic nerve or nerve sheath enhancement on MR. Orbital sarcoidosis has MR characteristics very similar to pseudotumor.

MRI of the spine.

In many instances, magnetic resonance imaging (MRI) has become the initial imaging modality in the evaluation of the spine. The authors present a broad review of the MRI features of the major disease processes which can involve the spine. Disk disease, failed back syndrome, infectious spondylitis, epidural abscess, and neoplastic disease are all discussed.

Bone marrow imaging using STIR at 0.5 and 1.5 T.

We retrospectively examined MR images in 82 patients to evaluate the usefulness of short inversion time inversion recovery (STIR) in bone marrow imaging at 0.5 and 1.5 T. The study included 56 patients at 1.5 T and 26 patients at 0.5 T with a variety of pathologic bone marrow lesions (principally oncological), and compared the contrast and image quality of STIR imaging with spin-echo short repetition time/echo time (TR/TE), long TR/TE, and gradient-echo sequences. The pulse sequences were adjusted for optimal image quality, contrast, and fat nulling. STIR appears especially useful for the evaluation of red marrow (e.g., spine), where contrast between normal and infiltrated marrow is greater than with either gradient-echo or T1-weighted images. STIR is also extremely sensitive for evaluation of osteomyelitis, including soft tissue extent. In more peripheral (yellow) marrow, T1-weighted images are usually as sensitive as STIR. Limitations of STIR include artifacts, in particular motion artifact that at high field strength necessitates motion compensation. At 0.5 T, however, motion compensation is usually not necessary. Also, because of extreme sensitivity to water content, STIR may overstate the margins of a marrow lesion. With these limitations in mind, STIR is a very effective pulse sequence at both 0.5 and 1.5 T for evaluation of marrow abnormalities.

MRI diagnosis of thoracic ossification of posterior longitudinal ligament with concomitant disc herniation.

Ossification of the posterior longitudinal ligament is a potentially curable cause of thoracic myelopathy. As this case illustrates, MRI can confirm the diagnosis, demonstrate other concomitant pathology such as disc herniation, and help assess the clinical significance of OPLL by showing spinal word compression.

Epidemiologic features of asymptomatic cerebral infarction in patients with nonvalvular atrial fibrillation.

We performed unenhanced computed tomographic scans on 141 asymptomatic patients with nonvalvular atrial fibrillation. Thirty-six patients (26%) had hypodense areas consistent with cerebral infarction. The majority of these were small deep infarcts, seen in 29 patients (21%), but 13 patients (9%) had cortical or large deep infarctions. Twelve patients had more than one infarct on computed tomographic scan. Increasing age and increased left atrial diameter were the only clinical features associated with asymptomatic infarction. Patients older than 65 years with a left atrial diameter greater than 5.0 cm (n = 23) had a 52% prevalence of asymptomatic infarction. Patients younger than 65 years with a left atrial diameter less than 5.0 cm (n = 38) had an 11% prevalence of silent infarction. Patients with only one of these risk factors (n = 72) had a 24% prevalence of silent infarction. Infarction was more common in those with chronic (34%) as opposed to intermittent (22%) nonvalvular atrial fibrillation, but this difference was not significant. Hypertension, diabetes, duration of atrial fibrillation, congestive heart failure, history of myocardial infarction, and echocardiographic evidence of left ventricular dysfunction were not associated with asymptomatic infarction. A history of hypertension was present in only 35% of our patients with small-deep asymptomatic infarction, similar to the percentage in patients without stroke. Asymptomatic cerebral infarction is common in nonvalvular atrial fibrillation. The association with enlarged left atria and the lack of correlation with major cerebrovascular risk factors suggests a cardioembolic mechanism. Further study is needed to determine the functional and prognostic significance of these strokes.

Spinal cord compression due to metastatic disease: diagnosis with MR imaging versus myelography.

To determine the efficacy of magnetic resonance (MR) imaging and myelography for the diagnosis of spinal cord compression due to metastatic disease, the authors prospectively examined 70 patients who had known or suspected spinal involvement by malignancy. Most MR examinations consisted of T1-weighted sagittal imaging of the entire spine, with additional sequences as needed for clarification. Extradural masses were found in 46 patients, 25 of whom had cord compression. For extradural masses causing cord compression, the sensitivity and specificity of MR imaging was .92 and .90, respectively, compared with .95 and .88 for myelography. For extradural masses without cord compression the sensitivity and specificity of MR imaging was .73 and .90, versus .49 and .88 for myelography. MR imaging was much more sensitive for metastases to bone (.90 vs .49), as expected. MR imaging is an acceptable alternative to myelography for diagnosing spinal cord compression and is preferable as a first study because it is noninvasive and better tolerated.

Detection of pneumothorax: comparison of digital and conventional chest imaging.

To investigate radiologists' performance at interpreting digital radiographic images, we compared the detectability of pneumothoraces on computed radiographic chest images with 0.2-mm pixel size (2.5 Ip/mm) with their detectability on matched conventional screen-film images (5 Ip/mm). Eight radiologists reviewed 50 computed and 50 screen-film chest radiographs from 25 patients with pneumothoraces and 25 patients with other (or no) abnormalities. Four of the readers who best detected pneumothoraces on screen-film examinations performed worse when interpreting computed radiographic studies; the other four readers detected pneumothoraces similarly with both techniques. No relationship was found between the size of a pneumothorax and its likelihood of detection by either technique. These results raise concerns about implementing computed radiography for comprehensive chest imaging.

Conventional vs computed radiography: evaluation of myelography.

A prospective study was performed to compare the diagnostic efficacy of conventional film-screen (FS) imaging with computed radiography (CR) in myelography. Forty examinations were done with both methods. Digital myelography was found to have diagnostic accuracy equal to that of conventional film-screen examinations.

Computed tomography in hematologic malignancies of paranasal sinuses.

Hematologic malignancies of the paranasal sinuses are uncommon. Four young patients with ophthalmologic abnormalities as a chief complaint are presented. Lymphoma or leukemia should be considered in the differential diagnosis of destructive lesions in the paranasal sinuses, particularly in children and young adults.