Safety of MR imaging in patients who have retained metallic materials after cardiac surgery.

OBJECTIVE: Epicardial pacing wires retained in patients who undergo cardiac surgery are thought to be a relative contraindication to MR imaging. However, to our knowledge no published evidence supports this belief. Because other metallic materials retained after cardiac surgery might represent a hazard to patients who undergo MR imaging, we sought to determine the safety of such imaging. SUBJECTS AND METHODS: We examined 200 patients who underwent MR imaging at 1 or 1.5 T after cardiac surgery. Eighty-one were examined with ECG monitoring. The presence of temporary epicardial pacing wires, prosthetic valves, and other metal materials was confirmed by chest radiography. RESULTS: Of the 200 patients reviewed, all had postoperative metallic material visible on chest radiographs. Temporary epicardial pacing wire, cut short at the skin, was seen in 51 patients. Of the 81 patients examined with ECG monitoring, we found that MR imaging produced no changes from baseline ECG rhythms. None of the 200 patients reported symptoms suggesting arrhythmia or other cardiac dysfunction during MR imaging. CONCLUSION: MR imaging can be performed safely in patients who have undergone cardiac surgery and have retained metallic material, including valve replacements and temporary epicardial pacing wires cut short at the skin. MR imaging of patients with pacemakers was not evaluated, and we recommend that pacemakers remain a contraindication to MR imaging.

MR venography of left renal vein anomalies.

The examinations of 71 patients having comprehensive 2D time of flight (TOF) abdominal magnetic resonance venography (MRV) in three planes (axial, sagittal and 10 degrees offset coronal) were evaluated to assess the appearances of anomalous left renal veins as shown by MRV. Six cases of circumaortic left renal vein (CLRV) (8.5%) and one example of retro-aortic left renal vein only (1.4%) were identified, an incidence higher than that in previous computed tomography (CT) studies but comparable to venographic and post-mortem investigations. All retro-aortic components passed in a caudal direction to join the inferior vena cava (IVC) inferior to the anterior limb. MRV acquired in the sagittal plane was found to be most useful for identifying these variants and provided highest signal by avoidance of in-plane flow saturation effects.

Automatic motion correction for breast MR imaging.

In 29 gadolinium-enhanced breast magnetic resonance (MR) examinations, breast motion prevented accurate and efficient image processing. To compensate for global rotations and translations, an automatic motion correction method with a ratio-variance minimization algorithm was used to align images at multiple time points through an iterative process. This method reduced breast motion and improved the accuracy and efficiency of lesion detection.

Stereoscopically guided characterization of three-dimensional dynamic MR images of the breast.

A workstation was used to postprocess volume-rendered three-dimensional (3D) dynamic contrast material-enhanced magnetic resonance (MR) images of a breast carcinoma and a breast adenoma. Use of a 3D cursor allowed stereoscopic interactive probing of specific voxels to quantify contrast enhancement over time, which was mapped to a gray scale that effectively displayed enhancement as a fourth dimension. This technique is generally applicable to any time-dependent 3D imaging modality.

MRI of infarction of a cavernous sinus tumor in Nelson's syndrome.

We report the MRI appearances of an infarcted cavernous sinus tumor in a patient with Nelson's syndrome. Invasive tumors of the pituitary extending to the cavernous sinus are discussed and the role of MRI in preoperative investigation is highlighted.

Pre-operative imaging of esthesioneuroblastoma.

The pre-operative images of three patients with biopsy proven esthesioneuroblastoma are presented. The role of computed tomography (CT) and magnetic resonance imaging (MRI) in the pre-operative determination of tumour extent is discussed.

Osteosarcoma of the hard palate.

We present the appearances of a primary osteosarcoma of the maxilla in a 26-year-old man. The role of computed tomography--specifically, sagittal and 3-D reconstructions--and the differential diagnosis of bone lesions occurring at this site are discussed.

The prevalence and clinical significance of lymphadenopathy in primary biliary cirrhosis.

We present the results of a retrospective review of abdominal computed tomography, ultrasound, and magnetic resonance examinations of 12 patients with primary biliary cirrhosis undertaken to determine the prevalence and clinical significance of previously reported coexistent intra-abdominal lymphadenopathy in patients with this disorder. Lymphadenopathy, in the form of bulky periportal and retroperitoneal nodes, was identified in a single patient secondary to an occult metastatic adenocarcinoma. We conclude that coexistent intra-abdominal lymphadenopathy occurring in patients with primary biliary cirrhosis is uncommon. Although it may represent a benign component of the primary disease, it may equally be due to unsuspected coexistent occult malignancy.

Clival marrow changes in AIDS: findings at MR imaging.

PURPOSE: To determine the prevalence and clinical significance of marrow changes in the clivus identified at magnetic resonance (MR) imaging in patients with the acquired immunodeficiency syndrome (AIDS). MATERIALS AND METHODS: MR images of the head of 119 patients with AIDS and 119 control subjects were retrospectively reviewed. Marrow signal intensity patterns in the clivus of each patient were evaluated and scored as type 1 (homogeneous high signal intensity on T1-weighted images [normal]), type 2 (heterogeneous low signal intensity on T1-weighted images [abnormal]), or type 3 (homogeneous low signal intensity on T1-weighted images [abnormal]) and correlated with clinical parameters including CD4 counts, evidence of previous systemic disease, and presence of coexistent disease on corresponding MR head images. RESULTS: Abnormal clival signal intensity (type 2 and 3) was observed in 64 (54%) patients with AIDS and nine (7.5%) control subjects (P < .001), correlating with both a marked decrease in CD4 count (P < .001) and the presence of systemic disease (P < .001). CONCLUSION: Clival marrow signal abnormality is commonly identified in patients with AIDS and may be a marker of advanced disease.

Magnetic resonance imaging in drug-induced meningitis.

Pathologic meningeal enhancement has been reported in patients with bacterial and viral meningitis. The authors describe a 52-year-old woman with drug-induced aseptic meningitis in whom diffuse meningeal enhancement was observed with magnetic resonance imaging after administration of gadolinium diethylenediaminepenta-acetic acid. The cause and mechanism of drug-induced aseptic meningitis and the value of magnetic resonance imaging in the diagnosis of this uncommon condition are stressed.

Magnetic resonance angiography in transjugular intrahepatic portosystemic stenting: comparison with contrast hepatic and portal venography.

In order to highlight the role of magnetic resonance angiography [MRA] in the assessment of patients pre-transjugular intrahepatic portosystemic shunt (TIPS) stenting, the MRA images of portal and hepatic veins of 21 patients were compared with the images from contrast portal and hepatic venograms performed on the same patients at the time of TIPS stenting (20 patients). MRA enabled accurate, non-invasive, multiplanar imaging of portal and systemic venous anatomy in each of the patients studied. MRA facilitated accurate determination of vessel patency and flow direction, images correlating exactly with contrast venograms of hepatic and portal veins in each case. In one patient, identification of occult hepatocellular carcinoma extending to the portal vein lead to the postponement of the TIPS procedure.

Steps in the evolution of extracranial time-of-flight MR angiography.

Magnetic resonance (MR) angiography is not a set technique but is constantly evolving. This article illustrates changes in image quality in extracranial MR angiography that have been achieved over the past few years by the introduction of several technical developments. Images from patients examined at intervals of 12 months or more demonstrate the improvements in image quality that have resulted from these technical changes. These include bandwidth optimization for operation at 1.0 T and changes in flip angle section thickness, repetition time, and echo time. Improved image quality was assessed with objective measures of contrast-to-noise and signal-to-noise ratios. The cases illustrated show the use of MR angiography to evaluate the portal or systemic veins in patients being evaluated for liver transplantation, venous occlusion, and other venous disease. Improvements in image quality are subjectively apparent and emphasize the importance of keeping pace with technical improvements in MR angiography.

Magnetic resonance imaging of hemochromatosis arthropathy.

This study was undertaken to compare plain film radiography and magnetic resonance imaging in the assessment of hemochromatosis arthropathy of the knees of ten patients with a biopsy-proven diagnosis. Both modalities enabled visualisation of bony degenerative changes; magnetic resonance imaging enabled additional visualization of deformity of both cartilage and menisci. Magnetic resonance imaging failed reliably to confirm the presence of intra-articular iron in the patients studied. No correlation was observed between synovial fluid magnetic resonance signal values, corresponding serum ferritin levels, or the severity of the observed degenerative changes.

Intraocular silicone oil: in vitro and in vivo MR and CT characteristics.

PURPOSE: To describe the CT and MR characteristics of intraocular silicone oil (polydimethylsiloxane), which is used with increasing frequency to treat complicated retinal detachments. METHODS: CT was performed on a silicone oil/water phantom and on a patient with retinal detachments secondary to cytomegalovirus retinitis, treated by bilateral intraocular injections of silicone oil. CT appearance and CT number of silicone oil were evaluated. Proton MR spectroscopy was performed with a 200-MHz spectrometer on a sample of polydimethylsiloxane within a tube of deuterated water. MR imaging was performed on a silicone oil/water phantom and on two patients with retinal detachments treated with silicone oil injection. RESULTS: Silicone oil is relatively radiodense; its CT attenuation is approximately 130 HU. On spectroscopy, silicone oil gave a single peak at 0.33 ppm. Relative to water silicone oil was hyperintense on T1-weighted images and hypointense on spin-density and T2-weighted images. Estimated T1 and T2 were 716 msec and 68 msec, respectively. Chemical shift artifacts were seen on MR images and were exaggerated when a narrow sampling bandwidth was used. In clinical cases spectral saturation pulses normally used for lipid suppression could be adjusted to saturate only the silicone resonance; in this way, the chemical shift artifact was eliminated. CONCLUSION: Intraocular silicone oil has unique imaging characteristics with which radiologists must become familiar. These characteristics include high attenuation on CT and hyperintensity on T1-weighted MR, both of which may mimic hemorrhage. Elimination of the prominent chemical shift artifact on MR with selective saturation of the silicone resonance improves evaluation of the globe.

Bacterial and viral parenchymal infections of the brain.

Magnetic resonance imaging (MRI) has been proven to aid in the early detection and diagnosis of parenchymal infections of the brain. Pyogenic brain abscess, herpes encephalitis, Listeria rhombencephalitis, and Rasmussen's syndrome are examined in this article. Imaging characteristics, epidemiology, clinical presentations, therapies, and pathologic findings are discussed.

Meningeal metastasis of leiomyosarcoma mimicking meningioma: CT and MR findings.

A case of leiomyosarcoma metastatic to the meninges is reported. The tumor had imaging features typical for meningioma on CT and postcontrast magnetic resonance.