MR imaging in patients with metallic implants.

A total of 305 magnetic resonance (MR) examinations were performed in 236 patients with metallic implants. Most examinations were performed at 0.3 T. The metallic implants included central nervous system shunting devices, tantalum mesh, surgical wire, skin staples, surgical clips, metallic orthopedic devices, and a few miscellaneous metallic objects. Patients with cardiac pacemakers, electrical implants, prosthetic cardiac valves, and aneurysm clips were excluded from MR examinations. The images were reviewed for evidence of metallic artifact. The conspicuity of artifact was related to the composition, mass, orientation, and position of the metallic object in the body. In most instances, the metallic artifact did not interfere with the interpretation of the image. The patients' records were also reviewed for adverse effects noted by each patient during the MR examination. Only two patients reported discomfort that could possibly have been related to their metallic implants, but in both cases it seemed unlikely that the symptoms were actually related to the imaging process. There were no apparent short-term adverse effects demonstrated in these patients.

Cerebral venous angiomas imaged by MR.

The diagnostic efficacy of magnetic resonance (MR) in the evaluation of cerebral venous angioma was studied. The results of MR and computed tomography (CT) were compared in six cerebral venous angiomas in five patients. MR alone was diagnostically successful in only three of six cases. Venous angiomas appeared as tubular structures of extremely low signal intensity on MR images. Although CT was highly sensitive (100%) in detecting lesions, CT was diagnostically specific in only four of the six cases. Angiography was the only modality able to unquestionably detect all six lesions. By varying the MR pulse sequence, we greatly affected the ability of MR to demonstrate lesions. In the cases where MR helped define the abnormality, T2-weighted MR images were able to clearly demonstrate lesions in five of the six cases whereas T1-weighted images helped detect an abnormality in only two cases. Although MR shows great promise in the evaluation of central nervous system abnormalities, CT remains the best imaging modality for detecting venous angiomas. When CT is not conclusive, angiography can be performed for a definitive diagnosis.

Demonstration of diastematomyelia and associated abnormalities with MR imaging.

Three patients were studied with a 0.3 T superconducting magnet to assess the role of magnetic resonance (MR) imaging in the recognition and evaluation of diastematomyelia and associated abnormalities. Comparison was made with other imaging techniques, including metrizamide computed tomographic (CT) myelography. With MR imaging, the divided spinal cord was well imaged in its entire craniocaudal extent, comparable to CT myelography. The bony septum, when it contained a marrow cavity, was also seen well. In two patients, dural ectasia and low position of the spinal cord with and without associated lipoma were clearly imaged. MR imaging demonstrated associated syringohydromyelia in one patient that was not detected by other radiologic studies. This preliminary experience with MR imaging of diastematomyelia suggests that once the bony details of the abnormality are defined, MR imaging can delineate the presence and extent of the divided spinal cord as well as its associated abnormalities adequately, obviating other studies.

MR imaging of pediatric cerebral abnormalities.

One hundred sixteen magnetic resonance (MR) imaging studies from 105 pediatric patients with a variety of cerebral abnormalities were reviewed to determine the diagnostic efficacy of MR in the pediatric population. All subjects tolerated the MR procedure well, although sedation was necessary for younger children. Compared with CT, MR proved to be advantageous in detection and characterization of the pathology in 23 of 105 patients, especially when the abnormality was located along the base of the brain and midline, or when it involved primarily the white matter. Intracranial calcification was the one abnormality not detected with MR although dense calcifications could be seen as areas of low signal intensity. Some characteristics of various pathological entities were compared in an attempt to differentiate among abnormalities in the same anatomical location: craniopharyngioma from optic chiasm and hypothalamic glioma, cystic glioma from arachnoid cyst, and chronic subdural hematoma from subdural hygroma. The lack of ionizing radiation in MR is of particular interest in pediatric neuroradiology since radiation is of special concern in the young age group.

Magnetic resonance imaging of the adrenal glands: a comparison with computed tomography.

This investigation compared magnetic resonance imaging (MRI) with computed tomography (CT) in the evaluation of normal and abnormal adrenal glands. Thirty normal volunteers were studied with MRI, and the results were compared with a retrospective review of 30 normal CT examinations. CT identified both adrenal glands in all 30 patients. MRI identified both glands in 29 of 30 volunteers. There were no statistically significant differences between the two imaging techniques using chi-square analysis. Twenty-one patients with abnormal adrenal gland(s) detected with CT were also studied with MRI. The abnormalities studied included bilateral hyperplasia (three patients), adenoma (two), myelolipoma (one), adrenal metastases (six), adrenal hemorrhage (two), and neuroblastoma (seven). MRI detected the abnormal adrenal gland(s) in 20 of 21 patients. MRI was unable to detect calcifications in the lesions studied but more clearly showed the relations of adrenal masses to the major vascular structures. MRI demonstrated corticomedullary differentiation in patients with adrenal hyperplasia and in some normal volunteers. The CT and MRI features of the adrenal lesions are discussed.

MR imaging of the skull base.

Fifty-four patients with abnormalities primarily involving the base of the skull were evaluated by magnetic resonance (MR) imaging. The results were compared with information obtained by other radiologic studies, primarily X-ray CT. On MR imaging, better anatomic definition of soft tissues in the deep compartments of the nasopharynx was achieved through the high level of tissue contrast discrimination and lack of bone artifacts. The parapharyngeal fat plane, separating pterygoid from pharyngeal musculatures, was consistently demonstrated. However, the inability of MR to image compact bone proved to be a major drawback where bony detail was required. In general, MR imaging demonstrated 100% sensitivity to abnormalities involving the posterior compartment (clivus and craniovertebral junction) and was least valuable in the evaluation of the anterior compartment (orbits, cribiform plate, and sinuses.

Magnetic resonance imaging: evaluation of palliative systemic-pulmonary artery shunts.

Eleven patients with a total of 17 palliative systemic-pulmonary artery shunts underwent evaluation by electrocardiogram-gated magnetic resonance imaging (GMRI). GMRI successfully imaged 11 of 17 shunts (65%), including five of nine Blalock-Taussig shunts, four of six Glenn shunts, and both aortopulmonary shunts. All shunts except for the Waterston were imaged on coronal sections during end-systole. The single Waterston shunt was seen on sagittal and transverse scans. Shunt localization and identification were facilitated by obtaining multiple, contiguous sections through the body. Glenn shunts could be imaged entirely in one section, although multiple sections were required to locate the correct plane. Blalock-Taussig shunts generally required multiple sections to image different segments of the shunt. Both aortopulmonary shunts were seen as direct side-to-side connections of the aorta and pulmonary artery. GMRI permitted assessment of the size, course, patency, and distribution of systemic-pulmonary artery shunts as well as the size and morphology of the proximal pulmonary arteries. We conclude that GMRI is a useful, noninvasive method for imaging the anatomy of systemic-pulmonary artery shunts.

CT-guided liver biopsies: eight years' experience. Work in progress.

In the past eight years 180 patients with liver abnormalities demonstrated on computed tomography (CT) underwent CT-guided biopsies with 22-guage Madayag, 14-gauge Travenol, or 18-gauge Menghini needles used singly or in combination. Cytologic and pathologic results were tabulated and correlated with the subsequent surgical or autopsy findings and with clinical follow-up ranging from three months to three years. Complications of the procedures were also recorded. It is concluded that cutting needle biopsies provide a higher yield of diagnostic tissue compared with aspiration biopsies (89.9% versus 65%) without a significant increase in complications (1.44% versus 0.83%). The techniques utilized, risk of complications, and the indications for biopsy are discussed.

Gated magnetic resonance imaging of the normal and diseased heart.

Gated cardiac magnetic resonance (MR) images were obtained in two normal volunteers and 21 adults with a variety of cardiovascular abnormalities. The images were correlated with data from clinical examinations, electrocardiograms, and cardiac catheterization. Gated cardiac images were superior to nongated images. Combined cardiac and respiratory gated images were superior to images obtained with cardiac gating only, but acquisition time was longer. Portions of the coronary arteries were visualized in seven of 23 examinations (30%), and subacute and old myocardial infarcts were seen in five of nine patients (55%) as areas of thinned myocardium. No signal changes were observed in the patients with subacute infarctions or the patient with myocarditis. Coronary atherosclerotic lesions were not visualized in any of the patients. Normal cardiac anatomy (chambers, valves, and papillary muscles) was well visualized. Examples of aortic stenosis and atherosclerosis of the abdominal aorta are shown.

The effect of motion on two-dimensional Fourier transformation magnetic resonance images.

The effect of motion on two-dimensional Fourier transformation magnetic resonance (MR) images was investigated using phantoms, animals, and normal volunteers. All images were obtained with a 0.30-Tesla superconducting magnet using spin echo pulse sequences. Respiratory motion was simulated while imaging the phantoms. In addition to image blurring, motion produced ghost images, or image harmonics. These ghost images were copies of the static image that was produced at periodic intervals. Canine images, which were obtained during respiration and after the administration of curare, showed significant improvement after respiratory motion was eliminated. Images of normal volunteers were improved with respiratory and cardiac gating, but data acquisition time was significantly increased. These results indicate that MR image quality could be improved with a system that acquires all necessary data within a single breathhold .

Magnetic resonance imaging in the evaluation of the brainstem.

Magnetic resonance (MR) images of the brainstem region from 100 normal or asymptomatic individuals were reviewed in addition to those of 17 patients with intra-axial brainstem lesions and 15 patients with extra-axial masses around the brainstem. MR was able to demonstrate consistently the normal anatomy of the brainstem and adjacent cisterns, though the distinction between gray and white matter was seldom possible with the present technology. Masses in and around the brainstem were all accurately identified on MR and its sensitivity was superior to that of x-ray computed tomography (CT). These study results show that despite its technical limitations, MR is presently the examination of choice for the evaluation of brainstem abnormalities and eventually it will undoubtedly replace metrizamide CT cisternography.

Magnetic resonance imaging of the orbit: a preliminary experience.

Eleven patients with various space-occupying lesions in the orbit were examined, using a 0.3-tesla superconducting magnet to assess the capabilities and limitations of magnetic resonance (MR) imaging in the investigation of orbital lesions. Although the images provided valuable anatomic data, the bright signal intensity of fat and the partial volume effects of large section thickness resulted in loss of resolution for small, low-signal-intensity structures. The limitations of MR imaging were also reaffirmed by the lack of visualization of calcifications and of the bony orbit. These preliminary results show that MR offers no advantage over x-ray computed tomography except for its lack of ionizing radiation. Further technical improvements are needed before MR imaging will be made useful in this area.

Magnetic resonance imaging of the breast. Work in progress.

Ten normal volunteers and 45 patients with breast abnormalities were examined with magnetic resonance (MR), utilizing a 0.3-tesla superconducting magnet. In all patients, MR detected an abnormality that corresponded to the area of pathology seen on either a mammogram or computed tomographic (CT) scan. An appreciable advantage of MR over mammography was observed in patients with cysts and in those with areas of asymmetric dysplastic breast tissue. Abnormalities on MR images appeared as areas of low signal intensity relative to adjacent normal ductal and fatty tissue. The configuration of a lesion on MR permitted distinction between a benign and a malignant process.

CT-guided percutaneous biopsies in pediatric patients.

Twenty (5%) of 432 pediatric patients scanned during the last 36 months underwent percutaneous biopsy with CT guidance. Sixteen patients had suspected or a known malignancy. Four patients were clinically suspected of having an inflammatory process. Cytologic and histologic specimens were taken when technically possible. Total diagnostic tissue recovery rate equalled 88% in the patients with known or suspected malignancy. Diagnostic tissue was obtained in three of four patients with inflammatory disease. No immediate or delayed complications were encountered. Although the percutaneous method under CT guidance has been shown to be advantageous in various aspects of medical care, the utilization of this modality in the pediatric population, to our knowledge, has been limited. We have found this technique to be useful in the tissue diagnosis of pediatric disease, and in guiding the subsequent clinical treatment. The clinical indications, technique, and results utilizing this method are presented.

Gated magnetic resonance imaging of congenital cardiac malformations.

Magnetic resonance (MR) images of a variety of cardiac malformations in 19 patients aged 1 week to 33 years were obtained using pulse plethysmographic- or ECG-gated spin echo pulse sequences. Coronal, axial, and sagittal images displaying intracardiac structures with excellent spatial and contrast resolution were acquired during systole or diastole. It is concluded that MR will be a valuable noninvasive method of diagnosing congenital heart disease.

Head trauma evaluated by magnetic resonance and computed tomography: a comparison.

Magnetic resonance (MR) images and computed tomograms of 25 patients with head trauma were compared. MR proved to be superior in many ways for demonstrating extracerebral as well as intracerebral traumatic lesions. Isodense subdural hematomas, which present a diagnostic dilemma on CT images were clearly seen on MR, regardless of their varying CT densities. In a case of epidural hematoma, the dura mater was shown directly as nearly devoid of signal on MR. Direct coronal images provided excellent visualization of extracerebral collections along the peritentorial space and subtemporal area. In a patient with intracerebral hematoma, CT failed to demonstrate residual parenchymal changes in a 3-month follow-up study, but MR clearly depicted the abnormalities. The superiority of MR over CT was also well illustrated in a patient with post-traumatic osteomyelitis of the calvarium.

NMR imaging of the spine.

The usefulness of nuclear magnetic resonance (NMR) images in the evaluation of spinal disorders below the craniocervical junction was studied. Six normal subjects and 41 patients with various spinal abnormalities were examined. NMR proved capable of demonstrating important normal and pathologic anatomic structures; it was useful in the evaluation of syringohydromyelia and cystic spinal cord tumors, and the bright signal intensity of lipoma was quite impressive. In the evaluation of herniated disk, NMR images offered a new perspective by visualizing abnormal degradation of the signal intensity of the nucleus pulposus itself. NMR images were least valuable in the evaluation of spondylosis and spinal stenosis. Although NMR imaging of the spine is still in a very early developmental stage, the absence of both ionizing radiation and risks associated with contrast material makes it especially attractive as a new diagnostic method. This limited experience with currently available equipment suggests that, with technical refinement, the efficacy of NMR of the spine will increase.