Localization of auditory response sources using magnetoencephalography and magnetic resonance imaging.

Magnetoencephalography offers the possibility of localizing accurately and noninvasively the source of intracranial currents associated with normal and abnormal brain activity. The purpose of this study was to assess the validity and across-subject reliability of localization of cortical sources responding to ipsilateral and contralateral auditory stimulation. Magnetic evoked fields to both stimulation conditions were measured in eight consecutive normal subjects, and the cortical sources of these fields were estimated on the basis of these measurements. Subsequent projection of the source location coordinates onto magnetic resonance images showed that in all subjects the sources were accurately estimated to fall in the vicinity of the auditory cortex and that two separate sources may account for the response to ipsilateral and contralateral stimulation.

Magnetic resonance imaging and neuropsychological findings in human immunodeficiency virus infection.

Neurobehavioral functioning and magnetic resonance imaging (MRI) were investigated in 25 patients with various Centers for Disease Control (CDC) stages of human immunodeficiency virus (HIV) infection and in a control group of seven normal subjects. Unequivocal slowing of information processing speed and cerebral atrophy were related to the stage of HIV infection, with patients in CDC group IV exhibiting the most abnormal findings. Slowing of response speed was directly related to the severity of cerebral atrophy.

Magnetic resonance imaging in pulmonary arterial hypertension.

Magnetic resonance imaging (MRI) was used to examine the right ventricle and pulmonary arteries in 17 patients with pulmonary artery (PA) hypertension documented by cardiac catheterization. The study population consisted of 7 patients with primary pulmonary hypertension, 7 with Eisenmenger's syndrome and 3 with pulmonary hypertension secondary to lung disease. The MRI studies of patients were compared with those of 10 normal volunteers. Multislice gated transaxial images encompassed the right ventricle and central pulmonary arteries, showing the severity of right ventricular (RV) hypertrophy in proportion to the elevation of PA pressure and reversal of septal curvature when PA pressure approximated systemic pressure. End-diastolic RV wall thickness and mean pulmonary pressure correlated well (r = 0.79). MRI showed enlargement of PAs in all patients with PA hypertension. A magnetic resonance signal was present in the PAs throughout the cardiac cycle in patients with severe PA hypertension (more than 90 mm Hg) and was absent during systole in normal subjects. A signal within the PAs in systole is consistent with decreased flow velocity in patients with severe PA hypertension. MRI was useful in detecting each of the congenital anatomic defects in patients with Eisenmenger's syndrome. This study indicates the potential of MRI for evaluating the severity of PA hypertension by providing direct measurements of RV wall thickness and PA diameter and by detecting abnormal intraluminal signal intensity during the cardiac cycle.

Paraganglioma of the heart. The value of magnetic resonance imaging in the preoperative evaluation.

Although the 131I-metaiodobenzylguanidine scan has proven reliable in identifying mediastinal paragangliomas, further localization has usually required dynamic computerized tomographic scanning which requires rapid bolus injection of contrast material. In the case presented herein, magnetic resonance imaging provided accurate preoperative localization and added important anatomic detail that was not appreciated with dynamic computerized tomograms or with other studies. Magnetic resonance imaging can accurately localize cardiac paragangliomas without injection of contrast material and may provide more detailed information for better guidance for surgical excision.

Theoretical considerations for optimizing intensity differences between primary musculoskeletal tumors and normal tissue with spin-echo magnetic resonance imaging.

In the radiographic assessment of primary musculoskeletal tumors, it is important for therapy planning to accurately define the extent of a tumor. Using a double spin-echo pulse sequence, the T1 and T2 relaxation times and relative hydrogen densities of several neoplastic tissues and of several normal tissues in four patients were measured. Neoplasms measured included one fibrosarcoma, two osteosarcomas, and one giant cell tumor. Normal tissues measured included normal muscle, fat, and bone marrow. Using a mathematical model of the double spin-echo pulse sequence, the intensity difference between each tumor and each normal tissue for multiple values of TR and TE was calculated. These calculated intensity differences were then used to plot isodifference contour curves for each tissue pair. These plots enabled us to pick combinations of TR and TE that optimized the signal difference between tumor and normal tissue. When comparing tumor with predominantly fatty tissue such as marrow or subcutaneous fat, optimal signal difference in our imager occurred at a TR of 600 to 800 msec and a very short TE. When comparing tumor with muscle, optimal signal difference occurred with very long TR times, and TE times ranging from 30 to 90 msec. These preliminary results suggest that an optimal scanning protocol for primary musculoskeletal tumors should contain at least two different pulse sequences with widely separated TR values (500 and 2000 msec in our instrument), and short to intermediate values of TE (28 and 56 msec in our instrument). It is believed that analysis of isodifference contour plots is a useful method for optimizing intensity differences between any two tissue types.

Lithopedion: stone baby.

Two cases of lithopedion were encountered. In one case, computerized tomographic (CT) findings are illustrated. There are no classical clinical signs or symptoms that aid in the diagnosis of this rare condition. A calcified fetus and investing membranes are readily identified on a plain film of the abdomen, and these constitute an absolute sign of lithopedion. Excretory urography, barium enema examination, ultrasound, and CT represent other diagnostic modalities in the evaluation of this condition, but they are rarely indicated or valuable.

Surface coil MR of spinal trauma: preliminary experience.

Nineteen fractured vertebral bodies involving the spine from C1 to L2 in 14 patients were imaged with a 0.6-T magnet using prototypical surface coils. Ten of these patients were studied within the first week of trauma. CT and plain films are superior to MR in detecting fractures and identifying the origin of displaced fragments in cases of extensive comminution. However, all body fractures and most posterior element fractures in the thoracolumbar spine were visible on MR. Fractures involving the cervical neural arch were difficult to detect on transverse section without CT correlation. Our results indicate that MR can probably replace CT in the thoracolumbar region. MR is superior to CT in demonstrating ligamentous injury and trauma to the disk. Unlike CT, MR shows the relation of the thecal sac and spinal cord to retropulsed fragments and epidural hematoma. MR also visualizes cord parenchyma; two cases of cord hemorrhage were not seen on CT. Even at this early stage of development, surface coil MR promises to become important in the evaluation of spinal trauma, not only in assessing the integrity of the spinal canal and cord, but in separating stable from unstable fractures on the basis of disruption of the posterior ligaments and elements. Additionally, the demonstration of rupture of specific ligaments may have an impact on surgical management.

Cerebral blood volume in a rat model of ischemia by MR imaging at 4.7 T.

Perturbation of the cerebral circulation by occlusion of the vertebral arteries and a carotid artery can be visualized by using MR imaging and the intravascular contrast agent Gd-DTPA complexed to albumin. This tracer consistently reduced the T1 relaxation time in the brain and blood. The difference between hemispheres was revealed by less T1 reduction in the occluded hemisphere and by an adjustment in the display contrast of images that revealed the territory of decreased perfusion. These results were confirmed by comparing them with cerebral blood flow using radioactive microspheres and the intravascular blood volume tracer 51Cr-EDTA. This method, combined with high-resolution MR imaging, can be applied to serial noninvasive studies of cerebral blood volume in ischemia and other conditions.

Magnetic resonance imaging after closed head injury in children.

Magnetic resonance imaging (MRI) was performed in a series of 21 children and adolescents who had been hospitalized after sustaining closed head injuries of varying severity at least 6 months previously. Areas of high intensity in the parenchyma were present in 8 of the 11 severely injured patients, whereas MRI findings were normal in all 10 patients with mild-to-moderate head injuries. Lesions involving the subcortical white matter were confined to severely injured patients whose clinical features were compatible with diffuse axonal injury. Neuropsychological assessment disclosed deficits primarily in the severely injured patients; these deficits were significantly associated with persistent lesions visualized by MRI. Serial MRI and neurobehavioral assessment following early injury may be useful in documenting cognitive impairment in relation to structural alterations of the young brain.

Relationship of depth of brain lesions to consciousness and outcome after closed head injury.

Magnetic resonance (MR) imaging was performed in 94 patients who sustained closed head injury of varying severity. Results of MR studies obtained after the intensive care phase of treatment disclosed that intracranial lesions were present in about 88% of the patients. Consistent with the centripetal model of progressive brain injury proposed in 1974 by Ommaya and Gennarelli, the depth of brain lesion was positively related to the degree and duration of impaired consciousness. Further analysis indicated that the relationship between depth of brain lesion and impaired consciousness could not be attributed to secondary effects of raised intracranial pressure or to the size of intracranial lesion(s).

Surface coil magnetic resonance imaging of the normal larynx.

The use of specialized surface coils has made it possible to obtain high-signal, high-resolution magnetic resonance (MR) images of the neck. We describe the normal anatomy of the larynx imaged with surface coils and a technique adapted from respiratory gating to reduce motion from swallowing and coughing. Compared with computed tomography, MR has superior discrimination of tissues that on computed tomography appear to be of similar density. The intrinsic laryngeal muscles and carotid sheath are well seen. Multiplanar imaging capability allows easy distinction of false and true cords and optimal evaluation of the preepiglottic and paralaryngeal spaces. Computed tomography is easier to perform than MR and is superior to MR in depicting the laryngeal cartilages. However, with improved technology, MR may become the imaging modality of choice in evaluation of the larynx and adjacent hypopharynx and subglottic regions.

Preclinical evaluation of manganese carbonate particles for magnetic resonance imaging of the liver.

RATIONALE AND OBJECTIVES: We characterized the physical, biological, and imaging properties of a manganese (Mn) carbonate particle suspension, a contrast agent for hepatic magnetic resonance (MR) imaging. METHODS: Mn carbonate suspensions were produced by controlled precipitation and characterized using light microscopy, transmission electron microscopy, and in vitro relaxivity studies. Efficacy of the agent was studied in normal and tumor-bearing rats using T1-weighted MR imaging. RESULTS: Following intravenous injection of Mn carbonate particles at doses ranging from 10 to 100 mumol Mn/kg, peak hepatic contrast enhancement of approximately 35% occurred from about 125 min until the termination of the MR imaging studies that varied from 125 to 305 min. Lesion conspicuity was increased because of relative intensity differences between normal liver and tumor. Data also showed that Mn carbonate particles dissolved on delivery to the liver, allowing Mn to interact with intrahepatic macromolecular complexes to provide positive contrast enhancement. CONCLUSION: Mn carbonate particles produce significant and sustained hepatic enhancement and should improve detection of small or isointense liver lesions.

Multiple simultaneous percutaneous needle biopsy (MSPNB) technique for masses of the abdomen and peritoneum.

A technique for the biopsy of abdominal masses consisting of the simultaneous insertion of multiple needles is described. This technique was employed in 45 patients. The results were compared with the author's preceding experience with 32 cases performed with a conventional technique of sequential biopsies. Adequate specimens were obtained in 42 (93.3%) cases with the multiple simultaneous percutaneous needle biopsy (MSPNB) technique. This compares with a diagnostic adequacy yield of 84.3% for the sequential technique. In 25 cases performed under CT guidance, the average CT utilization time was 12 minutes, and the average number of slices was 3, as compared to 45 minutes and 12 slices with the conventional sequential technique. No complications were encountered. We conclude that the MSPNB technique is a safe time- and cost-effective technique with a high yield of adequate and diagnostic specimens.

MRI of cervical carcinoma.

MRI is useful for demonstrating enlarged retroperitoneal lymph nodes and for demonstrating the carcinoma mass in patients with carcinoma of the cervix. MRI evaluation of the parametria appears promising, but further studies are necessary to elucidate the optimal imaging parameters and to better define the overall accuracy of MRI compared to the clinical evaluation of the parametria.

Neurobehavioral and magnetic resonance imaging findings in two cases of decompression sickness.

Two divers underwent neurobehavioral examinations and magnetic resonance imaging (MRI) while hospitalized during the first 2 weeks after sustaining decompression sickness (DCS). Their neurologic findings included a Brown-Séquard Syndrome consistent with spinal cord lesion, and focal deficits consistent with cerebral lesion(s). MRI revealed subcortical white matter lesions in the brains of both divers, whereas no lesion of the spinal cord was demonstrated. The patients exhibited neurobehavioral sequelae including disturbances of memory, divergent thinking, and visuospatial and motor functioning. Focal neurologic deficits resolved in both patients, and their cognitive and memory problems improved slowly. Findings in these two divers raise the possibility that cerebral insult more frequently accompanies spinal cord injury in DCS than previously thought.

Page kidney.

The computed tomographic (CT) findings of a classic case of Page kidney (hypertension resulting from compression of the renal parenchyma by a subcapsular hematoma) is presented. An excretory urogram and renal arteriogram performed prior to the CT study resulted in nonspecific findings. The CT findings of a well circumscribed, elliptically shaped, low density, subcapsular hematoma producing parenchymal compression was correlated with the onset of hypertension following remote trauma, permitting the CT diagnosis of Page kidney.

MR imaging of blue rubber bleb nevus syndrome.

This report describes the use of magnetic resonance imaging in the evaluation of a patient with blue rubber bleb nevus syndrome, a rare entity consisting of multiple cutaneous and visceral hemangiomas. The bright signal obtained on T2-weighted images is probably the result of slow flow or thrombosis, typically present in these lesions, and allows for easy recognition.

MR demonstration of extensive pelvic involvement in vulvar hemangiomas.

Magnetic resonance imaging of two patients with vulvar hemangiomas noninvasively demonstrated unexpected pelvic involvement. Magnetic resonance is an excellent method for initial evaluation and follow-up of these lesions.

MR imaging of uterine cervical carcinoma.

We retrospectively analyzed the magnetic resonance (MR) imaging findings of 20 consecutive patients with primary untreated carcinoma of the cervix who underwent surgery and one patient who underwent percutaneous needle biopsy of enlarged pelvic lymph nodes. Most of the patients were clinical Stage IB. The clinical assessment of the parametria in these patients was more accurate than the MR assessment of the parametria (95 versus 79%). Magnetic resonance was valuable for detecting metastatic pelvic lymphadenopathy. Enlarged pelvic lymph nodes (greater than 1.5 cm in diameter) were demonstrated by MR in all three patients with histologic verification of metastatic lymphadenopathy. In summary, the major therapeutic value of MR in patients with untreated cervical carcinoma is in assessing the pelvic lymph nodes. In patients with clinical Stage IB disease, MR assessment of the parametria does not add useful additional information.

Benign urachal cyst in an adult.

Benign urachal cyst is a rare lesion in the adult. Prompt diagnosis and management are important to avoid complications. This report illustrates the value of computed tomography (CT) in establishing the diagnosis of urachal cyst in a case in which conventional radiography and ultrasonography were normal. In any patient with a history or physical findings suggestive of a urachal anomaly, CT is most useful in establishing the nature of the anomaly and extent of the lesion. In this case, CT findings of a soft tissue mass at the bladder apex continuing superiorly as a tubular structure were consistent with infected urachal cyst.