Pediatric metrizamide CT cisternography: cerebrospinal fluid circulation and hydrocephalus.

The technique of intrathecal enhancement using metrizamide (Amipaque) combined with CT imaging enables both the morphologic and dynamic (serial) evaluation of the intracranial cerebrospinal fluid pathways. Three distinct metrizamide CT cisternographic patterns (delayed, intermediate, and normal) emerge in pediatric patients with hydrocephalus. The findings correlate well with radionuclide cisternographic patterns; however, CT also provides excellent morphologic definition.

Magnetic resonance imaging in pathologically proven Hallervorden-Spatz disease.

We present an 11-year-old girl in whom high field strength MRI performed 2 1/2 years and 6 months before her death showed prominent hypointensity in the globus pallidus and substantia nigra consistent with iron deposition. This finding suggested Hallervorden-Spatz disease, which was confirmed at autopsy.

A comparison of iopromide with iopamidol and iohexol for contrast-enhanced computed tomography.

RATIONALE AND OBJECTIVES: Iopromide is a new monomeric, nonionic contrast agent that exhibits low osmolality and low viscosity in high concentration in aqueous solutions. Double-blind, randomized clinical trials have established the efficacy, safety, and tolerance of iopromide for excretory urography, coronary angiography, routine and digital subtraction angiography, and phlebography. However, iopromide had not previously been evaluated in blinded clinical trials for contrast-enhanced computed tomography (CECT). Thus, a double-blind, prospective randomized trial was performed to compare the efficacy, safety, adverse experience profile, and tolerance of iopromide to that of iopamidol and iohexol in patients requiring CECT of the head or body. METHODS: Of 190 patients entered into the study, 95 received iopromide and 95 received a comparator (iopamidol, n = 55; and iohexol, n = 40) at 300 mg I/mL. Efficacy, adverse experiences (AEs), and tolerance were measured, and a safety profile was obtained that monitored changes at 24 hours in physical examination, vital signs, hematologic profile, and blood chemistries. RESULTS: Efficacy was similar for all drugs with excellent/good visualization in 98.4% of studies. The total number of patients reporting AEs was equivalent (iopromide 13.8%, comparators 12.6%; P > .10). However, although 2.5% of patients in the iopromide and iopamidol groups had possibly related mild AEs, 15% receiving iohexol had related AEs, one of which was severe. Excellent tolerance was noted, with no patients reporting localized pain; there were low rates of mild to moderate warmth on injection (8.5% for iopromide versus 9.5% for comparators; P > .10). Safety profiles were comparable. Postprocedure, there were no significant changes or significant differences between groups, except for a significantly increased incidence of systolic blood pressure decrease by greater than 20 mm Hg at 24 hours in the comparator group. CONCLUSIONS: Iopromide has an efficacy, safety, and tolerance profile comparable to that of iopamidol and iohexol at 300 mg I/mL for head and body CECT. It may have a superior adverse experience profile to iohexol, but is similar to iopamidol. Thus, iopromide is a reasonable choice of nonionic contrast medium for all CECT procedures.

Comparative cranial CT enhancement in the normal primate.

The application of intravenous, intrathecal, and inhalation enhancement techniques to the CT evaluation of the nonhuman primate (Papio cynocephalus/anubis) is described. The falx cerebri cortical vasculature, vein of Galen, straight sinus and tentorium cerebelli were defined with intravenous enhancement. Intrathecal CT enhancement with air was limited by distortion in cerebrospinal fluid spaces. Intrathecal CT enhancement using a low dose of metrizamide accurately delineated the subarachnoid spaces and the brain substance they surrounded with minimal morbidity. Symmetrical brain enhancement (perfusion) was prominent following inhalation CT enhancement; the degree of enhancement correlated with the estimated xenon concentration in the bloodstream. In addition, by performing repeated CT scans during the clearance of xenon from the brain, an approximate analysis of regional cerebral blood flow was obtained.

Pharmacokinetics of nitroxide NMR contrast agents.

Pharmacokinetics of the nitroxide stable free radical functionality of compounds containing this moiety were evaluated in the rat. The agents were injected i.v. at either high (1.75 mmoles/kg) or low (10 mumoles/kg) dose, and timed blood samples were drawn and assayed for nitroxide concentration by EPR spectrometry. Similarly, various organs and tissues were removed at specified times after injection and homogenized for determination of nitroxide concentration. Urine was collected by catheter for estimation of urinary excretion of the intact nitroxide free radical. At high doses, the various nitroxides exhibited an initial rapid disposition phase, followed by a terminal disposition phase with disappearance from the blood showing apparent log-linear half-lives of about 5 to 30 minutes. Generally, 20 to 60% of the dose was recovered in the urine. At low doses, dissimilar results were obtained. Blood levels again showed biphasic decay; however, blood concentrations at all times were much lower than those predicted by the high dose kinetics, indicating probably nonlinear pharmacokinetic behavior. Tissue homogenate studies showed low or nondetectable levels of nitroxide signal, demonstrating that the low blood concentrations could not be accounted for by a rapid uptake into specific tissues. Moreover, only 2 to 6% of the nitroxide could be recovered in the urine. Additional studies demonstrated that at the low dose a rapid in vivo bioreduction occurred which appeared to be saturable at the higher dose.

Safety and efficacy of iopromide in cerebral arteriography.

RATIONALE AND OBJECTIVES: Iopromide is a new nonionic monomeric contrast medium for cerebral arteriography. This agent has been approved for sale in over 45 countries; however, it is still undergoing clinical review in the United States. This study evaluated the safety and efficacy of iopromide in comparison with two other nonionic contrast media. METHODS: A total of 173 patients participated in the study, which was prospective, double-blind, and randomized. In two centers, patients received iopromide or iohexol; in the other three centers, patients received iopromide or iopamidol. Adverse events were monitored by investigators, and efficacy was evaluated by grading the radiographic images. RESULTS: Most adverse events were mild or moderate in severity; all resolved completely. Twenty-one percent of patients given iopromide were reported to have a drug-related adverse event, versus 44% of patients given a comparator. No statistically significant difference emerged between iopromide and the comparators with regard to efficacy. CONCLUSIONS: These study results indicate that iopromide is a safe and effective contrast medium for cerebral angiography.

Magnetic resonance imaging of optic gliomas.

We compared magnetic resonance imaging of the optic nerves and chiasm with computed tomography in four patients (a 17-year-old girl, a 14-year-old boy, a 13-year-old girl, and a 22-year-old woman) with biopsy-proven or suspected optic gliomas. Orbital abnormalities were effectively viewed by both techniques. Gliomatous and normal optic nerves had similar spin-echo magnetic resonance imaging characteristics. Magnetic resonance was superior to contrast-enhanced computed tomography for identification of the intracranial optic nerves, chiasm, and optic tracts, but computed tomography delineated orbital anatomic and spatial relationships better.

Functional applications of CT of the central nervous system.

Although CT has developed as a morphologic technique, its anatomic specificity may be used to map physiologic events. Using intravenously infused iodinated contrast media, CT offers unique analysis of the integrity of the blood-brain barrier. If the barrier is not disrupted, the same iodinated indicators may be used to estimate vascular transit time and cerebral blood volume. Nonradioactive xenon, a freely diffusible indicator, enhances the brain substance and may be used to evaluate both cerebral blood flow and tissue integrity in well defined anatomic locales. However, these functional determinations have distinct limitations. Future use of CT, including providing more sophisticated tissue characterization, indicator development, and advances in scanner technology, are discussed.

Pathophysiology of "reverse" edema in global cerebral ischemia.

A small percentage of patients who suffer a global cerebral hypoxic/ischemic event develop reversal of the normal density relationships of gray and white matter on CT. CT and pathologic findings in the three cases presented indicate that this phenomenon appears to result from distension of deep medullary veins secondary to partial obstruction of venous outflow from elevated intracranial pressure. The "reverse" edema sign indicates a severe hypoxic/ischemic injury to the brain and has a poor clinical prognosis.

MR imaging of pericallosal lipoma.

Early pathologic reports of corpus callosal lipoma described a consistent relationship between the lipoma and the dorsal surface of the corpus callosum, particularly when the lipoma is not associated with corpus callosal agenesis. MR imaging, especially T1-weighted sagittal acquisitions, exquisitely demonstrated this anatomic relationship in three relatively asymptomatic patients. Therefore, in most cases, a lipoma of the corpus callosum is more accurately described as a pericallosal lipoma. In one individual, common associated findings (partial agenesis of the corpus callosum and choroid plexus lipoma) were also noted. Surgical therapy is usually not indicated because symptoms are generally not related and the anterior cerebral artery is often encased by the lipoma.

Anatomic applications of xenon-enhanced CT scanning: visual image analysis and brain-blood partition coefficient studies in man.

The inhalation of nonradioactive xenon, an inert gas that diffuses freely across the blood-brain barrier, resulted in brain enhancement which was quantitated and visualized by computed tomography (CT). Serial CT scans obtained during the buildup and equilibrium phase of xenon inhalation were used in a numerical and visual analysis of xenon accumulation in multiple selected gray- and white-matter regions in 12 patients. The calculated brain-blood partition coefficient (lambda) in normal gray matter was 0.92 +/- 0.11 and in normal white matter, 1.38 +/- 0.14. Asymmetries and delays in xenon enhancement were often visually apparent. The estimated partition coefficient was diminished more with cerebral infarction, intracerebral hematoma, and vasogenic edema than with hypoxic encephalopathy or glioblastoma multiforme. An increase in the rate of xenon accumulation was apparent by visual inspection of the motor cortex contralateral to complex hand movements. Technical factors and potential difficulties in conducting xenon-enhanced CT studies are discussed.

Intracranial MR angiography: its role in the integrated approach to brain infarction.

PURPOSE: To determine the contribution of cranial MR angiography (MRA) for the evaluation of patients with acute and subacute brain infarction. METHODS: MR and MRA studies performed on 78 adult patients with acute and subacute stroke were retrospectively reviewed and correlated with the clinical records. RESULTS: There were 50 acute and 28 subacute infarctions in our series. Five of 78 MRA exams (6%) were nondiagnostic. Sixty examinations (80%) were positive for stenosis or occlusion. The distribution of stenotic or occlusive vascular lesions correlated with the location of infarction in 56 of the 60 positive cases (93%). MRA provided information not obtained from the MR images in 40 cases (55%). One hundred four individual vessels in 8 patients who underwent conventional cerebral angiography were compared with the MRA appearance. The MRA interpretations correlated with the conventional angiographic evaluations for 90 vessels (87%). CONCLUSIONS: Vascular lesions demonstrated on intracranial MRA show a high correlation with infarct distribution. MRA provides information adjunctive to conventional MR in a majority of cases. We conclude that MRA is an important component of the complete evaluation of brain infarction.

Synovial cysts of the lumbosacral spine: diagnosis by MR imaging.

Intraspinal synovial or ganglion cysts are uncommon lesions associated with degenerative lumbosacral spine disease. CT usually reveals cystic lesions adjacent to a facet joint, and they may show calcification. MR imaging of four surgically confirmed cases of intraspinal synovial cysts revealed subtle signal changes compared with CSF. Short TR/TE images showed the lesions to be slightly hyperintense in three cases and isointense in one case. Long TR/TE sequences revealed a hyperintense appearance in two cases and a hypointense appearance in the others. A peripheral rim of decreased signal on long TR/TE images probably reflects fine calcification or hemorrhage in the margins of the cysts. The multiplanar and contrast characteristics of MR make this technique well suited to the diagnosis of herniated disk, degenerative facet disease, and synovial cyst.

Pharmacokinetics of lopamidol after intrathecal administration in humans.

The kinetics of iopamidol, a new nonionic radiocontrast agent, were evaluated in 10 patients undergoing lumbar myelography. The doses of iopamidol administered intrathecally were 11 and 15 ml of a 200-mg iodine per ml solution in one and nine patients, respectively. Radiographs were made within 30 to 40 min and CTs were taken at about 1, 6, and 23 hr after iopamidol administration. The diagnostic quality and usefulness of the conventional and CT myelograms were considered excellent. In the lumbosacral subarachnoid space, the densitometry CT readings were maximal at 1 hr, whereas in the cervical subarachnoid space, peak CT values were reached at 6 hr. Plasma and urine samples were taken at frequent intervals up to 48 hr after the contrast agent was administered. Peak plasma levels of iopamidol were observed at 2.9 hr and were no longer detectable at 48 hr. The 48-hr urinary recovery for all patients averaged 66 +/- 8% of the dose. In all but one patient, iopamidol was cleared almost completely from the CSF within 24 hr. Side effects after iopamidol administration were transient and minor, and were not related to the CT readings or its systemic clearance.

MR angiography of cervical fibromuscular dysplasia.

The authors present examples of cephalic fibromuscular dysplasia (involving five vessels in two patients) using 2-D time-of-flight MR angiography and conventional angiography. Artifacts that can mimic the MR appearance of fibromuscular dysplasia will tend to decrease the sensitivity and specificity of MRA in its detection.

Intramedullary penetrance of metrizamide in the dog spinal cord.

Metrizamide computed tomography (CT) myelography is clinically useful in the detection of syringohydromyelia. The mechanism by which intrathecally injected metrizamide migrates into the intramedullary cavity is unknown, although reflux into the central canal of the cord via the obex has been postulated. Since intrathecally injected metrizamide has been shown to penetrate normal brain, similar penetrance of the spinal cord might be expected. Five anesthetized mongrel dogs were examined with sequential CT scanning of the cervical spine for 24 hr after intrathecal introduction of metrizamide. The attenuation values of the specified subarachnoid space and the spinal cord at the level of the atlantoaxial joint were recorded. A significant and reproducible increase with time in attenuation values within the cervical spinal cord accompanied by a progressive decrease in attenuation values of the subarachnoid space was observed. The proposed mechanism of cord enhancement, the implication for cord imaging, and the analysis of patients with syringohydromyelia are discussed.

Opacification of epidural venous plexus and dura in evaluation of cervical nerve roots: CT technique.

Thin-section computed tomography (CT) after bolus high-volume, intravenous contrast enhancement of the cervical epidural and intervertebral foraminal venous plexus was undertaken in eight patients. Visualization of exiting cervical nerve root by opacification of the surrounding intervertebral plexus was evaluated in 38 foramina. Visualization was judged as excellent in 77% and good in 21%. Thus the nerves were seen satisfactorily in all but one foramen. As the CT scan parallels the long axis of the cervical roots as they pass through the intervertebral foramen, anatomic delineation of the root out to the level of the vertebral artery is excellent. A local widening of the root, which was thought to represent the dorsal root ganglion, was seen in most foramina examined. Excellent filling of the epidural plexus was seen in seven of eight subjects; good opacification was seen in the other subject. In no instance did the study fail to satisfactorily fill the epidural plexus in the cervical vertebral canal. This technique appears to be an excellent method for evaluating the cervical nerve roots and the epidural space.

Evaluation of shared-view acquisition using repeated echoes (SHARE): a dual-echo fast spin-echo MR technique.

PURPOSE: To compare the clinical efficacy of a dual-echo fast spin-echo imaging technique, SHARE (share-view acquisition using repeated echoes), with conventional long-repetition-time spin-echo imaging. METHODS: Conventional spin-echo and SHARE fast spin-echo MR images of the brain were acquired in 50 randomized patients and interpreted separately in conjunction with the T1-weighted images. All images were reviewed independently by two neuroradiologists who were blinded to the clinical history and previous interpretations. RESULTS: The diagnoses rendered for the spin-echo and SHARE images were concordant in 48 of the 50 subjects (96%) by the first reader and in all 50 cases (100%) by the second reader. SHARE images were acquired in one-fourth of the imaging time yet image contrast, quality, and sensitivity to long T2 lesions were comparable. The SHARE technique was less sensitive to hemorrhagic residua. CONCLUSIONS: SHARE is a viable time-saving alternative to the conventional long-repetition-time pulse sequence. Although SHARE images are not as sensitive to magnetic susceptibility effects, the time saved using this technique could be used to perform a gradient-echo sequence when indicated.

Neurologic complications of cerebral angiography.

PURPOSE: To examine the incidence of neurologic complications associated with modern cerebral angiography and to assess patient characteristics associated with an increased risk of complications. METHODS: One thousand consecutive cerebral angiographic procedures were evaluated prospectively. Examinations were performed using transfemoral catheterization and film-screen methods. For purposes of this trial, a neurologic complication was defined as any new focal neurologic deficit or change in mental status occurring during the angiogram or within the following 24 hours. Patients were evaluated during and at the completion of angiography. Follow-up evaluations were performed on the day of and the day after angiography. RESULTS: There were a total of 10 neurologic complications within 24 hours of angiography, 5 of which were persistent. Onset of 5 of the deficits occurred during angiography, the other 5 (3 persistent) were delayed. All complications occurred in patients being evaluated for stroke/transient ischemic attack or (in one case) asymptomatic bruit. A higher average age, longer average procedure time, and greater volume of radiographic contrast was noted in these patients than in the study population. CONCLUSION: Cerebral angiography was associated with a 1% overall incidence of neurologic deficit and a 0.5% incidence of persistent deficit. All complications occurred in patients presenting with a history of stroke/transient ischemic accident or carotid bruit, which may reflect the difficulty of performing angiography in this population at risk for atherosclerotic changes.

MR assessment of myelination in infants and children: usefulness of marker sites.

A retrospective study was made of 60 patients, 1 month to 3 years old, to determine the normal progression of white matter myelination on MR imaging. All examinations were performed with a 1.5-T unit, and axial T1- and T2-weighted images were evaluated in each patient. Multiple sites in the cerebral hemisphere and cerebellum were examined in each case for the presence and degree of myelination. The results show that MR imaging is sensitive to the early changes of white matter myelination, and imaging patterns correlate with known patterns from pathologic studies. At the time of birth in a full-term infant the posterior limb of the internal capsule, central corona radiata, and cerebellar peduncles show visible myelination. Myelination in the centrum semiovale then proceeds anteriorly and posteriorly. Both T1- and T2-weighted images show these changes, which are best explained by a decrease in the water content of white matter as myelination progresses. Knowledge of these normal myelination patterns is essential in evaluating MR imaging studies in infants and children and in diagnosing delayed myelination.