A method to quantitatively measure transcapillary transport of iodinated compounds in canine brain tumors with computed tomography.

We present a quantitative method for determining a blood-to-tissue influx constant (K1), a tissue-to-blood efflux constant (k2), and tissue plasma vascular space (Vp) that uses a computed tomographic (CT) scanner to make tissue and plasma measurements of the concentration of an iodinated compound. Meglumine iothalamate was infused intravenously over time periods of 0.5-5 min, up to 49 CT scans were obtained at one brain level, and arterial plasma was sampled over a 30- to 40-min period. K1, k2, and Vp were calculated for each voxel of the 320 x 320 matrix, using a two-compartment pharmacokinetic model and nonlinear least-squares regression. The method was used in dogs with avian sarcoma virus-induced brain tumors. As many as four studies on different days were done in the same animal. In tumor-free cortex, K1 of meglumine iothalamate was 2.4 +/- 1.7 microliter g-1 min-1 (mean +/- SD) and Vp was 3.4 +/- 0.5 ml 100 g-1. Mean whole-brain tumor K1 values ranged from 3.3 to 97.9 microliters g-1 min-1; k2 ranged from 0.032 to 0.27 min-1; and Vp ranged from 1.1 to 11.4 ml 100 g-1. These values were reproducible in serial experiments in single animals. Independent verification of K1 values was obtained with quantitative autoradiographic measurements of alpha-aminoisobutyric acid, which has similar physicochemical properties to meglumine iothalamate. The CT methodology is capable of demonstrating regional variation of transcapillary transport in brain tumors and may be of value in the study of human brain tumors.

Quantitative measurements of capillary transport in human brain tumors by computed tomography.

The rate at which water-soluble chemotherapeutic drugs enter brain tumors can be extremely variable. The ability to measure or predict the rate of drug entry may have an important role in treatment. We have developed a method that uses information from contrast-enhanced computed tomographic scans to measure quantitatively the rate of transcapillary transport of iodinated compounds in brain tumors. In a group of 10 patients with brain tumors, we obtained serial measurements of tissue (Am) and arterial plasma (Cp) iodine concentration from timed computed tomographic scans done over 30 minutes, after intravenous infusion of meglumine iothalamate (Conray-60). These measurements were analyzed with a two-compartment pharmacokinetic model and nonlinear least-squares regression methods to obtain K1, a blood-to-tissue transfer constant; k2, a tissue-to-blood rate constant; and Vp, tissue plasma vascular volume. Images of K1, k2, and Vp were reconstructed after calculating these values for each 0.8 x 0.8 x 5-mm volume element of the original data. Mean whole tumor K1 values varied from 2.0 mu 1 gm-1 min-1 in a thalamic astrocytoma to 33.9 mu 1 gm-1 min-1 in a glioblastoma multiforme. The value of k2 varied from 0.034 to 0.108 min-1, and Vp varied from 2.4 to 7.9 ml 100 gm-1. In tumor-free brain, the K1 of meglumine iothalamate was 2.9 mu 1 gm-1 min-1; k2 was 0.058 min-1; and Vp was 2.1 ml 100 gm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracavernous carotid artery aneurysm presenting as recurrent epistaxis.

Massive epistaxis from a leaking intracavernous carotid artery aneurysm is a rare occurrence. Such an unusual case is presented with appropriate imaging and a successful treatment program.

Neonatal asphyxia: vulnerability of basal ganglia, thalamus, and brainstem.

Two infants who suffered acute intrapartum asphyxia resulting in severe neonatal encephalopathy are described. Although computed tomography revealed no abnormalities, magnetic resonance imaging documented unequivocal lesions in the thalamus, basal ganglia, parasagittal cortex, brainstem tectum, and midline cerebellum in one patient and in the basal ganglia and parasagittal cortex in the other. Thus, magnetic resonance imaging was more sensitive than computed tomography in detecting acute brain damage after neonatal asphyxia and may become an important tool in improving our understanding of the relationship between adverse perinatal events, neonatal encephalopathy, and neurologic morbidity.

Effect of hyperosmotic blood-brain barrier disruption on transcapillary transport in canine brain tumors.

Whether hyperosmotic blood-brain barrier (BBB) disruption is a technique that can be used to increase permeability of brain-tumor capillaries and thereby transiently increase drug delivery to the brain tumor is controversial. Nine virally induced brain tumors were studied in seven dogs, before and after hyperosmotic BBB disruption with 1.4 osmolar mannitol. Each dog was studied with computerized tomography (CT) after administration of the water-soluble tracer meglumine iothalamate. Each study lasted 30 minutes. A baseline CT scan and 35 to 40 additional CT scans were obtained to provide a time-related measurement of the amount of meglumine iothalamate in tissue (Am(t], and 30 plasma samples were collected to provide the time-related measurement of meglumine iothalamate in plasma (Cp(t]. The data were analyzed by three different methods: 1) a two-compartment model and nonlinear curve fitting were used to calculate K1 (blood-to-tissue or influx constant), k2 (tissue-to-blood or efflux constant), and Vp (plasma vascular space); 2) K1 values were calculated with a two-compartment model, assuming no efflux, at the time point for each CT scan; and 3) a "tissue advantage ratio" was calculated that expressed the ratio of tissue uptake of meglumine iothalamate at each time point, comparing values before and after BBB disruption. Regardless of which method of data analysis was used, there was a marked and significant increase in transcapillary transport of meglumine iothalamate to tumor-free brain regions, while there was only a small, transient, and insignificant increase to the brain tumors. Although there were often marked increases in delivery to cortex in the same hemisphere as the tumors, there was no significant increase to brain immediately surrounding the tumors, perhaps due to altered circulatory dynamics in this region. These data raise serious questions as to the wisdom of using this technique to increase drug delivery to brain tumors in patients and strongly support the continued study of this technique in experimental brain tumors before it is used in patients.

Myxoma of the heart presenting with recurrent episodes of hemorrhagic cerebral infarction: MR findings.

A case of surgically proven left atrial myxoma presented with multiple episodes of cerebral infarctions, both ischemic and hemorrhagic, documented on serial CT and magnetic resonance (MR). Magnetic resonance studies showed, as well, dilated blood vessels in the hemorrhagic areas, proven by angiography to represent mycotic aneurysms. One of these lesions was surgically removed and confirmed to represent a combination of hematoma, infarction, myxomatous nodules, and underlying mycotic aneurysms, as shown on MR scans. This case demonstrates a known delayed neurologic complication of cardiac myxoma that can occur long after resection of the tumor.

Spinal osteomyelitis: unusual findings on magnetic resonance imaging.

In bacterial infection of the spine the intervertebral disc and its adjoining vertebral bodies are usually involved in continuity with narrowing of the disc and indistinct irregular vertebral end plates. We report a case in which the MR imaging examination demonstrated intact vertebral end plates, although the adjacent vertebral bodies and disc were involved with anaerobic streptococcus infection extensive enough to cause paravertebral inflammatory masses. Thus, intact vertebral end plates do not exclude vertebral osteomyelitis in favor of metastatic disease on MR imaging studies.

MR imaging of pituitary tumors before and after surgical and/or medical treatment.

Four hundred fifteen cases of suspected pituitary tumors were examined by CT and magnetic resonance (MR). Forty-one microadenomas and 26 large sellar-suprasellar pituitary tumors were diagnosed and surgically removed (61 cases) or treated with bromocriptine (six cases). The present study demonstrated that (a) in cases of microadenomas, MR was more accurate than CT in three cases, as accurate as CT in 33 cases, but missed six cases diagnosed on CT, when MR images were suboptimal (thicker than 5 mm); (b) when the sellar-suprasellar mass was markedly constricted at the diaphragma sellae on MR sagittal slices (16 cases), transsphenoidal surgical approach was not only insufficient for total removal but could be dangerous, as the remaining suprasellar portion may rapidly increase in size following surgery from postoperative hemorrhage and/or acute edema with severe obstructive hydrocephalus (three cases) and/or acute blindness (two cases); (c) hemorrhage in pituitary tumors was easily seen on MR and missed on CT; (d) coronal MR slices visualized the carotid siphon obviating the need for angiography to rule out intrasellar aneurysm, which can mimic pituitary tumor on contrast CT; (e) postoperative MR was needed before considering radiotherapy to visualize accurately the relation of the optic chiasm to the residual tumor and to follow up its gradual change in size; (f) finally, in cases treated with bromocriptine, MR was more accurate than CT in following the gradual decrease of pituitary tumor.

Cerebral vasospasm and eclampsia.

We describe a patient who experienced focal cerebral and brainstem ischemia in the setting of postpartum eclampsia. Cerebral angiography showed spasm of large- and medium-caliber arteries. This case provides rare documentation that vasospasm may account for cerebral ischemia in eclamptic women with focal signs. This observation suggests that in such patients cerebral angiography may be informative and useful.

Magnetic resonance imaging and the diagnosis of avascular necrosis of the femoral head.

Low back pain and/or pain radiating to one or both lower limbs can result from causes other than intervertebral disc disease. Recently three patients presented with low back pain radiating down the legs. When CT examination of the lumbar spine proved unrewarding, magnetic resonance imaging (MRI) was performed. Avascular necrosis (AVN) of the femoral head was diagnosed and subsequently treated before femoral head collapse occurred. In patients with unexplained low back pain, AVN of the hip should be considered and ruled out by MRI, even if conventional plain films, polytomes, and radionuclide scans are negative. The early diagnosis of AVN of the femoral head may be critical in determining whether a surgical revascularization procedure might be successful in treatment, or replacement with an endoprosthesis will be necessary, if femoral head collapse has already occurred.

Hodgkin's disease of spine: computed tomography and magnetic resonance imaging.

Early recognition of spinal block in a young man by magnetic resonance imaging and immediate surgical decompression of the spinal cord by removing the epidural mass, which proved to be Hodgkin's disease, was a determining factor in the complete neurologic recovery of the patient. Postoperative and postchemotherapy repeat magnetic resonance imaging showed complete resolution of the compressing mass. We believe that magnetic resonance imaging has a prominent role in the diagnosis and follow-up studies of spinal lesions without the inherent risks of other neurologic diagnostic procedures.

Current concepts in neuroradiological diagnosis of acoustic neuromas.

Two hundred twenty-one cases with clinical suspicion of a cerebellopontine angle (CPA) and/or internal auditory canal (IAC) lesions were evaluated in our hospital in the last 21/2 years by various radiological modalities. Fifty-two tumors were diagnosed and surgically removed; 48 were acoustic neuromas (33 large tumors and 15 intracanalicular small tumors) and 4 meningiomas. Polytomography detected 10 lesions out of 15 (66.7%) with 5 false-negative (33.3%) and 4 false-positive (26.7%) studies. Routine CT scan visualized large and enhancing lesions (37 out of 52), but missed the small intracanalicular tumors (15 tumors) which were only visualized by CT scan combined with cisternography or magnetic resonance imaging (MRI). MRI diagnosed 23 lesions out of 23 (100%) with no false-positive or negative studies, including 8 intracanalicular small tumors missed on the routine CT scans. MRI is far more reliable in the radiological diagnosis of CPA and IAC lesions.

MR diagnosis of acoustic neuromas.

Two hundred forty-three patients with clinically suspected acoustic neuroma were evaluated radiologically by CT, and in selected cases CT cisternography and/or magnetic resonance imaging. Fifty-one acoustic neuromas were diagnosed and surgically removed; 36 were large tumors with extracanalicular extension and 15 were strictly intracanalicular small tumors. With routine CT (without and with contrast medium) large and enhancing lesions (36 of 51) were visualized, but small intracanalicular tumors (15 lesions) were missed. The latter were visualized by CT cisternography (seven cases) or MR (eight cases). Magnetic resonance, when used with spin-echo technique using both short as well as long sequences for axial and coronal thin slices (5 mm or smaller), demonstrated all the surgically verified lesions.

Focal cerebral vasculitis associated with circulating immune complexes and brain irradiation.

In this report we describe a patient with a benign glioma treated with surgery and radiation. After a period of stability he developed subacute bacterial endocarditis, and deteriorated neurologically. Computed tomographic scans did not show recurrent tumor. An angiogram showed vasculitis restricted to the previously irradiated area. Secondary to subacute bacterial endocarditis was the presence of high levels of circulating immune complexes. His neurological status was unchanged after antibiotics, but improved after treatment with dexamethasone. We interpret the clinical course as an immune-complex-mediated vasculitis superimposed on a subclinical radiation vasculitis. This case supports the hypothesis that immune mechanisms may be involved in delayed radiation injury to the nervous system.

Differentiation of cerebellopontine angle neuromas and meningiomas with MR imaging.

Postcontrast CT of the temporal bone is the neuroradiological study of choice for investigation of cerebellopontine angle (CPA) and internal auditory canal (IAC) lesions. Nonenhancing or small lesions may need CT combined with air or metrizamide cisternography for their detection. Magnetic resonance (MR) imaging has shown interesting capabilities as a noninvasive study for the visualization of the IAC, the neural bundle entering the canal, the brain stem, and cerebellum. In the present series of 24 cases, MR imaging detected the lesion in all 11 verified tumors. We feel that MR can replace invasive air and metrizamide cisternography in the diagnosis of CPA lesions and can help in the differentiation between acoustic neuromas and meningiomas.

Recognition of lumbar disc disease with magnetic resonance imaging.

Ten normal adult volunteers, 75 patients with low back pain and/or lumbar radiculopathy, 16 patients following chymopapain treatment, 14 patients with recurrent symptoms following disc surgery, and two patients with distal cord compression were scanned on Fonar 3000 permanent magnet scanner. Of all the patients 98 had additional computed tomography scans (CT) of the lumbar spine and 82 had myelography. Lumbar magnetic resonance imaging (MRI) and CT scans were both diagnostic in cases of herniated and extruded discs. MRI scan showed more information concerning the degenerative state of the intervertebral discs. It was relatively more accurate in detecting, small bulging and herniated discs without ruptured anulus and the relation of the migrated fragments of extruded discs to both the back of the vertebrae and the thecal sac. Moreover, lumbar MRI matched the clinical response of disc disease to chymopapain treatment more than lumbar CT scan. In addition, the MRI studies differentiated more accurately postoperative epidural fibrotic changes from recurrent herniated and/or extruded disc and detected distal spinal cord abnormalities. CT scan easily detected laterally herniated lumbar discs. Myelography was the diagnostic study in cases of arachnoiditis.

Lumbar spinal-lateral recess stenosis.

The syndrome of a lumbar spinal and lateral recess stenosis is characterized by pain and a variety of paresthetic symptoms occurring principally when the patient stands or walks. Sitting or lying down alleviate the symptoms promptly. The neurologic examination is characterized by a negative straight leg-raising test and a paucity of abnormal neurologic findings. The diagnosis is confirmed by a high-resolution CT scan. If conservative treatment fails, a myelogram is in order to establish a definitive diagnosis and assess the severity of neural compression prior to placing the indication for a surgical decompression of the stenotic spinal canal. The surgical procedure consists of a laminectomy and a partial facetectomy of the hypertrophied portion of the facet joint that compresses the adjacent lumbar nerve root from a dorsal direction. It is important to recognize all associated pathologic processes that must be dealt with accordingly at the same time in order to assure success of the operative procedure. The results of a surgical decompression for a lumbar spinal and lateral recess stenosis are excellent.