Comparison and evaluation of osmotic blood-brain barrier disruption following intracarotid mannitol and methylglucamine iothalamate.

The effect of intracarotid injections of methylglucamine iothalamate has been compared with that of mannitol solution of similar osmotic strength. The degree and distribution of blood-brain barrier disruption was assessed using Evans' Blue dye as a visual marker and by contrast enhancement measured by computer tomography (CT) scanner. Evans' Blue staining was found to match CT enhancement closely. It was also found that methylglucamine iothalamate injections resulted in significantly greater blood-brain barrier permeability. The relevance of these findings to chemotherapy of brain tumours is discussed briefly.

A randomized double-blind trial of ioversol and iopamidol in contrast-enhanced computed body tomography.

The authors compared iopamidol and ioversol in a double-blind study conducted on 81 patients (ioversol in 40 patients; iopamidol in 41 patients) undergoing computed body tomography (CT) for a variety of indications at the Flinders Medical Centre in South Australia. Each study was assessed for image quality and rated as diagnostic or nondiagnostic. Patients were monitored for blood pressure measurement, pulse rate, and respiration rate before and after contrast administration and were observed for the occurrence of side effects. Subjective assessments of heat and pain sensations also were obtained from the patients. With the exception of one patient studied with iopamidol, all investigations were rated as either good or excellent. In all cases, the examination was considered diagnostic. No adverse reactions were noted after administration of either contrast material, except in one patient who felt nauseated. Because the patient had reported feeling nauseated before the examination, this side effect was considered to be coincidental. One patient experienced mild pain from injection of iopamidol. In no cases were any drug-related or clinically significant changes in vital signs noted. In this study, both iopamidol and ioversol were well tolerated and effective, with few side effects after intravenous administration for contrast enhancement during whole-body CT.

Effects of nonionic contrast media on the blood-brain barrier. Osmolality versus chemotoxicity.

This study was performed to assess the relative contributions of contrast medium osmolality and chemotoxicity to contrast-induced blood-brain barrier (BBB) damage. Experimental carotid angiography was carried out in rabbits with mannitol at an osmolality of 714 mOsm/kg, with the nonionic, monomeric contrast media iohexol and ioversol at similar osmolalities, and with the nonionic, dimeric contrast media iodixanol and iotrolan at osmolalities less than half that of the mannitol. The amount of damage caused by the procedure was assessed by determining the amount of intracerebral extravasation of intravascularly injected technetium-99m-pertechnetate. Mannitol caused no detectable BBB damage, but all four contrast media caused BBB damage that was significantly more severe than that caused by mannitol. The BBB damage caused by carotid angiography with iohexol, ioversol, iodixanol, and iotrolan was not attributable to their osmolalities, but due to some other physical and/or chemical effects of these media on the BBB.

The in vitro activation of complement by radiologic contrast materials and its inhibition with epsilon-aminocaproic acid.

Radiologic contrast materials activate complement by both the classical and alternative pathways. This activation is time, dose, and temperature dependent and is able to proceed with equal facility in either the presence or absence of Ca++ or Mg++ chelating reagents (EGTA, EDTA). All the components examined (C1, C4, C2, Factor B, C3, and C5) were consumed during complement activation. Immune complexes are produced during interaction of serum with contrast materials. The activation of complement by contrast materials appears to be principally initiated by the activation of plasminogen to plasmin. Inhibition of plasminogen activators by epsilon-aminocaproic acid affects complement activation markedly.

Effect of additional cations on the twitching reaction to intracarotid, nonionic contrast media in rabbits.

Previous investigations in this laboratory have confirmed the observation of facial muscle twitching during intracarotid injections of nonionic contrast media (CM) in rabbits. The reaction appears to be a locally mediated effect. To further investigate this reaction, cortical electroencephalogram (EEG) and facial electromyogram (EMG) recordings were made from rabbits receiving selective internal carotid artery (ICA) and external carotid artery (ECA) injections of CM. The effects of iopromide and iohexol were compared with and without the addition of sodium (Na) and calcium (Ca) ions at different concentrations. External carotid injections of iopromide also were performed in some animals paralyzed with D-tubocurarine to exclude the possibility that the reaction is due to an effect on peripheral nerves. The addition of between 5 and 20 mM Ca ions to both CM prevented the reaction but while the addition of Na ions (up to 150 mM) to iopromide had some preventative effect, it did not totally abolish the reaction. In those animals paralyzed with D-tubocurarine, the reaction to iopromide, as observed and recorded by EMG, was the same as that occurring in nonparalyzed animals. This finding is consistent with this reaction being independent of the peripheral nervous system.

Brain parenchyma penetration by intrathecal nonionic iopamidol.

Iopamidol, a nonionic, water-soluble contrast medium, has been recently recommended for myelography. As with other such media, the extent of parenchymal penetration is of interest in relation to the genesis of clinical complications. In this study the degree and depth of brain penetration of intrathecal iopamidol, using an iodine concentration of 280 mg l/ml, were compared at 15 and 60 min in adult greyhound dogs using coronal computed tomographic scanning of the brain after removal. A significant but patchy penetration corresponding to the cortical sulci was demonstrated at 15 min, while by 60 min there had been a further increase in the distribution and concentration of the contrast medium. Comparing the present study with a previous series using metrizamide and methylglucamine iothalamate at a similar iodine concentration (280 mg l/ml), no significant difference in the depth or degree of penetration at 60 min was found between the three contrast media, indicating a similar rate of diffusion across the cerebrospinal fluid/brain interface. Therefore, any difference in neurotoxicity is not explained by a reduced concentration of contrast medium due to variation in the rate of diffusion across this interface.

Bilateral occipital calcification associated with celiac disease, folate deficiency, and epilepsy.

In a patient with celiac disease, folate and iron deficiency, and epilepsy, CT over a 4-month period showed parietoocipital calcifications in the corticomedullary junctions. The calcification was progressive, but it and the seizures stabilized after institution of a gluten-free diet and iron and folic acid supplements.

Effect of intravenous contrast material on the integrity of the blood-brain barrier: experimental study.

Increasingly large doses of contrast medium have been advocated for enhanced computed tomography. It is assumed that such large intravenous doses, which increase the osmolality of the blood, do not affect the blood-brain barrier in the same way as intracarotid injections of the same solutions. Using a qualitative marker, Evans blue dye, and a quantitative marker, 99mTc-pertechnetate, a study was performed in rabbits to assess the effect of intravenous sodium iothalamate (Conray-420) at a dose of 8 ml/kg on the integrity of the blood-brain barrier. No qualitative or quantitative evidence of disruption of the blood-brain barrier was demonstrated. Since histologic examination was not done, morphologic changes cannot be excluded.

The effect of contrast medium viscosity on the blood-brain barrier after intracarotid injection in the rabbit.

This study was undertaken to investigate the role of contrast medium viscosity in blood-brain barrier disruption after carotid angiography. Test solutions were injected into the carotid arteries of rabbits, and the degree of disruption was assessed by using 99mTc-pertechnetate and Evans blue as quantitative and qualitative markers, respectively. The seven test solutions consisted of basic solutions of physiological saline, iopromide, or methylglucamine iothalamate plus solutions derived from these by the addition of sufficient gelatin to augment their viscosities considerably. The solutions were injected over a 30-sec period, resulting in doses that varied inversely with viscosity. One of the high-viscosity solutions was also injected as a fixed dose, equal to the mean injection volume of its low-viscosity counterpart, without regard to the time used. Statistical comparison between the effects of the solutions showed that, under the conditions of the study, contrast medium viscosity, either by itself or as a consequence of its association with hyperosmolality, has no significant effect on the blood-brain barrier. However, under conditions of constant injection volume, higher viscosity solutions may require increased injection times, and this may lead to increased disruption of the blood-brain barrier.

CT and MR findings in patients with chordomas of the petrous apex.

Chordomas are rare neoplasms arising from remnants of the embryologic notochord. Although typically midline in site, intracranial tumors may arise off the midline, and a significant proportion of these arise unilaterally in the petrous bone. Three examples of this entity are presented, all demonstrating typical radiologic features. Dendritic branches of the cranial end of the notochord ramifying in the skull base are thought to provide the embryologic basis for this tumor. The CT and MR features demonstrated are similar to those of the more common midline chordomas. CT demonstrates a well-defined extraaxial soft-tissue mass associated with foci of calcification and bone destruction and occurring at a site corresponding with the embryologic distribution of notochordal material. On MR, prolonged T1 and T2 relaxation times result in hypointensity on T1-weighted images and marked hyperintensity on T2-weighted images. Signal voids result from the foci of calcification while hemorrhage may also lead to inhomogeneity.

Brain parenchyma penetration by intrathecal ionic and nonionic contrast media.

Metrizamide, a nonionic water-soluble contrast medium, has been shown to penetrate normal brain when injected intrathecally. Recently it was suggested that the complications following intrathecal metrizamide are directly related to the cerebral concentration reached. Metrizamide, both in experimental animals and clinically, is regarded as less neurotoxic than equivalent iodine concentrations of ionic contrast media. In this study the degree and depth of brain penetration of intrathecal metrizamide and methylglucamine iothalamate (Conray 280), using a similar iodine concentration (280 mg l/ml), was compared at 1 hr in adult greyhound dogs. The depth of penetration and concentration reached in the cortical gray matter was determined by coronal computed tomographic scanning of the brain after removal. No significant difference was found between the two contrast media, suggesting that the rate of diffusion across the cerebrospinal fluid-brain interface is similar and that the difference in neurotoxicity is not explained by a reduced concentration of contrast medium in the case of nonionic metrizamide, when compared with ionic methylglucamine iothalamate. Using Evans blue as a qualitative marker, no evidence of gross blood-brain disruption was demonstrated in the area of maximum penetration with either contrast medium.

Comparison of blood-brain barrier disruption by intracarotid iopamidol and methylglucamine iothalamate.

Using a canine model, the effect of intracarotid injections of the ionic contrast medium methylglucamine iothalamate was compared with that of the nonionic contrast medium iopamidol of similar iodine concentration (280 mg 1/ml). The degree and distribution of blood-brain barrier disruption was assessed using Evans blue stain as a visual marker and by contrast enhancement measured by a computed tomographic (CT) scanner. In all studies with methylglucamine iothalamate, Evans blue staining was demonstrated, and CT enhancement demonstrated a significant mean difference (p less than 0.01) between the control and injected hemispheres. The absence of blood-brain barrier disruption with iopamidol is probably related to its lower osmolality (570 mosmol/kg) compared with methylglucamine iothalamate (1,424 mosmol/kg) and the absence of any cation.

A comparison of blood-brain barrier disruption by intracarotid iohexol and iodixanol in the rabbit.

A rabbit model was used to compare the effect on the blood-brain barrier of the intracarotid injection of two new contrast media: iohexol, a nonionic monomer, and iodixanol, a nonionic dimer. It was hypothesized that the low osmolality of iodixanol (272 mOsm/kg at 300 mgl/ml) would cause less disruption of the blood-brain barrier than the relatively higher osmolality of iohexol (690 mOsm/kg at 300 mgl/ml). The degree of blood-brain barrier disruption was assessed qualitatively, by observing the degree of cortical staining with Evans' Blue dye, and quantitatively, by calculating the difference in uptake of 99mTc-pertechnetate between injected and noninjected hemispheres. Statistical analysis of the results showed that both iodixanol and iohexol had a significantly greater effect on blood-brain barrier disruption than did isotonic saline (0.005 greater than p greater than .001), but that the effect of iodixanol was not significantly different from that of iohexol with respect to either Evans' Blue staining (p greater than .05) or pertechnetate uptake (.75 less than p less than .90). Thus, the low-osmolality iodixanol has no significant advantage over iohexol in terms of blood-brain barrier disruption after experimental carotid angiography.

The effect of intracarotid nonionic contrast media on the blood-brain barrier in acute hypertension.

PURPOSE: To determine whether acute hypertension (HT) is a risk factor for damage to the blood-brain barrier in carotid angiography with nonionic contrast media. METHODS: Anesthetized rats received intravenous injections of technetium-99m-pertechnetate and horseradish peroxidase. Two groups of rats received metaraminol to raise their blood pressure to between 165 and 190 mmHg peak systolic and then received intracarotid injections of saline or iopamidol. Two other groups remained normotensive and received intracarotid injections of saline or iopamidol. Animals were perfused with a fixative solution and their brains removed. Activity of extravasated Tc-99m-pertechnetate was determined to assess blood-brain barrier breakdown. Brains were then sectioned, treated histochemically to visualize extravasated horseradish peroxidase, and ranked visually according to horseradish peroxidase staining. RESULTS: Extravasation of both tracers was significantly greater in the hypertensive group that received contrast media than in the other three groups. CONCLUSIONS: Acute hypertension potentiates the blood-brain barrier-damaging effects of nonionic contrast media during carotid angiography in rats.

Muscular and CNS effects of carotid artery administration of contrast media in rabbits.

Facial muscle twitching during intracarotid injections of nonionic contrast media has been observed in rabbits. To investigate the cause of this reaction, cortical EEG and facial EMG recordings were made from rabbits receiving selective internal and external carotid artery injections of control solutions (normal saline, mannitol), an ionic contrast medium (meglumine iothalamate), and three nonionic contrast media (iohexol, iopromide, and iotrolan). Internal carotid artery injections with all contrast media, both ionic and nonionic, produced ipsilateral EEG changes in 24 of 28 animals; however, ipsilateral EMG changes and visible twitching were observed only in animals injected with nonionic contrast media. Internal carotid artery injections with control ionic and nonionic solutions (physiological saline and mannitol, respectively) produced no EEG changes in any animals. Mannitol produced only ipsilateral EMG changes and visible twitching in most animals. The severity of the reaction to mannitol was generally less than that to the nonionic contrast media, and this difference was statistically significant when comparing mannitol with iohexol and iotrolan but not with iopromide. External carotid artery injections with nonionic solutions (contrast media and mannitol) produced significantly more severe ipsilateral EMG changes and visible twitching than were recorded with the internal carotid artery injections. Ionic solutions (contrast media and saline) had no effect. EEG changes were not observed after external carotid artery injection of any solution, with the exception of two of the seven animals injected with iotrolan. Angiography demonstrated retrograde filling of the external carotid arterial system from internal carotid artery injection via functioning orbital anastamoses. In contrast, internal carotid arterial vessels were not seen angiographically after external carotid artery injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiology in the diagnosis of colloid cysts of the third ventricle.

A series of 38 cases of colloid cyst of the 3rd ventricle is described in most of whom the diagnosis, important for curative surgery, was made radiologically. The most useful investigative technique was pneumography, by which the tumour was outlined in almost all cases. The lateral "hanging head" projection generally demonstrated the lesion most satisfactorily. Care in manipulating air introduced at ventriculography through the foramina of Monro into the 3rd ventricle was frequently rewarded by clear definition of the tumour. In more than one-third of the cases, the lateral plain skull radiograph showed truncation of the dorsum sellae indicative of chronic obstructive hydrocephalus, and, in the large majority of these, pneumography confirmed that the 3rd ventricle, rather than the interventricular foramen, was the site of obstruction to the drainage of cerebrospinal fluid. Carotid angiography, showing hydrocephalus, and in the same cases elevation and lateral displacement of the anterior portion of the internal cerebral veins yielded strong supportive evidence. Vertebral angiography was less specific, and isotope scanning was quite unhelpful.

Contrast media and the brain. The basis of CT and MR imaging enhancement.

Blood, cerebrospinal fluid, and extracellular fluid of the parenchyma form the fluid compartments of the brain with three interfaces between--the blood-brain interface, the CSF-brain interface, and the blood-CSF interface. These and other issues are discussed in this article.

Factors affecting the precision of bone mineral measurements. Part 1: Review of experimentally derived results obtained from single photon absorptiometry.

An evaluation of the factors which influence the precision of bone mineral measurements using single photon absorptiometry (SPA) is presented. This incorporates several techniques which have been developed over the past few years to improve the reliability of such measurements. As such, the figures obtained should provide an objective and up-to-date basis for critical comparison with other modalities such as quantitative computerized tomography (QCT), dual photon absorptiometry (DPA) using Gd-153, and quantitative digital radiography (QDR). Under optimum conditions, a precision of 0.3% was achievable for in vitro phantom measurements. Under realistic working conditions, however, a precision of 1.0% for phantoms and 1.4% for clinical studies was found to be more typical for bone mineral content (BMC) measurements. Derived parameters such as bone mineral density (BMD) were generally less reliable, with a precision of 4.7%. It is unlikely that these values can be improved upon substantially with current SPA technology.

Factors affecting the precision of bone mineral measurements. Part 2: Some statistical notes relating to photon counting statistics and rates of bone loss.

This paper discusses some statistical aspects of absorptiometric bone mineral measurements. In particular, the contribution of photon counting statistics to overall precision is estimated, and methods available for carrying out statistical comparisons of bone loss and determining their precision are reviewed. The use of replicate measurements as a means of improving measurement precision is also discussed.