Search

Purpose: Thrombus perviousness has been associated with favorable functional outcome in acute ischemic stroke (AIS) patients. Measuring thrombus perviousness on CTA may be suboptimal due to potential delay in contrast agent arrival in occluded arteries at the moment of imaging. Dynamic sequences acquired over time can potentially overcome this issue. We investigate if dynamic CTA has added value in assessing thrombus perviousness. Methods: Prospectively collected image data of AIS patients with proven occlusion of the anterior or posterior circulation with thin-slice multi-phase CTA (MCTA) and non-contrast CT were co-registered (n = 221). Thrombus attenuation increase (TAI; a perviousness measure) was measured for the arterial, venous, and delayed phase of the MCTA and time-invariant CTAs (TiCTA). Associations with favorable clinical outcome (90-day mRS ≤ 2) were assessed using univariate and multivariable regressions and calculating areas under receiver operating curves (AUC). Results: TAI determined from the arterial phase CTA was superior in the association with favorable outcome with OR = 1.21 per 10 HU increase (95%CI 1.04–1.41, AUC 0.62, p = 0.014) compared to any other phase (venous 1.14(95%CI 1.01–1.30, AUC 0.58, p = 0.033), delayed 1.046(95%CI 0.919–1.19, AUC 0.53, p = 0.50)), and TiCTA (1.15(95%CI 1.02–1.30, AUC 0.60, p = 0.022). In the multivariable model, only TAI on arterial phase was significantly associated with favorable outcome (aOR 1.59, 95%CI 1.04–2.43, p = 0.032). Conclusion: Association between TAI with functional outcome was optimal on arterial-phase CTA such that dynamic CTA imaging has no additional benefits in current thrombus perviousness assessment, thereby suggesting that the delay of contrast arrival at the clot is a key variable for patient functional outcome.

This study was conducted in order to evaluate the image quality of 70 kVp and 25 mL contrast medium (CM) volume for head and neck computed tomographic angiography (CTA) and assess the diagnostic accuracy for arterial stenosis.Fifty patients were prospectively divided into two groups randomly: group A (n = 25), 70 kVp with 25 mL CM, and group B (n = 25), 100 kVp with 40 mL CM. CT attenuation values, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the shoulder, neck, and cerebral arteries were measured for objective image quality. Subjective image quality of the shoulder and cerebral arteries was also evaluated. For patients undergoing digital subtracted angiography (DSA), diagnostic accuracy of CTA was assessed with DSA as reference standard.The SNRs of the shoulder, neck, and cerebral arteries in group A were higher than those in group B (P 0.05). The CNRs of the shoulder and neck arteries in group A were higher than those in group B (P 0.05). There was no significant difference in subjective image quality of arteries between group A and group B (P 0.05). The accuracy was noted as 94.0% (156/166) in group A and 97.1% (134/138) in group B for ≥ 50% stenosis. The accuracy of intracranial arterial stenosis was lower than that of extracranial arterial stenosis in group A. The radiation dose of group A was significantly decreased by 56% than that of group B.Head and neck CTA at 70 kVp using 25 mL CM can obtain diagnostic image quality with lower radiation dose while maintaining high accuracy in detecting the arterial stenosis compared with the 100-kVp and 40-mL CM.

Blood–brain barrier (BBB) damage aggravates perihematomal edema, and edema volume predicts prognosis independently. But the BBB permeability at the late stage of acute intracerebral hemorrhage (ICH) patients is uncertain. We aimed to assess the BBB permeability of spontaneous basal ganglia ICH using computed tomographic perfusion (CTP) and investigates its relationship with hematoma and perihematomal edema volume. We performed CTP on 54 consecutive ICH patients within 24 to 72 h after symptom onset. Permeability-surface area product (PS) derived from CTP imaging was measured in hematoma, “high-PS spot,” perihematoma, normal-appearing, hemispheric, and contralateral regions. Hematoma and edema volumes were calculated from non-contrast CT. “High-PS spot” and perihematoma regions had higher PS than the contralateral regions (p

Contrast-induced nephropathy is a common clinical concern in patients undergoing neuroendovascular procedures, especially in those with pre-existent kidney disease. We aimed to define the incidence of contrast-induced nephropathy in these high-risk patients in our practice. We analyzed data retrospectively from patients undergoing neuroendovascular procedures at two academic medical centers over a 4-year period. Contrast-induced nephropathy was determined by an absolute increase in serum creatinine of 0.5 mg/dL or a rise from its baseline value by ≥ 25%, at 48–72 h after exposure to contrast agent after excluding other causes of renal impairment. High-risk patients were identified as those with pre-procedural estimated glomerular filtration rate

Introduction We sought to establish whether CT angiography (CTA) can be applied to the planning and performance of clipping or coiling in ruptured intracranial aneurysms without recourse to intraarterial digital subtraction angiography (IA-DSA).Methods Over the period April 2003 to January 2006 in all patients presenting with a subarachnoid haemorrhage CTA was performed primarily. If CTA demonstrated an aneurysm, coiling or clipping was undertaken. IA-DSA was limited to patients with negative or inconclusive CTA findings. We compared CTA images with findings at surgery or coiling in patients with positive CTA findings and in patients with negative and inconclusive findings in whom IA-DSA had been performed.Results In this study, 224 consecutive patients (mean age 52.7 years, 135 women) were included. In 133 patients (59%) CTA demonstrated an aneurysm, and CTA was followed directly by neurosurgical (n=55) or endovascular treatment (n=78). In 31 patients (14%) CTA findings were categorized as inconclusive, and in 60 (27%) CTA findings were negative. One patient received surgical treatment on the basis of false-positive CTA findings. In 17 patients in whom CTA findings were inconclusive, IA-DSA provided further diagnostic information required for correct patient selection for any therapy. Five ruptured aneurysms in patients with a nonperimesencephalic SAH were negative on CTA, and four of these were also false-negative on IA-DSA. On a patient basis the positive predictive value, negative predictive value, sensitivity, specificity and accuracy of CTA for symptomatic aneurysms were 99%, 90%, 96%, 98% and 96%, respectively.Conclusion CTA should be used as the first diagnostic modality in the selection of patients for surgical or endovascular treatment of ruptured intracranial aneurysms. If CTA renders inconclusive results, IA-DSA should be performed. With negative CTA results the complementary value of IA-DSA is marginal. IA-DSA is not needed in patients with negative CTA and classic perimesencephalic SAH. Repeat IA-DSA or CTA should still be performed in patients with a nonperimesencephalic SAH.

Cerebral blood volume (CBV) measurement by flat panel detector CT (FPCT) in the angiography suite seems to be a promising tool for patient management during endovascular therapies. A steady state of contrast agent distribution is mandatory during acquisition for accurate FPCT CBV assessment. To the best of our knowledge, this was the first time that steady-state parameters were studied in clinical practice. Before the CBV study, test injections were performed and analyzed to determine a customized acquisition delay from injection for each patient. Injection protocol consisted in the administration of 72 mL of contrast agent material at the injection rate of 4.0 mL/s followed by a saline flush bolus at the same injection rate. Peripheral or central venous accesses were used depending on their availability. Twenty-four patients were treated for different types of neurovascular diseases. Maximal attenuation, steady-state length, and steady-state delay from injection were derived from the test injections’ time attenuation curves. With a 15 % threshold from maximum attenuation values, average steady-state duration was less than 10 s. Maximum average steady-state duration with minimal delay variation was obtained with central injection protocols. With clinically acceptable contrast agent volumes, steady state is a brief condition; thus, fast rotation speed acquisitions are needed. The use of central injections decreases the variability of steady-state’s delay from injection. Further studies are needed to optimize and standardize injection protocols to allow a larger diffusion of the FPCT CBV measurement during endovascular treatments.

Cerebral vasospasm (CV) is one of the most dreaded complications in patients who survive acute subarachnoid haemorrhage (SAH), and conventional cerebral angiography (DSA) is the gold standard for its diagnosis. We evaluated CT angiography (CTA) as a non-invasive alternative for diagnosis of CV and assessed if CTA could have a role in choosing appropriate treatment.Consecutive patients with SAH and suspected vasospasm were included when DSA was performed within 24 h from CTA. Two neuro-radiologists retrospectively analysed CTA and DSA studies independently. Assessment included presence of central and peripheral vasospasm and grading of severity of central CV. A treatment recommendation based on CTA was compared to actual treatment received.Final analysis included 34 patients. CTA was more accurate for diagnosis of central then for peripheral CV with high sensitivity (reader 1, 91%; reader 2, 92%), specificity (reader 1, 73%; reader 2, 90%), accuracy, positive predictive value and negative predictive value for central vasospasm. For grading the severity of CV CTA's sensitivity, specificity and accuracy were high for most central arteries. The reader's recommendation of angioplasty according to CTA was significantly predictive of actual receipt of angioplasty but overestimated actual receipt of triple H treatment.CTA is adequate for detecting central vasospasm in symptomatic SAH patients. A negative result should not prevent further investigation especially when evaluating arterial segments adjacent to metal artefacts from coils or clips. CTA is helpful in treatment decision making specifically regarding the need for balloon angioplasty.

We randomised 86 patients undergoing intra-arterial cerebral digital subtraction angiography (IADSA) to receive iodixanol (Visipaque; Nycomed, Oslo, Norway) 150 mgI/ml or iohexol (Omnipaque; Nycomed) 140 mgI/ml. The efficacy and safety of these two contrast media were compared: efficacy by evaluating the diagnostic information and radiographic density yielded by the angiograms, safety by recording all discomfort connected with the injections, and all adverse events up to 24 h after the investigation. Diagnostic information was optimal in all patients and the overall radiographic density optimal in all but one (iohexol) (P = 0.49). A feeling of warmth, the only discomfort reported, was experienced by 43% and 54% of patients receiving iodixanol and iohexol, respectively (P = 0.26). Two patients in the iodixanol group and five in the iohexol group reported one adverse event (nausea, dizziness, visual disturbance or paraesthesiae) (P = 0.30); all were of mild severity except for one moderate adverse event in each group. Iodixanol 150 mgI/ml and iohexol 140 mgI/ml were demonstrated to be suitable for IADSA, with no clinically or statistically significant differences in efficacy, discomfort or adverse events.

A 33-year-old woman with cryoglobulinaemia developed acute hydrocephalus 20 h after lumbar myelography using the water-soluble contrast medium iotrolan. After a ventricular drainage, she was free of symptoms and the hydrocephalus resolved. The development of acute hydrocephalus after myelography has not been reported previously.

Monomeric (iohexol 300 mg I/ml) and dimeric (iodixanol 270 mg I/ml) nonionic contrast media were compared in a double-blind, randomised, parallel group trial. Safety and efficacy of the media in intra-arterial cerebral digital subtraction angiography were evaluated by assessing adverse events, discomfort, EEG, heart rate and quality of radiodiagnostic information. Seventy-six patients underwent selective injection of the carotid and/or vertebral arteries. Both contrast media were well tolerated. No serious adverse events occurred. No effects on heart rate and EEG were evident. The arteriograms were of high quality and overall diagnostic information was optimal in 94% of the examinations. No clinically important differences between the two contrast media were found.

Diffusion of iohexol (300 and 240 mgI/ml), iopamidol (300 and 200 mgI/ml), and iotrolan (300 and 240 mgI/ml) in the cerebrospinal fluid (CSF) of 16 patients was studied in vitro. Test tubes containing CSF were kept in a waterbath at 37 degrees C. Contrast medium was injected along the wall into the tubes, and diffusion of contrast media in the tubes was followed with repeated computed tomography for 5 h. The contents of the tubes were then mixed by shaking, and the tubes were scanned immediately and 8 h later. The contrast media first settled in the bottom of the tubes and then diffused upwards. Iotrolan diffused more slowly than the other media, but the difference was only significant at a concentration of 300 mgI/ml. The difference between iohexol and iopamidol was minimal. In general, diffusion was slower in CSF samples with an elevated protein content, but the difference in the diffusion of contrast medium in normal and pathological CSF was seldom statistically significant, perhaps owing to the small number of samples (5) with an elevated protein content. All contrast medium-CSF mixtures remained homogeneous after mixing. These experiments showed measurable differences in the diffusion of contrast media in CSF, but it does not seem very likely that these would be significant in clinical practice.

A cross-over test in intra-arterial digital subtraction angiography (IADSA) of the carotid arteries was performed in 50 patients to evaluate image quality and side-effects with iohexol and metrizoate injected at concentrations of 100 mg I/ml by hand. The image quality was excellent or good in all cases. Although the severity and the frequency of side-effects were higher with metrizoate, both contrast media were suitable for IADSA at this low concentration. No complications were seen. It was assumed that the risk with IADSA was less than that of conventional precerebral angiography when performed semi-selectively and with small amounts of contrast media, as in this study.

A randomized double blind study with iohexol (Omnipaque) and metrizamide (Amipaque) in cervical myelography was performed in 50 patients, 29 with iohexol and 21 with metrizamide. The myelographies were performed either with lumbar or with C1-C2 puncture in about equal groups, using 300 mg I/ml and 240 mg I/ml of the contrast media respectively. The image quality was equal with both contrast media, excellent in about 4/5 and good in 1/5 of the examinations. Subjective side effects were twice as frequent with metrizamide as with iohexol. The most frequent side effect was headache, occurring in 34% with iohexol and in 67% with metrizamide. Altogether 24% or the patients had EEG changes after iohexol as compared to 47% after metrizamide. All EEG changes were slight dysrythmia-except in three patients with spike activity after metrizamide. These were the only ones with mental reactions as well. It can be concluded that in this trial iohexol was better suited for cervical myelography than metrizamide.

During a 14-day period, 45 of 78 rabbits were treated intravenously with chlorpromazine (5 mg kg-1 day-1). Metrizamide or iohexol was injected subarachnoidally and the neurotoxic effects of each substance on rabbit behaviour were evaluated for 3 h in both chlorpromazine-treated and non-treated rabbits. Chlorpromazine increased both the excitative and the depressive effects of metrizamide and the depressive effects of iohexol. No signs of excitation were observed in chlorpromazine-treated and non-treated rabbits after subarachnoid injections of iohexol. In spite of a free flow of clear fluid from the needle both before and after the intended subarachnoid injection, radiography disclosed that 26 of 67 suboccipital injections inadvertently resulted in a subdural deposition of the contrast medium. Contrast medium effects following subdural injection significantly differed from those following subarachnoid injection.

Cerebral angiography was performed in 100 patients in order to study the frequency of adverse effects and complications with a new non-ionic contrast medium, iohexol, compared with an ionic medium, meglumine metrizoate. The study was performed as a double blind clinical trial. Iohexol was better tolerated than meglumine metrizoate, since more patients experienced the injections as painful and unpleasant with metrizoate than with iohexol. However, the subjective adverse effects were minor with both contrast media. There was no statistically significant difference in the frequency of more serious side effects. Transient hemiparesis was seen in two patients who prior to the angiography had suffered from numerous similar attacks per day and in one patient in whom a nearly occluded internal carotid artery was occluded during the examination. These complications occurred in the iohexol group, but are more likely to be due to thromboembolism than to contrast medium toxicity.

During the last few years transfemoral epidural venography has increasingly been used for diagnosing lumbar disc herniation. Occasionally this method may reveal an unexpected malignant tumour with the clinical symptoms of lumbar disc disease. Therefore it is of interest to be acquainted with the venographic signs of malignancy in this area. Moreover transfemoral epidural venography can be of help in the delineation of a tumour in the vertebral canal. If the double-catheter method is used, the anterior epidural venous plexus will, as a rule, be adequately shown up to the level of T10. Occasionally higher thoracic levels also are visualised. The procedure can easily be performed on an out-patient basis and is well tolerated by the patient. The complication rate is very low. The use of ioxaglate (Hexabrix) minimizes the post-injection reactions to the contrast medium.

A rabbit model was used to assess the effects of intracarotid injections of ionic monomer (meglumine iothalamate), non-ionic monomer (iohexol, iopromide), and non-ionic dimer (iotrol) contrast materials on the blood-brain barrier. The degree of blood-brain barrier damage was assessed qualitatively using Evans' blue dye, and quantitatively by calculating the difference in pertechnetate uptake between injected and non-injected hemispheres. The results showed that the non-ionic dimer, iotrol, had the least effect on the blood-brain barrier, and that although iopromide and iohexol produced greater damage than iotrol, the ionic compound, meglumine iothalamate, caused the greatest disruption to the blood-brain barrier. The implications of these findings are discussed.

The side effects associated with the use of Iotrol were determined in 100 patients and compared with metrizamide and iopamidol in two double-blind studies. The relevance of the distribution of the contrast medium in the CSF space to the occurrence of headache is discussed. The low persistence of iotrol in the brain parenchyma is demonstrated on CT density profiles, compared with metrizamide and iopamidol. Iotrol seems to be the safest contrast substance for intrathecal use.

Hexabrix (ioxaglate), a new low osmolality contrast agent, has been compared with Télébrix (ioxitalamate) in a series of 50 lumbar epidural venograms. The intensity of the pain and heat sensation experienced by the patient was significantly lower following the injection of Hexabrix. For this reason Hexabrix may be considered the contrast medium of choice for epidural venography. In 15 additional cases Hexabrix was compared with Amipaque (metrizamide) in the same iodine concentration (320 mg/ml). In these patients hardly any difference in pain and heat sensation was observed after the injection of both contrast agents. Frequently only a slight feeling of warmth was noticed. A minimal sensation of pain was occasionally observed to the same degree with both contrast agents.

An open study with iohexol (Omnipaque) in cervical myelography has been performed in 20 patients to evaluate the properties and neurotoxicity of this new water soluble contrast medium. The image quality was good (30%) or excellent (70%) in all cases. The frequency of headache was 25%. No EEG changes were severe and the total frequency was 20%. We conclude that this study supports other reports of iohexol having a low neurotoxicity and is well suited for intrathecal use.

A test was carried out on 11 young, full sized mongrels to determine whether there is an interaction between chymopapain and the contrast agents iotrolan and iopamidol. A total of 75 intervertebral disks were punctured: nucleolysis alone was performed on 20, diskography with iotrolan and subsequent nucleolysis on 20, and diskography with iopamidol and subsequent nucleolysis on 10. Diskography alone was performed 10 times with iotrolan and 5 times with iopamidol. Aqua dest. was given intradiskally 5 times, and puncture was carried out 5 times without the administration of any substance. Following puncture, x-rays of the lumbar vertebral column were taken laterally: daily for the first 10 days, then weekly. Disk space narrowing typical of nucleolysis with chymopapain was found among the disks that were nucleolyzed only to the same extent as among those that had undergone diskography previously. There was no evidence of narrowing of the other disk spaces which had been punctured but not treated with chymopapain. On some of the dogs, CT and MRI examinations were carried out. The CTs showed a homogenous hypodensity in all of the disks, in which chymopapain had been injected. The MRI revealed a signal loss in all of the nucleolyzed disks. The results of short and long term follow up demonstrate that inhibition of chymopapain by iotrolan or iopamidol is not to be expected and therefore diskography prior to chemonucleolysis can be performed without danger of enzyme inactivation.

Using two different models, the effect on the blood-brain barrier of intracarotid injections of sodium/meglumine ioxaglate at similar iodine concentrations (280 mgI/ml) was investigated. In both models the degree of blood-brain barrier damage was assessed visually using Evans' Blue stain. Quantitative assessment of blood-brain barrier disruption was made by contrast enhancement as measured by CT of the dog brain, and by 99mTc-pertechnetate uptake by the brain in the rabbit model. No Evans' Blue staining was observed in any study using the canine/CT model. Slight staining was observed in two studies with ioxaglate using the rabbit/pertechnetate model. Statistical analysis of results from the canine/CT model did not detect any damage to the blood-brain barrier with either ioxaglate or saline control studies (P greater than 0.1). However, in the rabbit/pertechnetate model a slight increase in disruption of the blood-brain barrier was observed with ioxaglate compared with control studies, but this was only significant at the 0.1 level. The results suggest that the rabbit/pertechnetate model is a more sensitive measure of blood-brain barrier disruption than the canine/CT model. This study also demonstrates that blood-brain barrier disruption following intracarotid injection of ioxaglate is minimal.

Iohexol was introduced by lumbar puncture in a series of 148 consecutive children aged between 5 days and 16 years referred for myelography; no patient was excluded. Initially, iohexol 180 mgI/ml was used in dosage proportional to body weight varying between 5 ml and 15 ml. During the later part of the trial concentration of iodine was increased to 240 mg/ml for cases in which the dorsal region was of particular interest (69 patients) and to 300 mg/ml for 8 cervical studies. The total dose ranged up to 4.8 g and varied between 0.03 g and 0.51 gI/kg body weight. In all patients, neurological examinations were performed before and at 24 h and observations for adverse reactions continued over a period of 48 h. The contrast medium was run up to the foramen magnum or basal cisterns in 128 patients and to the upper dorsal region in the other 20. In the first 62 patients vital studies were performed over the period of the myelogram and for 24 h following, and an additional limited neurological examination was made at 6 h, and in the first 26 cases of the series EEG's were done before and at 24 h after the myelogram. Minor variations in pulse rate and blood pressure were observed but these were not of sufficient magnitude to be of clinical significance. In 7 patients there was minor, generally slow wave abnormality on the EEG taken after the procedure, but no spike or epileptogenic activity was obserse reactions. Focal increase in neurological signs, associated with backache and probably related to the mechaniccs of lumbar puncture and myelography, occurred in 3 tumour patients; otherwise no change in neurological condition was observed in any case. Minor reactions were observed in 24 other patients (16.2%); vomiting 14 (9.5%), headache 8 (5.7%), backache 6 (4.1%), stomache ache 2 (1.5%), mild pyrexia 3 (2.0%). The incidence and severity of these reactions was considerably less than with metrizamide myelography and all resolved within 2 days of the iohexol injection. In conclusion, iohexol has significant advantages over previously used non-ionic contrast media and is suitable for paediatric myelography.

Iohexol 300 mg I/ml, Conray meglumine 282 mg I/ml and Amipaque 300 mg I/ml have been compared in a randomized double-blind cross over study in which one injection of Iohexol 300 mg I/ml and Conray meglumine 282 mg I/ml was made in the same artery (common and internal carotid artery) of the same patient, and one injection of Iohexol 300 mg I/ml and Amipaque 300 mg I/ml was made in another artery (external carotid artery and vertebral artery). All together 63 cerebral artery branches were examined in 27 patients, who served as their own controls. The effect of the contrast injections on the intra-arterial blood pressure, pulse rate, ECG, circulatory rate and the patients' reactions were recorded under standardized conditions. The quality of the film was also evaluated. No significant difference was found in the cardiovascular effects after the injection of Iohexol or Conray meglumine into the common carotid or internal carotid. There was significantly less pain and sensation of warmth after the injection of Iohexol than after Conray meglumine 282. In the vertebral and the external carotid arteries, where a comparison between Iohexol and Amipaque was carried out, it was found that no significant difference in the cardiovascular effects occurred. There was less sensation of warmth after the injection of Amipaque into the vertebral artery than was caused by Iohexol. The degree of discomfort in form of pain reaction was the same for the two media, when these reactions occurred. No serious side effects were observed.

The absorption of iohexol from the subarachnoid space was studied in 9 patients. Serum concentrations of iohexol were measured for a minimum of 24 hours after injection. Peak serum concentrations were observed after 2.2 (1.7–2.7) hours. The half-life of the subsequent decrease in serum concentrations was 3.4 (2.2–7.9) hours. Concentrations of iohexol in cerebrospinal fluid were 0.29–4.3 mg I/ml 24 hours after injection (7 patients). Serum and cerebrospinal fluid concentrations of iohexol are comparable to those found after intrathecal injection of metrizamide.

Selective left vertebral angiography was carried out in 25 rabbits comparing the toxic effects of iohexol and metrizamide (Amipaque). The iodine concentration for iohexol was 280 and 350 mg/ml and for metrizamide 350 mg/ml. Short general convulsions were seen in many of the animals with iohexol in the concentration of 350 mg iodine/ml. Cardiovascular reactions were seen with both contrast media, but were more marked with iohexol than with metrizamide in the concentration of 350 mg iodine/ml. Both iohexol and metrizamide are far less toxic than the ionic contrast medium metrizoate, but metrizamide seems to be less toxic than iohexol in vertebral angiography.

Selective vertebral angiography was performed in 28 rabbits in order to compare the adverse effects of two monomeric (metrizamide, iohexol) and two dimeric (iodecol, 2-5410-3) non-ionic water-soluble contrast media. The dose was 2,5 ml and the iodine concentrations 300 mg per ml. Marked, but transitory changes were seen in the electrocardiographic and blood pressure recordings with all the contrast media and with no difference between them in this respect. The two monomers had a higher tendency than the dimers to cause spasm in the intracranial arteries. No serious complications were seen in the series.

The new non-ionic contrast medium iohexol was compared with Amipaque in selective cerebral angiography in a double blind study in 60 patients. There were no adverse reactions or reports of discomfort during the examinations or in the 24 h follow-up period. No differences were observed with regard to image quality or cerebral circulation time.

Equimolar doses of iohexol and metrizamide (0.48 mmol/kg body weight = 185 mg I/kg), administered in solutions iso- and hyperosmolar to the CSF, were injected subarachnoidally into rabbits under pentobarbital anaesthesia. No excitative effects of iohexol were observed in the behaviour of the rabbits during a 3-h period immediately after the injection. Metrizamide caused significant, severe excitative effects, ranging from hyperexcitability to repeated generalized seizures. The frequency and severity of excitative effects were independent of the osmolality of the metrizamide solutions injected.

In 55 patients, the blood flow in the carotid and supratrochlear arteries was examined by Doppler sonography during cerebral angiography. In general, a threefold response was observed: an initial phase of turbulence during the injection was followed by a phase of depressed and then of increased arterial flow. The second phase of reduced perfusion which probably is caused by the increased viscosity of the mixture of contrast medium and blood, is more pronounced in the internal carotid artery, whereas the third phase of accelerated flow is more marked in the external carotid artery. In patients with an occlusion of the internal carotid artery, the cerebral blood supply often depends on the collateral pathway via the ophthalmic artery. In these cases, the reduction of the blood flow is specially marked and long-lasting, as we could show. This may contribute to a higher angiographic risk of those cases with an important ophthalmic collateral flow.

A double blind study was carried out to evaluate safety, tolerability and visualization quality of the non-ionic contrast medium Iohexol compared to Meglumine-Ca-Metrizoate (Isopaque Cerebral) for cerebral angiography. The two contrast media were found equal in most respects. A slight increase in systolic blood pressure following Meglumine-Ca-Metrizoate injections and a slight decrease in diastolic blood pressure following Iohexol were statistically significant. Tachycardia following injections of Meglumine-Ca-Metrizoate in the aortic arch was also significant and may indicate more discomfort from this medium, although no difference was found in patient interviews. The changes in blood pressure and heart rate were small and of no clinical importance.

The commonly used contrast medium metrizoate (isopaque Cerebral®) or the new nonionic iohexol were injected intravenously for enhancement of cranial CT in a randomized double blind study. Each group consisted of 105 patients. No serious reactions occurred. Ten patients receiving metrizoate had minor reactions of mainly allergic type, whereas only one patient receiving iohexol reacted. No differences in enhancement efficiency could be observed.

Thirty patients underwent functional cervical myelography, i.e. radiographs in the lateral view were obtained in extension as well as in flexion of the neck. Sagittal tomography was performed in both positions. Widening of the subarachnoid space and decreased sagittal diameter of the spinal cord due to shortening were demonstrated in the lateral view in flexion. In some cases with advanced narrowing or spinal block in extension, such widening in flexion resulted in better diagnostic images by providing passage of the contrast medium caudally. Although iohexol (Omnipaque, Nyegaard & Co., Oslo) was regularly forced into the posterior cranial fossa by the movements, the frequency of side effects was approximately the same as in our former trials with iohexol in conventional cervical myelography. EEG changes occurred in two patients (7%). A sitting position for 3–4 min after the examination followed by an elevated head end of the bed was probably important for preventing side effects from the contrast medium. Specific questioning revealed twice as many subjective side effects as reported after general questions alone.

The nonionic contrast agent iohexol was compared with the ionic agent iothalamate for contrast enhancement of brain tumors and radiation brain damage in dogs. Tissue enhancement during infusion of contrast and 5, 10, 15 and 30 min later was measured using quantitative computed tomography. Blood iodine was measured using x-ray fluorescence. Peak contrast enhancement occurred during infusion in tumors and after 5 min in irradiated normal brain for both contrast agents. Absolute uptake of contrast in each lesion was the same for both agents when normalized to total grams of iodine administered. Blood iodine levels were slightly but not significantly higher using iohexol. The reduced osmotic load and similar contrast enhancement of lesions suggest that the nonionic contrast medium iohexol may be a useful agent for routine CT of the brain.

In a double blind cross-over study the non ionic, water soluble contrast medium iohexol has been compared to Urografin Meglumine by angiography in common carotid artery and vertebral artery. More subjective adverse effects were generally seen with Urografin than with iohexol and statistically there were significantly less changes in heart rate after iohexol but no significant changes in the intra-arterial recorded blood pressure.

After suboccipital injection of Iotrol and Iopamidol labelled with iodine 125 in rabbits, we measured residual radioactivity in the whole brain and optical density on autoradiographs of brain sections obtained 2, 8 and 24 h after injection. Residual radioactivity is higher with Iotrol than with Iopamidol after 8 h and 24 h. At densitometry, while the penetration of the cortex is the same with both media at 2 h (although subcortical passage of Iotrol is greater), by 8 h the concentration of Iopamidol is twice that of Iotrol, and at 24 h it is three times as high. A similar pattern was seen in the subcortical region. These densitometric findings are in agreement with previous electrophysiological studies, in which changes were less severe and more transient with Iotrol than with Iohexol. There is nevertheless and apparent lack of agreement between the studies of radioactivity and the electrical findings. The lower neurotoxicity of Iotrol may be explained by: 1, a longer half-life in the subarachnoid space; 2. its larger molecules, which inhibit diffusion in the extracellular fluid, and 3. its more hydrophilic nature, which reduces intracellular penetration.

Iohexol 300 was used for 55 selective spinal angiograms in 50 patients; all were of good quality. There was no significant change in vital signs during the angiographic procedure in any case. Two patients with spinal dural arteriovenous fistula draining into a coronal venous plexus developed transient subjective slight increase in their disability during the immediate post-angiographic period. Eight cases embolised at the time of angiography showed improvement in their neurological deficits within 24 h of the study. The other patients were unaffected by the procedure. Iohexol 300 is a very suitable contrast medium for spinal angiography.