Endovascular treatment of intracerebral arteriovenous malformations: procedural safety, complications, and results evaluated by MR imaging, including diffusion and perfusion imaging.

BACKGROUND AND PURPOSE: Endovascular embolization is an increasingly common method to treat intracerebral arteriovenous malformations (AVM). To date, however, published data are rather scarce, especially with regard to true procedure-related complications and their causes. The purpose of our study was to evaluate treatment safety and correlate anatomic results with clinical outcome by using MR imaging, including diffusion-weighted (DWI) and perfusion imaging (PI). METHODS: We performed 50 endovascular procedures in 21 patients. Most AVMs were supratentorial, Spetzler-Martin grades II-IV. MR imaging was scheduled within 1 week before and 3 days after each treatment. MR imaging findings were correlated to digital subtraction angiography, procedure reports, and the clinical course. Outcome was graded according to the modified Rankin scale (mRS) 3-6 months after treatment. RESULTS: In this study, 104 MR imaging examinations were performed; mean interval between the endovascular procedure and posttreatment MR imaging was 28 hours. Nine adverse events occurred in 7 patients during 8 procedures (16%), one causing a permanent deficit. New lesions were noted on MR imaging after 22/50 procedures. Ischemic lesions in 22% of the procedures, frequently located perinidally. Most lesions were small, frequently asymptomatic, and reversible (18/23). Four hematomas were found. Subacute hemorrhages developed from a vasogenic edema on 2 occasions. New lesions, including hematomas, developed between treatments in 4 patients, mainly because of progressive occlusion of the nidus or draining veins. PI overestimated the AVM nidus on most occasions, and transient worsening of the PI pattern was noted in 2 patients. Treatment-related mortality and morbidity were 0% and 14.2%, respectively (mRS 1-2). CONCLUSIONS: Endovascular procedures are rather safe but are associated with more ischemic events and followed by less hemodynamic disturbances than previously understood. Adverse procedural events and new MR imaging lesions were generally asymptomatic and most often transient, if symptomatic. Most lesions would not have been verified without MR imaging. DWI and PI were most useful to detect and understand the cause of various complications. The most clinically important complications were caused by late venous occlusions.

Iohexol in patients with previous adverse reactions to contrast media.

Iohexol (Omnipaque) was used for enhancement of brain CT in 17 patients with previous adverse reactions to contrast media. Two of these patients also had cerebral angiography using iohexol. No premedication was given. The only adverse reaction was a skin reaction 24 hours after the iohexol injection, which might have been induced by the contrast medium or treatment with antibiotics. Five of the patients had repeated iohexol injections at different occasions without adverse reactions.

Proteinuria produced by urographic contrast media.

All angiographic and urographic procedures expose the kidney to high contrast medium concentrations. The introduction of the triiodinated ionic contrast media has lowered the risk of contrast medium-induced renal damage. An increase in dose and use of "bolus urography" have, however, led to an increase in frequency of reports on renal damage following intravenous pyelography and angiography. The low general toxicity of the new nonionic contrast media should also include a lower toxicity towards the kidneys. The media are, however, concentrated in the kidney to twice the concentration of the ionic media, and this might blur the expected reduction in kidney toxicity. The authors examined this problem by studying enzymuria in rabbits and albuminuria in rats after injection of different ionic and nonionic contrast media. In the rabbit, the model should imitate a urography and in the rat, a nephroangiography. All contrast media resulted in enzymuria and albuminuria, but to different degrees. The time for maximum enzymuria differed from the time of maximum albuminuria. The proteinuria does not appear to be related to the osmotic pressure of the injected contrast medium. The clinical significance of these findings is discussed.

Contrast enhanced brain CT comparison between iohexol and metrizoate.

The commonly used contrast medium metrizoate (Isopaque Cerebral) or the new nonionic iohexol was 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.

Penetration of subarachnoid contrast medium into rabbit spinal cord. Comparison between metrizamide and iohexol.

The penetration into rabbit spinal cord of two nonionic contrast media, iohexol and metrizamide, and a reference tracer, technetium DTPA, were compared. The spinal subarachnoid space was perfused for 4 hours with a CSF solution to which technetium DTPA and either iohexol or metrizamide had been added. The contrast media and technetium DTPA concentrations reached a plateau level in CSF outflow within 80 minutes. The contrast media concentrations in CSF were higher than the technetium DTPA (P less than .001). In the cord tissue, technetium DTPA reached higher concentrations than the contrast media (P less than .001), and iohexol reached higher concentrations relative to technetium DTPA than metrizamide (P less than .001). The mean contrast media distribution volumes in the thoracic cord were 13% (iohexol) and 12% (metrizamide). The smaller distribution volume observed for metrizamide could be related to the larger effective size of "associated" metrizamide molecules or an interference with diffusion perhaps related to binding to glucose carriers.

In vivo proton MR spectroscopy of untreated and treated brain abscesses.

MR spectroscopy was performed in three patients with brain abscesses. In two patients, MR spectroscopy revealed end-products of bacterial breakdown (acetate, succinate, amino acids, lactate) in the abscess cysts. In one of these, the spectrum was reversed to a single lactate peak after treatment. In the third patient, MR spectroscopy was performed only after treatment and showed a single nonspecific lactate peak. MR spectroscopy is a potential tool for noninvasive diagnosis of brain abscess and might be useful for evaluating changes after treatment.

Gd-DTPA-enhanced MR of suspected spinal multiple sclerosis.

A prospective study was undertaken to evaluate the potential of Gd-DTPA-enhanced MR to differentiate active from inactive demyelinating lesions of the cervical spinal cord. Five patients with elongated high-signal-intensity lesions in the cervical cord on long TR/TE spin-echo MR images and a clinical suspicion of demyelinating disease had MR before and after IV Gd-DTPA. Delayed contrast enhancement (after 45-60 min) of the lesions was seen on short TR/TE images in two patients with clinically active disease, but no enhancement could be detected in three patients with stable disease. The patients with active disease underwent repeated MR examinations until the enhancement disappeared. The decrease in Gd-DTPA enhancement paralleled a decrease in clinical signs and symptoms of cervical myelopathy. MR is useful in evaluating patients suspected of having demyelinating disease. The MR finding of asymptomatic lesions in the brain lends support to the diagnosis of multiple sclerosis. Other possible causes of myelopathy, such as spinal cord compression and intramedullary tumor, can be excluded with the use of MR.

MR imaging of the cervical spine in rheumatoid arthritis.

The cervical spine was examined with MR imaging and conventional radiography in 23 patients with severe rheumatoid arthritis. All patients had neck pain and 17 also had neurologic symptoms. MR provided detailed information about soft-tissue lesions, vertebral dislocation, and narrowing of the spinal canal. Pannus surrounding the odontoid process was revealed in 14 patients, all with horizontal atlantoaxial subluxation. Compression of the medulla and/or spinal cord, caused by dislocated vertebrae and/or the soft-tissue mass around the odontoid process, was seen in 15 patients. When there was more than one dislocation the most important level could be determined. Posterior occipitocervical fusion had been performed in six of the patients, and in only two of these was adequate analysis of the upper cervical spine impossible because of artifacts from metal (stainless steel wires and pins). Sagittal MR in the neutral position combined with conventional radiography, including lateral views in flexion and extension, provided all the information necessary for further clinical management of rheumatoid arthritis of the cervical spine.

Comparison of MR imaging and CT in patients with intracranial aneurysm clips.

CT and MR imaging of the brain were performed without complications in 16 patients who had undergone surgery for a ruptured aneurysm with the use of nonferromagnetic Yasargil 316 or Sugita Elgiloy clips. MR was performed on a 0.3-T Fonar beta-3000M imaging system. The artifacts caused by the clips were smaller on MR than on CT, and, therefore, anatomic structures such as the brainstem and temporal lobes were better visualized on MR. Brain-tissue lesions corresponding to the frontotemporal surgical approach were seen with MR in seven patients and with CT in six. In three patients temporal-lobe lesions seen on MR were not seen on CT because of beam-hardening artifacts. Lesions unrelated to the region of surgery were seen with MR in nine patients and with CT in five. In conclusion, MR was safe and superior to CT both in demonstrating anatomic details and in detecting tissue lesions in patients with aneurysm clips.

Preoperative grading of glioma malignancy with thallium-201 single-photon emission CT: comparison with conventional CT.

PURPOSE: To compare thallium-201 single-photon emission CT with conventional CT in grading the malignancy of gliomas and to determine the reliability of each in tumor assessment. METHODS: We studied 37 patients who had gliomas (31 high grade and 6 low grade) and compared the CT findings with the thallium-201 index, which we defined as tumor uptake relative to the uptake in the contralateral hemisphere. RESULTS: Among the high-grade gliomas, we observed a significant correlation between breakdown volume of the blood-brain barrier and thallium-201 uptake. However, 8 of the high-grade gliomas had low thallium-201 uptake, in the same range as the low-grade gliomas. Of these, 2 were nonenhancing and the other 6 showed ring enhancement on CT scans. Analysis of variance showed no significant difference in thallium-201 indexes between low-grade gliomas and highly malignant (grade II-III) gliomas. Accuracy of thallium-201 imaging was lower (78%) than that of CT (84%) in identifying high-grade gliomas. CONCLUSIONS: Damage to the blood-brain barrier is a prerequisite for uptake of thallium-201 in gliomas. Tumors with central necrotic areas and moderate ring enhancement tend to be underestimated when evaluated by means of thallium-201 scintigraphy. The results indicate a need for caution when interpreting findings on images obtained with thallium-201 single-photon emission CT in preoperative evaluation of brain tumors.

Proton MR spectroscopy and preoperative diagnostic accuracy: an evaluation of intracranial mass lesions characterized by stereotactic biopsy findings.

BACKGROUND AND PURPOSE: MR imaging has made it easier to distinguish among the different types of intracranial mass lesions. Nevertheless, it is sometimes impossible to base a diagnosis solely on clinical and neuroradiologic findings, and, in these cases, biopsy must be performed. The purpose of this study was to evaluate the hypothesis that proton MR spectroscopy is able to improve preoperative diagnostic accuracy in cases of intracranial tumors and may therefore obviate stereotactic biopsy. METHODS: Twenty-six patients with intracranial tumors underwent MR imaging, proton MR spectroscopy, and stereotactic biopsy. MR spectroscopic findings were evaluated for the distribution pattern of pathologic spectra (NAA/Cho ratio < 1) across the lesion and neighboring tissue, for signal ratios in different tumor types, and for their potential to improve preoperative diagnostic accuracy. RESULTS: Gliomas and lymphomas showed pathologic spectra outside the area of contrast enhancement while four nonastrocytic circumscribed tumors (meningioma, pineocytoma, metastasis, and germinoma) showed no pathologic spectra outside the region of enhancement. No significant correlation was found between different tumor types and signal ratios. MR spectroscopy improved diagnostic accuracy by differentiating infiltrative from circumscribed tumors; however, diagnostic accuracy was not improved in terms of differentiating the types of infiltrative or circumscribed lesions. CONCLUSION: MR spectroscopy can improve diagnostic accuracy by differentiating circumscribed brain lesions from histologically infiltrating processes, which may be difficult or impossible solely on the basis of clinical or neuroradiologic findings.

Colloid cysts of the third ventricle: correlation of MR and CT findings with histology and chemical analysis.

Eight patients with colloid cysts of the third ventricle were examined with CT and MR. In six, surgical resection was performed and the material was subjected to histologic evaluation; the concentrations of trace elements were determined by particle-induced X-ray emission. Stereotaxic aspiration was performed in two. The investigation showed that colloid cysts are often iso- or hypodense relative to brain on CT (5/8), but sometimes have a center of increased density. Increased density did not correlate with increased concentration of calcium or other metals but did not correlate with high cholesterol content. Colloid cysts appear more heterogeneous on MR (6/8) than on CT (3/8), despite a homogeneous appearance at histology. High signal on short TR/TE sequences is correlated with a high cholesterol content. A marked shortening of the T2 relaxation time is often noticed in the central part of the cyst. Analysis of trace elements showed that this phenomenon is not related to the presence of metals with paramagnetic effects. Our analysis of the contents of colloid cysts does not support the theory that differing metallic concentrations are responsible for differences in MR signal intensity or CT density. We did find that increased CT density and high MR signal correlated with high cholesterol content.

Diagnosis of brain abscesses with indium-111-labeled leukocytes.

Sixteen patients with intracerebral mass lesions where computed tomography (CT) was not fully conclusive with respect to the differential diagnosis between brain tumor and abscess were examined with leukocyte brain scintigraphy (LBS). Autologous leukocytes were labeled with indium-111 oxinate and were reinjected intravenously; registration with a gamma camera was performed after 24 and 48 hours. In 10 of 11 patients with the final diagnosis of a brain tumor, no accumulation of radiolabeled leukocytes could be detected in the brain. In 4 of 5 patients with the final diagnosis of brain abscess, scintigraphy showed a pronounced increase of focal activity corresponding to the lesion demonstrated with CT. The reasons for the one false-positive and the one false-negative result are discussed, and it is concluded that LBS (a) can be used to detect intracranial infection and (b) may be a useful diagnostic tool for distinguishing between brain abscess and brain tumor.

Late magnetic resonance imaging related to neurobehavioral functioning after aneurysmal subarachnoid hemorrhage.

Twenty patients who underwent early aneurysm surgery--that is, surgery within 72 hours after rupture--underwent further follow-up examination including magnetic resonance imaging (MRI) of the brain and a comprehensive neuropsychological assessment. Significant statistical correlation between tissue loss as seen on a late MRI scan and neurobehavioral deficits could not be established. Among 9 patients with no tissue loss seen on MRI, 3 exhibited substantial cognitive dysfunction and 6 had mild impairment. Three patients showed minor but corresponding tissue loss and deficits. In 3 patients with pronounced pathological indications on MRI, evidence of cognitive dysfunction was absent in 2, and 1 patient showed substantial impairment. The remaining 5 individuals displayed moderate pathological indications on MRI, with no obvious correspondence to cognitive functioning. In 7 patients, small white matter lesions, probably silent infarcts not seen on computed tomographic scan, were discovered on MRI. There was a clear relationship between arterial hypertension prior to aneurysm rupture and the extent of tissue loss seen on MRI. Absence of pathological findings on MRI scan did not exclude cognitive malfunctioning, and vice-versa.

Magnetic resonance imaging and aneurysm clips. Magnetic properties and image artifacts.

The magnetic properties of 12 different types of aneurysm clip were investigated in order to identify which clips allow postoperative magnetic resonance (MR) imaging without risk. Clip-induced MR artifacts were also quantitatively studied using a geometrical phantom. Nonferromagnetic aneurysm clips like the Yasargil Phynox, Sugita Elgiloy, and Vari-Angle McFadden clips do not appear to contraindicate MR studies performed with a FONAR beta-3000M imager. There is no clip movement upon introduction of the phantom into the MR imager, and the image artifacts caused by the clips are so limited that patients harboring such clips may well be considered for MR imaging. This examination may reveal information not obtainable by any other radiological modality.

High-resolution diffusion imaging using phase-corrected segmented echo-planar imaging.

Diffusion magnetic resonance imaging (MRI) was performed with a high-resolution segmented echo-planar imaging technique, which provided images with substantially less susceptibility artifacts than images obtained with single-shot echo-planar imaging (EPI). Diffusion imaging performed with any multishot pulse sequence is inherently sensitive to motion artifacts and in order to reduce motion artifacts, the presented method utilizes navigator echo phase corrections, performed after a one-dimensional Fourier transform along the frequency-encoding direction. Navigator echo phases were fitted to a straight line prior to phase correction to avoid errors from internal motion. In vivo imaging was performed using electro cardiographic (ECG) triggering. Apparent diffusion coefficient (ADC) maps were calculated on a pixel-by-pixel basis using up to seven diffusion sensitivities, ranging from b = 0 to 1129 x 10(6) s/m(2).

Quality assessment of localization technique performance in small volume in vivo 1H MR spectroscopy.

A new phantom and evaluation method for experimental evaluation of 1H-magnetic resonance spectroscopy single volume localization techniques regarding signal contamination (C), defined as the part of the signal originating outside the volume of interest, is presented. The quality assessment method is based on a spherical phantom with an oil/water interface in order to reduce susceptibility effects, and applied for stimulated-echo acquisition method (STEAM) and spin-echo (SE) sequences, echo times of 270, 135, and 10 ms, and cubic volumes of interest (VOI) of 1(3), 1.5(3), 2(3), 2.5(3), and 3(3) cm3. To be able to mimic measurements of the contamination in three dimensions the physical gradients representing the three orthogonal directions for slice selection were shifted in the pulse sequences. Contamination values in one dimension differed between 6.5% and 8.4% in SE sequences, and between 0.7% and 13.8% in STEAM sequences. In STEAM sequences a decrease of C with increasing VOI size was observed while SE sequences showed comparable C values for the different VOI sizes tested. The total contamination in three dimensions were 19% and 18% in SE and STEAM sequences with a TE of 270 ms, and 7% in a STEAM sequence with a TE of 10 ms, respectively. The presented evaluation method is easily applied to the new phantom and showed high reproducibility.

Quantitative diffusion coefficient maps using fast spin-echo MRI.

In this work, we have evaluated the performance of a diffusion-sensitive fast spin-echo (FSE) pulse sequence. The proposed pulse sequence utilises velocity-compensating diffusion-encoding gradients and includes the collection of navigator echoes. Spoiler gradients were inserted in the slice-selecting direction to minimise effects from stimulated echoes. Calculations of the b values showed that cross-terms between imaging gradients and diffusion gradients only led to a marginal increase of b values. Pixel-wise calculation of apparent diffusion coefficient (ADC) maps was performed numerically, considering cross-terms between diffusion-encoding and imaging gradients. The sequences investigated used echo train lengths of 16, 8 and 4 echoes and were encoded in either the slice-, frequency- or phase-encoding direction. In order to allow for higher b values a pulse-sequence version using non-motion compensating diffusion-encoding gradients was written. Phantom measurements were performed and the diffusion coefficients of water and acetone were reasonable. Seven healthy volunteers (age 28-50 years) were examined and apparent diffusion coefficient values agreed well with expected values. Diffusion-weighted images, apparent diffusion coefficient maps and images corresponding to the trace of the diffusion tensor of good quality were retrieved in vivo.

No relationship between epidural fibrosis and sciatica in the lumbar postdiscectomy syndrome. A study with contrast-enhanced magnetic resonance imaging in symptomatic and asymptomatic patients.

STUDY DESIGN: Symptomatic patients were retrospectively analyzed and compared with a control group from an ongoing prospective and consecutive study. OBJECTIVES: To determine the presence and extent of epidural fibrosis in patients with and without recurrent sciatic pain after previous lumbar discectomy, contrast-enhanced magnetic resonance images were evaluated and correlated with surgical findings in the symptomatic patients. Recurrent hernia and bony stenosis were ruled out as the probable causative agent, as well as any morphologic explanation other than fibrosis. SUMMARY OF BACKGROUND DATA: Repeat surgical results for patients with the lumbar postdiscectomy syndrome with epidural fibrosis alone are often unfavorable. The pathogenic role of epidural fibrosis, however, has not been established. METHODS: The magnetic resonance images of eight patients with recurrent or persistent sciatic pain after lumbar discectomy were compared with those of eight asymptomatic patients constituting a control group. All were examined with magnetic resonance imaging on a 0.3 T unit before and after intravenous injection of gadolinium-DTPA, and clinically, 6 months to 4 years after surgery. The symptomatic patients subsequently underwent reoperation. RESULTS: Fourteen patients had focal or diffuse epidural fibrosis around the nerve root and/or the thecal sac at the operated level, whereas the postoperative findings for two patients were "normal," one in the operated and one in the control group. No difference between the groups regarding mass effect or affection of the nerve roots or thecal sac was noted. At reoperation of the eight symptomatic patients, fibrosis was the only pathologic finding in all cases except one, in which surgery confirmed the normal finding on magnetic resonance imaging. Six of the eight operated patients had recurrent or persistent symptoms within a year of the reoperation. CONCLUSION: No differences regarding the presence and extent of epidural fibrosis between the symptomatic and asymptomatic patients could be demonstrated with contrast-enhanced magnetic resonance imaging. The role of epidural fibrosis as the causative agent in the lumbar postdiscectomy syndrome is questioned.

A controlled comparison of myelography, computed tomography, and magnetic resonance imaging in clinically suspected lumbar disc herniation.

STUDY DESIGN: A controlled prospective blinded study. OBJECTIVES: To compare the diagnostic power of myelography, computed tomography and magnetic resonance imaging in the diagnosis of low lumbar disc herniation. METHODS: Eighty patients with monoradicular sciatica were examined by myelography, computed tomography, and magnetic resonance imaging, and all underwent subsequent surgery. The images were evaluated twice in a blinded fashion, and the diagnostic power of the modalities was expressed by a decision-analytic regret function. RESULTS: In 57 patients (71%) a disc herniation at the expected level was disclosed at surgery. The largest amount of diagnostic information was gained from computed tomography, followed by magnetic resonance imaging and myelography. Both computed tomography and magnetic resonance imaging were significantly informative, whereas this was not the case for myelography. CONCLUSION: The results indicate that computed tomography or magnetic resonance imaging should be the first choice for imaging in patients with suspected lumbar disc herniation.